xfs: constify the name argument to various directory functions

[linux-block.git] / fs / xfs / xfs_inode.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2000-2006 Silicon Graphics, Inc.
 * All Rights Reserved.
 */
#include <linux/iversion.h>

#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_defer.h"
#include "xfs_inode.h"
#include "xfs_dir2.h"
#include "xfs_attr.h"
#include "xfs_trans_space.h"
#include "xfs_trans.h"
#include "xfs_buf_item.h"
#include "xfs_inode_item.h"
#include "xfs_ialloc.h"
#include "xfs_bmap.h"
#include "xfs_bmap_util.h"
#include "xfs_errortag.h"
#include "xfs_error.h"
#include "xfs_quota.h"
#include "xfs_filestream.h"
#include "xfs_trace.h"
#include "xfs_icache.h"
#include "xfs_symlink.h"
#include "xfs_trans_priv.h"
#include "xfs_log.h"
#include "xfs_bmap_btree.h"
#include "xfs_reflink.h"
#include "xfs_ag.h"

struct kmem_cache *xfs_inode_cache;

/*
 * Used in xfs_itruncate_extents().  This is the maximum number of extents
 * freed from a file in a single transaction.
 */
#define XFS_ITRUNC_MAX_EXTENTS  2

STATIC int xfs_iunlink(struct xfs_trans *, struct xfs_inode *);
STATIC int xfs_iunlink_remove(struct xfs_trans *tp, struct xfs_perag *pag,
        struct xfs_inode *);

/*
 * helper function to extract extent size hint from inode
 */
xfs_extlen_t
xfs_get_extsz_hint(
        struct xfs_inode        *ip)
{
        /*
         * No point in aligning allocations if we need to COW to actually
         * write to them.
         */
        if (xfs_is_always_cow_inode(ip))
                return 0;
        if ((ip->i_diflags & XFS_DIFLAG_EXTSIZE) && ip->i_extsize)
                return ip->i_extsize;
        if (XFS_IS_REALTIME_INODE(ip))
                return ip->i_mount->m_sb.sb_rextsize;
        return 0;
}

/*
 * Helper function to extract CoW extent size hint from inode.
 * Between the extent size hint and the CoW extent size hint, we
 * return the greater of the two.  If the value is zero (automatic),
 * use the default size.
 */
xfs_extlen_t
xfs_get_cowextsz_hint(
        struct xfs_inode        *ip)
{
        xfs_extlen_t            a, b;

        a = 0;
        if (ip->i_diflags2 & XFS_DIFLAG2_COWEXTSIZE)
                a = ip->i_cowextsize;
        b = xfs_get_extsz_hint(ip);

        a = max(a, b);
        if (a == 0)
                return XFS_DEFAULT_COWEXTSZ_HINT;
        return a;
}

/*
 * These two are wrapper routines around the xfs_ilock() routine used to
 * centralize some grungy code.  They are used in places that wish to lock the
 * inode solely for reading the extents.  The reason these places can't just
 * call xfs_ilock(ip, XFS_ILOCK_SHARED) is that the inode lock also guards to
 * bringing in of the extents from disk for a file in b-tree format.  If the
 * inode is in b-tree format, then we need to lock the inode exclusively until
 * the extents are read in.  Locking it exclusively all the time would limit
 * our parallelism unnecessarily, though.  What we do instead is check to see
 * if the extents have been read in yet, and only lock the inode exclusively
 * if they have not.
 *
 * The functions return a value which should be given to the corresponding
 * xfs_iunlock() call.
 */
uint
xfs_ilock_data_map_shared(
        struct xfs_inode        *ip)
{
        uint                    lock_mode = XFS_ILOCK_SHARED;

        if (xfs_need_iread_extents(&ip->i_df))
                lock_mode = XFS_ILOCK_EXCL;
        xfs_ilock(ip, lock_mode);
        return lock_mode;
}

uint
xfs_ilock_attr_map_shared(
        struct xfs_inode        *ip)
{
        uint                    lock_mode = XFS_ILOCK_SHARED;

        if (ip->i_afp && xfs_need_iread_extents(ip->i_afp))
                lock_mode = XFS_ILOCK_EXCL;
        xfs_ilock(ip, lock_mode);
        return lock_mode;
}

/*
 * In addition to i_rwsem in the VFS inode, the xfs inode contains 2
 * multi-reader locks: invalidate_lock and the i_lock.  This routine allows
 * various combinations of the locks to be obtained.
 *
 * The 3 locks should always be ordered so that the IO lock is obtained first,
 * the mmap lock second and the ilock last in order to prevent deadlock.
 *
 * Basic locking order:
 *
 * i_rwsem -> invalidate_lock -> page_lock -> i_ilock
 *
 * mmap_lock locking order:
 *
 * i_rwsem -> page lock -> mmap_lock
 * mmap_lock -> invalidate_lock -> page_lock
 *
 * The difference in mmap_lock locking order mean that we cannot hold the
 * invalidate_lock over syscall based read(2)/write(2) based IO. These IO paths
 * can fault in pages during copy in/out (for buffered IO) or require the
 * mmap_lock in get_user_pages() to map the user pages into the kernel address
 * space for direct IO. Similarly the i_rwsem cannot be taken inside a page
 * fault because page faults already hold the mmap_lock.
 *
 * Hence to serialise fully against both syscall and mmap based IO, we need to
 * take both the i_rwsem and the invalidate_lock. These locks should *only* be
 * both taken in places where we need to invalidate the page cache in a race
 * free manner (e.g. truncate, hole punch and other extent manipulation
 * functions).
 */
void
xfs_ilock(
        xfs_inode_t             *ip,
        uint                    lock_flags)
{
        trace_xfs_ilock(ip, lock_flags, _RET_IP_);

        /*
         * You can't set both SHARED and EXCL for the same lock,
         * and only XFS_IOLOCK_SHARED, XFS_IOLOCK_EXCL, XFS_ILOCK_SHARED,
         * and XFS_ILOCK_EXCL are valid values to set in lock_flags.
         */
        ASSERT((lock_flags & (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL)) !=
               (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL));
        ASSERT((lock_flags & (XFS_MMAPLOCK_SHARED | XFS_MMAPLOCK_EXCL)) !=
               (XFS_MMAPLOCK_SHARED | XFS_MMAPLOCK_EXCL));
        ASSERT((lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) !=
               (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
        ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_SUBCLASS_MASK)) == 0);

        if (lock_flags & XFS_IOLOCK_EXCL) {
                down_write_nested(&VFS_I(ip)->i_rwsem,
                                  XFS_IOLOCK_DEP(lock_flags));
        } else if (lock_flags & XFS_IOLOCK_SHARED) {
                down_read_nested(&VFS_I(ip)->i_rwsem,
                                 XFS_IOLOCK_DEP(lock_flags));
        }

        if (lock_flags & XFS_MMAPLOCK_EXCL) {
                down_write_nested(&VFS_I(ip)->i_mapping->invalidate_lock,
                                  XFS_MMAPLOCK_DEP(lock_flags));
        } else if (lock_flags & XFS_MMAPLOCK_SHARED) {
                down_read_nested(&VFS_I(ip)->i_mapping->invalidate_lock,
                                 XFS_MMAPLOCK_DEP(lock_flags));
        }

        if (lock_flags & XFS_ILOCK_EXCL)
                mrupdate_nested(&ip->i_lock, XFS_ILOCK_DEP(lock_flags));
        else if (lock_flags & XFS_ILOCK_SHARED)
                mraccess_nested(&ip->i_lock, XFS_ILOCK_DEP(lock_flags));
}

/*
 * This is just like xfs_ilock(), except that the caller
 * is guaranteed not to sleep.  It returns 1 if it gets
 * the requested locks and 0 otherwise.  If the IO lock is
 * obtained but the inode lock cannot be, then the IO lock
 * is dropped before returning.
 *
 * ip -- the inode being locked
 * lock_flags -- this parameter indicates the inode's locks to be
 *       to be locked.  See the comment for xfs_ilock() for a list
 *       of valid values.
 */
int
xfs_ilock_nowait(
        xfs_inode_t             *ip,
        uint                    lock_flags)
{
        trace_xfs_ilock_nowait(ip, lock_flags, _RET_IP_);

        /*
         * You can't set both SHARED and EXCL for the same lock,
         * and only XFS_IOLOCK_SHARED, XFS_IOLOCK_EXCL, XFS_ILOCK_SHARED,
         * and XFS_ILOCK_EXCL are valid values to set in lock_flags.
         */
        ASSERT((lock_flags & (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL)) !=
               (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL));
        ASSERT((lock_flags & (XFS_MMAPLOCK_SHARED | XFS_MMAPLOCK_EXCL)) !=
               (XFS_MMAPLOCK_SHARED | XFS_MMAPLOCK_EXCL));
        ASSERT((lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) !=
               (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
        ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_SUBCLASS_MASK)) == 0);

        if (lock_flags & XFS_IOLOCK_EXCL) {
                if (!down_write_trylock(&VFS_I(ip)->i_rwsem))
                        goto out;
        } else if (lock_flags & XFS_IOLOCK_SHARED) {
                if (!down_read_trylock(&VFS_I(ip)->i_rwsem))
                        goto out;
        }

        if (lock_flags & XFS_MMAPLOCK_EXCL) {
                if (!down_write_trylock(&VFS_I(ip)->i_mapping->invalidate_lock))
                        goto out_undo_iolock;
        } else if (lock_flags & XFS_MMAPLOCK_SHARED) {
                if (!down_read_trylock(&VFS_I(ip)->i_mapping->invalidate_lock))
                        goto out_undo_iolock;
        }

        if (lock_flags & XFS_ILOCK_EXCL) {
                if (!mrtryupdate(&ip->i_lock))
                        goto out_undo_mmaplock;
        } else if (lock_flags & XFS_ILOCK_SHARED) {
                if (!mrtryaccess(&ip->i_lock))
                        goto out_undo_mmaplock;
        }
        return 1;

out_undo_mmaplock:
        if (lock_flags & XFS_MMAPLOCK_EXCL)
                up_write(&VFS_I(ip)->i_mapping->invalidate_lock);
        else if (lock_flags & XFS_MMAPLOCK_SHARED)
                up_read(&VFS_I(ip)->i_mapping->invalidate_lock);
out_undo_iolock:
        if (lock_flags & XFS_IOLOCK_EXCL)
                up_write(&VFS_I(ip)->i_rwsem);
        else if (lock_flags & XFS_IOLOCK_SHARED)
                up_read(&VFS_I(ip)->i_rwsem);
out:
        return 0;
}

/*
 * xfs_iunlock() is used to drop the inode locks acquired with
 * xfs_ilock() and xfs_ilock_nowait().  The caller must pass
 * in the flags given to xfs_ilock() or xfs_ilock_nowait() so
 * that we know which locks to drop.
 *
 * ip -- the inode being unlocked
 * lock_flags -- this parameter indicates the inode's locks to be
 *       to be unlocked.  See the comment for xfs_ilock() for a list
 *       of valid values for this parameter.
 *
 */
void
xfs_iunlock(
        xfs_inode_t             *ip,
        uint                    lock_flags)
{
        /*
         * You can't set both SHARED and EXCL for the same lock,
         * and only XFS_IOLOCK_SHARED, XFS_IOLOCK_EXCL, XFS_ILOCK_SHARED,
         * and XFS_ILOCK_EXCL are valid values to set in lock_flags.
         */
        ASSERT((lock_flags & (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL)) !=
               (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL));
        ASSERT((lock_flags & (XFS_MMAPLOCK_SHARED | XFS_MMAPLOCK_EXCL)) !=
               (XFS_MMAPLOCK_SHARED | XFS_MMAPLOCK_EXCL));
        ASSERT((lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) !=
               (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
        ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_SUBCLASS_MASK)) == 0);
        ASSERT(lock_flags != 0);

        if (lock_flags & XFS_IOLOCK_EXCL)
                up_write(&VFS_I(ip)->i_rwsem);
        else if (lock_flags & XFS_IOLOCK_SHARED)
                up_read(&VFS_I(ip)->i_rwsem);

        if (lock_flags & XFS_MMAPLOCK_EXCL)
                up_write(&VFS_I(ip)->i_mapping->invalidate_lock);
        else if (lock_flags & XFS_MMAPLOCK_SHARED)
                up_read(&VFS_I(ip)->i_mapping->invalidate_lock);

        if (lock_flags & XFS_ILOCK_EXCL)
                mrunlock_excl(&ip->i_lock);
        else if (lock_flags & XFS_ILOCK_SHARED)
                mrunlock_shared(&ip->i_lock);

        trace_xfs_iunlock(ip, lock_flags, _RET_IP_);
}

/*
 * give up write locks.  the i/o lock cannot be held nested
 * if it is being demoted.
 */
void
xfs_ilock_demote(
        xfs_inode_t             *ip,
        uint                    lock_flags)
{
        ASSERT(lock_flags & (XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL|XFS_ILOCK_EXCL));
        ASSERT((lock_flags &
                ~(XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL|XFS_ILOCK_EXCL)) == 0);

        if (lock_flags & XFS_ILOCK_EXCL)
                mrdemote(&ip->i_lock);
        if (lock_flags & XFS_MMAPLOCK_EXCL)
                downgrade_write(&VFS_I(ip)->i_mapping->invalidate_lock);
        if (lock_flags & XFS_IOLOCK_EXCL)
                downgrade_write(&VFS_I(ip)->i_rwsem);

        trace_xfs_ilock_demote(ip, lock_flags, _RET_IP_);
}

#if defined(DEBUG) || defined(XFS_WARN)
static inline bool
__xfs_rwsem_islocked(
        struct rw_semaphore     *rwsem,
        bool                    shared)
{
        if (!debug_locks)
                return rwsem_is_locked(rwsem);

        if (!shared)
                return lockdep_is_held_type(rwsem, 0);

        /*
         * We are checking that the lock is held at least in shared
         * mode but don't care that it might be held exclusively
         * (i.e. shared | excl). Hence we check if the lock is held
         * in any mode rather than an explicit shared mode.
         */
        return lockdep_is_held_type(rwsem, -1);
}

bool
xfs_isilocked(
        struct xfs_inode        *ip,
        uint                    lock_flags)
{
        if (lock_flags & (XFS_ILOCK_EXCL|XFS_ILOCK_SHARED)) {
                if (!(lock_flags & XFS_ILOCK_SHARED))
                        return !!ip->i_lock.mr_writer;
                return rwsem_is_locked(&ip->i_lock.mr_lock);
        }

        if (lock_flags & (XFS_MMAPLOCK_EXCL|XFS_MMAPLOCK_SHARED)) {
                return __xfs_rwsem_islocked(&VFS_I(ip)->i_rwsem,
                                (lock_flags & XFS_IOLOCK_SHARED));
        }

        if (lock_flags & (XFS_IOLOCK_EXCL | XFS_IOLOCK_SHARED)) {
                return __xfs_rwsem_islocked(&VFS_I(ip)->i_rwsem,
                                (lock_flags & XFS_IOLOCK_SHARED));
        }

        ASSERT(0);
        return false;
}
#endif

/*
 * xfs_lockdep_subclass_ok() is only used in an ASSERT, so is only called when
 * DEBUG or XFS_WARN is set. And MAX_LOCKDEP_SUBCLASSES is then only defined
 * when CONFIG_LOCKDEP is set. Hence the complex define below to avoid build
 * errors and warnings.
 */
#if (defined(DEBUG) || defined(XFS_WARN)) && defined(CONFIG_LOCKDEP)
static bool
xfs_lockdep_subclass_ok(
        int subclass)
{
        return subclass < MAX_LOCKDEP_SUBCLASSES;
}
#else
#define xfs_lockdep_subclass_ok(subclass)       (true)
#endif

/*
 * Bump the subclass so xfs_lock_inodes() acquires each lock with a different
 * value. This can be called for any type of inode lock combination, including
 * parent locking. Care must be taken to ensure we don't overrun the subclass
 * storage fields in the class mask we build.
 */
static inline int
xfs_lock_inumorder(int lock_mode, int subclass)
{
        int     class = 0;

        ASSERT(!(lock_mode & (XFS_ILOCK_PARENT | XFS_ILOCK_RTBITMAP |
                              XFS_ILOCK_RTSUM)));
        ASSERT(xfs_lockdep_subclass_ok(subclass));

        if (lock_mode & (XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL)) {
                ASSERT(subclass <= XFS_IOLOCK_MAX_SUBCLASS);
                class += subclass << XFS_IOLOCK_SHIFT;
        }

        if (lock_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL)) {
                ASSERT(subclass <= XFS_MMAPLOCK_MAX_SUBCLASS);
                class += subclass << XFS_MMAPLOCK_SHIFT;
        }

        if (lock_mode & (XFS_ILOCK_SHARED|XFS_ILOCK_EXCL)) {
                ASSERT(subclass <= XFS_ILOCK_MAX_SUBCLASS);
                class += subclass << XFS_ILOCK_SHIFT;
        }

        return (lock_mode & ~XFS_LOCK_SUBCLASS_MASK) | class;
}

/*
 * The following routine will lock n inodes in exclusive mode.  We assume the
 * caller calls us with the inodes in i_ino order.
 *
 * We need to detect deadlock where an inode that we lock is in the AIL and we
 * start waiting for another inode that is locked by a thread in a long running
 * transaction (such as truncate). This can result in deadlock since the long
 * running trans might need to wait for the inode we just locked in order to
 * push the tail and free space in the log.
 *
 * xfs_lock_inodes() can only be used to lock one type of lock at a time -
 * the iolock, the mmaplock or the ilock, but not more than one at a time. If we
 * lock more than one at a time, lockdep will report false positives saying we
 * have violated locking orders.
 */
static void
xfs_lock_inodes(
        struct xfs_inode        **ips,
        int                     inodes,
        uint                    lock_mode)
{
        int                     attempts = 0, i, j, try_lock;
        struct xfs_log_item     *lp;

        /*
         * Currently supports between 2 and 5 inodes with exclusive locking.  We
         * support an arbitrary depth of locking here, but absolute limits on
         * inodes depend on the type of locking and the limits placed by
         * lockdep annotations in xfs_lock_inumorder.  These are all checked by
         * the asserts.
         */
        ASSERT(ips && inodes >= 2 && inodes <= 5);
        ASSERT(lock_mode & (XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL |
                            XFS_ILOCK_EXCL));
        ASSERT(!(lock_mode & (XFS_IOLOCK_SHARED | XFS_MMAPLOCK_SHARED |
                              XFS_ILOCK_SHARED)));
        ASSERT(!(lock_mode & XFS_MMAPLOCK_EXCL) ||
                inodes <= XFS_MMAPLOCK_MAX_SUBCLASS + 1);
        ASSERT(!(lock_mode & XFS_ILOCK_EXCL) ||
                inodes <= XFS_ILOCK_MAX_SUBCLASS + 1);

        if (lock_mode & XFS_IOLOCK_EXCL) {
                ASSERT(!(lock_mode & (XFS_MMAPLOCK_EXCL | XFS_ILOCK_EXCL)));
        } else if (lock_mode & XFS_MMAPLOCK_EXCL)
                ASSERT(!(lock_mode & XFS_ILOCK_EXCL));

        try_lock = 0;
        i = 0;
again:
        for (; i < inodes; i++) {
                ASSERT(ips[i]);

                if (i && (ips[i] == ips[i - 1]))        /* Already locked */
                        continue;

                /*
                 * If try_lock is not set yet, make sure all locked inodes are
                 * not in the AIL.  If any are, set try_lock to be used later.
                 */
                if (!try_lock) {
                        for (j = (i - 1); j >= 0 && !try_lock; j--) {
                                lp = &ips[j]->i_itemp->ili_item;
                                if (lp && test_bit(XFS_LI_IN_AIL, &lp->li_flags))
                                        try_lock++;
                        }
                }

                /*
                 * If any of the previous locks we have locked is in the AIL,
                 * we must TRY to get the second and subsequent locks. If
                 * we can't get any, we must release all we have
                 * and try again.
                 */
                if (!try_lock) {
                        xfs_ilock(ips[i], xfs_lock_inumorder(lock_mode, i));
                        continue;
                }

                /* try_lock means we have an inode locked that is in the AIL. */
                ASSERT(i != 0);
                if (xfs_ilock_nowait(ips[i], xfs_lock_inumorder(lock_mode, i)))
                        continue;

                /*
                 * Unlock all previous guys and try again.  xfs_iunlock will try
                 * to push the tail if the inode is in the AIL.
                 */
                attempts++;
                for (j = i - 1; j >= 0; j--) {
                        /*
                         * Check to see if we've already unlocked this one.  Not
                         * the first one going back, and the inode ptr is the
                         * same.
                         */
                        if (j != (i - 1) && ips[j] == ips[j + 1])
                                continue;

                        xfs_iunlock(ips[j], lock_mode);
                }

                if ((attempts % 5) == 0) {
                        delay(1); /* Don't just spin the CPU */
                }
                i = 0;
                try_lock = 0;
                goto again;
        }
}

/*
 * xfs_lock_two_inodes() can only be used to lock ilock. The iolock and
 * mmaplock must be double-locked separately since we use i_rwsem and
 * invalidate_lock for that. We now support taking one lock EXCL and the
 * other SHARED.
 */
void
xfs_lock_two_inodes(
        struct xfs_inode        *ip0,
        uint                    ip0_mode,
        struct xfs_inode        *ip1,
        uint                    ip1_mode)
{
        int                     attempts = 0;
        struct xfs_log_item     *lp;

        ASSERT(hweight32(ip0_mode) == 1);
        ASSERT(hweight32(ip1_mode) == 1);
        ASSERT(!(ip0_mode & (XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL)));
        ASSERT(!(ip1_mode & (XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL)));
        ASSERT(!(ip0_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL)));
        ASSERT(!(ip1_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL)));
        ASSERT(ip0->i_ino != ip1->i_ino);

        if (ip0->i_ino > ip1->i_ino) {
                swap(ip0, ip1);
                swap(ip0_mode, ip1_mode);
        }

 again:
        xfs_ilock(ip0, xfs_lock_inumorder(ip0_mode, 0));

        /*
         * If the first lock we have locked is in the AIL, we must TRY to get
         * the second lock. If we can't get it, we must release the first one
         * and try again.
         */
        lp = &ip0->i_itemp->ili_item;
        if (lp && test_bit(XFS_LI_IN_AIL, &lp->li_flags)) {
                if (!xfs_ilock_nowait(ip1, xfs_lock_inumorder(ip1_mode, 1))) {
                        xfs_iunlock(ip0, ip0_mode);
                        if ((++attempts % 5) == 0)
                                delay(1); /* Don't just spin the CPU */
                        goto again;
                }
        } else {
                xfs_ilock(ip1, xfs_lock_inumorder(ip1_mode, 1));
        }
}

uint
xfs_ip2xflags(
        struct xfs_inode        *ip)
{
        uint                    flags = 0;

        if (ip->i_diflags & XFS_DIFLAG_ANY) {
                if (ip->i_diflags & XFS_DIFLAG_REALTIME)
                        flags |= FS_XFLAG_REALTIME;
                if (ip->i_diflags & XFS_DIFLAG_PREALLOC)
                        flags |= FS_XFLAG_PREALLOC;
                if (ip->i_diflags & XFS_DIFLAG_IMMUTABLE)
                        flags |= FS_XFLAG_IMMUTABLE;
                if (ip->i_diflags & XFS_DIFLAG_APPEND)
                        flags |= FS_XFLAG_APPEND;
                if (ip->i_diflags & XFS_DIFLAG_SYNC)
                        flags |= FS_XFLAG_SYNC;
                if (ip->i_diflags & XFS_DIFLAG_NOATIME)
                        flags |= FS_XFLAG_NOATIME;
                if (ip->i_diflags & XFS_DIFLAG_NODUMP)
                        flags |= FS_XFLAG_NODUMP;
                if (ip->i_diflags & XFS_DIFLAG_RTINHERIT)
                        flags |= FS_XFLAG_RTINHERIT;
                if (ip->i_diflags & XFS_DIFLAG_PROJINHERIT)
                        flags |= FS_XFLAG_PROJINHERIT;
                if (ip->i_diflags & XFS_DIFLAG_NOSYMLINKS)
                        flags |= FS_XFLAG_NOSYMLINKS;
                if (ip->i_diflags & XFS_DIFLAG_EXTSIZE)
                        flags |= FS_XFLAG_EXTSIZE;
                if (ip->i_diflags & XFS_DIFLAG_EXTSZINHERIT)
                        flags |= FS_XFLAG_EXTSZINHERIT;
                if (ip->i_diflags & XFS_DIFLAG_NODEFRAG)
                        flags |= FS_XFLAG_NODEFRAG;
                if (ip->i_diflags & XFS_DIFLAG_FILESTREAM)
                        flags |= FS_XFLAG_FILESTREAM;
        }

        if (ip->i_diflags2 & XFS_DIFLAG2_ANY) {
                if (ip->i_diflags2 & XFS_DIFLAG2_DAX)
                        flags |= FS_XFLAG_DAX;
                if (ip->i_diflags2 & XFS_DIFLAG2_COWEXTSIZE)
                        flags |= FS_XFLAG_COWEXTSIZE;
        }

        if (XFS_IFORK_Q(ip))
                flags |= FS_XFLAG_HASATTR;
        return flags;
}

/*
 * Lookups up an inode from "name". If ci_name is not NULL, then a CI match
 * is allowed, otherwise it has to be an exact match. If a CI match is found,
 * ci_name->name will point to a the actual name (caller must free) or
 * will be set to NULL if an exact match is found.
 */
int
xfs_lookup(
        struct xfs_inode        *dp,
        const struct xfs_name   *name,
        struct xfs_inode        **ipp,
        struct xfs_name         *ci_name)
{
        xfs_ino_t               inum;
        int                     error;

        trace_xfs_lookup(dp, name);

        if (xfs_is_shutdown(dp->i_mount))
                return -EIO;

        error = xfs_dir_lookup(NULL, dp, name, &inum, ci_name);
        if (error)
                goto out_unlock;

        error = xfs_iget(dp->i_mount, NULL, inum, 0, 0, ipp);
        if (error)
                goto out_free_name;

        return 0;

out_free_name:
        if (ci_name)
                kmem_free(ci_name->name);
out_unlock:
        *ipp = NULL;
        return error;
}

/* Propagate di_flags from a parent inode to a child inode. */
static void
xfs_inode_inherit_flags(
        struct xfs_inode        *ip,
        const struct xfs_inode  *pip)
{
        unsigned int            di_flags = 0;
        xfs_failaddr_t          failaddr;
        umode_t                 mode = VFS_I(ip)->i_mode;

        if (S_ISDIR(mode)) {
                if (pip->i_diflags & XFS_DIFLAG_RTINHERIT)
                        di_flags |= XFS_DIFLAG_RTINHERIT;
                if (pip->i_diflags & XFS_DIFLAG_EXTSZINHERIT) {
                        di_flags |= XFS_DIFLAG_EXTSZINHERIT;
                        ip->i_extsize = pip->i_extsize;
                }
                if (pip->i_diflags & XFS_DIFLAG_PROJINHERIT)
                        di_flags |= XFS_DIFLAG_PROJINHERIT;
        } else if (S_ISREG(mode)) {
                if ((pip->i_diflags & XFS_DIFLAG_RTINHERIT) &&
                    xfs_has_realtime(ip->i_mount))
                        di_flags |= XFS_DIFLAG_REALTIME;
                if (pip->i_diflags & XFS_DIFLAG_EXTSZINHERIT) {
                        di_flags |= XFS_DIFLAG_EXTSIZE;
                        ip->i_extsize = pip->i_extsize;
                }
        }
        if ((pip->i_diflags & XFS_DIFLAG_NOATIME) &&
            xfs_inherit_noatime)
                di_flags |= XFS_DIFLAG_NOATIME;
        if ((pip->i_diflags & XFS_DIFLAG_NODUMP) &&
            xfs_inherit_nodump)
                di_flags |= XFS_DIFLAG_NODUMP;
        if ((pip->i_diflags & XFS_DIFLAG_SYNC) &&
            xfs_inherit_sync)
                di_flags |= XFS_DIFLAG_SYNC;
        if ((pip->i_diflags & XFS_DIFLAG_NOSYMLINKS) &&
            xfs_inherit_nosymlinks)
                di_flags |= XFS_DIFLAG_NOSYMLINKS;
        if ((pip->i_diflags & XFS_DIFLAG_NODEFRAG) &&
            xfs_inherit_nodefrag)
                di_flags |= XFS_DIFLAG_NODEFRAG;
        if (pip->i_diflags & XFS_DIFLAG_FILESTREAM)
                di_flags |= XFS_DIFLAG_FILESTREAM;

        ip->i_diflags |= di_flags;

        /*
         * Inode verifiers on older kernels only check that the extent size
         * hint is an integer multiple of the rt extent size on realtime files.
         * They did not check the hint alignment on a directory with both
         * rtinherit and extszinherit flags set.  If the misaligned hint is
         * propagated from a directory into a new realtime file, new file
         * allocations will fail due to math errors in the rt allocator and/or
         * trip the verifiers.  Validate the hint settings in the new file so
         * that we don't let broken hints propagate.
         */
        failaddr = xfs_inode_validate_extsize(ip->i_mount, ip->i_extsize,
                        VFS_I(ip)->i_mode, ip->i_diflags);
        if (failaddr) {
                ip->i_diflags &= ~(XFS_DIFLAG_EXTSIZE |
                                   XFS_DIFLAG_EXTSZINHERIT);
                ip->i_extsize = 0;
        }
}

/* Propagate di_flags2 from a parent inode to a child inode. */
static void
xfs_inode_inherit_flags2(
        struct xfs_inode        *ip,
        const struct xfs_inode  *pip)
{
        xfs_failaddr_t          failaddr;

        if (pip->i_diflags2 & XFS_DIFLAG2_COWEXTSIZE) {
                ip->i_diflags2 |= XFS_DIFLAG2_COWEXTSIZE;
                ip->i_cowextsize = pip->i_cowextsize;
        }
        if (pip->i_diflags2 & XFS_DIFLAG2_DAX)
                ip->i_diflags2 |= XFS_DIFLAG2_DAX;

        /* Don't let invalid cowextsize hints propagate. */
        failaddr = xfs_inode_validate_cowextsize(ip->i_mount, ip->i_cowextsize,
                        VFS_I(ip)->i_mode, ip->i_diflags, ip->i_diflags2);
        if (failaddr) {
                ip->i_diflags2 &= ~XFS_DIFLAG2_COWEXTSIZE;
                ip->i_cowextsize = 0;
        }
}

/*
 * Initialise a newly allocated inode and return the in-core inode to the
 * caller locked exclusively.
 */
int
xfs_init_new_inode(
        struct user_namespace   *mnt_userns,
        struct xfs_trans        *tp,
        struct xfs_inode        *pip,
        xfs_ino_t               ino,
        umode_t                 mode,
        xfs_nlink_t             nlink,
        dev_t                   rdev,
        prid_t                  prid,
        bool                    init_xattrs,
        struct xfs_inode        **ipp)
{
        struct inode            *dir = pip ? VFS_I(pip) : NULL;
        struct xfs_mount        *mp = tp->t_mountp;
        struct xfs_inode        *ip;
        unsigned int            flags;
        int                     error;
        struct timespec64       tv;
        struct inode            *inode;

        /*
         * Protect against obviously corrupt allocation btree records. Later
         * xfs_iget checks will catch re-allocation of other active in-memory
         * and on-disk inodes. If we don't catch reallocating the parent inode
         * here we will deadlock in xfs_iget() so we have to do these checks
         * first.
         */
        if ((pip && ino == pip->i_ino) || !xfs_verify_dir_ino(mp, ino)) {
                xfs_alert(mp, "Allocated a known in-use inode 0x%llx!", ino);
                return -EFSCORRUPTED;
        }

        /*
         * Get the in-core inode with the lock held exclusively to prevent
         * others from looking at until we're done.
         */
        error = xfs_iget(mp, tp, ino, XFS_IGET_CREATE, XFS_ILOCK_EXCL, &ip);
        if (error)
                return error;

        ASSERT(ip != NULL);
        inode = VFS_I(ip);
        set_nlink(inode, nlink);
        inode->i_rdev = rdev;
        ip->i_projid = prid;

        if (dir && !(dir->i_mode & S_ISGID) && xfs_has_grpid(mp)) {
                inode_fsuid_set(inode, mnt_userns);
                inode->i_gid = dir->i_gid;
                inode->i_mode = mode;
        } else {
                inode_init_owner(mnt_userns, inode, dir, mode);
        }

        /*
         * If the group ID of the new file does not match the effective group
         * ID or one of the supplementary group IDs, the S_ISGID bit is cleared
         * (and only if the irix_sgid_inherit compatibility variable is set).
         */
        if (irix_sgid_inherit &&
            (inode->i_mode & S_ISGID) &&
            !in_group_p(i_gid_into_mnt(mnt_userns, inode)))
                inode->i_mode &= ~S_ISGID;

        ip->i_disk_size = 0;
        ip->i_df.if_nextents = 0;
        ASSERT(ip->i_nblocks == 0);

        tv = current_time(inode);
        inode->i_mtime = tv;
        inode->i_atime = tv;
        inode->i_ctime = tv;

        ip->i_extsize = 0;
        ip->i_diflags = 0;

        if (xfs_has_v3inodes(mp)) {
                inode_set_iversion(inode, 1);
                ip->i_cowextsize = 0;
                ip->i_crtime = tv;
        }

        flags = XFS_ILOG_CORE;
        switch (mode & S_IFMT) {
        case S_IFIFO:
        case S_IFCHR:
        case S_IFBLK:
        case S_IFSOCK:
                ip->i_df.if_format = XFS_DINODE_FMT_DEV;
                flags |= XFS_ILOG_DEV;
                break;
        case S_IFREG:
        case S_IFDIR:
                if (pip && (pip->i_diflags & XFS_DIFLAG_ANY))
                        xfs_inode_inherit_flags(ip, pip);
                if (pip && (pip->i_diflags2 & XFS_DIFLAG2_ANY))
                        xfs_inode_inherit_flags2(ip, pip);
                fallthrough;
        case S_IFLNK:
                ip->i_df.if_format = XFS_DINODE_FMT_EXTENTS;
                ip->i_df.if_bytes = 0;
                ip->i_df.if_u1.if_root = NULL;
                break;
        default:
                ASSERT(0);
        }

        /*
         * If we need to create attributes immediately after allocating the
         * inode, initialise an empty attribute fork right now. We use the
         * default fork offset for attributes here as we don't know exactly what
         * size or how many attributes we might be adding. We can do this
         * safely here because we know the data fork is completely empty and
         * this saves us from needing to run a separate transaction to set the
         * fork offset in the immediate future.
         */
        if (init_xattrs && xfs_has_attr(mp)) {
                ip->i_forkoff = xfs_default_attroffset(ip) >> 3;
                ip->i_afp = xfs_ifork_alloc(XFS_DINODE_FMT_EXTENTS, 0);
        }

        /*
         * Log the new values stuffed into the inode.
         */
        xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
        xfs_trans_log_inode(tp, ip, flags);

        /* now that we have an i_mode we can setup the inode structure */
        xfs_setup_inode(ip);

        *ipp = ip;
        return 0;
}

/*
 * Decrement the link count on an inode & log the change.  If this causes the
 * link count to go to zero, move the inode to AGI unlinked list so that it can
 * be freed when the last active reference goes away via xfs_inactive().
 */
static int                      /* error */
xfs_droplink(
        xfs_trans_t *tp,
        xfs_inode_t *ip)
{
        xfs_trans_ichgtime(tp, ip, XFS_ICHGTIME_CHG);

        drop_nlink(VFS_I(ip));
        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);

        if (VFS_I(ip)->i_nlink)
                return 0;

        return xfs_iunlink(tp, ip);
}

/*
 * Increment the link count on an inode & log the change.
 */
static void
xfs_bumplink(
        xfs_trans_t *tp,
        xfs_inode_t *ip)
{
        xfs_trans_ichgtime(tp, ip, XFS_ICHGTIME_CHG);

        inc_nlink(VFS_I(ip));
        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
}

int
xfs_create(
        struct user_namespace   *mnt_userns,
        xfs_inode_t             *dp,
        struct xfs_name         *name,
        umode_t                 mode,
        dev_t                   rdev,
        bool                    init_xattrs,
        xfs_inode_t             **ipp)
{
        int                     is_dir = S_ISDIR(mode);
        struct xfs_mount        *mp = dp->i_mount;
        struct xfs_inode        *ip = NULL;
        struct xfs_trans        *tp = NULL;
        int                     error;
        bool                    unlock_dp_on_error = false;
        prid_t                  prid;
        struct xfs_dquot        *udqp = NULL;
        struct xfs_dquot        *gdqp = NULL;
        struct xfs_dquot        *pdqp = NULL;
        struct xfs_trans_res    *tres;
        uint                    resblks;
        xfs_ino_t               ino;

        trace_xfs_create(dp, name);

        if (xfs_is_shutdown(mp))
                return -EIO;

        prid = xfs_get_initial_prid(dp);

        /*
         * Make sure that we have allocated dquot(s) on disk.
         */
        error = xfs_qm_vop_dqalloc(dp, mapped_fsuid(mnt_userns, &init_user_ns),
                        mapped_fsgid(mnt_userns, &init_user_ns), prid,
                        XFS_QMOPT_QUOTALL | XFS_QMOPT_INHERIT,
                        &udqp, &gdqp, &pdqp);
        if (error)
                return error;

        if (is_dir) {
                resblks = XFS_MKDIR_SPACE_RES(mp, name->len);
                tres = &M_RES(mp)->tr_mkdir;
        } else {
                resblks = XFS_CREATE_SPACE_RES(mp, name->len);
                tres = &M_RES(mp)->tr_create;
        }

        /*
         * Initially assume that the file does not exist and
         * reserve the resources for that case.  If that is not
         * the case we'll drop the one we have and get a more
         * appropriate transaction later.
         */
        error = xfs_trans_alloc_icreate(mp, tres, udqp, gdqp, pdqp, resblks,
                        &tp);
        if (error == -ENOSPC) {
                /* flush outstanding delalloc blocks and retry */
                xfs_flush_inodes(mp);
                error = xfs_trans_alloc_icreate(mp, tres, udqp, gdqp, pdqp,
                                resblks, &tp);
        }
        if (error)
                goto out_release_dquots;

        xfs_ilock(dp, XFS_ILOCK_EXCL | XFS_ILOCK_PARENT);
        unlock_dp_on_error = true;

        error = xfs_iext_count_may_overflow(dp, XFS_DATA_FORK,
                        XFS_IEXT_DIR_MANIP_CNT(mp));
        if (error)
                goto out_trans_cancel;

        /*
         * A newly created regular or special file just has one directory
         * entry pointing to them, but a directory also the "." entry
         * pointing to itself.
         */
        error = xfs_dialloc(&tp, dp->i_ino, mode, &ino);
        if (!error)
                error = xfs_init_new_inode(mnt_userns, tp, dp, ino, mode,
                                is_dir ? 2 : 1, rdev, prid, init_xattrs, &ip);
        if (error)
                goto out_trans_cancel;

        /*
         * Now we join the directory inode to the transaction.  We do not do it
         * earlier because xfs_dialloc might commit the previous transaction
         * (and release all the locks).  An error from here on will result in
         * the transaction cancel unlocking dp so don't do it explicitly in the
         * error path.
         */
        xfs_trans_ijoin(tp, dp, XFS_ILOCK_EXCL);
        unlock_dp_on_error = false;

        error = xfs_dir_createname(tp, dp, name, ip->i_ino,
                                        resblks - XFS_IALLOC_SPACE_RES(mp));
        if (error) {
                ASSERT(error != -ENOSPC);
                goto out_trans_cancel;
        }
        xfs_trans_ichgtime(tp, dp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
        xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);

        if (is_dir) {
                error = xfs_dir_init(tp, ip, dp);
                if (error)
                        goto out_trans_cancel;

                xfs_bumplink(tp, dp);
        }

        /*
         * If this is a synchronous mount, make sure that the
         * create transaction goes to disk before returning to
         * the user.
         */
        if (xfs_has_wsync(mp) || xfs_has_dirsync(mp))
                xfs_trans_set_sync(tp);

        /*
         * Attach the dquot(s) to the inodes and modify them incore.
         * These ids of the inode couldn't have changed since the new
         * inode has been locked ever since it was created.
         */
        xfs_qm_vop_create_dqattach(tp, ip, udqp, gdqp, pdqp);

        error = xfs_trans_commit(tp);
        if (error)
                goto out_release_inode;

        xfs_qm_dqrele(udqp);
        xfs_qm_dqrele(gdqp);
        xfs_qm_dqrele(pdqp);

        *ipp = ip;
        return 0;

 out_trans_cancel:
        xfs_trans_cancel(tp);
 out_release_inode:
        /*
         * Wait until after the current transaction is aborted to finish the
         * setup of the inode and release the inode.  This prevents recursive
         * transactions and deadlocks from xfs_inactive.
         */
        if (ip) {
                xfs_finish_inode_setup(ip);
                xfs_irele(ip);
        }
 out_release_dquots:
        xfs_qm_dqrele(udqp);
        xfs_qm_dqrele(gdqp);
        xfs_qm_dqrele(pdqp);

        if (unlock_dp_on_error)
                xfs_iunlock(dp, XFS_ILOCK_EXCL);
        return error;
}

int
xfs_create_tmpfile(
        struct user_namespace   *mnt_userns,
        struct xfs_inode        *dp,
        umode_t                 mode,
        struct xfs_inode        **ipp)
{
        struct xfs_mount        *mp = dp->i_mount;
        struct xfs_inode        *ip = NULL;
        struct xfs_trans        *tp = NULL;
        int                     error;
        prid_t                  prid;
        struct xfs_dquot        *udqp = NULL;
        struct xfs_dquot        *gdqp = NULL;
        struct xfs_dquot        *pdqp = NULL;
        struct xfs_trans_res    *tres;
        uint                    resblks;
        xfs_ino_t               ino;

        if (xfs_is_shutdown(mp))
                return -EIO;

        prid = xfs_get_initial_prid(dp);

        /*
         * Make sure that we have allocated dquot(s) on disk.
         */
        error = xfs_qm_vop_dqalloc(dp, mapped_fsuid(mnt_userns, &init_user_ns),
                        mapped_fsgid(mnt_userns, &init_user_ns), prid,
                        XFS_QMOPT_QUOTALL | XFS_QMOPT_INHERIT,
                        &udqp, &gdqp, &pdqp);
        if (error)
                return error;

        resblks = XFS_IALLOC_SPACE_RES(mp);
        tres = &M_RES(mp)->tr_create_tmpfile;

        error = xfs_trans_alloc_icreate(mp, tres, udqp, gdqp, pdqp, resblks,
                        &tp);
        if (error)
                goto out_release_dquots;

        error = xfs_dialloc(&tp, dp->i_ino, mode, &ino);
        if (!error)
                error = xfs_init_new_inode(mnt_userns, tp, dp, ino, mode,
                                0, 0, prid, false, &ip);
        if (error)
                goto out_trans_cancel;

        if (xfs_has_wsync(mp))
                xfs_trans_set_sync(tp);

        /*
         * Attach the dquot(s) to the inodes and modify them incore.
         * These ids of the inode couldn't have changed since the new
         * inode has been locked ever since it was created.
         */
        xfs_qm_vop_create_dqattach(tp, ip, udqp, gdqp, pdqp);

        error = xfs_iunlink(tp, ip);
        if (error)
                goto out_trans_cancel;

        error = xfs_trans_commit(tp);
        if (error)
                goto out_release_inode;

        xfs_qm_dqrele(udqp);
        xfs_qm_dqrele(gdqp);
        xfs_qm_dqrele(pdqp);

        *ipp = ip;
        return 0;

 out_trans_cancel:
        xfs_trans_cancel(tp);
 out_release_inode:
        /*
         * Wait until after the current transaction is aborted to finish the
         * setup of the inode and release the inode.  This prevents recursive
         * transactions and deadlocks from xfs_inactive.
         */
        if (ip) {
                xfs_finish_inode_setup(ip);
                xfs_irele(ip);
        }
 out_release_dquots:
        xfs_qm_dqrele(udqp);
        xfs_qm_dqrele(gdqp);
        xfs_qm_dqrele(pdqp);

        return error;
}

int
xfs_link(
        xfs_inode_t             *tdp,
        xfs_inode_t             *sip,
        struct xfs_name         *target_name)
{
        xfs_mount_t             *mp = tdp->i_mount;
        xfs_trans_t             *tp;
        int                     error, nospace_error = 0;
        int                     resblks;

        trace_xfs_link(tdp, target_name);

        ASSERT(!S_ISDIR(VFS_I(sip)->i_mode));

        if (xfs_is_shutdown(mp))
                return -EIO;

        error = xfs_qm_dqattach(sip);
        if (error)
                goto std_return;

        error = xfs_qm_dqattach(tdp);
        if (error)
                goto std_return;

        resblks = XFS_LINK_SPACE_RES(mp, target_name->len);
        error = xfs_trans_alloc_dir(tdp, &M_RES(mp)->tr_link, sip, &resblks,
                        &tp, &nospace_error);
        if (error)
                goto std_return;

        error = xfs_iext_count_may_overflow(tdp, XFS_DATA_FORK,
                        XFS_IEXT_DIR_MANIP_CNT(mp));
        if (error)
                goto error_return;

        /*
         * If we are using project inheritance, we only allow hard link
         * creation in our tree when the project IDs are the same; else
         * the tree quota mechanism could be circumvented.
         */
        if (unlikely((tdp->i_diflags & XFS_DIFLAG_PROJINHERIT) &&
                     tdp->i_projid != sip->i_projid)) {
                error = -EXDEV;
                goto error_return;
        }

        if (!resblks) {
                error = xfs_dir_canenter(tp, tdp, target_name);
                if (error)
                        goto error_return;
        }

        /*
         * Handle initial link state of O_TMPFILE inode
         */
        if (VFS_I(sip)->i_nlink == 0) {
                struct xfs_perag        *pag;

                pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, sip->i_ino));
                error = xfs_iunlink_remove(tp, pag, sip);
                xfs_perag_put(pag);
                if (error)
                        goto error_return;
        }

        error = xfs_dir_createname(tp, tdp, target_name, sip->i_ino,
                                   resblks);
        if (error)
                goto error_return;
        xfs_trans_ichgtime(tp, tdp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
        xfs_trans_log_inode(tp, tdp, XFS_ILOG_CORE);

        xfs_bumplink(tp, sip);

        /*
         * If this is a synchronous mount, make sure that the
         * link transaction goes to disk before returning to
         * the user.
         */
        if (xfs_has_wsync(mp) || xfs_has_dirsync(mp))
                xfs_trans_set_sync(tp);

        return xfs_trans_commit(tp);

 error_return:
        xfs_trans_cancel(tp);
 std_return:
        if (error == -ENOSPC && nospace_error)
                error = nospace_error;
        return error;
}

/* Clear the reflink flag and the cowblocks tag if possible. */
static void
xfs_itruncate_clear_reflink_flags(
        struct xfs_inode        *ip)
{
        struct xfs_ifork        *dfork;
        struct xfs_ifork        *cfork;

        if (!xfs_is_reflink_inode(ip))
                return;
        dfork = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
        cfork = XFS_IFORK_PTR(ip, XFS_COW_FORK);
        if (dfork->if_bytes == 0 && cfork->if_bytes == 0)
                ip->i_diflags2 &= ~XFS_DIFLAG2_REFLINK;
        if (cfork->if_bytes == 0)
                xfs_inode_clear_cowblocks_tag(ip);
}

/*
 * Free up the underlying blocks past new_size.  The new size must be smaller
 * than the current size.  This routine can be used both for the attribute and
 * data fork, and does not modify the inode size, which is left to the caller.
 *
 * The transaction passed to this routine must have made a permanent log
 * reservation of at least XFS_ITRUNCATE_LOG_RES.  This routine may commit the
 * given transaction and start new ones, so make sure everything involved in
 * the transaction is tidy before calling here.  Some transaction will be
 * returned to the caller to be committed.  The incoming transaction must
 * already include the inode, and both inode locks must be held exclusively.
 * The inode must also be "held" within the transaction.  On return the inode
 * will be "held" within the returned transaction.  This routine does NOT
 * require any disk space to be reserved for it within the transaction.
 *
 * If we get an error, we must return with the inode locked and linked into the
 * current transaction. This keeps things simple for the higher level code,
 * because it always knows that the inode is locked and held in the transaction
 * that returns to it whether errors occur or not.  We don't mark the inode
 * dirty on error so that transactions can be easily aborted if possible.
 */
int
xfs_itruncate_extents_flags(
        struct xfs_trans        **tpp,
        struct xfs_inode        *ip,
        int                     whichfork,
        xfs_fsize_t             new_size,
        int                     flags)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_trans        *tp = *tpp;
        xfs_fileoff_t           first_unmap_block;
        xfs_filblks_t           unmap_len;
        int                     error = 0;

        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
        ASSERT(!atomic_read(&VFS_I(ip)->i_count) ||
               xfs_isilocked(ip, XFS_IOLOCK_EXCL));
        ASSERT(new_size <= XFS_ISIZE(ip));
        ASSERT(tp->t_flags & XFS_TRANS_PERM_LOG_RES);
        ASSERT(ip->i_itemp != NULL);
        ASSERT(ip->i_itemp->ili_lock_flags == 0);
        ASSERT(!XFS_NOT_DQATTACHED(mp, ip));

        trace_xfs_itruncate_extents_start(ip, new_size);

        flags |= xfs_bmapi_aflag(whichfork);

        /*
         * Since it is possible for space to become allocated beyond
         * the end of the file (in a crash where the space is allocated
         * but the inode size is not yet updated), simply remove any
         * blocks which show up between the new EOF and the maximum
         * possible file size.
         *
         * We have to free all the blocks to the bmbt maximum offset, even if
         * the page cache can't scale that far.
         */
        first_unmap_block = XFS_B_TO_FSB(mp, (xfs_ufsize_t)new_size);
        if (!xfs_verify_fileoff(mp, first_unmap_block)) {
                WARN_ON_ONCE(first_unmap_block > XFS_MAX_FILEOFF);
                return 0;
        }

        unmap_len = XFS_MAX_FILEOFF - first_unmap_block + 1;
        while (unmap_len > 0) {
                ASSERT(tp->t_firstblock == NULLFSBLOCK);
                error = __xfs_bunmapi(tp, ip, first_unmap_block, &unmap_len,
                                flags, XFS_ITRUNC_MAX_EXTENTS);
                if (error)
                        goto out;

                /* free the just unmapped extents */
                error = xfs_defer_finish(&tp);
                if (error)
                        goto out;
        }

        if (whichfork == XFS_DATA_FORK) {
                /* Remove all pending CoW reservations. */
                error = xfs_reflink_cancel_cow_blocks(ip, &tp,
                                first_unmap_block, XFS_MAX_FILEOFF, true);
                if (error)
                        goto out;

                xfs_itruncate_clear_reflink_flags(ip);
        }

        /*
         * Always re-log the inode so that our permanent transaction can keep
         * on rolling it forward in the log.
         */
        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);

        trace_xfs_itruncate_extents_end(ip, new_size);

out:
        *tpp = tp;
        return error;
}

int
xfs_release(
        xfs_inode_t     *ip)
{
        xfs_mount_t     *mp = ip->i_mount;
        int             error = 0;

        if (!S_ISREG(VFS_I(ip)->i_mode) || (VFS_I(ip)->i_mode == 0))
                return 0;

        /* If this is a read-only mount, don't do this (would generate I/O) */
        if (xfs_is_readonly(mp))
                return 0;

        if (!xfs_is_shutdown(mp)) {
                int truncated;

                /*
                 * If we previously truncated this file and removed old data
                 * in the process, we want to initiate "early" writeout on
                 * the last close.  This is an attempt to combat the notorious
                 * NULL files problem which is particularly noticeable from a
                 * truncate down, buffered (re-)write (delalloc), followed by
                 * a crash.  What we are effectively doing here is
                 * significantly reducing the time window where we'd otherwise
                 * be exposed to that problem.
                 */
                truncated = xfs_iflags_test_and_clear(ip, XFS_ITRUNCATED);
                if (truncated) {
                        xfs_iflags_clear(ip, XFS_IDIRTY_RELEASE);
                        if (ip->i_delayed_blks > 0) {
                                error = filemap_flush(VFS_I(ip)->i_mapping);
                                if (error)
                                        return error;
                        }
                }
        }

        if (VFS_I(ip)->i_nlink == 0)
                return 0;

        /*
         * If we can't get the iolock just skip truncating the blocks past EOF
         * because we could deadlock with the mmap_lock otherwise. We'll get
         * another chance to drop them once the last reference to the inode is
         * dropped, so we'll never leak blocks permanently.
         */
        if (!xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL))
                return 0;

        if (xfs_can_free_eofblocks(ip, false)) {
                /*
                 * Check if the inode is being opened, written and closed
                 * frequently and we have delayed allocation blocks outstanding
                 * (e.g. streaming writes from the NFS server), truncating the
                 * blocks past EOF will cause fragmentation to occur.
                 *
                 * In this case don't do the truncation, but we have to be
                 * careful how we detect this case. Blocks beyond EOF show up as
                 * i_delayed_blks even when the inode is clean, so we need to
                 * truncate them away first before checking for a dirty release.
                 * Hence on the first dirty close we will still remove the
                 * speculative allocation, but after that we will leave it in
                 * place.
                 */
                if (xfs_iflags_test(ip, XFS_IDIRTY_RELEASE))
                        goto out_unlock;

                error = xfs_free_eofblocks(ip);
                if (error)
                        goto out_unlock;

                /* delalloc blocks after truncation means it really is dirty */
                if (ip->i_delayed_blks)
                        xfs_iflags_set(ip, XFS_IDIRTY_RELEASE);
        }

out_unlock:
        xfs_iunlock(ip, XFS_IOLOCK_EXCL);
        return error;
}

/*
 * xfs_inactive_truncate
 *
 * Called to perform a truncate when an inode becomes unlinked.
 */
STATIC int
xfs_inactive_truncate(
        struct xfs_inode *ip)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_trans        *tp;
        int                     error;

        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp);
        if (error) {
                ASSERT(xfs_is_shutdown(mp));
                return error;
        }
        xfs_ilock(ip, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(tp, ip, 0);

        /*
         * Log the inode size first to prevent stale data exposure in the event
         * of a system crash before the truncate completes. See the related
         * comment in xfs_vn_setattr_size() for details.
         */
        ip->i_disk_size = 0;
        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);

        error = xfs_itruncate_extents(&tp, ip, XFS_DATA_FORK, 0);
        if (error)
                goto error_trans_cancel;

        ASSERT(ip->i_df.if_nextents == 0);

        error = xfs_trans_commit(tp);
        if (error)
                goto error_unlock;

        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return 0;

error_trans_cancel:
        xfs_trans_cancel(tp);
error_unlock:
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return error;
}

/*
 * xfs_inactive_ifree()
 *
 * Perform the inode free when an inode is unlinked.
 */
STATIC int
xfs_inactive_ifree(
        struct xfs_inode *ip)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_trans        *tp;
        int                     error;

        /*
         * We try to use a per-AG reservation for any block needed by the finobt
         * tree, but as the finobt feature predates the per-AG reservation
         * support a degraded file system might not have enough space for the
         * reservation at mount time.  In that case try to dip into the reserved
         * pool and pray.
         *
         * Send a warning if the reservation does happen to fail, as the inode
         * now remains allocated and sits on the unlinked list until the fs is
         * repaired.
         */
        if (unlikely(mp->m_finobt_nores)) {
                error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ifree,
                                XFS_IFREE_SPACE_RES(mp), 0, XFS_TRANS_RESERVE,
                                &tp);
        } else {
                error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ifree, 0, 0, 0, &tp);
        }
        if (error) {
                if (error == -ENOSPC) {
                        xfs_warn_ratelimited(mp,
                        "Failed to remove inode(s) from unlinked list. "
                        "Please free space, unmount and run xfs_repair.");
                } else {
                        ASSERT(xfs_is_shutdown(mp));
                }
                return error;
        }

        /*
         * We do not hold the inode locked across the entire rolling transaction
         * here. We only need to hold it for the first transaction that
         * xfs_ifree() builds, which may mark the inode XFS_ISTALE if the
         * underlying cluster buffer is freed. Relogging an XFS_ISTALE inode
         * here breaks the relationship between cluster buffer invalidation and
         * stale inode invalidation on cluster buffer item journal commit
         * completion, and can result in leaving dirty stale inodes hanging
         * around in memory.
         *
         * We have no need for serialising this inode operation against other
         * operations - we freed the inode and hence reallocation is required
         * and that will serialise on reallocating the space the deferops need
         * to free. Hence we can unlock the inode on the first commit of
         * the transaction rather than roll it right through the deferops. This
         * avoids relogging the XFS_ISTALE inode.
         *
         * We check that xfs_ifree() hasn't grown an internal transaction roll
         * by asserting that the inode is still locked when it returns.
         */
        xfs_ilock(ip, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);

        error = xfs_ifree(tp, ip);
        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
        if (error) {
                /*
                 * If we fail to free the inode, shut down.  The cancel
                 * might do that, we need to make sure.  Otherwise the
                 * inode might be lost for a long time or forever.
                 */
                if (!xfs_is_shutdown(mp)) {
                        xfs_notice(mp, "%s: xfs_ifree returned error %d",
                                __func__, error);
                        xfs_force_shutdown(mp, SHUTDOWN_META_IO_ERROR);
                }
                xfs_trans_cancel(tp);
                return error;
        }

        /*
         * Credit the quota account(s). The inode is gone.
         */
        xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_ICOUNT, -1);

        /*
         * Just ignore errors at this point.  There is nothing we can do except
         * to try to keep going. Make sure it's not a silent error.
         */
        error = xfs_trans_commit(tp);
        if (error)
                xfs_notice(mp, "%s: xfs_trans_commit returned error %d",
                        __func__, error);

        return 0;
}

/*
 * Returns true if we need to update the on-disk metadata before we can free
 * the memory used by this inode.  Updates include freeing post-eof
 * preallocations; freeing COW staging extents; and marking the inode free in
 * the inobt if it is on the unlinked list.
 */
bool
xfs_inode_needs_inactive(
        struct xfs_inode        *ip)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_ifork        *cow_ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);

        /*
         * If the inode is already free, then there can be nothing
         * to clean up here.
         */
        if (VFS_I(ip)->i_mode == 0)
                return false;

        /* If this is a read-only mount, don't do this (would generate I/O) */
        if (xfs_is_readonly(mp))
                return false;

        /* If the log isn't running, push inodes straight to reclaim. */
        if (xfs_is_shutdown(mp) || xfs_has_norecovery(mp))
                return false;

        /* Metadata inodes require explicit resource cleanup. */
        if (xfs_is_metadata_inode(ip))
                return false;

        /* Want to clean out the cow blocks if there are any. */
        if (cow_ifp && cow_ifp->if_bytes > 0)
                return true;

        /* Unlinked files must be freed. */
        if (VFS_I(ip)->i_nlink == 0)
                return true;

        /*
         * This file isn't being freed, so check if there are post-eof blocks
         * to free.  @force is true because we are evicting an inode from the
         * cache.  Post-eof blocks must be freed, lest we end up with broken
         * free space accounting.
         *
         * Note: don't bother with iolock here since lockdep complains about
         * acquiring it in reclaim context. We have the only reference to the
         * inode at this point anyways.
         */
        return xfs_can_free_eofblocks(ip, true);
}

/*
 * xfs_inactive
 *
 * This is called when the vnode reference count for the vnode
 * goes to zero.  If the file has been unlinked, then it must
 * now be truncated.  Also, we clear all of the read-ahead state
 * kept for the inode here since the file is now closed.
 */
void
xfs_inactive(
        xfs_inode_t     *ip)
{
        struct xfs_mount        *mp;
        int                     error;
        int                     truncate = 0;

        /*
         * If the inode is already free, then there can be nothing
         * to clean up here.
         */
        if (VFS_I(ip)->i_mode == 0) {
                ASSERT(ip->i_df.if_broot_bytes == 0);
                goto out;
        }

        mp = ip->i_mount;
        ASSERT(!xfs_iflags_test(ip, XFS_IRECOVERY));

        /* If this is a read-only mount, don't do this (would generate I/O) */
        if (xfs_is_readonly(mp))
                goto out;

        /* Metadata inodes require explicit resource cleanup. */
        if (xfs_is_metadata_inode(ip))
                goto out;

        /* Try to clean out the cow blocks if there are any. */
        if (xfs_inode_has_cow_data(ip))
                xfs_reflink_cancel_cow_range(ip, 0, NULLFILEOFF, true);

        if (VFS_I(ip)->i_nlink != 0) {
                /*
                 * force is true because we are evicting an inode from the
                 * cache. Post-eof blocks must be freed, lest we end up with
                 * broken free space accounting.
                 *
                 * Note: don't bother with iolock here since lockdep complains
                 * about acquiring it in reclaim context. We have the only
                 * reference to the inode at this point anyways.
                 */
                if (xfs_can_free_eofblocks(ip, true))
                        xfs_free_eofblocks(ip);

                goto out;
        }

        if (S_ISREG(VFS_I(ip)->i_mode) &&
            (ip->i_disk_size != 0 || XFS_ISIZE(ip) != 0 ||
             ip->i_df.if_nextents > 0 || ip->i_delayed_blks > 0))
                truncate = 1;

        error = xfs_qm_dqattach(ip);
        if (error)
                goto out;

        if (S_ISLNK(VFS_I(ip)->i_mode))
                error = xfs_inactive_symlink(ip);
        else if (truncate)
                error = xfs_inactive_truncate(ip);
        if (error)
                goto out;

        /*
         * If there are attributes associated with the file then blow them away
         * now.  The code calls a routine that recursively deconstructs the
         * attribute fork. If also blows away the in-core attribute fork.
         */
        if (XFS_IFORK_Q(ip)) {
                error = xfs_attr_inactive(ip);
                if (error)
                        goto out;
        }

        ASSERT(!ip->i_afp);
        ASSERT(ip->i_forkoff == 0);

        /*
         * Free the inode.
         */
        xfs_inactive_ifree(ip);

out:
        /*
         * We're done making metadata updates for this inode, so we can release
         * the attached dquots.
         */
        xfs_qm_dqdetach(ip);
}

/*
 * In-Core Unlinked List Lookups
 * =============================
 *
 * Every inode is supposed to be reachable from some other piece of metadata
 * with the exception of the root directory.  Inodes with a connection to a
 * file descriptor but not linked from anywhere in the on-disk directory tree
 * are collectively known as unlinked inodes, though the filesystem itself
 * maintains links to these inodes so that on-disk metadata are consistent.
 *
 * XFS implements a per-AG on-disk hash table of unlinked inodes.  The AGI
 * header contains a number of buckets that point to an inode, and each inode
 * record has a pointer to the next inode in the hash chain.  This
 * singly-linked list causes scaling problems in the iunlink remove function
 * because we must walk that list to find the inode that points to the inode
 * being removed from the unlinked hash bucket list.
 *
 * What if we modelled the unlinked list as a collection of records capturing
 * "X.next_unlinked = Y" relations?  If we indexed those records on Y, we'd
 * have a fast way to look up unlinked list predecessors, which avoids the
 * slow list walk.  That's exactly what we do here (in-core) with a per-AG
 * rhashtable.
 *
 * Because this is a backref cache, we ignore operational failures since the
 * iunlink code can fall back to the slow bucket walk.  The only errors that
 * should bubble out are for obviously incorrect situations.
 *
 * All users of the backref cache MUST hold the AGI buffer lock to serialize
 * access or have otherwise provided for concurrency control.
 */

/* Capture a "X.next_unlinked = Y" relationship. */
struct xfs_iunlink {
        struct rhash_head       iu_rhash_head;
        xfs_agino_t             iu_agino;               /* X */
        xfs_agino_t             iu_next_unlinked;       /* Y */
};

/* Unlinked list predecessor lookup hashtable construction */
static int
xfs_iunlink_obj_cmpfn(
        struct rhashtable_compare_arg   *arg,
        const void                      *obj)
{
        const xfs_agino_t               *key = arg->key;
        const struct xfs_iunlink        *iu = obj;

        if (iu->iu_next_unlinked != *key)
                return 1;
        return 0;
}

static const struct rhashtable_params xfs_iunlink_hash_params = {
        .min_size               = XFS_AGI_UNLINKED_BUCKETS,
        .key_len                = sizeof(xfs_agino_t),
        .key_offset             = offsetof(struct xfs_iunlink,
                                           iu_next_unlinked),
        .head_offset            = offsetof(struct xfs_iunlink, iu_rhash_head),
        .automatic_shrinking    = true,
        .obj_cmpfn              = xfs_iunlink_obj_cmpfn,
};

/*
 * Return X, where X.next_unlinked == @agino.  Returns NULLAGINO if no such
 * relation is found.
 */
static xfs_agino_t
xfs_iunlink_lookup_backref(
        struct xfs_perag        *pag,
        xfs_agino_t             agino)
{
        struct xfs_iunlink      *iu;

        iu = rhashtable_lookup_fast(&pag->pagi_unlinked_hash, &agino,
                        xfs_iunlink_hash_params);
        return iu ? iu->iu_agino : NULLAGINO;
}

/*
 * Take ownership of an iunlink cache entry and insert it into the hash table.
 * If successful, the entry will be owned by the cache; if not, it is freed.
 * Either way, the caller does not own @iu after this call.
 */
static int
xfs_iunlink_insert_backref(
        struct xfs_perag        *pag,
        struct xfs_iunlink      *iu)
{
        int                     error;

        error = rhashtable_insert_fast(&pag->pagi_unlinked_hash,
                        &iu->iu_rhash_head, xfs_iunlink_hash_params);
        /*
         * Fail loudly if there already was an entry because that's a sign of
         * corruption of in-memory data.  Also fail loudly if we see an error
         * code we didn't anticipate from the rhashtable code.  Currently we
         * only anticipate ENOMEM.
         */
        if (error) {
                WARN(error != -ENOMEM, "iunlink cache insert error %d", error);
                kmem_free(iu);
        }
        /*
         * Absorb any runtime errors that aren't a result of corruption because
         * this is a cache and we can always fall back to bucket list scanning.
         */
        if (error != 0 && error != -EEXIST)
                error = 0;
        return error;
}

/* Remember that @prev_agino.next_unlinked = @this_agino. */
static int
xfs_iunlink_add_backref(
        struct xfs_perag        *pag,
        xfs_agino_t             prev_agino,
        xfs_agino_t             this_agino)
{
        struct xfs_iunlink      *iu;

        if (XFS_TEST_ERROR(false, pag->pag_mount, XFS_ERRTAG_IUNLINK_FALLBACK))
                return 0;

        iu = kmem_zalloc(sizeof(*iu), KM_NOFS);
        iu->iu_agino = prev_agino;
        iu->iu_next_unlinked = this_agino;

        return xfs_iunlink_insert_backref(pag, iu);
}

/*
 * Replace X.next_unlinked = @agino with X.next_unlinked = @next_unlinked.
 * If @next_unlinked is NULLAGINO, we drop the backref and exit.  If there
 * wasn't any such entry then we don't bother.
 */
static int
xfs_iunlink_change_backref(
        struct xfs_perag        *pag,
        xfs_agino_t             agino,
        xfs_agino_t             next_unlinked)
{
        struct xfs_iunlink      *iu;
        int                     error;

        /* Look up the old entry; if there wasn't one then exit. */
        iu = rhashtable_lookup_fast(&pag->pagi_unlinked_hash, &agino,
                        xfs_iunlink_hash_params);
        if (!iu)
                return 0;

        /*
         * Remove the entry.  This shouldn't ever return an error, but if we
         * couldn't remove the old entry we don't want to add it again to the
         * hash table, and if the entry disappeared on us then someone's
         * violated the locking rules and we need to fail loudly.  Either way
         * we cannot remove the inode because internal state is or would have
         * been corrupt.
         */
        error = rhashtable_remove_fast(&pag->pagi_unlinked_hash,
                        &iu->iu_rhash_head, xfs_iunlink_hash_params);
        if (error)
                return error;

        /* If there is no new next entry just free our item and return. */
        if (next_unlinked == NULLAGINO) {
                kmem_free(iu);
                return 0;
        }

        /* Update the entry and re-add it to the hash table. */
        iu->iu_next_unlinked = next_unlinked;
        return xfs_iunlink_insert_backref(pag, iu);
}

/* Set up the in-core predecessor structures. */
int
xfs_iunlink_init(
        struct xfs_perag        *pag)
{
        return rhashtable_init(&pag->pagi_unlinked_hash,
                        &xfs_iunlink_hash_params);
}

/* Free the in-core predecessor structures. */
static void
xfs_iunlink_free_item(
        void                    *ptr,
        void                    *arg)
{
        struct xfs_iunlink      *iu = ptr;
        bool                    *freed_anything = arg;

        *freed_anything = true;
        kmem_free(iu);
}

void
xfs_iunlink_destroy(
        struct xfs_perag        *pag)
{
        bool                    freed_anything = false;

        rhashtable_free_and_destroy(&pag->pagi_unlinked_hash,
                        xfs_iunlink_free_item, &freed_anything);

        ASSERT(freed_anything == false || xfs_is_shutdown(pag->pag_mount));
}

/*
 * Point the AGI unlinked bucket at an inode and log the results.  The caller
 * is responsible for validating the old value.
 */
STATIC int
xfs_iunlink_update_bucket(
        struct xfs_trans        *tp,
        struct xfs_perag        *pag,
        struct xfs_buf          *agibp,
        unsigned int            bucket_index,
        xfs_agino_t             new_agino)
{
        struct xfs_agi          *agi = agibp->b_addr;
        xfs_agino_t             old_value;
        int                     offset;

        ASSERT(xfs_verify_agino_or_null(tp->t_mountp, pag->pag_agno, new_agino));

        old_value = be32_to_cpu(agi->agi_unlinked[bucket_index]);
        trace_xfs_iunlink_update_bucket(tp->t_mountp, pag->pag_agno, bucket_index,
                        old_value, new_agino);

        /*
         * We should never find the head of the list already set to the value
         * passed in because either we're adding or removing ourselves from the
         * head of the list.
         */
        if (old_value == new_agino) {
                xfs_buf_mark_corrupt(agibp);
                return -EFSCORRUPTED;
        }

        agi->agi_unlinked[bucket_index] = cpu_to_be32(new_agino);
        offset = offsetof(struct xfs_agi, agi_unlinked) +
                        (sizeof(xfs_agino_t) * bucket_index);
        xfs_trans_log_buf(tp, agibp, offset, offset + sizeof(xfs_agino_t) - 1);
        return 0;
}

/* Set an on-disk inode's next_unlinked pointer. */
STATIC void
xfs_iunlink_update_dinode(
        struct xfs_trans        *tp,
        struct xfs_perag        *pag,
        xfs_agino_t             agino,
        struct xfs_buf          *ibp,
        struct xfs_dinode       *dip,
        struct xfs_imap         *imap,
        xfs_agino_t             next_agino)
{
        struct xfs_mount        *mp = tp->t_mountp;
        int                     offset;

        ASSERT(xfs_verify_agino_or_null(mp, pag->pag_agno, next_agino));

        trace_xfs_iunlink_update_dinode(mp, pag->pag_agno, agino,
                        be32_to_cpu(dip->di_next_unlinked), next_agino);

        dip->di_next_unlinked = cpu_to_be32(next_agino);
        offset = imap->im_boffset +
                        offsetof(struct xfs_dinode, di_next_unlinked);

        /* need to recalc the inode CRC if appropriate */
        xfs_dinode_calc_crc(mp, dip);
        xfs_trans_inode_buf(tp, ibp);
        xfs_trans_log_buf(tp, ibp, offset, offset + sizeof(xfs_agino_t) - 1);
}

/* Set an in-core inode's unlinked pointer and return the old value. */
STATIC int
xfs_iunlink_update_inode(
        struct xfs_trans        *tp,
        struct xfs_inode        *ip,
        struct xfs_perag        *pag,
        xfs_agino_t             next_agino,
        xfs_agino_t             *old_next_agino)
{
        struct xfs_mount        *mp = tp->t_mountp;
        struct xfs_dinode       *dip;
        struct xfs_buf          *ibp;
        xfs_agino_t             old_value;
        int                     error;

        ASSERT(xfs_verify_agino_or_null(mp, pag->pag_agno, next_agino));

        error = xfs_imap_to_bp(mp, tp, &ip->i_imap, &ibp);
        if (error)
                return error;
        dip = xfs_buf_offset(ibp, ip->i_imap.im_boffset);

        /* Make sure the old pointer isn't garbage. */
        old_value = be32_to_cpu(dip->di_next_unlinked);
        if (!xfs_verify_agino_or_null(mp, pag->pag_agno, old_value)) {
                xfs_inode_verifier_error(ip, -EFSCORRUPTED, __func__, dip,
                                sizeof(*dip), __this_address);
                error = -EFSCORRUPTED;
                goto out;
        }

        /*
         * Since we're updating a linked list, we should never find that the
         * current pointer is the same as the new value, unless we're
         * terminating the list.
         */
        *old_next_agino = old_value;
        if (old_value == next_agino) {
                if (next_agino != NULLAGINO) {
                        xfs_inode_verifier_error(ip, -EFSCORRUPTED, __func__,
                                        dip, sizeof(*dip), __this_address);
                        error = -EFSCORRUPTED;
                }
                goto out;
        }

        /* Ok, update the new pointer. */
        xfs_iunlink_update_dinode(tp, pag, XFS_INO_TO_AGINO(mp, ip->i_ino),
                        ibp, dip, &ip->i_imap, next_agino);
        return 0;
out:
        xfs_trans_brelse(tp, ibp);
        return error;
}

/*
 * This is called when the inode's link count has gone to 0 or we are creating
 * a tmpfile via O_TMPFILE.  The inode @ip must have nlink == 0.
 *
 * We place the on-disk inode on a list in the AGI.  It will be pulled from this
 * list when the inode is freed.
 */
STATIC int
xfs_iunlink(
        struct xfs_trans        *tp,
        struct xfs_inode        *ip)
{
        struct xfs_mount        *mp = tp->t_mountp;
        struct xfs_perag        *pag;
        struct xfs_agi          *agi;
        struct xfs_buf          *agibp;
        xfs_agino_t             next_agino;
        xfs_agino_t             agino = XFS_INO_TO_AGINO(mp, ip->i_ino);
        short                   bucket_index = agino % XFS_AGI_UNLINKED_BUCKETS;
        int                     error;

        ASSERT(VFS_I(ip)->i_nlink == 0);
        ASSERT(VFS_I(ip)->i_mode != 0);
        trace_xfs_iunlink(ip);

        pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ip->i_ino));

        /* Get the agi buffer first.  It ensures lock ordering on the list. */
        error = xfs_read_agi(mp, tp, pag->pag_agno, &agibp);
        if (error)
                goto out;
        agi = agibp->b_addr;

        /*
         * Get the index into the agi hash table for the list this inode will
         * go on.  Make sure the pointer isn't garbage and that this inode
         * isn't already on the list.
         */
        next_agino = be32_to_cpu(agi->agi_unlinked[bucket_index]);
        if (next_agino == agino ||
            !xfs_verify_agino_or_null(mp, pag->pag_agno, next_agino)) {
                xfs_buf_mark_corrupt(agibp);
                error = -EFSCORRUPTED;
                goto out;
        }

        if (next_agino != NULLAGINO) {
                xfs_agino_t             old_agino;

                /*
                 * There is already another inode in the bucket, so point this
                 * inode to the current head of the list.
                 */
                error = xfs_iunlink_update_inode(tp, ip, pag, next_agino,
                                &old_agino);
                if (error)
                        goto out;
                ASSERT(old_agino == NULLAGINO);

                /*
                 * agino has been unlinked, add a backref from the next inode
                 * back to agino.
                 */
                error = xfs_iunlink_add_backref(pag, agino, next_agino);
                if (error)
                        goto out;
        }

        /* Point the head of the list to point to this inode. */
        error = xfs_iunlink_update_bucket(tp, pag, agibp, bucket_index, agino);
out:
        xfs_perag_put(pag);
        return error;
}

/* Return the imap, dinode pointer, and buffer for an inode. */
STATIC int
xfs_iunlink_map_ino(
        struct xfs_trans        *tp,
        xfs_agnumber_t          agno,
        xfs_agino_t             agino,
        struct xfs_imap         *imap,
        struct xfs_dinode       **dipp,
        struct xfs_buf          **bpp)
{
        struct xfs_mount        *mp = tp->t_mountp;
        int                     error;

        imap->im_blkno = 0;
        error = xfs_imap(mp, tp, XFS_AGINO_TO_INO(mp, agno, agino), imap, 0);
        if (error) {
                xfs_warn(mp, "%s: xfs_imap returned error %d.",
                                __func__, error);
                return error;
        }

        error = xfs_imap_to_bp(mp, tp, imap, bpp);
        if (error) {
                xfs_warn(mp, "%s: xfs_imap_to_bp returned error %d.",
                                __func__, error);
                return error;
        }

        *dipp = xfs_buf_offset(*bpp, imap->im_boffset);
        return 0;
}

/*
 * Walk the unlinked chain from @head_agino until we find the inode that
 * points to @target_agino.  Return the inode number, map, dinode pointer,
 * and inode cluster buffer of that inode as @agino, @imap, @dipp, and @bpp.
 *
 * @tp, @pag, @head_agino, and @target_agino are input parameters.
 * @agino, @imap, @dipp, and @bpp are all output parameters.
 *
 * Do not call this function if @target_agino is the head of the list.
 */
STATIC int
xfs_iunlink_map_prev(
        struct xfs_trans        *tp,
        struct xfs_perag        *pag,
        xfs_agino_t             head_agino,
        xfs_agino_t             target_agino,
        xfs_agino_t             *agino,
        struct xfs_imap         *imap,
        struct xfs_dinode       **dipp,
        struct xfs_buf          **bpp)
{
        struct xfs_mount        *mp = tp->t_mountp;
        xfs_agino_t             next_agino;
        int                     error;

        ASSERT(head_agino != target_agino);
        *bpp = NULL;

        /* See if our backref cache can find it faster. */
        *agino = xfs_iunlink_lookup_backref(pag, target_agino);
        if (*agino != NULLAGINO) {
                error = xfs_iunlink_map_ino(tp, pag->pag_agno, *agino, imap,
                                dipp, bpp);
                if (error)
                        return error;

                if (be32_to_cpu((*dipp)->di_next_unlinked) == target_agino)
                        return 0;

                /*
                 * If we get here the cache contents were corrupt, so drop the
                 * buffer and fall back to walking the bucket list.
                 */
                xfs_trans_brelse(tp, *bpp);
                *bpp = NULL;
                WARN_ON_ONCE(1);
        }

        trace_xfs_iunlink_map_prev_fallback(mp, pag->pag_agno);

        /* Otherwise, walk the entire bucket until we find it. */
        next_agino = head_agino;
        while (next_agino != target_agino) {
                xfs_agino_t     unlinked_agino;

                if (*bpp)
                        xfs_trans_brelse(tp, *bpp);

                *agino = next_agino;
                error = xfs_iunlink_map_ino(tp, pag->pag_agno, next_agino, imap,
                                dipp, bpp);
                if (error)
                        return error;

                unlinked_agino = be32_to_cpu((*dipp)->di_next_unlinked);
                /*
                 * Make sure this pointer is valid and isn't an obvious
                 * infinite loop.
                 */
                if (!xfs_verify_agino(mp, pag->pag_agno, unlinked_agino) ||
                    next_agino == unlinked_agino) {
                        XFS_CORRUPTION_ERROR(__func__,
                                        XFS_ERRLEVEL_LOW, mp,
                                        *dipp, sizeof(**dipp));
                        error = -EFSCORRUPTED;
                        return error;
                }
                next_agino = unlinked_agino;
        }

        return 0;
}

/*
 * Pull the on-disk inode from the AGI unlinked list.
 */
STATIC int
xfs_iunlink_remove(
        struct xfs_trans        *tp,
        struct xfs_perag        *pag,
        struct xfs_inode        *ip)
{
        struct xfs_mount        *mp = tp->t_mountp;
        struct xfs_agi          *agi;
        struct xfs_buf          *agibp;
        struct xfs_buf          *last_ibp;
        struct xfs_dinode       *last_dip = NULL;
        xfs_agino_t             agino = XFS_INO_TO_AGINO(mp, ip->i_ino);
        xfs_agino_t             next_agino;
        xfs_agino_t             head_agino;
        short                   bucket_index = agino % XFS_AGI_UNLINKED_BUCKETS;
        int                     error;

        trace_xfs_iunlink_remove(ip);

        /* Get the agi buffer first.  It ensures lock ordering on the list. */
        error = xfs_read_agi(mp, tp, pag->pag_agno, &agibp);
        if (error)
                return error;
        agi = agibp->b_addr;

        /*
         * Get the index into the agi hash table for the list this inode will
         * go on.  Make sure the head pointer isn't garbage.
         */
        head_agino = be32_to_cpu(agi->agi_unlinked[bucket_index]);
        if (!xfs_verify_agino(mp, pag->pag_agno, head_agino)) {
                XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp,
                                agi, sizeof(*agi));
                return -EFSCORRUPTED;
        }

        /*
         * Set our inode's next_unlinked pointer to NULL and then return
         * the old pointer value so that we can update whatever was previous
         * to us in the list to point to whatever was next in the list.
         */
        error = xfs_iunlink_update_inode(tp, ip, pag, NULLAGINO, &next_agino);
        if (error)
                return error;

        /*
         * If there was a backref pointing from the next inode back to this
         * one, remove it because we've removed this inode from the list.
         *
         * Later, if this inode was in the middle of the list we'll update
         * this inode's backref to point from the next inode.
         */
        if (next_agino != NULLAGINO) {
                error = xfs_iunlink_change_backref(pag, next_agino, NULLAGINO);
                if (error)
                        return error;
        }

        if (head_agino != agino) {
                struct xfs_imap imap;
                xfs_agino_t     prev_agino;

                /* We need to search the list for the inode being freed. */
                error = xfs_iunlink_map_prev(tp, pag, head_agino, agino,
                                &prev_agino, &imap, &last_dip, &last_ibp);
                if (error)
                        return error;

                /* Point the previous inode on the list to the next inode. */
                xfs_iunlink_update_dinode(tp, pag, prev_agino, last_ibp,
                                last_dip, &imap, next_agino);

                /*
                 * Now we deal with the backref for this inode.  If this inode
                 * pointed at a real inode, change the backref that pointed to
                 * us to point to our old next.  If this inode was the end of
                 * the list, delete the backref that pointed to us.  Note that
                 * change_backref takes care of deleting the backref if
                 * next_agino is NULLAGINO.
                 */
                return xfs_iunlink_change_backref(agibp->b_pag, agino,
                                next_agino);
        }

        /* Point the head of the list to the next unlinked inode. */
        return xfs_iunlink_update_bucket(tp, pag, agibp, bucket_index,
                        next_agino);
}

/*
 * Look up the inode number specified and if it is not already marked XFS_ISTALE
 * mark it stale. We should only find clean inodes in this lookup that aren't
 * already stale.
 */
static void
xfs_ifree_mark_inode_stale(
        struct xfs_perag        *pag,
        struct xfs_inode        *free_ip,
        xfs_ino_t               inum)
{
        struct xfs_mount        *mp = pag->pag_mount;
        struct xfs_inode_log_item *iip;
        struct xfs_inode        *ip;

retry:
        rcu_read_lock();
        ip = radix_tree_lookup(&pag->pag_ici_root, XFS_INO_TO_AGINO(mp, inum));

        /* Inode not in memory, nothing to do */
        if (!ip) {
                rcu_read_unlock();
                return;
        }

        /*
         * because this is an RCU protected lookup, we could find a recently
         * freed or even reallocated inode during the lookup. We need to check
         * under the i_flags_lock for a valid inode here. Skip it if it is not
         * valid, the wrong inode or stale.
         */
        spin_lock(&ip->i_flags_lock);
        if (ip->i_ino != inum || __xfs_iflags_test(ip, XFS_ISTALE))
                goto out_iflags_unlock;

        /*
         * Don't try to lock/unlock the current inode, but we _cannot_ skip the
         * other inodes that we did not find in the list attached to the buffer
         * and are not already marked stale. If we can't lock it, back off and
         * retry.
         */
        if (ip != free_ip) {
                if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL)) {
                        spin_unlock(&ip->i_flags_lock);
                        rcu_read_unlock();
                        delay(1);
                        goto retry;
                }
        }
        ip->i_flags |= XFS_ISTALE;

        /*
         * If the inode is flushing, it is already attached to the buffer.  All
         * we needed to do here is mark the inode stale so buffer IO completion
         * will remove it from the AIL.
         */
        iip = ip->i_itemp;
        if (__xfs_iflags_test(ip, XFS_IFLUSHING)) {
                ASSERT(!list_empty(&iip->ili_item.li_bio_list));
                ASSERT(iip->ili_last_fields);
                goto out_iunlock;
        }

        /*
         * Inodes not attached to the buffer can be released immediately.
         * Everything else has to go through xfs_iflush_abort() on journal
         * commit as the flock synchronises removal of the inode from the
         * cluster buffer against inode reclaim.
         */
        if (!iip || list_empty(&iip->ili_item.li_bio_list))
                goto out_iunlock;

        __xfs_iflags_set(ip, XFS_IFLUSHING);
        spin_unlock(&ip->i_flags_lock);
        rcu_read_unlock();

        /* we have a dirty inode in memory that has not yet been flushed. */
        spin_lock(&iip->ili_lock);
        iip->ili_last_fields = iip->ili_fields;
        iip->ili_fields = 0;
        iip->ili_fsync_fields = 0;
        spin_unlock(&iip->ili_lock);
        ASSERT(iip->ili_last_fields);

        if (ip != free_ip)
                xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return;

out_iunlock:
        if (ip != free_ip)
                xfs_iunlock(ip, XFS_ILOCK_EXCL);
out_iflags_unlock:
        spin_unlock(&ip->i_flags_lock);
        rcu_read_unlock();
}

/*
 * A big issue when freeing the inode cluster is that we _cannot_ skip any
 * inodes that are in memory - they all must be marked stale and attached to
 * the cluster buffer.
 */
static int
xfs_ifree_cluster(
        struct xfs_trans        *tp,
        struct xfs_perag        *pag,
        struct xfs_inode        *free_ip,
        struct xfs_icluster     *xic)
{
        struct xfs_mount        *mp = free_ip->i_mount;
        struct xfs_ino_geometry *igeo = M_IGEO(mp);
        struct xfs_buf          *bp;
        xfs_daddr_t             blkno;
        xfs_ino_t               inum = xic->first_ino;
        int                     nbufs;
        int                     i, j;
        int                     ioffset;
        int                     error;

        nbufs = igeo->ialloc_blks / igeo->blocks_per_cluster;

        for (j = 0; j < nbufs; j++, inum += igeo->inodes_per_cluster) {
                /*
                 * The allocation bitmap tells us which inodes of the chunk were
                 * physically allocated. Skip the cluster if an inode falls into
                 * a sparse region.
                 */
                ioffset = inum - xic->first_ino;
                if ((xic->alloc & XFS_INOBT_MASK(ioffset)) == 0) {
                        ASSERT(ioffset % igeo->inodes_per_cluster == 0);
                        continue;
                }

                blkno = XFS_AGB_TO_DADDR(mp, XFS_INO_TO_AGNO(mp, inum),
                                         XFS_INO_TO_AGBNO(mp, inum));

                /*
                 * We obtain and lock the backing buffer first in the process
                 * here to ensure dirty inodes attached to the buffer remain in
                 * the flushing state while we mark them stale.
                 *
                 * If we scan the in-memory inodes first, then buffer IO can
                 * complete before we get a lock on it, and hence we may fail
                 * to mark all the active inodes on the buffer stale.
                 */
                error = xfs_trans_get_buf(tp, mp->m_ddev_targp, blkno,
                                mp->m_bsize * igeo->blocks_per_cluster,
                                XBF_UNMAPPED, &bp);
                if (error)
                        return error;

                /*
                 * This buffer may not have been correctly initialised as we
                 * didn't read it from disk. That's not important because we are
                 * only using to mark the buffer as stale in the log, and to
                 * attach stale cached inodes on it. That means it will never be
                 * dispatched for IO. If it is, we want to know about it, and we
                 * want it to fail. We can acheive this by adding a write
                 * verifier to the buffer.
                 */
                bp->b_ops = &xfs_inode_buf_ops;

                /*
                 * Now we need to set all the cached clean inodes as XFS_ISTALE,
                 * too. This requires lookups, and will skip inodes that we've
                 * already marked XFS_ISTALE.
                 */
                for (i = 0; i < igeo->inodes_per_cluster; i++)
                        xfs_ifree_mark_inode_stale(pag, free_ip, inum + i);

                xfs_trans_stale_inode_buf(tp, bp);
                xfs_trans_binval(tp, bp);
        }
        return 0;
}

/*
 * This is called to return an inode to the inode free list.
 * The inode should already be truncated to 0 length and have
 * no pages associated with it.  This routine also assumes that
 * the inode is already a part of the transaction.
 *
 * The on-disk copy of the inode will have been added to the list
 * of unlinked inodes in the AGI. We need to remove the inode from
 * that list atomically with respect to freeing it here.
 */
int
xfs_ifree(
        struct xfs_trans        *tp,
        struct xfs_inode        *ip)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_perag        *pag;
        struct xfs_icluster     xic = { 0 };
        struct xfs_inode_log_item *iip = ip->i_itemp;
        int                     error;

        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
        ASSERT(VFS_I(ip)->i_nlink == 0);
        ASSERT(ip->i_df.if_nextents == 0);
        ASSERT(ip->i_disk_size == 0 || !S_ISREG(VFS_I(ip)->i_mode));
        ASSERT(ip->i_nblocks == 0);

        pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ip->i_ino));

        /*
         * Pull the on-disk inode from the AGI unlinked list.
         */
        error = xfs_iunlink_remove(tp, pag, ip);
        if (error)
                goto out;

        error = xfs_difree(tp, pag, ip->i_ino, &xic);
        if (error)
                goto out;

        /*
         * Free any local-format data sitting around before we reset the
         * data fork to extents format.  Note that the attr fork data has
         * already been freed by xfs_attr_inactive.
         */
        if (ip->i_df.if_format == XFS_DINODE_FMT_LOCAL) {
                kmem_free(ip->i_df.if_u1.if_data);
                ip->i_df.if_u1.if_data = NULL;
                ip->i_df.if_bytes = 0;
        }

        VFS_I(ip)->i_mode = 0;          /* mark incore inode as free */
        ip->i_diflags = 0;
        ip->i_diflags2 = mp->m_ino_geo.new_diflags2;
        ip->i_forkoff = 0;              /* mark the attr fork not in use */
        ip->i_df.if_format = XFS_DINODE_FMT_EXTENTS;
        if (xfs_iflags_test(ip, XFS_IPRESERVE_DM_FIELDS))
                xfs_iflags_clear(ip, XFS_IPRESERVE_DM_FIELDS);

        /* Don't attempt to replay owner changes for a deleted inode */
        spin_lock(&iip->ili_lock);
        iip->ili_fields &= ~(XFS_ILOG_AOWNER | XFS_ILOG_DOWNER);
        spin_unlock(&iip->ili_lock);

        /*
         * Bump the generation count so no one will be confused
         * by reincarnations of this inode.
         */
        VFS_I(ip)->i_generation++;
        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);

        if (xic.deleted)
                error = xfs_ifree_cluster(tp, pag, ip, &xic);
out:
        xfs_perag_put(pag);
        return error;
}

/*
 * This is called to unpin an inode.  The caller must have the inode locked
 * in at least shared mode so that the buffer cannot be subsequently pinned
 * once someone is waiting for it to be unpinned.
 */
static void
xfs_iunpin(
        struct xfs_inode        *ip)
{
        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_ILOCK_SHARED));

        trace_xfs_inode_unpin_nowait(ip, _RET_IP_);

        /* Give the log a push to start the unpinning I/O */
        xfs_log_force_seq(ip->i_mount, ip->i_itemp->ili_commit_seq, 0, NULL);

}

static void
__xfs_iunpin_wait(
        struct xfs_inode        *ip)
{
        wait_queue_head_t *wq = bit_waitqueue(&ip->i_flags, __XFS_IPINNED_BIT);
        DEFINE_WAIT_BIT(wait, &ip->i_flags, __XFS_IPINNED_BIT);

        xfs_iunpin(ip);

        do {
                prepare_to_wait(wq, &wait.wq_entry, TASK_UNINTERRUPTIBLE);
                if (xfs_ipincount(ip))
                        io_schedule();
        } while (xfs_ipincount(ip));
        finish_wait(wq, &wait.wq_entry);
}

void
xfs_iunpin_wait(
        struct xfs_inode        *ip)
{
        if (xfs_ipincount(ip))
                __xfs_iunpin_wait(ip);
}

/*
 * Removing an inode from the namespace involves removing the directory entry
 * and dropping the link count on the inode. Removing the directory entry can
 * result in locking an AGF (directory blocks were freed) and removing a link
 * count can result in placing the inode on an unlinked list which results in
 * locking an AGI.
 *
 * The big problem here is that we have an ordering constraint on AGF and AGI
 * locking - inode allocation locks the AGI, then can allocate a new extent for
 * new inodes, locking the AGF after the AGI. Similarly, freeing the inode
 * removes the inode from the unlinked list, requiring that we lock the AGI
 * first, and then freeing the inode can result in an inode chunk being freed
 * and hence freeing disk space requiring that we lock an AGF.
 *
 * Hence the ordering that is imposed by other parts of the code is AGI before
 * AGF. This means we cannot remove the directory entry before we drop the inode
 * reference count and put it on the unlinked list as this results in a lock
 * order of AGF then AGI, and this can deadlock against inode allocation and
 * freeing. Therefore we must drop the link counts before we remove the
 * directory entry.
 *
 * This is still safe from a transactional point of view - it is not until we
 * get to xfs_defer_finish() that we have the possibility of multiple
 * transactions in this operation. Hence as long as we remove the directory
 * entry and drop the link count in the first transaction of the remove
 * operation, there are no transactional constraints on the ordering here.
 */
int
xfs_remove(
        xfs_inode_t             *dp,
        struct xfs_name         *name,
        xfs_inode_t             *ip)
{
        xfs_mount_t             *mp = dp->i_mount;
        xfs_trans_t             *tp = NULL;
        int                     is_dir = S_ISDIR(VFS_I(ip)->i_mode);
        int                     dontcare;
        int                     error = 0;
        uint                    resblks;

        trace_xfs_remove(dp, name);

        if (xfs_is_shutdown(mp))
                return -EIO;

        error = xfs_qm_dqattach(dp);
        if (error)
                goto std_return;

        error = xfs_qm_dqattach(ip);
        if (error)
                goto std_return;

        /*
         * We try to get the real space reservation first, allowing for
         * directory btree deletion(s) implying possible bmap insert(s).  If we
         * can't get the space reservation then we use 0 instead, and avoid the
         * bmap btree insert(s) in the directory code by, if the bmap insert
         * tries to happen, instead trimming the LAST block from the directory.
         *
         * Ignore EDQUOT and ENOSPC being returned via nospace_error because
         * the directory code can handle a reservationless update and we don't
         * want to prevent a user from trying to free space by deleting things.
         */
        resblks = XFS_REMOVE_SPACE_RES(mp);
        error = xfs_trans_alloc_dir(dp, &M_RES(mp)->tr_remove, ip, &resblks,
                        &tp, &dontcare);
        if (error) {
                ASSERT(error != -ENOSPC);
                goto std_return;
        }

        /*
         * If we're removing a directory perform some additional validation.
         */
        if (is_dir) {
                ASSERT(VFS_I(ip)->i_nlink >= 2);
                if (VFS_I(ip)->i_nlink != 2) {
                        error = -ENOTEMPTY;
                        goto out_trans_cancel;
                }
                if (!xfs_dir_isempty(ip)) {
                        error = -ENOTEMPTY;
                        goto out_trans_cancel;
                }

                /* Drop the link from ip's "..".  */
                error = xfs_droplink(tp, dp);
                if (error)
                        goto out_trans_cancel;

                /* Drop the "." link from ip to self.  */
                error = xfs_droplink(tp, ip);
                if (error)
                        goto out_trans_cancel;

                /*
                 * Point the unlinked child directory's ".." entry to the root
                 * directory to eliminate back-references to inodes that may
                 * get freed before the child directory is closed.  If the fs
                 * gets shrunk, this can lead to dirent inode validation errors.
                 */
                if (dp->i_ino != tp->t_mountp->m_sb.sb_rootino) {
                        error = xfs_dir_replace(tp, ip, &xfs_name_dotdot,
                                        tp->t_mountp->m_sb.sb_rootino, 0);
                        if (error)
                                return error;
                }
        } else {
                /*
                 * When removing a non-directory we need to log the parent
                 * inode here.  For a directory this is done implicitly
                 * by the xfs_droplink call for the ".." entry.
                 */
                xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);
        }
        xfs_trans_ichgtime(tp, dp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);

        /* Drop the link from dp to ip. */
        error = xfs_droplink(tp, ip);
        if (error)
                goto out_trans_cancel;

        error = xfs_dir_removename(tp, dp, name, ip->i_ino, resblks);
        if (error) {
                ASSERT(error != -ENOENT);
                goto out_trans_cancel;
        }

        /*
         * If this is a synchronous mount, make sure that the
         * remove transaction goes to disk before returning to
         * the user.
         */
        if (xfs_has_wsync(mp) || xfs_has_dirsync(mp))
                xfs_trans_set_sync(tp);

        error = xfs_trans_commit(tp);
        if (error)
                goto std_return;

        if (is_dir && xfs_inode_is_filestream(ip))
                xfs_filestream_deassociate(ip);

        return 0;

 out_trans_cancel:
        xfs_trans_cancel(tp);
 std_return:
        return error;
}

/*
 * Enter all inodes for a rename transaction into a sorted array.
 */
#define __XFS_SORT_INODES       5
STATIC void
xfs_sort_for_rename(
        struct xfs_inode        *dp1,   /* in: old (source) directory inode */
        struct xfs_inode        *dp2,   /* in: new (target) directory inode */
        struct xfs_inode        *ip1,   /* in: inode of old entry */
        struct xfs_inode        *ip2,   /* in: inode of new entry */
        struct xfs_inode        *wip,   /* in: whiteout inode */
        struct xfs_inode        **i_tab,/* out: sorted array of inodes */
        int                     *num_inodes)  /* in/out: inodes in array */
{
        int                     i, j;

        ASSERT(*num_inodes == __XFS_SORT_INODES);
        memset(i_tab, 0, *num_inodes * sizeof(struct xfs_inode *));

        /*
         * i_tab contains a list of pointers to inodes.  We initialize
         * the table here & we'll sort it.  We will then use it to
         * order the acquisition of the inode locks.
         *
         * Note that the table may contain duplicates.  e.g., dp1 == dp2.
         */
        i = 0;
        i_tab[i++] = dp1;
        i_tab[i++] = dp2;
        i_tab[i++] = ip1;
        if (ip2)
                i_tab[i++] = ip2;
        if (wip)
                i_tab[i++] = wip;
        *num_inodes = i;

        /*
         * Sort the elements via bubble sort.  (Remember, there are at
         * most 5 elements to sort, so this is adequate.)
         */
        for (i = 0; i < *num_inodes; i++) {
                for (j = 1; j < *num_inodes; j++) {
                        if (i_tab[j]->i_ino < i_tab[j-1]->i_ino) {
                                struct xfs_inode *temp = i_tab[j];
                                i_tab[j] = i_tab[j-1];
                                i_tab[j-1] = temp;
                        }
                }
        }
}

static int
xfs_finish_rename(
        struct xfs_trans        *tp)
{
        /*
         * If this is a synchronous mount, make sure that the rename transaction
         * goes to disk before returning to the user.
         */
        if (xfs_has_wsync(tp->t_mountp) || xfs_has_dirsync(tp->t_mountp))
                xfs_trans_set_sync(tp);

        return xfs_trans_commit(tp);
}

/*
 * xfs_cross_rename()
 *
 * responsible for handling RENAME_EXCHANGE flag in renameat2() syscall
 */
STATIC int
xfs_cross_rename(
        struct xfs_trans        *tp,
        struct xfs_inode        *dp1,
        struct xfs_name         *name1,
        struct xfs_inode        *ip1,
        struct xfs_inode        *dp2,
        struct xfs_name         *name2,
        struct xfs_inode        *ip2,
        int                     spaceres)
{
        int             error = 0;
        int             ip1_flags = 0;
        int             ip2_flags = 0;
        int             dp2_flags = 0;

        /* Swap inode number for dirent in first parent */
        error = xfs_dir_replace(tp, dp1, name1, ip2->i_ino, spaceres);
        if (error)
                goto out_trans_abort;

        /* Swap inode number for dirent in second parent */
        error = xfs_dir_replace(tp, dp2, name2, ip1->i_ino, spaceres);
        if (error)
                goto out_trans_abort;

        /*
         * If we're renaming one or more directories across different parents,
         * update the respective ".." entries (and link counts) to match the new
         * parents.
         */
        if (dp1 != dp2) {
                dp2_flags = XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG;

                if (S_ISDIR(VFS_I(ip2)->i_mode)) {
                        error = xfs_dir_replace(tp, ip2, &xfs_name_dotdot,
                                                dp1->i_ino, spaceres);
                        if (error)
                                goto out_trans_abort;

                        /* transfer ip2 ".." reference to dp1 */
                        if (!S_ISDIR(VFS_I(ip1)->i_mode)) {
                                error = xfs_droplink(tp, dp2);
                                if (error)
                                        goto out_trans_abort;
                                xfs_bumplink(tp, dp1);
                        }

                        /*
                         * Although ip1 isn't changed here, userspace needs
                         * to be warned about the change, so that applications
                         * relying on it (like backup ones), will properly
                         * notify the change
                         */
                        ip1_flags |= XFS_ICHGTIME_CHG;
                        ip2_flags |= XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG;
                }

                if (S_ISDIR(VFS_I(ip1)->i_mode)) {
                        error = xfs_dir_replace(tp, ip1, &xfs_name_dotdot,
                                                dp2->i_ino, spaceres);
                        if (error)
                                goto out_trans_abort;

                        /* transfer ip1 ".." reference to dp2 */
                        if (!S_ISDIR(VFS_I(ip2)->i_mode)) {
                                error = xfs_droplink(tp, dp1);
                                if (error)
                                        goto out_trans_abort;
                                xfs_bumplink(tp, dp2);
                        }

                        /*
                         * Although ip2 isn't changed here, userspace needs
                         * to be warned about the change, so that applications
                         * relying on it (like backup ones), will properly
                         * notify the change
                         */
                        ip1_flags |= XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG;
                        ip2_flags |= XFS_ICHGTIME_CHG;
                }
        }

        if (ip1_flags) {
                xfs_trans_ichgtime(tp, ip1, ip1_flags);
                xfs_trans_log_inode(tp, ip1, XFS_ILOG_CORE);
        }
        if (ip2_flags) {
                xfs_trans_ichgtime(tp, ip2, ip2_flags);
                xfs_trans_log_inode(tp, ip2, XFS_ILOG_CORE);
        }
        if (dp2_flags) {
                xfs_trans_ichgtime(tp, dp2, dp2_flags);
                xfs_trans_log_inode(tp, dp2, XFS_ILOG_CORE);
        }
        xfs_trans_ichgtime(tp, dp1, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
        xfs_trans_log_inode(tp, dp1, XFS_ILOG_CORE);
        return xfs_finish_rename(tp);

out_trans_abort:
        xfs_trans_cancel(tp);
        return error;
}

/*
 * xfs_rename_alloc_whiteout()
 *
 * Return a referenced, unlinked, unlocked inode that can be used as a
 * whiteout in a rename transaction. We use a tmpfile inode here so that if we
 * crash between allocating the inode and linking it into the rename transaction
 * recovery will free the inode and we won't leak it.
 */
static int
xfs_rename_alloc_whiteout(
        struct user_namespace   *mnt_userns,
        struct xfs_inode        *dp,
        struct xfs_inode        **wip)
{
        struct xfs_inode        *tmpfile;
        int                     error;

        error = xfs_create_tmpfile(mnt_userns, dp, S_IFCHR | WHITEOUT_MODE,
                                   &tmpfile);
        if (error)
                return error;

        /*
         * Prepare the tmpfile inode as if it were created through the VFS.
         * Complete the inode setup and flag it as linkable.  nlink is already
         * zero, so we can skip the drop_nlink.
         */
        xfs_setup_iops(tmpfile);
        xfs_finish_inode_setup(tmpfile);
        VFS_I(tmpfile)->i_state |= I_LINKABLE;

        *wip = tmpfile;
        return 0;
}

/*
 * xfs_rename
 */
int
xfs_rename(
        struct user_namespace   *mnt_userns,
        struct xfs_inode        *src_dp,
        struct xfs_name         *src_name,
        struct xfs_inode        *src_ip,
        struct xfs_inode        *target_dp,
        struct xfs_name         *target_name,
        struct xfs_inode        *target_ip,
        unsigned int            flags)
{
        struct xfs_mount        *mp = src_dp->i_mount;
        struct xfs_trans        *tp;
        struct xfs_inode        *wip = NULL;            /* whiteout inode */
        struct xfs_inode        *inodes[__XFS_SORT_INODES];
        int                     i;
        int                     num_inodes = __XFS_SORT_INODES;
        bool                    new_parent = (src_dp != target_dp);
        bool                    src_is_directory = S_ISDIR(VFS_I(src_ip)->i_mode);
        int                     spaceres;
        bool                    retried = false;
        int                     error, nospace_error = 0;

        trace_xfs_rename(src_dp, target_dp, src_name, target_name);

        if ((flags & RENAME_EXCHANGE) && !target_ip)
                return -EINVAL;

        /*
         * If we are doing a whiteout operation, allocate the whiteout inode
         * we will be placing at the target and ensure the type is set
         * appropriately.
         */
        if (flags & RENAME_WHITEOUT) {
                error = xfs_rename_alloc_whiteout(mnt_userns, target_dp, &wip);
                if (error)
                        return error;

                /* setup target dirent info as whiteout */
                src_name->type = XFS_DIR3_FT_CHRDEV;
        }

        xfs_sort_for_rename(src_dp, target_dp, src_ip, target_ip, wip,
                                inodes, &num_inodes);

retry:
        nospace_error = 0;
        spaceres = XFS_RENAME_SPACE_RES(mp, target_name->len);
        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_rename, spaceres, 0, 0, &tp);
        if (error == -ENOSPC) {
                nospace_error = error;
                spaceres = 0;
                error = xfs_trans_alloc(mp, &M_RES(mp)->tr_rename, 0, 0, 0,
                                &tp);
        }
        if (error)
                goto out_release_wip;

        /*
         * Attach the dquots to the inodes
         */
        error = xfs_qm_vop_rename_dqattach(inodes);
        if (error)
                goto out_trans_cancel;

        /*
         * Lock all the participating inodes. Depending upon whether
         * the target_name exists in the target directory, and
         * whether the target directory is the same as the source
         * directory, we can lock from 2 to 4 inodes.
         */
        xfs_lock_inodes(inodes, num_inodes, XFS_ILOCK_EXCL);

        /*
         * Join all the inodes to the transaction. From this point on,
         * we can rely on either trans_commit or trans_cancel to unlock
         * them.
         */
        xfs_trans_ijoin(tp, src_dp, XFS_ILOCK_EXCL);
        if (new_parent)
                xfs_trans_ijoin(tp, target_dp, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(tp, src_ip, XFS_ILOCK_EXCL);
        if (target_ip)
                xfs_trans_ijoin(tp, target_ip, XFS_ILOCK_EXCL);
        if (wip)
                xfs_trans_ijoin(tp, wip, XFS_ILOCK_EXCL);

        /*
         * If we are using project inheritance, we only allow renames
         * into our tree when the project IDs are the same; else the
         * tree quota mechanism would be circumvented.
         */
        if (unlikely((target_dp->i_diflags & XFS_DIFLAG_PROJINHERIT) &&
                     target_dp->i_projid != src_ip->i_projid)) {
                error = -EXDEV;
                goto out_trans_cancel;
        }

        /* RENAME_EXCHANGE is unique from here on. */
        if (flags & RENAME_EXCHANGE)
                return xfs_cross_rename(tp, src_dp, src_name, src_ip,
                                        target_dp, target_name, target_ip,
                                        spaceres);

        /*
         * Try to reserve quota to handle an expansion of the target directory.
         * We'll allow the rename to continue in reservationless mode if we hit
         * a space usage constraint.  If we trigger reservationless mode, save
         * the errno if there isn't any free space in the target directory.
         */
        if (spaceres != 0) {
                error = xfs_trans_reserve_quota_nblks(tp, target_dp, spaceres,
                                0, false);
                if (error == -EDQUOT || error == -ENOSPC) {
                        if (!retried) {
                                xfs_trans_cancel(tp);
                                xfs_blockgc_free_quota(target_dp, 0);
                                retried = true;
                                goto retry;
                        }

                        nospace_error = error;
                        spaceres = 0;
                        error = 0;
                }
                if (error)
                        goto out_trans_cancel;
        }

        /*
         * Check for expected errors before we dirty the transaction
         * so we can return an error without a transaction abort.
         *
         * Extent count overflow check:
         *
         * From the perspective of src_dp, a rename operation is essentially a
         * directory entry remove operation. Hence the only place where we check
         * for extent count overflow for src_dp is in
         * xfs_bmap_del_extent_real(). xfs_bmap_del_extent_real() returns
         * -ENOSPC when it detects a possible extent count overflow and in
         * response, the higher layers of directory handling code do the
         * following:
         * 1. Data/Free blocks: XFS lets these blocks linger until a
         *    future remove operation removes them.
         * 2. Dabtree blocks: XFS swaps the blocks with the last block in the
         *    Leaf space and unmaps the last block.
         *
         * For target_dp, there are two cases depending on whether the
         * destination directory entry exists or not.
         *
         * When destination directory entry does not exist (i.e. target_ip ==
         * NULL), extent count overflow check is performed only when transaction
         * has a non-zero sized space reservation associated with it.  With a
         * zero-sized space reservation, XFS allows a rename operation to
         * continue only when the directory has sufficient free space in its
         * data/leaf/free space blocks to hold the new entry.
         *
         * When destination directory entry exists (i.e. target_ip != NULL), all
         * we need to do is change the inode number associated with the already
         * existing entry. Hence there is no need to perform an extent count
         * overflow check.
         */
        if (target_ip == NULL) {
                /*
                 * If there's no space reservation, check the entry will
                 * fit before actually inserting it.
                 */
                if (!spaceres) {
                        error = xfs_dir_canenter(tp, target_dp, target_name);
                        if (error)
                                goto out_trans_cancel;
                } else {
                        error = xfs_iext_count_may_overflow(target_dp,
                                        XFS_DATA_FORK,
                                        XFS_IEXT_DIR_MANIP_CNT(mp));
                        if (error)
                                goto out_trans_cancel;
                }
        } else {
                /*
                 * If target exists and it's a directory, check that whether
                 * it can be destroyed.
                 */
                if (S_ISDIR(VFS_I(target_ip)->i_mode) &&
                    (!xfs_dir_isempty(target_ip) ||
                     (VFS_I(target_ip)->i_nlink > 2))) {
                        error = -EEXIST;
                        goto out_trans_cancel;
                }
        }

        /*
         * Lock the AGI buffers we need to handle bumping the nlink of the
         * whiteout inode off the unlinked list and to handle dropping the
         * nlink of the target inode.  Per locking order rules, do this in
         * increasing AG order and before directory block allocation tries to
         * grab AGFs because we grab AGIs before AGFs.
         *
         * The (vfs) caller must ensure that if src is a directory then
         * target_ip is either null or an empty directory.
         */
        for (i = 0; i < num_inodes && inodes[i] != NULL; i++) {
                if (inodes[i] == wip ||
                    (inodes[i] == target_ip &&
                     (VFS_I(target_ip)->i_nlink == 1 || src_is_directory))) {
                        struct xfs_buf  *bp;
                        xfs_agnumber_t  agno;

                        agno = XFS_INO_TO_AGNO(mp, inodes[i]->i_ino);
                        error = xfs_read_agi(mp, tp, agno, &bp);
                        if (error)
                                goto out_trans_cancel;
                }
        }

        /*
         * Directory entry creation below may acquire the AGF. Remove
         * the whiteout from the unlinked list first to preserve correct
         * AGI/AGF locking order. This dirties the transaction so failures
         * after this point will abort and log recovery will clean up the
         * mess.
         *
         * For whiteouts, we need to bump the link count on the whiteout
         * inode. After this point, we have a real link, clear the tmpfile
         * state flag from the inode so it doesn't accidentally get misused
         * in future.
         */
        if (wip) {
                struct xfs_perag        *pag;

                ASSERT(VFS_I(wip)->i_nlink == 0);

                pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, wip->i_ino));
                error = xfs_iunlink_remove(tp, pag, wip);
                xfs_perag_put(pag);
                if (error)
                        goto out_trans_cancel;

                xfs_bumplink(tp, wip);
                VFS_I(wip)->i_state &= ~I_LINKABLE;
        }

        /*
         * Set up the target.
         */
        if (target_ip == NULL) {
                /*
                 * If target does not exist and the rename crosses
                 * directories, adjust the target directory link count
                 * to account for the ".." reference from the new entry.
                 */
                error = xfs_dir_createname(tp, target_dp, target_name,
                                           src_ip->i_ino, spaceres);
                if (error)
                        goto out_trans_cancel;

                xfs_trans_ichgtime(tp, target_dp,
                                        XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);

                if (new_parent && src_is_directory) {
                        xfs_bumplink(tp, target_dp);
                }
        } else { /* target_ip != NULL */
                /*
                 * Link the source inode under the target name.
                 * If the source inode is a directory and we are moving
                 * it across directories, its ".." entry will be
                 * inconsistent until we replace that down below.
                 *
                 * In case there is already an entry with the same
                 * name at the destination directory, remove it first.
                 */
                error = xfs_dir_replace(tp, target_dp, target_name,
                                        src_ip->i_ino, spaceres);
                if (error)
                        goto out_trans_cancel;

                xfs_trans_ichgtime(tp, target_dp,
                                        XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);

                /*
                 * Decrement the link count on the target since the target
                 * dir no longer points to it.
                 */
                error = xfs_droplink(tp, target_ip);
                if (error)
                        goto out_trans_cancel;

                if (src_is_directory) {
                        /*
                         * Drop the link from the old "." entry.
                         */
                        error = xfs_droplink(tp, target_ip);
                        if (error)
                                goto out_trans_cancel;
                }
        } /* target_ip != NULL */

        /*
         * Remove the source.
         */
        if (new_parent && src_is_directory) {
                /*
                 * Rewrite the ".." entry to point to the new
                 * directory.
                 */
                error = xfs_dir_replace(tp, src_ip, &xfs_name_dotdot,
                                        target_dp->i_ino, spaceres);
                ASSERT(error != -EEXIST);
                if (error)
                        goto out_trans_cancel;
        }

        /*
         * We always want to hit the ctime on the source inode.
         *
         * This isn't strictly required by the standards since the source
         * inode isn't really being changed, but old unix file systems did
         * it and some incremental backup programs won't work without it.
         */
        xfs_trans_ichgtime(tp, src_ip, XFS_ICHGTIME_CHG);
        xfs_trans_log_inode(tp, src_ip, XFS_ILOG_CORE);

        /*
         * Adjust the link count on src_dp.  This is necessary when
         * renaming a directory, either within one parent when
         * the target existed, or across two parent directories.
         */
        if (src_is_directory && (new_parent || target_ip != NULL)) {

                /*
                 * Decrement link count on src_directory since the
                 * entry that's moved no longer points to it.
                 */
                error = xfs_droplink(tp, src_dp);
                if (error)
                        goto out_trans_cancel;
        }

        /*
         * For whiteouts, we only need to update the source dirent with the
         * inode number of the whiteout inode rather than removing it
         * altogether.
         */
        if (wip) {
                error = xfs_dir_replace(tp, src_dp, src_name, wip->i_ino,
                                        spaceres);
        } else {
                /*
                 * NOTE: We don't need to check for extent count overflow here
                 * because the dir remove name code will leave the dir block in
                 * place if the extent count would overflow.
                 */
                error = xfs_dir_removename(tp, src_dp, src_name, src_ip->i_ino,
                                           spaceres);
        }

        if (error)
                goto out_trans_cancel;

        xfs_trans_ichgtime(tp, src_dp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
        xfs_trans_log_inode(tp, src_dp, XFS_ILOG_CORE);
        if (new_parent)
                xfs_trans_log_inode(tp, target_dp, XFS_ILOG_CORE);

        error = xfs_finish_rename(tp);
        if (wip)
                xfs_irele(wip);
        return error;

out_trans_cancel:
        xfs_trans_cancel(tp);
out_release_wip:
        if (wip)
                xfs_irele(wip);
        if (error == -ENOSPC && nospace_error)
                error = nospace_error;
        return error;
}

static int
xfs_iflush(
        struct xfs_inode        *ip,
        struct xfs_buf          *bp)
{
        struct xfs_inode_log_item *iip = ip->i_itemp;
        struct xfs_dinode       *dip;
        struct xfs_mount        *mp = ip->i_mount;
        int                     error;

        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_ILOCK_SHARED));
        ASSERT(xfs_iflags_test(ip, XFS_IFLUSHING));
        ASSERT(ip->i_df.if_format != XFS_DINODE_FMT_BTREE ||
               ip->i_df.if_nextents > XFS_IFORK_MAXEXT(ip, XFS_DATA_FORK));
        ASSERT(iip->ili_item.li_buf == bp);

        dip = xfs_buf_offset(bp, ip->i_imap.im_boffset);

        /*
         * We don't flush the inode if any of the following checks fail, but we
         * do still update the log item and attach to the backing buffer as if
         * the flush happened. This is a formality to facilitate predictable
         * error handling as the caller will shutdown and fail the buffer.
         */
        error = -EFSCORRUPTED;
        if (XFS_TEST_ERROR(dip->di_magic != cpu_to_be16(XFS_DINODE_MAGIC),
                               mp, XFS_ERRTAG_IFLUSH_1)) {
                xfs_alert_tag(mp, XFS_PTAG_IFLUSH,
                        "%s: Bad inode %Lu magic number 0x%x, ptr "PTR_FMT,
                        __func__, ip->i_ino, be16_to_cpu(dip->di_magic), dip);
                goto flush_out;
        }
        if (S_ISREG(VFS_I(ip)->i_mode)) {
                if (XFS_TEST_ERROR(
                    ip->i_df.if_format != XFS_DINODE_FMT_EXTENTS &&
                    ip->i_df.if_format != XFS_DINODE_FMT_BTREE,
                    mp, XFS_ERRTAG_IFLUSH_3)) {
                        xfs_alert_tag(mp, XFS_PTAG_IFLUSH,
                                "%s: Bad regular inode %Lu, ptr "PTR_FMT,
                                __func__, ip->i_ino, ip);
                        goto flush_out;
                }
        } else if (S_ISDIR(VFS_I(ip)->i_mode)) {
                if (XFS_TEST_ERROR(
                    ip->i_df.if_format != XFS_DINODE_FMT_EXTENTS &&
                    ip->i_df.if_format != XFS_DINODE_FMT_BTREE &&
                    ip->i_df.if_format != XFS_DINODE_FMT_LOCAL,
                    mp, XFS_ERRTAG_IFLUSH_4)) {
                        xfs_alert_tag(mp, XFS_PTAG_IFLUSH,
                                "%s: Bad directory inode %Lu, ptr "PTR_FMT,
                                __func__, ip->i_ino, ip);
                        goto flush_out;
                }
        }
        if (XFS_TEST_ERROR(ip->i_df.if_nextents + xfs_ifork_nextents(ip->i_afp) >
                                ip->i_nblocks, mp, XFS_ERRTAG_IFLUSH_5)) {
                xfs_alert_tag(mp, XFS_PTAG_IFLUSH,
                        "%s: detected corrupt incore inode %Lu, "
                        "total extents = %d, nblocks = %Ld, ptr "PTR_FMT,
                        __func__, ip->i_ino,
                        ip->i_df.if_nextents + xfs_ifork_nextents(ip->i_afp),
                        ip->i_nblocks, ip);
                goto flush_out;
        }
        if (XFS_TEST_ERROR(ip->i_forkoff > mp->m_sb.sb_inodesize,
                                mp, XFS_ERRTAG_IFLUSH_6)) {
                xfs_alert_tag(mp, XFS_PTAG_IFLUSH,
                        "%s: bad inode %Lu, forkoff 0x%x, ptr "PTR_FMT,
                        __func__, ip->i_ino, ip->i_forkoff, ip);
                goto flush_out;
        }

        /*
         * Inode item log recovery for v2 inodes are dependent on the flushiter
         * count for correct sequencing.  We bump the flush iteration count so
         * we can detect flushes which postdate a log record during recovery.
         * This is redundant as we now log every change and hence this can't
         * happen but we need to still do it to ensure backwards compatibility
         * with old kernels that predate logging all inode changes.
         */
        if (!xfs_has_v3inodes(mp))
                ip->i_flushiter++;

        /*
         * If there are inline format data / attr forks attached to this inode,
         * make sure they are not corrupt.
         */
        if (ip->i_df.if_format == XFS_DINODE_FMT_LOCAL &&
            xfs_ifork_verify_local_data(ip))
                goto flush_out;
        if (ip->i_afp && ip->i_afp->if_format == XFS_DINODE_FMT_LOCAL &&
            xfs_ifork_verify_local_attr(ip))
                goto flush_out;

        /*
         * Copy the dirty parts of the inode into the on-disk inode.  We always
         * copy out the core of the inode, because if the inode is dirty at all
         * the core must be.
         */
        xfs_inode_to_disk(ip, dip, iip->ili_item.li_lsn);

        /* Wrap, we never let the log put out DI_MAX_FLUSH */
        if (!xfs_has_v3inodes(mp)) {
                if (ip->i_flushiter == DI_MAX_FLUSH)
                        ip->i_flushiter = 0;
        }

        xfs_iflush_fork(ip, dip, iip, XFS_DATA_FORK);
        if (XFS_IFORK_Q(ip))
                xfs_iflush_fork(ip, dip, iip, XFS_ATTR_FORK);

        /*
         * We've recorded everything logged in the inode, so we'd like to clear
         * the ili_fields bits so we don't log and flush things unnecessarily.
         * However, we can't stop logging all this information until the data
         * we've copied into the disk buffer is written to disk.  If we did we
         * might overwrite the copy of the inode in the log with all the data
         * after re-logging only part of it, and in the face of a crash we
         * wouldn't have all the data we need to recover.
         *
         * What we do is move the bits to the ili_last_fields field.  When
         * logging the inode, these bits are moved back to the ili_fields field.
         * In the xfs_buf_inode_iodone() routine we clear ili_last_fields, since
         * we know that the information those bits represent is permanently on
         * disk.  As long as the flush completes before the inode is logged
         * again, then both ili_fields and ili_last_fields will be cleared.
         */
        error = 0;
flush_out:
        spin_lock(&iip->ili_lock);
        iip->ili_last_fields = iip->ili_fields;
        iip->ili_fields = 0;
        iip->ili_fsync_fields = 0;
        spin_unlock(&iip->ili_lock);

        /*
         * Store the current LSN of the inode so that we can tell whether the
         * item has moved in the AIL from xfs_buf_inode_iodone().
         */
        xfs_trans_ail_copy_lsn(mp->m_ail, &iip->ili_flush_lsn,
                                &iip->ili_item.li_lsn);

        /* generate the checksum. */
        xfs_dinode_calc_crc(mp, dip);
        return error;
}

/*
 * Non-blocking flush of dirty inode metadata into the backing buffer.
 *
 * The caller must have a reference to the inode and hold the cluster buffer
 * locked. The function will walk across all the inodes on the cluster buffer it
 * can find and lock without blocking, and flush them to the cluster buffer.
 *
 * On successful flushing of at least one inode, the caller must write out the
 * buffer and release it. If no inodes are flushed, -EAGAIN will be returned and
 * the caller needs to release the buffer. On failure, the filesystem will be
 * shut down, the buffer will have been unlocked and released, and EFSCORRUPTED
 * will be returned.
 */
int
xfs_iflush_cluster(
        struct xfs_buf          *bp)
{
        struct xfs_mount        *mp = bp->b_mount;
        struct xfs_log_item     *lip, *n;
        struct xfs_inode        *ip;
        struct xfs_inode_log_item *iip;
        int                     clcount = 0;
        int                     error = 0;

        /*
         * We must use the safe variant here as on shutdown xfs_iflush_abort()
         * can remove itself from the list.
         */
        list_for_each_entry_safe(lip, n, &bp->b_li_list, li_bio_list) {
                iip = (struct xfs_inode_log_item *)lip;
                ip = iip->ili_inode;

                /*
                 * Quick and dirty check to avoid locks if possible.
                 */
                if (__xfs_iflags_test(ip, XFS_IRECLAIM | XFS_IFLUSHING))
                        continue;
                if (xfs_ipincount(ip))
                        continue;

                /*
                 * The inode is still attached to the buffer, which means it is
                 * dirty but reclaim might try to grab it. Check carefully for
                 * that, and grab the ilock while still holding the i_flags_lock
                 * to guarantee reclaim will not be able to reclaim this inode
                 * once we drop the i_flags_lock.
                 */
                spin_lock(&ip->i_flags_lock);
                ASSERT(!__xfs_iflags_test(ip, XFS_ISTALE));
                if (__xfs_iflags_test(ip, XFS_IRECLAIM | XFS_IFLUSHING)) {
                        spin_unlock(&ip->i_flags_lock);
                        continue;
                }

                /*
                 * ILOCK will pin the inode against reclaim and prevent
                 * concurrent transactions modifying the inode while we are
                 * flushing the inode. If we get the lock, set the flushing
                 * state before we drop the i_flags_lock.
                 */
                if (!xfs_ilock_nowait(ip, XFS_ILOCK_SHARED)) {
                        spin_unlock(&ip->i_flags_lock);
                        continue;
                }
                __xfs_iflags_set(ip, XFS_IFLUSHING);
                spin_unlock(&ip->i_flags_lock);

                /*
                 * Abort flushing this inode if we are shut down because the
                 * inode may not currently be in the AIL. This can occur when
                 * log I/O failure unpins the inode without inserting into the
                 * AIL, leaving a dirty/unpinned inode attached to the buffer
                 * that otherwise looks like it should be flushed.
                 */
                if (xfs_is_shutdown(mp)) {
                        xfs_iunpin_wait(ip);
                        xfs_iflush_abort(ip);
                        xfs_iunlock(ip, XFS_ILOCK_SHARED);
                        error = -EIO;
                        continue;
                }

                /* don't block waiting on a log force to unpin dirty inodes */
                if (xfs_ipincount(ip)) {
                        xfs_iflags_clear(ip, XFS_IFLUSHING);
                        xfs_iunlock(ip, XFS_ILOCK_SHARED);
                        continue;
                }

                if (!xfs_inode_clean(ip))
                        error = xfs_iflush(ip, bp);
                else
                        xfs_iflags_clear(ip, XFS_IFLUSHING);
                xfs_iunlock(ip, XFS_ILOCK_SHARED);
                if (error)
                        break;
                clcount++;
        }

        if (error) {
                bp->b_flags |= XBF_ASYNC;
                xfs_buf_ioend_fail(bp);
                xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
                return error;
        }

        if (!clcount)
                return -EAGAIN;

        XFS_STATS_INC(mp, xs_icluster_flushcnt);
        XFS_STATS_ADD(mp, xs_icluster_flushinode, clcount);
        return 0;

}

/* Release an inode. */
void
xfs_irele(
        struct xfs_inode        *ip)
{
        trace_xfs_irele(ip, _RET_IP_);
        iput(VFS_I(ip));
}

/*
 * Ensure all commited transactions touching the inode are written to the log.
 */
int
xfs_log_force_inode(
        struct xfs_inode        *ip)
{
        xfs_csn_t               seq = 0;

        xfs_ilock(ip, XFS_ILOCK_SHARED);
        if (xfs_ipincount(ip))
                seq = ip->i_itemp->ili_commit_seq;
        xfs_iunlock(ip, XFS_ILOCK_SHARED);

        if (!seq)
                return 0;
        return xfs_log_force_seq(ip->i_mount, seq, XFS_LOG_SYNC, NULL);
}

/*
 * Grab the exclusive iolock for a data copy from src to dest, making sure to
 * abide vfs locking order (lowest pointer value goes first) and breaking the
 * layout leases before proceeding.  The loop is needed because we cannot call
 * the blocking break_layout() with the iolocks held, and therefore have to
 * back out both locks.
 */
static int
xfs_iolock_two_inodes_and_break_layout(
        struct inode            *src,
        struct inode            *dest)
{
        int                     error;

        if (src > dest)
                swap(src, dest);

retry:
        /* Wait to break both inodes' layouts before we start locking. */
        error = break_layout(src, true);
        if (error)
                return error;
        if (src != dest) {
                error = break_layout(dest, true);
                if (error)
                        return error;
        }

        /* Lock one inode and make sure nobody got in and leased it. */
        inode_lock(src);
        error = break_layout(src, false);
        if (error) {
                inode_unlock(src);
                if (error == -EWOULDBLOCK)
                        goto retry;
                return error;
        }

        if (src == dest)
                return 0;

        /* Lock the other inode and make sure nobody got in and leased it. */
        inode_lock_nested(dest, I_MUTEX_NONDIR2);
        error = break_layout(dest, false);
        if (error) {
                inode_unlock(src);
                inode_unlock(dest);
                if (error == -EWOULDBLOCK)
                        goto retry;
                return error;
        }

        return 0;
}

/*
 * Lock two inodes so that userspace cannot initiate I/O via file syscalls or
 * mmap activity.
 */
int
xfs_ilock2_io_mmap(
        struct xfs_inode        *ip1,
        struct xfs_inode        *ip2)
{
        int                     ret;

        ret = xfs_iolock_two_inodes_and_break_layout(VFS_I(ip1), VFS_I(ip2));
        if (ret)
                return ret;
        filemap_invalidate_lock_two(VFS_I(ip1)->i_mapping,
                                    VFS_I(ip2)->i_mapping);
        return 0;
}

/* Unlock both inodes to allow IO and mmap activity. */
void
xfs_iunlock2_io_mmap(
        struct xfs_inode        *ip1,
        struct xfs_inode        *ip2)
{
        filemap_invalidate_unlock_two(VFS_I(ip1)->i_mapping,
                                      VFS_I(ip2)->i_mapping);
        inode_unlock(VFS_I(ip2));
        if (ip1 != ip2)
                inode_unlock(VFS_I(ip1));
}