Merge branch 'for-4.16-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj...

[linux-2.6-block.git] / fs / xfs / xfs_iomap.c

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 66e1edbfb2b2bcd7d278226a33f0531bb0043b97..046469fcc1b8a66075806080ca175277e2716dcd 100644 (file)
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -955,15 +955,29 @@ static inline bool imap_needs_alloc(struct inode *inode,
                (IS_DAX(inode) && imap->br_state == XFS_EXT_UNWRITTEN);
 }
 
+static inline bool needs_cow_for_zeroing(struct xfs_bmbt_irec *imap, int nimaps)
+{
+       return nimaps &&
+               imap->br_startblock != HOLESTARTBLOCK &&
+               imap->br_state != XFS_EXT_UNWRITTEN;
+}
+
 static inline bool need_excl_ilock(struct xfs_inode *ip, unsigned flags)
 {
        /*
-        * COW writes will allocate delalloc space, so we need to make sure
-        * to take the lock exclusively here.
+        * COW writes may allocate delalloc space or convert unwritten COW
+        * extents, so we need to make sure to take the lock exclusively here.
         */
        if (xfs_is_reflink_inode(ip) && (flags & (IOMAP_WRITE | IOMAP_ZERO)))
                return true;
-       if ((flags & IOMAP_DIRECT) && (flags & IOMAP_WRITE))
+
+       /*
+        * Extents not yet cached requires exclusive access, don't block.
+        * This is an opencoded xfs_ilock_data_map_shared() to cater for the
+        * non-blocking behaviour.
+        */
+       if (ip->i_d.di_format == XFS_DINODE_FMT_BTREE &&
+           !(ip->i_df.if_flags & XFS_IFEXTENTS))
                return true;
        return false;
 }
@@ -993,16 +1007,18 @@ xfs_file_iomap_begin(
                return xfs_file_iomap_begin_delay(inode, offset, length, iomap);
        }
 
-       if (need_excl_ilock(ip, flags)) {
+       if (need_excl_ilock(ip, flags))
                lockmode = XFS_ILOCK_EXCL;
-               xfs_ilock(ip, XFS_ILOCK_EXCL);
-       } else {
-               lockmode = xfs_ilock_data_map_shared(ip);
-       }
+       else
+               lockmode = XFS_ILOCK_SHARED;
 
-       if ((flags & IOMAP_NOWAIT) && !(ip->i_df.if_flags & XFS_IFEXTENTS)) {
-               error = -EAGAIN;
-               goto out_unlock;
+       if (flags & IOMAP_NOWAIT) {
+               if (!(ip->i_df.if_flags & XFS_IFEXTENTS))
+                       return -EAGAIN;
+               if (!xfs_ilock_nowait(ip, lockmode))
+                       return -EAGAIN;
+       } else {
+               xfs_ilock(ip, lockmode);
        }
 
        ASSERT(offset <= mp->m_super->s_maxbytes);
@@ -1024,7 +1040,9 @@ xfs_file_iomap_begin(
                        goto out_unlock;
        }
 
-       if ((flags & (IOMAP_WRITE | IOMAP_ZERO)) && xfs_is_reflink_inode(ip)) {
+       if (xfs_is_reflink_inode(ip) &&
+           ((flags & IOMAP_WRITE) ||
+            ((flags & IOMAP_ZERO) && needs_cow_for_zeroing(&imap, nimaps)))) {
                if (flags & IOMAP_DIRECT) {
                        /*
                         * A reflinked inode will result in CoW alloc.