Merge tag 'locking-core-2023-05-05' of git://git.kernel.org/pub/scm/linux/kernel...

[linux-block.git] / fs / nfs / nfs4state.c

/*
 *  fs/nfs/nfs4state.c
 *
 *  Client-side XDR for NFSv4.
 *
 *  Copyright (c) 2002 The Regents of the University of Michigan.
 *  All rights reserved.
 *
 *  Kendrick Smith <kmsmith@umich.edu>
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *  3. Neither the name of the University nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 *  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 *  DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 *  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 *  BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Implementation of the NFSv4 state model.  For the time being,
 * this is minimal, but will be made much more complex in a
 * subsequent patch.
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/nfs_fs.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/ratelimit.h>
#include <linux/workqueue.h>
#include <linux/bitops.h>
#include <linux/jiffies.h>
#include <linux/sched/mm.h>

#include <linux/sunrpc/clnt.h>

#include "nfs4_fs.h"
#include "callback.h"
#include "delegation.h"
#include "internal.h"
#include "nfs4idmap.h"
#include "nfs4session.h"
#include "pnfs.h"
#include "netns.h"
#include "nfs4trace.h"

#define NFSDBG_FACILITY         NFSDBG_STATE

#define OPENOWNER_POOL_SIZE     8

static void nfs4_state_start_reclaim_reboot(struct nfs_client *clp);

const nfs4_stateid zero_stateid = {
        { .data = { 0 } },
        .type = NFS4_SPECIAL_STATEID_TYPE,
};
const nfs4_stateid invalid_stateid = {
        {
                /* Funky initialiser keeps older gcc versions happy */
                .data = { 0xff, 0xff, 0xff, 0xff, 0 },
        },
        .type = NFS4_INVALID_STATEID_TYPE,
};

const nfs4_stateid current_stateid = {
        {
                /* Funky initialiser keeps older gcc versions happy */
                .data = { 0x0, 0x0, 0x0, 0x1, 0 },
        },
        .type = NFS4_SPECIAL_STATEID_TYPE,
};

static DEFINE_MUTEX(nfs_clid_init_mutex);

static int nfs4_setup_state_renewal(struct nfs_client *clp)
{
        int status;
        struct nfs_fsinfo fsinfo;

        if (!test_bit(NFS_CS_CHECK_LEASE_TIME, &clp->cl_res_state)) {
                nfs4_schedule_state_renewal(clp);
                return 0;
        }

        status = nfs4_proc_get_lease_time(clp, &fsinfo);
        if (status == 0) {
                nfs4_set_lease_period(clp, fsinfo.lease_time * HZ);
                nfs4_schedule_state_renewal(clp);
        }

        return status;
}

int nfs4_init_clientid(struct nfs_client *clp, const struct cred *cred)
{
        struct nfs4_setclientid_res clid = {
                .clientid = clp->cl_clientid,
                .confirm = clp->cl_confirm,
        };
        unsigned short port;
        int status;
        struct nfs_net *nn = net_generic(clp->cl_net, nfs_net_id);

        if (test_bit(NFS4CLNT_LEASE_CONFIRM, &clp->cl_state))
                goto do_confirm;
        port = nn->nfs_callback_tcpport;
        if (clp->cl_addr.ss_family == AF_INET6)
                port = nn->nfs_callback_tcpport6;

        status = nfs4_proc_setclientid(clp, NFS4_CALLBACK, port, cred, &clid);
        if (status != 0)
                goto out;
        clp->cl_clientid = clid.clientid;
        clp->cl_confirm = clid.confirm;
        set_bit(NFS4CLNT_LEASE_CONFIRM, &clp->cl_state);
do_confirm:
        status = nfs4_proc_setclientid_confirm(clp, &clid, cred);
        if (status != 0)
                goto out;
        clear_bit(NFS4CLNT_LEASE_CONFIRM, &clp->cl_state);
        nfs4_setup_state_renewal(clp);
out:
        return status;
}

/**
 * nfs40_discover_server_trunking - Detect server IP address trunking (mv0)
 *
 * @clp: nfs_client under test
 * @result: OUT: found nfs_client, or clp
 * @cred: credential to use for trunking test
 *
 * Returns zero, a negative errno, or a negative NFS4ERR status.
 * If zero is returned, an nfs_client pointer is planted in
 * "result".
 *
 * Note: The returned client may not yet be marked ready.
 */
int nfs40_discover_server_trunking(struct nfs_client *clp,
                                   struct nfs_client **result,
                                   const struct cred *cred)
{
        struct nfs4_setclientid_res clid = {
                .clientid = clp->cl_clientid,
                .confirm = clp->cl_confirm,
        };
        struct nfs_net *nn = net_generic(clp->cl_net, nfs_net_id);
        unsigned short port;
        int status;

        port = nn->nfs_callback_tcpport;
        if (clp->cl_addr.ss_family == AF_INET6)
                port = nn->nfs_callback_tcpport6;

        status = nfs4_proc_setclientid(clp, NFS4_CALLBACK, port, cred, &clid);
        if (status != 0)
                goto out;
        clp->cl_clientid = clid.clientid;
        clp->cl_confirm = clid.confirm;

        status = nfs40_walk_client_list(clp, result, cred);
        if (status == 0) {
                /* Sustain the lease, even if it's empty.  If the clientid4
                 * goes stale it's of no use for trunking discovery. */
                nfs4_schedule_state_renewal(*result);

                /* If the client state need to recover, do it. */
                if (clp->cl_state)
                        nfs4_schedule_state_manager(clp);
        }
out:
        return status;
}

const struct cred *nfs4_get_machine_cred(struct nfs_client *clp)
{
        return get_cred(rpc_machine_cred());
}

static void nfs4_root_machine_cred(struct nfs_client *clp)
{

        /* Force root creds instead of machine */
        clp->cl_principal = NULL;
        clp->cl_rpcclient->cl_principal = NULL;
}

static const struct cred *
nfs4_get_renew_cred_server_locked(struct nfs_server *server)
{
        const struct cred *cred = NULL;
        struct nfs4_state_owner *sp;
        struct rb_node *pos;

        for (pos = rb_first(&server->state_owners);
             pos != NULL;
             pos = rb_next(pos)) {
                sp = rb_entry(pos, struct nfs4_state_owner, so_server_node);
                if (list_empty(&sp->so_states))
                        continue;
                cred = get_cred(sp->so_cred);
                break;
        }
        return cred;
}

/**
 * nfs4_get_renew_cred - Acquire credential for a renew operation
 * @clp: client state handle
 *
 * Returns an rpc_cred with reference count bumped, or NULL.
 * Caller must hold clp->cl_lock.
 */
const struct cred *nfs4_get_renew_cred(struct nfs_client *clp)
{
        const struct cred *cred = NULL;
        struct nfs_server *server;

        /* Use machine credentials if available */
        cred = nfs4_get_machine_cred(clp);
        if (cred != NULL)
                goto out;

        spin_lock(&clp->cl_lock);
        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
                cred = nfs4_get_renew_cred_server_locked(server);
                if (cred != NULL)
                        break;
        }
        rcu_read_unlock();
        spin_unlock(&clp->cl_lock);

out:
        return cred;
}

static void nfs4_end_drain_slot_table(struct nfs4_slot_table *tbl)
{
        if (test_and_clear_bit(NFS4_SLOT_TBL_DRAINING, &tbl->slot_tbl_state)) {
                spin_lock(&tbl->slot_tbl_lock);
                nfs41_wake_slot_table(tbl);
                spin_unlock(&tbl->slot_tbl_lock);
        }
}

static void nfs4_end_drain_session(struct nfs_client *clp)
{
        struct nfs4_session *ses = clp->cl_session;

        if (clp->cl_slot_tbl) {
                nfs4_end_drain_slot_table(clp->cl_slot_tbl);
                return;
        }

        if (ses != NULL) {
                nfs4_end_drain_slot_table(&ses->bc_slot_table);
                nfs4_end_drain_slot_table(&ses->fc_slot_table);
        }
}

static int nfs4_drain_slot_tbl(struct nfs4_slot_table *tbl)
{
        set_bit(NFS4_SLOT_TBL_DRAINING, &tbl->slot_tbl_state);
        spin_lock(&tbl->slot_tbl_lock);
        if (tbl->highest_used_slotid != NFS4_NO_SLOT) {
                reinit_completion(&tbl->complete);
                spin_unlock(&tbl->slot_tbl_lock);
                return wait_for_completion_interruptible(&tbl->complete);
        }
        spin_unlock(&tbl->slot_tbl_lock);
        return 0;
}

static int nfs4_begin_drain_session(struct nfs_client *clp)
{
        struct nfs4_session *ses = clp->cl_session;
        int ret;

        if (clp->cl_slot_tbl)
                return nfs4_drain_slot_tbl(clp->cl_slot_tbl);

        /* back channel */
        ret = nfs4_drain_slot_tbl(&ses->bc_slot_table);
        if (ret)
                return ret;
        /* fore channel */
        return nfs4_drain_slot_tbl(&ses->fc_slot_table);
}

#if defined(CONFIG_NFS_V4_1)

static void nfs41_finish_session_reset(struct nfs_client *clp)
{
        clear_bit(NFS4CLNT_LEASE_CONFIRM, &clp->cl_state);
        clear_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state);
        /* create_session negotiated new slot table */
        clear_bit(NFS4CLNT_BIND_CONN_TO_SESSION, &clp->cl_state);
        nfs4_setup_state_renewal(clp);
}

int nfs41_init_clientid(struct nfs_client *clp, const struct cred *cred)
{
        int status;

        if (test_bit(NFS4CLNT_LEASE_CONFIRM, &clp->cl_state))
                goto do_confirm;
        status = nfs4_proc_exchange_id(clp, cred);
        if (status != 0)
                goto out;
        set_bit(NFS4CLNT_LEASE_CONFIRM, &clp->cl_state);
do_confirm:
        status = nfs4_proc_create_session(clp, cred);
        if (status != 0)
                goto out;
        if (!(clp->cl_exchange_flags & EXCHGID4_FLAG_CONFIRMED_R))
                nfs4_state_start_reclaim_reboot(clp);
        nfs41_finish_session_reset(clp);
        nfs_mark_client_ready(clp, NFS_CS_READY);
out:
        return status;
}

/**
 * nfs41_discover_server_trunking - Detect server IP address trunking (mv1)
 *
 * @clp: nfs_client under test
 * @result: OUT: found nfs_client, or clp
 * @cred: credential to use for trunking test
 *
 * Returns NFS4_OK, a negative errno, or a negative NFS4ERR status.
 * If NFS4_OK is returned, an nfs_client pointer is planted in
 * "result".
 *
 * Note: The returned client may not yet be marked ready.
 */
int nfs41_discover_server_trunking(struct nfs_client *clp,
                                   struct nfs_client **result,
                                   const struct cred *cred)
{
        int status;

        status = nfs4_proc_exchange_id(clp, cred);
        if (status != NFS4_OK)
                return status;

        status = nfs41_walk_client_list(clp, result, cred);
        if (status < 0)
                return status;
        if (clp != *result)
                return 0;

        /*
         * Purge state if the client id was established in a prior
         * instance and the client id could not have arrived on the
         * server via Transparent State Migration.
         */
        if (clp->cl_exchange_flags & EXCHGID4_FLAG_CONFIRMED_R) {
                if (!test_bit(NFS_CS_TSM_POSSIBLE, &clp->cl_flags))
                        set_bit(NFS4CLNT_PURGE_STATE, &clp->cl_state);
                else
                        set_bit(NFS4CLNT_LEASE_CONFIRM, &clp->cl_state);
        }
        nfs4_schedule_state_manager(clp);
        status = nfs_wait_client_init_complete(clp);
        if (status < 0)
                nfs_put_client(clp);
        return status;
}

#endif /* CONFIG_NFS_V4_1 */

/**
 * nfs4_get_clid_cred - Acquire credential for a setclientid operation
 * @clp: client state handle
 *
 * Returns a cred with reference count bumped, or NULL.
 */
const struct cred *nfs4_get_clid_cred(struct nfs_client *clp)
{
        const struct cred *cred;

        cred = nfs4_get_machine_cred(clp);
        return cred;
}

static struct nfs4_state_owner *
nfs4_find_state_owner_locked(struct nfs_server *server, const struct cred *cred)
{
        struct rb_node **p = &server->state_owners.rb_node,
                       *parent = NULL;
        struct nfs4_state_owner *sp;
        int cmp;

        while (*p != NULL) {
                parent = *p;
                sp = rb_entry(parent, struct nfs4_state_owner, so_server_node);
                cmp = cred_fscmp(cred, sp->so_cred);

                if (cmp < 0)
                        p = &parent->rb_left;
                else if (cmp > 0)
                        p = &parent->rb_right;
                else {
                        if (!list_empty(&sp->so_lru))
                                list_del_init(&sp->so_lru);
                        atomic_inc(&sp->so_count);
                        return sp;
                }
        }
        return NULL;
}

static struct nfs4_state_owner *
nfs4_insert_state_owner_locked(struct nfs4_state_owner *new)
{
        struct nfs_server *server = new->so_server;
        struct rb_node **p = &server->state_owners.rb_node,
                       *parent = NULL;
        struct nfs4_state_owner *sp;
        int cmp;

        while (*p != NULL) {
                parent = *p;
                sp = rb_entry(parent, struct nfs4_state_owner, so_server_node);
                cmp = cred_fscmp(new->so_cred, sp->so_cred);

                if (cmp < 0)
                        p = &parent->rb_left;
                else if (cmp > 0)
                        p = &parent->rb_right;
                else {
                        if (!list_empty(&sp->so_lru))
                                list_del_init(&sp->so_lru);
                        atomic_inc(&sp->so_count);
                        return sp;
                }
        }
        rb_link_node(&new->so_server_node, parent, p);
        rb_insert_color(&new->so_server_node, &server->state_owners);
        return new;
}

static void
nfs4_remove_state_owner_locked(struct nfs4_state_owner *sp)
{
        struct nfs_server *server = sp->so_server;

        if (!RB_EMPTY_NODE(&sp->so_server_node))
                rb_erase(&sp->so_server_node, &server->state_owners);
}

static void
nfs4_init_seqid_counter(struct nfs_seqid_counter *sc)
{
        sc->create_time = ktime_get();
        sc->flags = 0;
        sc->counter = 0;
        spin_lock_init(&sc->lock);
        INIT_LIST_HEAD(&sc->list);
        rpc_init_wait_queue(&sc->wait, "Seqid_waitqueue");
}

static void
nfs4_destroy_seqid_counter(struct nfs_seqid_counter *sc)
{
        rpc_destroy_wait_queue(&sc->wait);
}

/*
 * nfs4_alloc_state_owner(): this is called on the OPEN or CREATE path to
 * create a new state_owner.
 *
 */
static struct nfs4_state_owner *
nfs4_alloc_state_owner(struct nfs_server *server,
                const struct cred *cred,
                gfp_t gfp_flags)
{
        struct nfs4_state_owner *sp;

        sp = kzalloc(sizeof(*sp), gfp_flags);
        if (!sp)
                return NULL;
        sp->so_seqid.owner_id = ida_alloc(&server->openowner_id, gfp_flags);
        if (sp->so_seqid.owner_id < 0) {
                kfree(sp);
                return NULL;
        }
        sp->so_server = server;
        sp->so_cred = get_cred(cred);
        spin_lock_init(&sp->so_lock);
        INIT_LIST_HEAD(&sp->so_states);
        nfs4_init_seqid_counter(&sp->so_seqid);
        atomic_set(&sp->so_count, 1);
        INIT_LIST_HEAD(&sp->so_lru);
        seqcount_spinlock_init(&sp->so_reclaim_seqcount, &sp->so_lock);
        mutex_init(&sp->so_delegreturn_mutex);
        return sp;
}

static void
nfs4_reset_state_owner(struct nfs4_state_owner *sp)
{
        /* This state_owner is no longer usable, but must
         * remain in place so that state recovery can find it
         * and the opens associated with it.
         * It may also be used for new 'open' request to
         * return a delegation to the server.
         * So update the 'create_time' so that it looks like
         * a new state_owner.  This will cause the server to
         * request an OPEN_CONFIRM to start a new sequence.
         */
        sp->so_seqid.create_time = ktime_get();
}

static void nfs4_free_state_owner(struct nfs4_state_owner *sp)
{
        nfs4_destroy_seqid_counter(&sp->so_seqid);
        put_cred(sp->so_cred);
        ida_free(&sp->so_server->openowner_id, sp->so_seqid.owner_id);
        kfree(sp);
}

static void nfs4_gc_state_owners(struct nfs_server *server)
{
        struct nfs_client *clp = server->nfs_client;
        struct nfs4_state_owner *sp, *tmp;
        unsigned long time_min, time_max;
        LIST_HEAD(doomed);

        spin_lock(&clp->cl_lock);
        time_max = jiffies;
        time_min = (long)time_max - (long)clp->cl_lease_time;
        list_for_each_entry_safe(sp, tmp, &server->state_owners_lru, so_lru) {
                /* NB: LRU is sorted so that oldest is at the head */
                if (time_in_range(sp->so_expires, time_min, time_max))
                        break;
                list_move(&sp->so_lru, &doomed);
                nfs4_remove_state_owner_locked(sp);
        }
        spin_unlock(&clp->cl_lock);

        list_for_each_entry_safe(sp, tmp, &doomed, so_lru) {
                list_del(&sp->so_lru);
                nfs4_free_state_owner(sp);
        }
}

/**
 * nfs4_get_state_owner - Look up a state owner given a credential
 * @server: nfs_server to search
 * @cred: RPC credential to match
 * @gfp_flags: allocation mode
 *
 * Returns a pointer to an instantiated nfs4_state_owner struct, or NULL.
 */
struct nfs4_state_owner *nfs4_get_state_owner(struct nfs_server *server,
                                              const struct cred *cred,
                                              gfp_t gfp_flags)
{
        struct nfs_client *clp = server->nfs_client;
        struct nfs4_state_owner *sp, *new;

        spin_lock(&clp->cl_lock);
        sp = nfs4_find_state_owner_locked(server, cred);
        spin_unlock(&clp->cl_lock);
        if (sp != NULL)
                goto out;
        new = nfs4_alloc_state_owner(server, cred, gfp_flags);
        if (new == NULL)
                goto out;
        spin_lock(&clp->cl_lock);
        sp = nfs4_insert_state_owner_locked(new);
        spin_unlock(&clp->cl_lock);
        if (sp != new)
                nfs4_free_state_owner(new);
out:
        nfs4_gc_state_owners(server);
        return sp;
}

/**
 * nfs4_put_state_owner - Release a nfs4_state_owner
 * @sp: state owner data to release
 *
 * Note that we keep released state owners on an LRU
 * list.
 * This caches valid state owners so that they can be
 * reused, to avoid the OPEN_CONFIRM on minor version 0.
 * It also pins the uniquifier of dropped state owners for
 * a while, to ensure that those state owner names are
 * never reused.
 */
void nfs4_put_state_owner(struct nfs4_state_owner *sp)
{
        struct nfs_server *server = sp->so_server;
        struct nfs_client *clp = server->nfs_client;

        if (!atomic_dec_and_lock(&sp->so_count, &clp->cl_lock))
                return;

        sp->so_expires = jiffies;
        list_add_tail(&sp->so_lru, &server->state_owners_lru);
        spin_unlock(&clp->cl_lock);
}

/**
 * nfs4_purge_state_owners - Release all cached state owners
 * @server: nfs_server with cached state owners to release
 * @head: resulting list of state owners
 *
 * Called at umount time.  Remaining state owners will be on
 * the LRU with ref count of zero.
 * Note that the state owners are not freed, but are added
 * to the list @head, which can later be used as an argument
 * to nfs4_free_state_owners.
 */
void nfs4_purge_state_owners(struct nfs_server *server, struct list_head *head)
{
        struct nfs_client *clp = server->nfs_client;
        struct nfs4_state_owner *sp, *tmp;

        spin_lock(&clp->cl_lock);
        list_for_each_entry_safe(sp, tmp, &server->state_owners_lru, so_lru) {
                list_move(&sp->so_lru, head);
                nfs4_remove_state_owner_locked(sp);
        }
        spin_unlock(&clp->cl_lock);
}

/**
 * nfs4_free_state_owners - Release all cached state owners
 * @head: resulting list of state owners
 *
 * Frees a list of state owners that was generated by
 * nfs4_purge_state_owners
 */
void nfs4_free_state_owners(struct list_head *head)
{
        struct nfs4_state_owner *sp, *tmp;

        list_for_each_entry_safe(sp, tmp, head, so_lru) {
                list_del(&sp->so_lru);
                nfs4_free_state_owner(sp);
        }
}

static struct nfs4_state *
nfs4_alloc_open_state(void)
{
        struct nfs4_state *state;

        state = kzalloc(sizeof(*state), GFP_KERNEL_ACCOUNT);
        if (!state)
                return NULL;
        refcount_set(&state->count, 1);
        INIT_LIST_HEAD(&state->lock_states);
        spin_lock_init(&state->state_lock);
        seqlock_init(&state->seqlock);
        init_waitqueue_head(&state->waitq);
        return state;
}

void
nfs4_state_set_mode_locked(struct nfs4_state *state, fmode_t fmode)
{
        if (state->state == fmode)
                return;
        /* NB! List reordering - see the reclaim code for why.  */
        if ((fmode & FMODE_WRITE) != (state->state & FMODE_WRITE)) {
                if (fmode & FMODE_WRITE)
                        list_move(&state->open_states, &state->owner->so_states);
                else
                        list_move_tail(&state->open_states, &state->owner->so_states);
        }
        state->state = fmode;
}

static struct nfs4_state *
__nfs4_find_state_byowner(struct inode *inode, struct nfs4_state_owner *owner)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        struct nfs4_state *state;

        list_for_each_entry_rcu(state, &nfsi->open_states, inode_states) {
                if (state->owner != owner)
                        continue;
                if (!nfs4_valid_open_stateid(state))
                        continue;
                if (refcount_inc_not_zero(&state->count))
                        return state;
        }
        return NULL;
}

static void
nfs4_free_open_state(struct nfs4_state *state)
{
        kfree_rcu(state, rcu_head);
}

struct nfs4_state *
nfs4_get_open_state(struct inode *inode, struct nfs4_state_owner *owner)
{
        struct nfs4_state *state, *new;
        struct nfs_inode *nfsi = NFS_I(inode);

        rcu_read_lock();
        state = __nfs4_find_state_byowner(inode, owner);
        rcu_read_unlock();
        if (state)
                goto out;
        new = nfs4_alloc_open_state();
        spin_lock(&owner->so_lock);
        spin_lock(&inode->i_lock);
        state = __nfs4_find_state_byowner(inode, owner);
        if (state == NULL && new != NULL) {
                state = new;
                state->owner = owner;
                atomic_inc(&owner->so_count);
                ihold(inode);
                state->inode = inode;
                list_add_rcu(&state->inode_states, &nfsi->open_states);
                spin_unlock(&inode->i_lock);
                /* Note: The reclaim code dictates that we add stateless
                 * and read-only stateids to the end of the list */
                list_add_tail(&state->open_states, &owner->so_states);
                spin_unlock(&owner->so_lock);
        } else {
                spin_unlock(&inode->i_lock);
                spin_unlock(&owner->so_lock);
                if (new)
                        nfs4_free_open_state(new);
        }
out:
        return state;
}

void nfs4_put_open_state(struct nfs4_state *state)
{
        struct inode *inode = state->inode;
        struct nfs4_state_owner *owner = state->owner;

        if (!refcount_dec_and_lock(&state->count, &owner->so_lock))
                return;
        spin_lock(&inode->i_lock);
        list_del_rcu(&state->inode_states);
        list_del(&state->open_states);
        spin_unlock(&inode->i_lock);
        spin_unlock(&owner->so_lock);
        nfs4_inode_return_delegation_on_close(inode);
        iput(inode);
        nfs4_free_open_state(state);
        nfs4_put_state_owner(owner);
}

/*
 * Close the current file.
 */
static void __nfs4_close(struct nfs4_state *state,
                fmode_t fmode, gfp_t gfp_mask, int wait)
{
        struct nfs4_state_owner *owner = state->owner;
        int call_close = 0;
        fmode_t newstate;

        atomic_inc(&owner->so_count);
        /* Protect against nfs4_find_state() */
        spin_lock(&owner->so_lock);
        switch (fmode & (FMODE_READ | FMODE_WRITE)) {
                case FMODE_READ:
                        state->n_rdonly--;
                        break;
                case FMODE_WRITE:
                        state->n_wronly--;
                        break;
                case FMODE_READ|FMODE_WRITE:
                        state->n_rdwr--;
        }
        newstate = FMODE_READ|FMODE_WRITE;
        if (state->n_rdwr == 0) {
                if (state->n_rdonly == 0) {
                        newstate &= ~FMODE_READ;
                        call_close |= test_bit(NFS_O_RDONLY_STATE, &state->flags);
                        call_close |= test_bit(NFS_O_RDWR_STATE, &state->flags);
                }
                if (state->n_wronly == 0) {
                        newstate &= ~FMODE_WRITE;
                        call_close |= test_bit(NFS_O_WRONLY_STATE, &state->flags);
                        call_close |= test_bit(NFS_O_RDWR_STATE, &state->flags);
                }
                if (newstate == 0)
                        clear_bit(NFS_DELEGATED_STATE, &state->flags);
        }
        nfs4_state_set_mode_locked(state, newstate);
        spin_unlock(&owner->so_lock);

        if (!call_close) {
                nfs4_put_open_state(state);
                nfs4_put_state_owner(owner);
        } else
                nfs4_do_close(state, gfp_mask, wait);
}

void nfs4_close_state(struct nfs4_state *state, fmode_t fmode)
{
        __nfs4_close(state, fmode, GFP_KERNEL, 0);
}

void nfs4_close_sync(struct nfs4_state *state, fmode_t fmode)
{
        __nfs4_close(state, fmode, GFP_KERNEL, 1);
}

/*
 * Search the state->lock_states for an existing lock_owner
 * that is compatible with either of the given owners.
 * If the second is non-zero, then the first refers to a Posix-lock
 * owner (current->files) and the second refers to a flock/OFD
 * owner (struct file*).  In that case, prefer a match for the first
 * owner.
 * If both sorts of locks are held on the one file we cannot know
 * which stateid was intended to be used, so a "correct" choice cannot
 * be made.  Failing that, a "consistent" choice is preferable.  The
 * consistent choice we make is to prefer the first owner, that of a
 * Posix lock.
 */
static struct nfs4_lock_state *
__nfs4_find_lock_state(struct nfs4_state *state,
                       fl_owner_t fl_owner, fl_owner_t fl_owner2)
{
        struct nfs4_lock_state *pos, *ret = NULL;
        list_for_each_entry(pos, &state->lock_states, ls_locks) {
                if (pos->ls_owner == fl_owner) {
                        ret = pos;
                        break;
                }
                if (pos->ls_owner == fl_owner2)
                        ret = pos;
        }
        if (ret)
                refcount_inc(&ret->ls_count);
        return ret;
}

/*
 * Return a compatible lock_state. If no initialized lock_state structure
 * exists, return an uninitialized one.
 *
 */
static struct nfs4_lock_state *nfs4_alloc_lock_state(struct nfs4_state *state, fl_owner_t fl_owner)
{
        struct nfs4_lock_state *lsp;
        struct nfs_server *server = state->owner->so_server;

        lsp = kzalloc(sizeof(*lsp), GFP_KERNEL_ACCOUNT);
        if (lsp == NULL)
                return NULL;
        nfs4_init_seqid_counter(&lsp->ls_seqid);
        refcount_set(&lsp->ls_count, 1);
        lsp->ls_state = state;
        lsp->ls_owner = fl_owner;
        lsp->ls_seqid.owner_id = ida_alloc(&server->lockowner_id, GFP_KERNEL_ACCOUNT);
        if (lsp->ls_seqid.owner_id < 0)
                goto out_free;
        INIT_LIST_HEAD(&lsp->ls_locks);
        return lsp;
out_free:
        kfree(lsp);
        return NULL;
}

void nfs4_free_lock_state(struct nfs_server *server, struct nfs4_lock_state *lsp)
{
        ida_free(&server->lockowner_id, lsp->ls_seqid.owner_id);
        nfs4_destroy_seqid_counter(&lsp->ls_seqid);
        kfree(lsp);
}

/*
 * Return a compatible lock_state. If no initialized lock_state structure
 * exists, return an uninitialized one.
 *
 */
static struct nfs4_lock_state *nfs4_get_lock_state(struct nfs4_state *state, fl_owner_t owner)
{
        struct nfs4_lock_state *lsp, *new = NULL;
        
        for(;;) {
                spin_lock(&state->state_lock);
                lsp = __nfs4_find_lock_state(state, owner, NULL);
                if (lsp != NULL)
                        break;
                if (new != NULL) {
                        list_add(&new->ls_locks, &state->lock_states);
                        set_bit(LK_STATE_IN_USE, &state->flags);
                        lsp = new;
                        new = NULL;
                        break;
                }
                spin_unlock(&state->state_lock);
                new = nfs4_alloc_lock_state(state, owner);
                if (new == NULL)
                        return NULL;
        }
        spin_unlock(&state->state_lock);
        if (new != NULL)
                nfs4_free_lock_state(state->owner->so_server, new);
        return lsp;
}

/*
 * Release reference to lock_state, and free it if we see that
 * it is no longer in use
 */
void nfs4_put_lock_state(struct nfs4_lock_state *lsp)
{
        struct nfs_server *server;
        struct nfs4_state *state;

        if (lsp == NULL)
                return;
        state = lsp->ls_state;
        if (!refcount_dec_and_lock(&lsp->ls_count, &state->state_lock))
                return;
        list_del(&lsp->ls_locks);
        if (list_empty(&state->lock_states))
                clear_bit(LK_STATE_IN_USE, &state->flags);
        spin_unlock(&state->state_lock);
        server = state->owner->so_server;
        if (test_bit(NFS_LOCK_INITIALIZED, &lsp->ls_flags)) {
                struct nfs_client *clp = server->nfs_client;

                clp->cl_mvops->free_lock_state(server, lsp);
        } else
                nfs4_free_lock_state(server, lsp);
}

static void nfs4_fl_copy_lock(struct file_lock *dst, struct file_lock *src)
{
        struct nfs4_lock_state *lsp = src->fl_u.nfs4_fl.owner;

        dst->fl_u.nfs4_fl.owner = lsp;
        refcount_inc(&lsp->ls_count);
}

static void nfs4_fl_release_lock(struct file_lock *fl)
{
        nfs4_put_lock_state(fl->fl_u.nfs4_fl.owner);
}

static const struct file_lock_operations nfs4_fl_lock_ops = {
        .fl_copy_lock = nfs4_fl_copy_lock,
        .fl_release_private = nfs4_fl_release_lock,
};

int nfs4_set_lock_state(struct nfs4_state *state, struct file_lock *fl)
{
        struct nfs4_lock_state *lsp;

        if (fl->fl_ops != NULL)
                return 0;
        lsp = nfs4_get_lock_state(state, fl->fl_owner);
        if (lsp == NULL)
                return -ENOMEM;
        fl->fl_u.nfs4_fl.owner = lsp;
        fl->fl_ops = &nfs4_fl_lock_ops;
        return 0;
}

static int nfs4_copy_lock_stateid(nfs4_stateid *dst,
                struct nfs4_state *state,
                const struct nfs_lock_context *l_ctx)
{
        struct nfs4_lock_state *lsp;
        fl_owner_t fl_owner, fl_flock_owner;
        int ret = -ENOENT;

        if (l_ctx == NULL)
                goto out;

        if (test_bit(LK_STATE_IN_USE, &state->flags) == 0)
                goto out;

        fl_owner = l_ctx->lockowner;
        fl_flock_owner = l_ctx->open_context->flock_owner;

        spin_lock(&state->state_lock);
        lsp = __nfs4_find_lock_state(state, fl_owner, fl_flock_owner);
        if (lsp && test_bit(NFS_LOCK_LOST, &lsp->ls_flags))
                ret = -EIO;
        else if (lsp != NULL && test_bit(NFS_LOCK_INITIALIZED, &lsp->ls_flags) != 0) {
                nfs4_stateid_copy(dst, &lsp->ls_stateid);
                ret = 0;
        }
        spin_unlock(&state->state_lock);
        nfs4_put_lock_state(lsp);
out:
        return ret;
}

bool nfs4_copy_open_stateid(nfs4_stateid *dst, struct nfs4_state *state)
{
        bool ret;
        const nfs4_stateid *src;
        int seq;

        do {
                ret = false;
                src = &zero_stateid;
                seq = read_seqbegin(&state->seqlock);
                if (test_bit(NFS_OPEN_STATE, &state->flags)) {
                        src = &state->open_stateid;
                        ret = true;
                }
                nfs4_stateid_copy(dst, src);
        } while (read_seqretry(&state->seqlock, seq));
        return ret;
}

/*
 * Byte-range lock aware utility to initialize the stateid of read/write
 * requests.
 */
int nfs4_select_rw_stateid(struct nfs4_state *state,
                fmode_t fmode, const struct nfs_lock_context *l_ctx,
                nfs4_stateid *dst, const struct cred **cred)
{
        int ret;

        if (!nfs4_valid_open_stateid(state))
                return -EIO;
        if (cred != NULL)
                *cred = NULL;
        ret = nfs4_copy_lock_stateid(dst, state, l_ctx);
        if (ret == -EIO)
                /* A lost lock - don't even consider delegations */
                goto out;
        /* returns true if delegation stateid found and copied */
        if (nfs4_copy_delegation_stateid(state->inode, fmode, dst, cred)) {
                ret = 0;
                goto out;
        }
        if (ret != -ENOENT)
                /* nfs4_copy_delegation_stateid() didn't over-write
                 * dst, so it still has the lock stateid which we now
                 * choose to use.
                 */
                goto out;
        ret = nfs4_copy_open_stateid(dst, state) ? 0 : -EAGAIN;
out:
        if (nfs_server_capable(state->inode, NFS_CAP_STATEID_NFSV41))
                dst->seqid = 0;
        return ret;
}

struct nfs_seqid *nfs_alloc_seqid(struct nfs_seqid_counter *counter, gfp_t gfp_mask)
{
        struct nfs_seqid *new;

        new = kmalloc(sizeof(*new), gfp_mask);
        if (new == NULL)
                return ERR_PTR(-ENOMEM);
        new->sequence = counter;
        INIT_LIST_HEAD(&new->list);
        new->task = NULL;
        return new;
}

void nfs_release_seqid(struct nfs_seqid *seqid)
{
        struct nfs_seqid_counter *sequence;

        if (seqid == NULL || list_empty(&seqid->list))
                return;
        sequence = seqid->sequence;
        spin_lock(&sequence->lock);
        list_del_init(&seqid->list);
        if (!list_empty(&sequence->list)) {
                struct nfs_seqid *next;

                next = list_first_entry(&sequence->list,
                                struct nfs_seqid, list);
                rpc_wake_up_queued_task(&sequence->wait, next->task);
        }
        spin_unlock(&sequence->lock);
}

void nfs_free_seqid(struct nfs_seqid *seqid)
{
        nfs_release_seqid(seqid);
        kfree(seqid);
}

/*
 * Increment the seqid if the OPEN/OPEN_DOWNGRADE/CLOSE succeeded, or
 * failed with a seqid incrementing error -
 * see comments nfs4.h:seqid_mutating_error()
 */
static void nfs_increment_seqid(int status, struct nfs_seqid *seqid)
{
        switch (status) {
                case 0:
                        break;
                case -NFS4ERR_BAD_SEQID:
                        if (seqid->sequence->flags & NFS_SEQID_CONFIRMED)
                                return;
                        pr_warn_ratelimited("NFS: v4 server returned a bad"
                                        " sequence-id error on an"
                                        " unconfirmed sequence %p!\n",
                                        seqid->sequence);
                        return;
                case -NFS4ERR_STALE_CLIENTID:
                case -NFS4ERR_STALE_STATEID:
                case -NFS4ERR_BAD_STATEID:
                case -NFS4ERR_BADXDR:
                case -NFS4ERR_RESOURCE:
                case -NFS4ERR_NOFILEHANDLE:
                case -NFS4ERR_MOVED:
                        /* Non-seqid mutating errors */
                        return;
        }
        /*
         * Note: no locking needed as we are guaranteed to be first
         * on the sequence list
         */
        seqid->sequence->counter++;
}

void nfs_increment_open_seqid(int status, struct nfs_seqid *seqid)
{
        struct nfs4_state_owner *sp;

        if (seqid == NULL)
                return;

        sp = container_of(seqid->sequence, struct nfs4_state_owner, so_seqid);
        if (status == -NFS4ERR_BAD_SEQID)
                nfs4_reset_state_owner(sp);
        if (!nfs4_has_session(sp->so_server->nfs_client))
                nfs_increment_seqid(status, seqid);
}

/*
 * Increment the seqid if the LOCK/LOCKU succeeded, or
 * failed with a seqid incrementing error -
 * see comments nfs4.h:seqid_mutating_error()
 */
void nfs_increment_lock_seqid(int status, struct nfs_seqid *seqid)
{
        if (seqid != NULL)
                nfs_increment_seqid(status, seqid);
}

int nfs_wait_on_sequence(struct nfs_seqid *seqid, struct rpc_task *task)
{
        struct nfs_seqid_counter *sequence;
        int status = 0;

        if (seqid == NULL)
                goto out;
        sequence = seqid->sequence;
        spin_lock(&sequence->lock);
        seqid->task = task;
        if (list_empty(&seqid->list))
                list_add_tail(&seqid->list, &sequence->list);
        if (list_first_entry(&sequence->list, struct nfs_seqid, list) == seqid)
                goto unlock;
        rpc_sleep_on(&sequence->wait, task, NULL);
        status = -EAGAIN;
unlock:
        spin_unlock(&sequence->lock);
out:
        return status;
}

static int nfs4_run_state_manager(void *);

static void nfs4_clear_state_manager_bit(struct nfs_client *clp)
{
        clear_and_wake_up_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state);
        rpc_wake_up(&clp->cl_rpcwaitq);
}

/*
 * Schedule the nfs_client asynchronous state management routine
 */
void nfs4_schedule_state_manager(struct nfs_client *clp)
{
        struct task_struct *task;
        char buf[INET6_ADDRSTRLEN + sizeof("-manager") + 1];

        set_bit(NFS4CLNT_RUN_MANAGER, &clp->cl_state);
        if (test_and_set_bit(NFS4CLNT_MANAGER_AVAILABLE, &clp->cl_state) != 0) {
                wake_up_var(&clp->cl_state);
                return;
        }
        set_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state);
        __module_get(THIS_MODULE);
        refcount_inc(&clp->cl_count);

        /* The rcu_read_lock() is not strictly necessary, as the state
         * manager is the only thread that ever changes the rpc_xprt
         * after it's initialized.  At this point, we're single threaded. */
        rcu_read_lock();
        snprintf(buf, sizeof(buf), "%s-manager",
                        rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_ADDR));
        rcu_read_unlock();
        task = kthread_run(nfs4_run_state_manager, clp, "%s", buf);
        if (IS_ERR(task)) {
                printk(KERN_ERR "%s: kthread_run: %ld\n",
                        __func__, PTR_ERR(task));
                if (!nfs_client_init_is_complete(clp))
                        nfs_mark_client_ready(clp, PTR_ERR(task));
                nfs4_clear_state_manager_bit(clp);
                clear_bit(NFS4CLNT_MANAGER_AVAILABLE, &clp->cl_state);
                nfs_put_client(clp);
                module_put(THIS_MODULE);
        }
}

/*
 * Schedule a lease recovery attempt
 */
void nfs4_schedule_lease_recovery(struct nfs_client *clp)
{
        if (!clp)
                return;
        if (!test_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state))
                set_bit(NFS4CLNT_CHECK_LEASE, &clp->cl_state);
        dprintk("%s: scheduling lease recovery for server %s\n", __func__,
                        clp->cl_hostname);
        nfs4_schedule_state_manager(clp);
}
EXPORT_SYMBOL_GPL(nfs4_schedule_lease_recovery);

/**
 * nfs4_schedule_migration_recovery - trigger migration recovery
 *
 * @server: FSID that is migrating
 *
 * Returns zero if recovery has started, otherwise a negative NFS4ERR
 * value is returned.
 */
int nfs4_schedule_migration_recovery(const struct nfs_server *server)
{
        struct nfs_client *clp = server->nfs_client;

        if (server->fh_expire_type != NFS4_FH_PERSISTENT) {
                pr_err("NFS: volatile file handles not supported (server %s)\n",
                                clp->cl_hostname);
                return -NFS4ERR_IO;
        }

        if (test_bit(NFS_MIG_FAILED, &server->mig_status))
                return -NFS4ERR_IO;

        dprintk("%s: scheduling migration recovery for (%llx:%llx) on %s\n",
                        __func__,
                        (unsigned long long)server->fsid.major,
                        (unsigned long long)server->fsid.minor,
                        clp->cl_hostname);

        set_bit(NFS_MIG_IN_TRANSITION,
                        &((struct nfs_server *)server)->mig_status);
        set_bit(NFS4CLNT_MOVED, &clp->cl_state);

        nfs4_schedule_state_manager(clp);
        return 0;
}
EXPORT_SYMBOL_GPL(nfs4_schedule_migration_recovery);

/**
 * nfs4_schedule_lease_moved_recovery - start lease-moved recovery
 *
 * @clp: server to check for moved leases
 *
 */
void nfs4_schedule_lease_moved_recovery(struct nfs_client *clp)
{
        dprintk("%s: scheduling lease-moved recovery for client ID %llx on %s\n",
                __func__, clp->cl_clientid, clp->cl_hostname);

        set_bit(NFS4CLNT_LEASE_MOVED, &clp->cl_state);
        nfs4_schedule_state_manager(clp);
}
EXPORT_SYMBOL_GPL(nfs4_schedule_lease_moved_recovery);

int nfs4_wait_clnt_recover(struct nfs_client *clp)
{
        int res;

        might_sleep();

        refcount_inc(&clp->cl_count);
        res = wait_on_bit_action(&clp->cl_state, NFS4CLNT_MANAGER_RUNNING,
                                 nfs_wait_bit_killable,
                                 TASK_KILLABLE|TASK_FREEZABLE_UNSAFE);
        if (res)
                goto out;
        if (clp->cl_cons_state < 0)
                res = clp->cl_cons_state;
out:
        nfs_put_client(clp);
        return res;
}

int nfs4_client_recover_expired_lease(struct nfs_client *clp)
{
        unsigned int loop;
        int ret;

        for (loop = NFS4_MAX_LOOP_ON_RECOVER; loop != 0; loop--) {
                ret = nfs4_wait_clnt_recover(clp);
                if (ret != 0)
                        break;
                if (!test_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state) &&
                    !test_bit(NFS4CLNT_CHECK_LEASE,&clp->cl_state))
                        break;
                nfs4_schedule_state_manager(clp);
                ret = -EIO;
        }
        return ret;
}

/*
 * nfs40_handle_cb_pathdown - return all delegations after NFS4ERR_CB_PATH_DOWN
 * @clp: client to process
 *
 * Set the NFS4CLNT_LEASE_EXPIRED state in order to force a
 * resend of the SETCLIENTID and hence re-establish the
 * callback channel. Then return all existing delegations.
 */
static void nfs40_handle_cb_pathdown(struct nfs_client *clp)
{
        set_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state);
        nfs_expire_all_delegations(clp);
        dprintk("%s: handling CB_PATHDOWN recovery for server %s\n", __func__,
                        clp->cl_hostname);
}

void nfs4_schedule_path_down_recovery(struct nfs_client *clp)
{
        nfs40_handle_cb_pathdown(clp);
        nfs4_schedule_state_manager(clp);
}

static int nfs4_state_mark_reclaim_reboot(struct nfs_client *clp, struct nfs4_state *state)
{

        if (!nfs4_valid_open_stateid(state))
                return 0;
        set_bit(NFS_STATE_RECLAIM_REBOOT, &state->flags);
        /* Don't recover state that expired before the reboot */
        if (test_bit(NFS_STATE_RECLAIM_NOGRACE, &state->flags)) {
                clear_bit(NFS_STATE_RECLAIM_REBOOT, &state->flags);
                return 0;
        }
        set_bit(NFS_OWNER_RECLAIM_REBOOT, &state->owner->so_flags);
        set_bit(NFS4CLNT_RECLAIM_REBOOT, &clp->cl_state);
        return 1;
}

int nfs4_state_mark_reclaim_nograce(struct nfs_client *clp, struct nfs4_state *state)
{
        if (!nfs4_valid_open_stateid(state))
                return 0;
        set_bit(NFS_STATE_RECLAIM_NOGRACE, &state->flags);
        clear_bit(NFS_STATE_RECLAIM_REBOOT, &state->flags);
        set_bit(NFS_OWNER_RECLAIM_NOGRACE, &state->owner->so_flags);
        set_bit(NFS4CLNT_RECLAIM_NOGRACE, &clp->cl_state);
        return 1;
}

int nfs4_schedule_stateid_recovery(const struct nfs_server *server, struct nfs4_state *state)
{
        struct nfs_client *clp = server->nfs_client;

        if (!nfs4_state_mark_reclaim_nograce(clp, state))
                return -EBADF;
        nfs_inode_find_delegation_state_and_recover(state->inode,
                        &state->stateid);
        dprintk("%s: scheduling stateid recovery for server %s\n", __func__,
                        clp->cl_hostname);
        nfs4_schedule_state_manager(clp);
        return 0;
}
EXPORT_SYMBOL_GPL(nfs4_schedule_stateid_recovery);

static struct nfs4_lock_state *
nfs_state_find_lock_state_by_stateid(struct nfs4_state *state,
                const nfs4_stateid *stateid)
{
        struct nfs4_lock_state *pos;

        list_for_each_entry(pos, &state->lock_states, ls_locks) {
                if (!test_bit(NFS_LOCK_INITIALIZED, &pos->ls_flags))
                        continue;
                if (nfs4_stateid_match_or_older(&pos->ls_stateid, stateid))
                        return pos;
        }
        return NULL;
}

static bool nfs_state_lock_state_matches_stateid(struct nfs4_state *state,
                const nfs4_stateid *stateid)
{
        bool found = false;

        if (test_bit(LK_STATE_IN_USE, &state->flags)) {
                spin_lock(&state->state_lock);
                if (nfs_state_find_lock_state_by_stateid(state, stateid))
                        found = true;
                spin_unlock(&state->state_lock);
        }
        return found;
}

void nfs_inode_find_state_and_recover(struct inode *inode,
                const nfs4_stateid *stateid)
{
        struct nfs_client *clp = NFS_SERVER(inode)->nfs_client;
        struct nfs_inode *nfsi = NFS_I(inode);
        struct nfs_open_context *ctx;
        struct nfs4_state *state;
        bool found = false;

        rcu_read_lock();
        list_for_each_entry_rcu(ctx, &nfsi->open_files, list) {
                state = ctx->state;
                if (state == NULL)
                        continue;
                if (nfs4_stateid_match_or_older(&state->stateid, stateid) &&
                    nfs4_state_mark_reclaim_nograce(clp, state)) {
                        found = true;
                        continue;
                }
                if (test_bit(NFS_OPEN_STATE, &state->flags) &&
                    nfs4_stateid_match_or_older(&state->open_stateid, stateid) &&
                    nfs4_state_mark_reclaim_nograce(clp, state)) {
                        found = true;
                        continue;
                }
                if (nfs_state_lock_state_matches_stateid(state, stateid) &&
                    nfs4_state_mark_reclaim_nograce(clp, state))
                        found = true;
        }
        rcu_read_unlock();

        nfs_inode_find_delegation_state_and_recover(inode, stateid);
        if (found)
                nfs4_schedule_state_manager(clp);
}

static void nfs4_state_mark_open_context_bad(struct nfs4_state *state, int err)
{
        struct inode *inode = state->inode;
        struct nfs_inode *nfsi = NFS_I(inode);
        struct nfs_open_context *ctx;

        rcu_read_lock();
        list_for_each_entry_rcu(ctx, &nfsi->open_files, list) {
                if (ctx->state != state)
                        continue;
                set_bit(NFS_CONTEXT_BAD, &ctx->flags);
                pr_warn("NFSv4: state recovery failed for open file %pd2, "
                                "error = %d\n", ctx->dentry, err);
        }
        rcu_read_unlock();
}

static void nfs4_state_mark_recovery_failed(struct nfs4_state *state, int error)
{
        set_bit(NFS_STATE_RECOVERY_FAILED, &state->flags);
        nfs4_state_mark_open_context_bad(state, error);
}


static int nfs4_reclaim_locks(struct nfs4_state *state, const struct nfs4_state_recovery_ops *ops)
{
        struct inode *inode = state->inode;
        struct nfs_inode *nfsi = NFS_I(inode);
        struct file_lock *fl;
        struct nfs4_lock_state *lsp;
        int status = 0;
        struct file_lock_context *flctx = locks_inode_context(inode);
        struct list_head *list;

        if (flctx == NULL)
                return 0;

        list = &flctx->flc_posix;

        /* Guard against delegation returns and new lock/unlock calls */
        down_write(&nfsi->rwsem);
        spin_lock(&flctx->flc_lock);
restart:
        list_for_each_entry(fl, list, fl_list) {
                if (nfs_file_open_context(fl->fl_file)->state != state)
                        continue;
                spin_unlock(&flctx->flc_lock);
                status = ops->recover_lock(state, fl);
                switch (status) {
                case 0:
                        break;
                case -ETIMEDOUT:
                case -ESTALE:
                case -NFS4ERR_ADMIN_REVOKED:
                case -NFS4ERR_STALE_STATEID:
                case -NFS4ERR_BAD_STATEID:
                case -NFS4ERR_EXPIRED:
                case -NFS4ERR_NO_GRACE:
                case -NFS4ERR_STALE_CLIENTID:
                case -NFS4ERR_BADSESSION:
                case -NFS4ERR_BADSLOT:
                case -NFS4ERR_BAD_HIGH_SLOT:
                case -NFS4ERR_CONN_NOT_BOUND_TO_SESSION:
                        goto out;
                default:
                        pr_err("NFS: %s: unhandled error %d\n",
                                        __func__, status);
                        fallthrough;
                case -ENOMEM:
                case -NFS4ERR_DENIED:
                case -NFS4ERR_RECLAIM_BAD:
                case -NFS4ERR_RECLAIM_CONFLICT:
                        lsp = fl->fl_u.nfs4_fl.owner;
                        if (lsp)
                                set_bit(NFS_LOCK_LOST, &lsp->ls_flags);
                        status = 0;
                }
                spin_lock(&flctx->flc_lock);
        }
        if (list == &flctx->flc_posix) {
                list = &flctx->flc_flock;
                goto restart;
        }
        spin_unlock(&flctx->flc_lock);
out:
        up_write(&nfsi->rwsem);
        return status;
}

#ifdef CONFIG_NFS_V4_2
static void nfs42_complete_copies(struct nfs4_state_owner *sp, struct nfs4_state *state)
{
        struct nfs4_copy_state *copy;

        if (!test_bit(NFS_CLNT_DST_SSC_COPY_STATE, &state->flags) &&
                !test_bit(NFS_CLNT_SRC_SSC_COPY_STATE, &state->flags))
                return;

        spin_lock(&sp->so_server->nfs_client->cl_lock);
        list_for_each_entry(copy, &sp->so_server->ss_copies, copies) {
                if ((test_bit(NFS_CLNT_DST_SSC_COPY_STATE, &state->flags) &&
                                !nfs4_stateid_match_other(&state->stateid,
                                &copy->parent_dst_state->stateid)))
                                continue;
                copy->flags = 1;
                if (test_and_clear_bit(NFS_CLNT_DST_SSC_COPY_STATE,
                                &state->flags)) {
                        clear_bit(NFS_CLNT_SRC_SSC_COPY_STATE, &state->flags);
                        complete(&copy->completion);
                }
        }
        list_for_each_entry(copy, &sp->so_server->ss_copies, src_copies) {
                if ((test_bit(NFS_CLNT_SRC_SSC_COPY_STATE, &state->flags) &&
                                !nfs4_stateid_match_other(&state->stateid,
                                &copy->parent_src_state->stateid)))
                                continue;
                copy->flags = 1;
                if (test_and_clear_bit(NFS_CLNT_DST_SSC_COPY_STATE,
                                &state->flags))
                        complete(&copy->completion);
        }
        spin_unlock(&sp->so_server->nfs_client->cl_lock);
}
#else /* !CONFIG_NFS_V4_2 */
static inline void nfs42_complete_copies(struct nfs4_state_owner *sp,
                                         struct nfs4_state *state)
{
}
#endif /* CONFIG_NFS_V4_2 */

static int __nfs4_reclaim_open_state(struct nfs4_state_owner *sp, struct nfs4_state *state,
                                     const struct nfs4_state_recovery_ops *ops,
                                     int *lost_locks)
{
        struct nfs4_lock_state *lock;
        int status;

        status = ops->recover_open(sp, state);
        if (status < 0)
                return status;

        status = nfs4_reclaim_locks(state, ops);
        if (status < 0)
                return status;

        if (!test_bit(NFS_DELEGATED_STATE, &state->flags)) {
                spin_lock(&state->state_lock);
                list_for_each_entry(lock, &state->lock_states, ls_locks) {
                        trace_nfs4_state_lock_reclaim(state, lock);
                        if (!test_bit(NFS_LOCK_INITIALIZED, &lock->ls_flags) &&
                            !test_bit(NFS_LOCK_UNLOCKING, &lock->ls_flags))
                                *lost_locks += 1;
                }
                spin_unlock(&state->state_lock);
        }

        nfs42_complete_copies(sp, state);
        clear_bit(NFS_STATE_RECLAIM_NOGRACE, &state->flags);
        return status;
}

static int nfs4_reclaim_open_state(struct nfs4_state_owner *sp,
                                   const struct nfs4_state_recovery_ops *ops,
                                   int *lost_locks)
{
        struct nfs4_state *state;
        unsigned int loop = 0;
        int status = 0;
#ifdef CONFIG_NFS_V4_2
        bool found_ssc_copy_state = false;
#endif /* CONFIG_NFS_V4_2 */

        /* Note: we rely on the sp->so_states list being ordered 
         * so that we always reclaim open(O_RDWR) and/or open(O_WRITE)
         * states first.
         * This is needed to ensure that the server won't give us any
         * read delegations that we have to return if, say, we are
         * recovering after a network partition or a reboot from a
         * server that doesn't support a grace period.
         */
        spin_lock(&sp->so_lock);
        raw_write_seqcount_begin(&sp->so_reclaim_seqcount);
restart:
        list_for_each_entry(state, &sp->so_states, open_states) {
                if (!test_and_clear_bit(ops->state_flag_bit, &state->flags))
                        continue;
                if (!nfs4_valid_open_stateid(state))
                        continue;
                if (state->state == 0)
                        continue;
#ifdef CONFIG_NFS_V4_2
                if (test_bit(NFS_SRV_SSC_COPY_STATE, &state->flags)) {
                        nfs4_state_mark_recovery_failed(state, -EIO);
                        found_ssc_copy_state = true;
                        continue;
                }
#endif /* CONFIG_NFS_V4_2 */
                refcount_inc(&state->count);
                spin_unlock(&sp->so_lock);
                status = __nfs4_reclaim_open_state(sp, state, ops, lost_locks);

                switch (status) {
                default:
                        if (status >= 0) {
                                loop = 0;
                                break;
                        }
                        printk(KERN_ERR "NFS: %s: unhandled error %d\n", __func__, status);
                        fallthrough;
                case -ENOENT:
                case -ENOMEM:
                case -EACCES:
                case -EROFS:
                case -EIO:
                case -ESTALE:
                        /* Open state on this file cannot be recovered */
                        nfs4_state_mark_recovery_failed(state, status);
                        break;
                case -EAGAIN:
                        ssleep(1);
                        if (loop++ < 10) {
                                set_bit(ops->state_flag_bit, &state->flags);
                                break;
                        }
                        fallthrough;
                case -NFS4ERR_ADMIN_REVOKED:
                case -NFS4ERR_STALE_STATEID:
                case -NFS4ERR_OLD_STATEID:
                case -NFS4ERR_BAD_STATEID:
                case -NFS4ERR_RECLAIM_BAD:
                case -NFS4ERR_RECLAIM_CONFLICT:
                        nfs4_state_mark_reclaim_nograce(sp->so_server->nfs_client, state);
                        break;
                case -NFS4ERR_EXPIRED:
                case -NFS4ERR_NO_GRACE:
                        nfs4_state_mark_reclaim_nograce(sp->so_server->nfs_client, state);
                        fallthrough;
                case -NFS4ERR_STALE_CLIENTID:
                case -NFS4ERR_BADSESSION:
                case -NFS4ERR_BADSLOT:
                case -NFS4ERR_BAD_HIGH_SLOT:
                case -NFS4ERR_CONN_NOT_BOUND_TO_SESSION:
                case -ETIMEDOUT:
                        goto out_err;
                }
                nfs4_put_open_state(state);
                spin_lock(&sp->so_lock);
                goto restart;
        }
        raw_write_seqcount_end(&sp->so_reclaim_seqcount);
        spin_unlock(&sp->so_lock);
#ifdef CONFIG_NFS_V4_2
        if (found_ssc_copy_state)
                return -EIO;
#endif /* CONFIG_NFS_V4_2 */
        return 0;
out_err:
        nfs4_put_open_state(state);
        spin_lock(&sp->so_lock);
        raw_write_seqcount_end(&sp->so_reclaim_seqcount);
        spin_unlock(&sp->so_lock);
        return status;
}

static void nfs4_clear_open_state(struct nfs4_state *state)
{
        struct nfs4_lock_state *lock;

        clear_bit(NFS_DELEGATED_STATE, &state->flags);
        clear_bit(NFS_O_RDONLY_STATE, &state->flags);
        clear_bit(NFS_O_WRONLY_STATE, &state->flags);
        clear_bit(NFS_O_RDWR_STATE, &state->flags);
        spin_lock(&state->state_lock);
        list_for_each_entry(lock, &state->lock_states, ls_locks) {
                lock->ls_seqid.flags = 0;
                clear_bit(NFS_LOCK_INITIALIZED, &lock->ls_flags);
        }
        spin_unlock(&state->state_lock);
}

static void nfs4_reset_seqids(struct nfs_server *server,
        int (*mark_reclaim)(struct nfs_client *clp, struct nfs4_state *state))
{
        struct nfs_client *clp = server->nfs_client;
        struct nfs4_state_owner *sp;
        struct rb_node *pos;
        struct nfs4_state *state;

        spin_lock(&clp->cl_lock);
        for (pos = rb_first(&server->state_owners);
             pos != NULL;
             pos = rb_next(pos)) {
                sp = rb_entry(pos, struct nfs4_state_owner, so_server_node);
                sp->so_seqid.flags = 0;
                spin_lock(&sp->so_lock);
                list_for_each_entry(state, &sp->so_states, open_states) {
                        if (mark_reclaim(clp, state))
                                nfs4_clear_open_state(state);
                }
                spin_unlock(&sp->so_lock);
        }
        spin_unlock(&clp->cl_lock);
}

static void nfs4_state_mark_reclaim_helper(struct nfs_client *clp,
        int (*mark_reclaim)(struct nfs_client *clp, struct nfs4_state *state))
{
        struct nfs_server *server;

        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
                nfs4_reset_seqids(server, mark_reclaim);
        rcu_read_unlock();
}

static void nfs4_state_start_reclaim_reboot(struct nfs_client *clp)
{
        set_bit(NFS4CLNT_RECLAIM_REBOOT, &clp->cl_state);
        /* Mark all delegations for reclaim */
        nfs_delegation_mark_reclaim(clp);
        nfs4_state_mark_reclaim_helper(clp, nfs4_state_mark_reclaim_reboot);
}

static int nfs4_reclaim_complete(struct nfs_client *clp,
                                 const struct nfs4_state_recovery_ops *ops,
                                 const struct cred *cred)
{
        /* Notify the server we're done reclaiming our state */
        if (ops->reclaim_complete)
                return ops->reclaim_complete(clp, cred);
        return 0;
}

static void nfs4_clear_reclaim_server(struct nfs_server *server)
{
        struct nfs_client *clp = server->nfs_client;
        struct nfs4_state_owner *sp;
        struct rb_node *pos;
        struct nfs4_state *state;

        spin_lock(&clp->cl_lock);
        for (pos = rb_first(&server->state_owners);
             pos != NULL;
             pos = rb_next(pos)) {
                sp = rb_entry(pos, struct nfs4_state_owner, so_server_node);
                spin_lock(&sp->so_lock);
                list_for_each_entry(state, &sp->so_states, open_states) {
                        if (!test_and_clear_bit(NFS_STATE_RECLAIM_REBOOT,
                                                &state->flags))
                                continue;
                        nfs4_state_mark_reclaim_nograce(clp, state);
                }
                spin_unlock(&sp->so_lock);
        }
        spin_unlock(&clp->cl_lock);
}

static int nfs4_state_clear_reclaim_reboot(struct nfs_client *clp)
{
        struct nfs_server *server;

        if (!test_and_clear_bit(NFS4CLNT_RECLAIM_REBOOT, &clp->cl_state))
                return 0;

        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
                nfs4_clear_reclaim_server(server);
        rcu_read_unlock();

        nfs_delegation_reap_unclaimed(clp);
        return 1;
}

static void nfs4_state_end_reclaim_reboot(struct nfs_client *clp)
{
        const struct nfs4_state_recovery_ops *ops;
        const struct cred *cred;
        int err;

        if (!nfs4_state_clear_reclaim_reboot(clp))
                return;
        ops = clp->cl_mvops->reboot_recovery_ops;
        cred = nfs4_get_clid_cred(clp);
        err = nfs4_reclaim_complete(clp, ops, cred);
        put_cred(cred);
        if (err == -NFS4ERR_CONN_NOT_BOUND_TO_SESSION)
                set_bit(NFS4CLNT_RECLAIM_REBOOT, &clp->cl_state);
}

static void nfs4_state_start_reclaim_nograce(struct nfs_client *clp)
{
        nfs_mark_test_expired_all_delegations(clp);
        nfs4_state_mark_reclaim_helper(clp, nfs4_state_mark_reclaim_nograce);
}

static int nfs4_recovery_handle_error(struct nfs_client *clp, int error)
{
        switch (error) {
        case 0:
                break;
        case -NFS4ERR_CB_PATH_DOWN:
                nfs40_handle_cb_pathdown(clp);
                break;
        case -NFS4ERR_NO_GRACE:
                nfs4_state_end_reclaim_reboot(clp);
                break;
        case -NFS4ERR_STALE_CLIENTID:
                set_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state);
                nfs4_state_start_reclaim_reboot(clp);
                break;
        case -NFS4ERR_EXPIRED:
                set_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state);
                nfs4_state_start_reclaim_nograce(clp);
                break;
        case -NFS4ERR_BADSESSION:
        case -NFS4ERR_BADSLOT:
        case -NFS4ERR_BAD_HIGH_SLOT:
        case -NFS4ERR_DEADSESSION:
        case -NFS4ERR_SEQ_FALSE_RETRY:
        case -NFS4ERR_SEQ_MISORDERED:
                set_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state);
                /* Zero session reset errors */
                break;
        case -NFS4ERR_CONN_NOT_BOUND_TO_SESSION:
                set_bit(NFS4CLNT_BIND_CONN_TO_SESSION, &clp->cl_state);
                break;
        default:
                dprintk("%s: failed to handle error %d for server %s\n",
                                __func__, error, clp->cl_hostname);
                return error;
        }
        dprintk("%s: handled error %d for server %s\n", __func__, error,
                        clp->cl_hostname);
        return 0;
}

static int nfs4_do_reclaim(struct nfs_client *clp, const struct nfs4_state_recovery_ops *ops)
{
        struct nfs4_state_owner *sp;
        struct nfs_server *server;
        struct rb_node *pos;
        LIST_HEAD(freeme);
        int status = 0;
        int lost_locks = 0;

restart:
        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
                nfs4_purge_state_owners(server, &freeme);
                spin_lock(&clp->cl_lock);
                for (pos = rb_first(&server->state_owners);
                     pos != NULL;
                     pos = rb_next(pos)) {
                        sp = rb_entry(pos,
                                struct nfs4_state_owner, so_server_node);
                        if (!test_and_clear_bit(ops->owner_flag_bit,
                                                        &sp->so_flags))
                                continue;
                        if (!atomic_inc_not_zero(&sp->so_count))
                                continue;
                        spin_unlock(&clp->cl_lock);
                        rcu_read_unlock();

                        status = nfs4_reclaim_open_state(sp, ops, &lost_locks);
                        if (status < 0) {
                                if (lost_locks)
                                        pr_warn("NFS: %s: lost %d locks\n",
                                                clp->cl_hostname, lost_locks);
                                set_bit(ops->owner_flag_bit, &sp->so_flags);
                                nfs4_put_state_owner(sp);
                                status = nfs4_recovery_handle_error(clp, status);
                                return (status != 0) ? status : -EAGAIN;
                        }

                        nfs4_put_state_owner(sp);
                        goto restart;
                }
                spin_unlock(&clp->cl_lock);
        }
        rcu_read_unlock();
        nfs4_free_state_owners(&freeme);
        if (lost_locks)
                pr_warn("NFS: %s: lost %d locks\n",
                        clp->cl_hostname, lost_locks);
        return 0;
}

static int nfs4_check_lease(struct nfs_client *clp)
{
        const struct cred *cred;
        const struct nfs4_state_maintenance_ops *ops =
                clp->cl_mvops->state_renewal_ops;
        int status;

        /* Is the client already known to have an expired lease? */
        if (test_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state))
                return 0;
        cred = ops->get_state_renewal_cred(clp);
        if (cred == NULL) {
                cred = nfs4_get_clid_cred(clp);
                status = -ENOKEY;
                if (cred == NULL)
                        goto out;
        }
        status = ops->renew_lease(clp, cred);
        put_cred(cred);
        if (status == -ETIMEDOUT) {
                set_bit(NFS4CLNT_CHECK_LEASE, &clp->cl_state);
                return 0;
        }
out:
        return nfs4_recovery_handle_error(clp, status);
}

/* Set NFS4CLNT_LEASE_EXPIRED and reclaim reboot state for all v4.0 errors
 * and for recoverable errors on EXCHANGE_ID for v4.1
 */
static int nfs4_handle_reclaim_lease_error(struct nfs_client *clp, int status)
{
        switch (status) {
        case -NFS4ERR_SEQ_MISORDERED:
                if (test_and_set_bit(NFS4CLNT_PURGE_STATE, &clp->cl_state))
                        return -ESERVERFAULT;
                /* Lease confirmation error: retry after purging the lease */
                ssleep(1);
                clear_bit(NFS4CLNT_LEASE_CONFIRM, &clp->cl_state);
                break;
        case -NFS4ERR_STALE_CLIENTID:
                clear_bit(NFS4CLNT_LEASE_CONFIRM, &clp->cl_state);
                nfs4_state_start_reclaim_reboot(clp);
                break;
        case -NFS4ERR_CLID_INUSE:
                pr_err("NFS: Server %s reports our clientid is in use\n",
                        clp->cl_hostname);
                nfs_mark_client_ready(clp, -EPERM);
                clear_bit(NFS4CLNT_LEASE_CONFIRM, &clp->cl_state);
                return -EPERM;
        case -EACCES:
        case -NFS4ERR_DELAY:
        case -EAGAIN:
                ssleep(1);
                break;

        case -NFS4ERR_MINOR_VERS_MISMATCH:
                if (clp->cl_cons_state == NFS_CS_SESSION_INITING)
                        nfs_mark_client_ready(clp, -EPROTONOSUPPORT);
                dprintk("%s: exit with error %d for server %s\n",
                                __func__, -EPROTONOSUPPORT, clp->cl_hostname);
                return -EPROTONOSUPPORT;
        case -ENOSPC:
                if (clp->cl_cons_state == NFS_CS_SESSION_INITING)
                        nfs_mark_client_ready(clp, -EIO);
                return -EIO;
        case -NFS4ERR_NOT_SAME: /* FixMe: implement recovery
                                 * in nfs4_exchange_id */
        default:
                dprintk("%s: exit with error %d for server %s\n", __func__,
                                status, clp->cl_hostname);
                return status;
        }
        set_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state);
        dprintk("%s: handled error %d for server %s\n", __func__, status,
                        clp->cl_hostname);
        return 0;
}

static int nfs4_establish_lease(struct nfs_client *clp)
{
        const struct cred *cred;
        const struct nfs4_state_recovery_ops *ops =
                clp->cl_mvops->reboot_recovery_ops;
        int status;

        status = nfs4_begin_drain_session(clp);
        if (status != 0)
                return status;
        cred = nfs4_get_clid_cred(clp);
        if (cred == NULL)
                return -ENOENT;
        status = ops->establish_clid(clp, cred);
        put_cred(cred);
        if (status != 0)
                return status;
        pnfs_destroy_all_layouts(clp);
        return 0;
}

/*
 * Returns zero or a negative errno.  NFS4ERR values are converted
 * to local errno values.
 */
static int nfs4_reclaim_lease(struct nfs_client *clp)
{
        int status;

        status = nfs4_establish_lease(clp);
        if (status < 0)
                return nfs4_handle_reclaim_lease_error(clp, status);
        if (test_and_clear_bit(NFS4CLNT_SERVER_SCOPE_MISMATCH, &clp->cl_state))
                nfs4_state_start_reclaim_nograce(clp);
        if (!test_bit(NFS4CLNT_RECLAIM_NOGRACE, &clp->cl_state))
                set_bit(NFS4CLNT_RECLAIM_REBOOT, &clp->cl_state);
        clear_bit(NFS4CLNT_CHECK_LEASE, &clp->cl_state);
        clear_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state);
        return 0;
}

static int nfs4_purge_lease(struct nfs_client *clp)
{
        int status;

        status = nfs4_establish_lease(clp);
        if (status < 0)
                return nfs4_handle_reclaim_lease_error(clp, status);
        clear_bit(NFS4CLNT_PURGE_STATE, &clp->cl_state);
        set_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state);
        nfs4_state_start_reclaim_nograce(clp);
        return 0;
}

/*
 * Try remote migration of one FSID from a source server to a
 * destination server.  The source server provides a list of
 * potential destinations.
 *
 * Returns zero or a negative NFS4ERR status code.
 */
static int nfs4_try_migration(struct nfs_server *server, const struct cred *cred)
{
        struct nfs_client *clp = server->nfs_client;
        struct nfs4_fs_locations *locations = NULL;
        struct inode *inode;
        struct page *page;
        int status, result;

        dprintk("--> %s: FSID %llx:%llx on \"%s\"\n", __func__,
                        (unsigned long long)server->fsid.major,
                        (unsigned long long)server->fsid.minor,
                        clp->cl_hostname);

        result = 0;
        page = alloc_page(GFP_KERNEL);
        locations = kmalloc(sizeof(struct nfs4_fs_locations), GFP_KERNEL);
        if (page == NULL || locations == NULL) {
                dprintk("<-- %s: no memory\n", __func__);
                goto out;
        }
        locations->fattr = nfs_alloc_fattr();
        if (locations->fattr == NULL) {
                dprintk("<-- %s: no memory\n", __func__);
                goto out;
        }

        inode = d_inode(server->super->s_root);
        result = nfs4_proc_get_locations(server, NFS_FH(inode), locations,
                                         page, cred);
        if (result) {
                dprintk("<-- %s: failed to retrieve fs_locations: %d\n",
                        __func__, result);
                goto out;
        }

        result = -NFS4ERR_NXIO;
        if (!locations->nlocations)
                goto out;

        if (!(locations->fattr->valid & NFS_ATTR_FATTR_V4_LOCATIONS)) {
                dprintk("<-- %s: No fs_locations data, migration skipped\n",
                        __func__);
                goto out;
        }

        status = nfs4_begin_drain_session(clp);
        if (status != 0) {
                result = status;
                goto out;
        }

        status = nfs4_replace_transport(server, locations);
        if (status != 0) {
                dprintk("<-- %s: failed to replace transport: %d\n",
                        __func__, status);
                goto out;
        }

        result = 0;
        dprintk("<-- %s: migration succeeded\n", __func__);

out:
        if (page != NULL)
                __free_page(page);
        if (locations != NULL)
                kfree(locations->fattr);
        kfree(locations);
        if (result) {
                pr_err("NFS: migration recovery failed (server %s)\n",
                                clp->cl_hostname);
                set_bit(NFS_MIG_FAILED, &server->mig_status);
        }
        return result;
}

/*
 * Returns zero or a negative NFS4ERR status code.
 */
static int nfs4_handle_migration(struct nfs_client *clp)
{
        const struct nfs4_state_maintenance_ops *ops =
                                clp->cl_mvops->state_renewal_ops;
        struct nfs_server *server;
        const struct cred *cred;

        dprintk("%s: migration reported on \"%s\"\n", __func__,
                        clp->cl_hostname);

        cred = ops->get_state_renewal_cred(clp);
        if (cred == NULL)
                return -NFS4ERR_NOENT;

        clp->cl_mig_gen++;
restart:
        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
                int status;

                if (server->mig_gen == clp->cl_mig_gen)
                        continue;
                server->mig_gen = clp->cl_mig_gen;

                if (!test_and_clear_bit(NFS_MIG_IN_TRANSITION,
                                                &server->mig_status))
                        continue;

                rcu_read_unlock();
                status = nfs4_try_migration(server, cred);
                if (status < 0) {
                        put_cred(cred);
                        return status;
                }
                goto restart;
        }
        rcu_read_unlock();
        put_cred(cred);
        return 0;
}

/*
 * Test each nfs_server on the clp's cl_superblocks list to see
 * if it's moved to another server.  Stop when the server no longer
 * returns NFS4ERR_LEASE_MOVED.
 */
static int nfs4_handle_lease_moved(struct nfs_client *clp)
{
        const struct nfs4_state_maintenance_ops *ops =
                                clp->cl_mvops->state_renewal_ops;
        struct nfs_server *server;
        const struct cred *cred;

        dprintk("%s: lease moved reported on \"%s\"\n", __func__,
                        clp->cl_hostname);

        cred = ops->get_state_renewal_cred(clp);
        if (cred == NULL)
                return -NFS4ERR_NOENT;

        clp->cl_mig_gen++;
restart:
        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
                struct inode *inode;
                int status;

                if (server->mig_gen == clp->cl_mig_gen)
                        continue;
                server->mig_gen = clp->cl_mig_gen;

                rcu_read_unlock();

                inode = d_inode(server->super->s_root);
                status = nfs4_proc_fsid_present(inode, cred);
                if (status != -NFS4ERR_MOVED)
                        goto restart;   /* wasn't this one */
                if (nfs4_try_migration(server, cred) == -NFS4ERR_LEASE_MOVED)
                        goto restart;   /* there are more */
                goto out;
        }
        rcu_read_unlock();

out:
        put_cred(cred);
        return 0;
}

/**
 * nfs4_discover_server_trunking - Detect server IP address trunking
 *
 * @clp: nfs_client under test
 * @result: OUT: found nfs_client, or clp
 *
 * Returns zero or a negative errno.  If zero is returned,
 * an nfs_client pointer is planted in "result".
 *
 * Note: since we are invoked in process context, and
 * not from inside the state manager, we cannot use
 * nfs4_handle_reclaim_lease_error().
 */
int nfs4_discover_server_trunking(struct nfs_client *clp,
                                  struct nfs_client **result)
{
        const struct nfs4_state_recovery_ops *ops =
                                clp->cl_mvops->reboot_recovery_ops;
        struct rpc_clnt *clnt;
        const struct cred *cred;
        int i, status;

        dprintk("NFS: %s: testing '%s'\n", __func__, clp->cl_hostname);

        clnt = clp->cl_rpcclient;
        i = 0;

        mutex_lock(&nfs_clid_init_mutex);
again:
        status  = -ENOENT;
        cred = nfs4_get_clid_cred(clp);
        if (cred == NULL)
                goto out_unlock;

        status = ops->detect_trunking(clp, result, cred);
        put_cred(cred);
        switch (status) {
        case 0:
        case -EINTR:
        case -ERESTARTSYS:
                break;
        case -ETIMEDOUT:
                if (clnt->cl_softrtry)
                        break;
                fallthrough;
        case -NFS4ERR_DELAY:
        case -EAGAIN:
                ssleep(1);
                fallthrough;
        case -NFS4ERR_STALE_CLIENTID:
                dprintk("NFS: %s after status %d, retrying\n",
                        __func__, status);
                goto again;
        case -EACCES:
                if (i++ == 0) {
                        nfs4_root_machine_cred(clp);
                        goto again;
                }
                if (clnt->cl_auth->au_flavor == RPC_AUTH_UNIX)
                        break;
                fallthrough;
        case -NFS4ERR_CLID_INUSE:
        case -NFS4ERR_WRONGSEC:
                /* No point in retrying if we already used RPC_AUTH_UNIX */
                if (clnt->cl_auth->au_flavor == RPC_AUTH_UNIX) {
                        status = -EPERM;
                        break;
                }
                clnt = rpc_clone_client_set_auth(clnt, RPC_AUTH_UNIX);
                if (IS_ERR(clnt)) {
                        status = PTR_ERR(clnt);
                        break;
                }
                /* Note: this is safe because we haven't yet marked the
                 * client as ready, so we are the only user of
                 * clp->cl_rpcclient
                 */
                clnt = xchg(&clp->cl_rpcclient, clnt);
                rpc_shutdown_client(clnt);
                clnt = clp->cl_rpcclient;
                goto again;

        case -NFS4ERR_MINOR_VERS_MISMATCH:
                status = -EPROTONOSUPPORT;
                break;

        case -EKEYEXPIRED:
        case -NFS4ERR_NOT_SAME: /* FixMe: implement recovery
                                 * in nfs4_exchange_id */
                status = -EKEYEXPIRED;
                break;
        default:
                pr_warn("NFS: %s unhandled error %d. Exiting with error EIO\n",
                                __func__, status);
                status = -EIO;
        }

out_unlock:
        mutex_unlock(&nfs_clid_init_mutex);
        dprintk("NFS: %s: status = %d\n", __func__, status);
        return status;
}

#ifdef CONFIG_NFS_V4_1
void nfs4_schedule_session_recovery(struct nfs4_session *session, int err)
{
        struct nfs_client *clp = session->clp;

        switch (err) {
        default:
                set_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state);
                break;
        case -NFS4ERR_CONN_NOT_BOUND_TO_SESSION:
                set_bit(NFS4CLNT_BIND_CONN_TO_SESSION, &clp->cl_state);
        }
        nfs4_schedule_state_manager(clp);
}
EXPORT_SYMBOL_GPL(nfs4_schedule_session_recovery);

void nfs41_notify_server(struct nfs_client *clp)
{
        /* Use CHECK_LEASE to ping the server with a SEQUENCE */
        set_bit(NFS4CLNT_CHECK_LEASE, &clp->cl_state);
        nfs4_schedule_state_manager(clp);
}

static void nfs4_reset_all_state(struct nfs_client *clp)
{
        if (test_and_set_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state) == 0) {
                set_bit(NFS4CLNT_PURGE_STATE, &clp->cl_state);
                clear_bit(NFS4CLNT_LEASE_CONFIRM, &clp->cl_state);
                nfs4_state_start_reclaim_nograce(clp);
                dprintk("%s: scheduling reset of all state for server %s!\n",
                                __func__, clp->cl_hostname);
                nfs4_schedule_state_manager(clp);
        }
}

static void nfs41_handle_server_reboot(struct nfs_client *clp)
{
        if (test_and_set_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state) == 0) {
                nfs4_state_start_reclaim_reboot(clp);
                dprintk("%s: server %s rebooted!\n", __func__,
                                clp->cl_hostname);
                nfs4_schedule_state_manager(clp);
        }
}

static void nfs41_handle_all_state_revoked(struct nfs_client *clp)
{
        nfs4_reset_all_state(clp);
        dprintk("%s: state revoked on server %s\n", __func__, clp->cl_hostname);
}

static void nfs41_handle_some_state_revoked(struct nfs_client *clp)
{
        nfs4_state_start_reclaim_nograce(clp);
        nfs4_schedule_state_manager(clp);

        dprintk("%s: state revoked on server %s\n", __func__, clp->cl_hostname);
}

static void nfs41_handle_recallable_state_revoked(struct nfs_client *clp)
{
        /* FIXME: For now, we destroy all layouts. */
        pnfs_destroy_all_layouts(clp);
        nfs_test_expired_all_delegations(clp);
        dprintk("%s: Recallable state revoked on server %s!\n", __func__,
                        clp->cl_hostname);
}

static void nfs41_handle_backchannel_fault(struct nfs_client *clp)
{
        set_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state);
        nfs4_schedule_state_manager(clp);

        dprintk("%s: server %s declared a backchannel fault\n", __func__,
                        clp->cl_hostname);
}

static void nfs41_handle_cb_path_down(struct nfs_client *clp)
{
        if (test_and_set_bit(NFS4CLNT_BIND_CONN_TO_SESSION,
                &clp->cl_state) == 0)
                nfs4_schedule_state_manager(clp);
}

void nfs41_handle_sequence_flag_errors(struct nfs_client *clp, u32 flags,
                bool recovery)
{
        if (!flags)
                return;

        dprintk("%s: \"%s\" (client ID %llx) flags=0x%08x\n",
                __func__, clp->cl_hostname, clp->cl_clientid, flags);
        /*
         * If we're called from the state manager thread, then assume we're
         * already handling the RECLAIM_NEEDED and/or STATE_REVOKED.
         * Those flags are expected to remain set until we're done
         * recovering (see RFC5661, section 18.46.3).
         */
        if (recovery)
                goto out_recovery;

        if (flags & SEQ4_STATUS_RESTART_RECLAIM_NEEDED)
                nfs41_handle_server_reboot(clp);
        if (flags & (SEQ4_STATUS_EXPIRED_ALL_STATE_REVOKED))
                nfs41_handle_all_state_revoked(clp);
        if (flags & (SEQ4_STATUS_EXPIRED_SOME_STATE_REVOKED |
                            SEQ4_STATUS_ADMIN_STATE_REVOKED))
                nfs41_handle_some_state_revoked(clp);
        if (flags & SEQ4_STATUS_LEASE_MOVED)
                nfs4_schedule_lease_moved_recovery(clp);
        if (flags & SEQ4_STATUS_RECALLABLE_STATE_REVOKED)
                nfs41_handle_recallable_state_revoked(clp);
out_recovery:
        if (flags & SEQ4_STATUS_BACKCHANNEL_FAULT)
                nfs41_handle_backchannel_fault(clp);
        else if (flags & (SEQ4_STATUS_CB_PATH_DOWN |
                                SEQ4_STATUS_CB_PATH_DOWN_SESSION))
                nfs41_handle_cb_path_down(clp);
}

static int nfs4_reset_session(struct nfs_client *clp)
{
        const struct cred *cred;
        int status;

        if (!nfs4_has_session(clp))
                return 0;
        status = nfs4_begin_drain_session(clp);
        if (status != 0)
                return status;
        cred = nfs4_get_clid_cred(clp);
        status = nfs4_proc_destroy_session(clp->cl_session, cred);
        switch (status) {
        case 0:
        case -NFS4ERR_BADSESSION:
        case -NFS4ERR_DEADSESSION:
                break;
        case -NFS4ERR_BACK_CHAN_BUSY:
        case -NFS4ERR_DELAY:
                set_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state);
                status = 0;
                ssleep(1);
                goto out;
        default:
                status = nfs4_recovery_handle_error(clp, status);
                goto out;
        }

        memset(clp->cl_session->sess_id.data, 0, NFS4_MAX_SESSIONID_LEN);
        status = nfs4_proc_create_session(clp, cred);
        if (status) {
                dprintk("%s: session reset failed with status %d for server %s!\n",
                        __func__, status, clp->cl_hostname);
                status = nfs4_handle_reclaim_lease_error(clp, status);
                goto out;
        }
        nfs41_finish_session_reset(clp);
        dprintk("%s: session reset was successful for server %s!\n",
                        __func__, clp->cl_hostname);
out:
        put_cred(cred);
        return status;
}

static int nfs4_bind_conn_to_session(struct nfs_client *clp)
{
        const struct cred *cred;
        int ret;

        if (!nfs4_has_session(clp))
                return 0;
        ret = nfs4_begin_drain_session(clp);
        if (ret != 0)
                return ret;
        cred = nfs4_get_clid_cred(clp);
        ret = nfs4_proc_bind_conn_to_session(clp, cred);
        put_cred(cred);
        clear_bit(NFS4CLNT_BIND_CONN_TO_SESSION, &clp->cl_state);
        switch (ret) {
        case 0:
                dprintk("%s: bind_conn_to_session was successful for server %s!\n",
                        __func__, clp->cl_hostname);
                break;
        case -NFS4ERR_DELAY:
                ssleep(1);
                set_bit(NFS4CLNT_BIND_CONN_TO_SESSION, &clp->cl_state);
                break;
        default:
                return nfs4_recovery_handle_error(clp, ret);
        }
        return 0;
}

static void nfs4_layoutreturn_any_run(struct nfs_client *clp)
{
        int iomode = 0;

        if (test_and_clear_bit(NFS4CLNT_RECALL_ANY_LAYOUT_READ, &clp->cl_state))
                iomode += IOMODE_READ;
        if (test_and_clear_bit(NFS4CLNT_RECALL_ANY_LAYOUT_RW, &clp->cl_state))
                iomode += IOMODE_RW;
        /* Note: IOMODE_READ + IOMODE_RW == IOMODE_ANY */
        if (iomode) {
                pnfs_layout_return_unused_byclid(clp, iomode);
                set_bit(NFS4CLNT_RUN_MANAGER, &clp->cl_state);
        }
}
#else /* CONFIG_NFS_V4_1 */
static int nfs4_reset_session(struct nfs_client *clp) { return 0; }

static int nfs4_bind_conn_to_session(struct nfs_client *clp)
{
        return 0;
}

static void nfs4_layoutreturn_any_run(struct nfs_client *clp)
{
}
#endif /* CONFIG_NFS_V4_1 */

static void nfs4_state_manager(struct nfs_client *clp)
{
        unsigned int memflags;
        int status = 0;
        const char *section = "", *section_sep = "";

        /*
         * State recovery can deadlock if the direct reclaim code tries
         * start NFS writeback. So ensure memory allocations are all
         * GFP_NOFS.
         */
        memflags = memalloc_nofs_save();

        /* Ensure exclusive access to NFSv4 state */
        do {
                trace_nfs4_state_mgr(clp);
                clear_bit(NFS4CLNT_RUN_MANAGER, &clp->cl_state);
                if (test_bit(NFS4CLNT_PURGE_STATE, &clp->cl_state)) {
                        section = "purge state";
                        status = nfs4_purge_lease(clp);
                        if (status < 0)
                                goto out_error;
                        continue;
                }

                if (test_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state)) {
                        section = "lease expired";
                        /* We're going to have to re-establish a clientid */
                        status = nfs4_reclaim_lease(clp);
                        if (status < 0)
                                goto out_error;
                        continue;
                }

                /* Initialize or reset the session */
                if (test_and_clear_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state)) {
                        section = "reset session";
                        status = nfs4_reset_session(clp);
                        if (test_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state))
                                continue;
                        if (status < 0)
                                goto out_error;
                }

                /* Send BIND_CONN_TO_SESSION */
                if (test_and_clear_bit(NFS4CLNT_BIND_CONN_TO_SESSION,
                                &clp->cl_state)) {
                        section = "bind conn to session";
                        status = nfs4_bind_conn_to_session(clp);
                        if (status < 0)
                                goto out_error;
                        continue;
                }

                if (test_and_clear_bit(NFS4CLNT_CHECK_LEASE, &clp->cl_state)) {
                        section = "check lease";
                        status = nfs4_check_lease(clp);
                        if (status < 0)
                                goto out_error;
                        continue;
                }

                if (test_and_clear_bit(NFS4CLNT_MOVED, &clp->cl_state)) {
                        section = "migration";
                        status = nfs4_handle_migration(clp);
                        if (status < 0)
                                goto out_error;
                }

                if (test_and_clear_bit(NFS4CLNT_LEASE_MOVED, &clp->cl_state)) {
                        section = "lease moved";
                        status = nfs4_handle_lease_moved(clp);
                        if (status < 0)
                                goto out_error;
                }

                /* First recover reboot state... */
                if (test_bit(NFS4CLNT_RECLAIM_REBOOT, &clp->cl_state)) {
                        section = "reclaim reboot";
                        status = nfs4_do_reclaim(clp,
                                clp->cl_mvops->reboot_recovery_ops);
                        if (status == -EAGAIN)
                                continue;
                        if (status < 0)
                                goto out_error;
                        nfs4_state_end_reclaim_reboot(clp);
                        continue;
                }

                /* Detect expired delegations... */
                if (test_and_clear_bit(NFS4CLNT_DELEGATION_EXPIRED, &clp->cl_state)) {
                        section = "detect expired delegations";
                        nfs_reap_expired_delegations(clp);
                        continue;
                }

                /* Now recover expired state... */
                if (test_bit(NFS4CLNT_RECLAIM_NOGRACE, &clp->cl_state)) {
                        section = "reclaim nograce";
                        status = nfs4_do_reclaim(clp,
                                clp->cl_mvops->nograce_recovery_ops);
                        if (status == -EAGAIN)
                                continue;
                        if (status < 0)
                                goto out_error;
                        clear_bit(NFS4CLNT_RECLAIM_NOGRACE, &clp->cl_state);
                }

                memalloc_nofs_restore(memflags);
                nfs4_end_drain_session(clp);
                nfs4_clear_state_manager_bit(clp);

                if (!test_and_set_bit(NFS4CLNT_RECALL_RUNNING, &clp->cl_state)) {
                        if (test_and_clear_bit(NFS4CLNT_DELEGRETURN, &clp->cl_state)) {
                                nfs_client_return_marked_delegations(clp);
                                set_bit(NFS4CLNT_RUN_MANAGER, &clp->cl_state);
                        }
                        nfs4_layoutreturn_any_run(clp);
                        clear_bit(NFS4CLNT_RECALL_RUNNING, &clp->cl_state);
                }

                return;

        } while (refcount_read(&clp->cl_count) > 1 && !signalled());
        goto out_drain;

out_error:
        if (strlen(section))
                section_sep = ": ";
        trace_nfs4_state_mgr_failed(clp, section, status);
        pr_warn_ratelimited("NFS: state manager%s%s failed on NFSv4 server %s"
                        " with error %d\n", section_sep, section,
                        clp->cl_hostname, -status);
        ssleep(1);
out_drain:
        memalloc_nofs_restore(memflags);
        nfs4_end_drain_session(clp);
        nfs4_clear_state_manager_bit(clp);
}

static int nfs4_run_state_manager(void *ptr)
{
        struct nfs_client *clp = ptr;
        struct rpc_clnt *cl = clp->cl_rpcclient;

        while (cl != cl->cl_parent)
                cl = cl->cl_parent;

        allow_signal(SIGKILL);
again:
        set_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state);
        nfs4_state_manager(clp);
        if (atomic_read(&cl->cl_swapper)) {
                wait_var_event_interruptible(&clp->cl_state,
                                             test_bit(NFS4CLNT_RUN_MANAGER,
                                                      &clp->cl_state));
                if (atomic_read(&cl->cl_swapper) &&
                    test_bit(NFS4CLNT_RUN_MANAGER, &clp->cl_state))
                        goto again;
                /* Either no longer a swapper, or were signalled */
        }
        clear_bit(NFS4CLNT_MANAGER_AVAILABLE, &clp->cl_state);

        if (refcount_read(&clp->cl_count) > 1 && !signalled() &&
            test_bit(NFS4CLNT_RUN_MANAGER, &clp->cl_state) &&
            !test_and_set_bit(NFS4CLNT_MANAGER_AVAILABLE, &clp->cl_state))
                goto again;

        nfs_put_client(clp);
        module_put_and_kthread_exit(0);
        return 0;
}