[PATCH] g_file_storage: fix obscure race condition

[linux-2.6/cjktty.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/config.h>
#include <linux/slab.h>
#include <linux/smp_lock.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_idmap.h>
#include <linux/workqueue.h>
#include <linux/bitops.h>

#include "nfs4_fs.h"
#include "callback.h"
#include "delegation.h"

#define OPENOWNER_POOL_SIZE     8

const nfs4_stateid zero_stateid;

static DEFINE_SPINLOCK(state_spinlock);
static LIST_HEAD(nfs4_clientid_list);

static void nfs4_recover_state(void *);

void
init_nfsv4_state(struct nfs_server *server)
{
        server->nfs4_state = NULL;
        INIT_LIST_HEAD(&server->nfs4_siblings);
}

void
destroy_nfsv4_state(struct nfs_server *server)
{
        if (server->mnt_path) {
                kfree(server->mnt_path);
                server->mnt_path = NULL;
        }
        if (server->nfs4_state) {
                nfs4_put_client(server->nfs4_state);
                server->nfs4_state = NULL;
        }
}

/*
 * nfs4_get_client(): returns an empty client structure
 * nfs4_put_client(): drops reference to client structure
 *
 * Since these are allocated/deallocated very rarely, we don't
 * bother putting them in a slab cache...
 */
static struct nfs4_client *
nfs4_alloc_client(struct in_addr *addr)
{
        struct nfs4_client *clp;

        if (nfs_callback_up() < 0)
                return NULL;
        if ((clp = kmalloc(sizeof(*clp), GFP_KERNEL)) == NULL) {
                nfs_callback_down();
                return NULL;
        }
        memset(clp, 0, sizeof(*clp));
        memcpy(&clp->cl_addr, addr, sizeof(clp->cl_addr));
        init_rwsem(&clp->cl_sem);
        INIT_LIST_HEAD(&clp->cl_delegations);
        INIT_LIST_HEAD(&clp->cl_state_owners);
        INIT_LIST_HEAD(&clp->cl_unused);
        spin_lock_init(&clp->cl_lock);
        atomic_set(&clp->cl_count, 1);
        INIT_WORK(&clp->cl_recoverd, nfs4_recover_state, clp);
        INIT_WORK(&clp->cl_renewd, nfs4_renew_state, clp);
        INIT_LIST_HEAD(&clp->cl_superblocks);
        init_waitqueue_head(&clp->cl_waitq);
        rpc_init_wait_queue(&clp->cl_rpcwaitq, "NFS4 client");
        clp->cl_rpcclient = ERR_PTR(-EINVAL);
        clp->cl_boot_time = CURRENT_TIME;
        clp->cl_state = 1 << NFS4CLNT_OK;
        return clp;
}

static void
nfs4_free_client(struct nfs4_client *clp)
{
        struct nfs4_state_owner *sp;

        while (!list_empty(&clp->cl_unused)) {
                sp = list_entry(clp->cl_unused.next,
                                struct nfs4_state_owner,
                                so_list);
                list_del(&sp->so_list);
                kfree(sp);
        }
        BUG_ON(!list_empty(&clp->cl_state_owners));
        if (clp->cl_cred)
                put_rpccred(clp->cl_cred);
        nfs_idmap_delete(clp);
        if (!IS_ERR(clp->cl_rpcclient))
                rpc_shutdown_client(clp->cl_rpcclient);
        kfree(clp);
        nfs_callback_down();
}

static struct nfs4_client *__nfs4_find_client(struct in_addr *addr)
{
        struct nfs4_client *clp;
        list_for_each_entry(clp, &nfs4_clientid_list, cl_servers) {
                if (memcmp(&clp->cl_addr, addr, sizeof(clp->cl_addr)) == 0) {
                        atomic_inc(&clp->cl_count);
                        return clp;
                }
        }
        return NULL;
}

struct nfs4_client *nfs4_find_client(struct in_addr *addr)
{
        struct nfs4_client *clp;
        spin_lock(&state_spinlock);
        clp = __nfs4_find_client(addr);
        spin_unlock(&state_spinlock);
        return clp;
}

struct nfs4_client *
nfs4_get_client(struct in_addr *addr)
{
        struct nfs4_client *clp, *new = NULL;

        spin_lock(&state_spinlock);
        for (;;) {
                clp = __nfs4_find_client(addr);
                if (clp != NULL)
                        break;
                clp = new;
                if (clp != NULL) {
                        list_add(&clp->cl_servers, &nfs4_clientid_list);
                        new = NULL;
                        break;
                }
                spin_unlock(&state_spinlock);
                new = nfs4_alloc_client(addr);
                spin_lock(&state_spinlock);
                if (new == NULL)
                        break;
        }
        spin_unlock(&state_spinlock);
        if (new)
                nfs4_free_client(new);
        return clp;
}

void
nfs4_put_client(struct nfs4_client *clp)
{
        if (!atomic_dec_and_lock(&clp->cl_count, &state_spinlock))
                return;
        list_del(&clp->cl_servers);
        spin_unlock(&state_spinlock);
        BUG_ON(!list_empty(&clp->cl_superblocks));
        wake_up_all(&clp->cl_waitq);
        rpc_wake_up(&clp->cl_rpcwaitq);
        nfs4_kill_renewd(clp);
        nfs4_free_client(clp);
}

static int __nfs4_init_client(struct nfs4_client *clp)
{
        int status = nfs4_proc_setclientid(clp, NFS4_CALLBACK, nfs_callback_tcpport);
        if (status == 0)
                status = nfs4_proc_setclientid_confirm(clp);
        if (status == 0)
                nfs4_schedule_state_renewal(clp);
        return status;
}

int nfs4_init_client(struct nfs4_client *clp)
{
        return nfs4_map_errors(__nfs4_init_client(clp));
}

u32
nfs4_alloc_lockowner_id(struct nfs4_client *clp)
{
        return clp->cl_lockowner_id ++;
}

static struct nfs4_state_owner *
nfs4_client_grab_unused(struct nfs4_client *clp, struct rpc_cred *cred)
{
        struct nfs4_state_owner *sp = NULL;

        if (!list_empty(&clp->cl_unused)) {
                sp = list_entry(clp->cl_unused.next, struct nfs4_state_owner, so_list);
                atomic_inc(&sp->so_count);
                sp->so_cred = cred;
                list_move(&sp->so_list, &clp->cl_state_owners);
                clp->cl_nunused--;
        }
        return sp;
}

static struct nfs4_state_owner *
nfs4_find_state_owner(struct nfs4_client *clp, struct rpc_cred *cred)
{
        struct nfs4_state_owner *sp, *res = NULL;

        list_for_each_entry(sp, &clp->cl_state_owners, so_list) {
                if (sp->so_cred != cred)
                        continue;
                atomic_inc(&sp->so_count);
                /* Move to the head of the list */
                list_move(&sp->so_list, &clp->cl_state_owners);
                res = sp;
                break;
        }
        return res;
}

/*
 * 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(void)
{
        struct nfs4_state_owner *sp;

        sp = kzalloc(sizeof(*sp),GFP_KERNEL);
        if (!sp)
                return NULL;
        spin_lock_init(&sp->so_lock);
        INIT_LIST_HEAD(&sp->so_states);
        INIT_LIST_HEAD(&sp->so_delegations);
        rpc_init_wait_queue(&sp->so_sequence.wait, "Seqid_waitqueue");
        sp->so_seqid.sequence = &sp->so_sequence;
        spin_lock_init(&sp->so_sequence.lock);
        INIT_LIST_HEAD(&sp->so_sequence.list);
        atomic_set(&sp->so_count, 1);
        return sp;
}

void
nfs4_drop_state_owner(struct nfs4_state_owner *sp)
{
        struct nfs4_client *clp = sp->so_client;
        spin_lock(&clp->cl_lock);
        list_del_init(&sp->so_list);
        spin_unlock(&clp->cl_lock);
}

/*
 * Note: must be called with clp->cl_sem held in order to prevent races
 *       with reboot recovery!
 */
struct nfs4_state_owner *nfs4_get_state_owner(struct nfs_server *server, struct rpc_cred *cred)
{
        struct nfs4_client *clp = server->nfs4_state;
        struct nfs4_state_owner *sp, *new;

        get_rpccred(cred);
        new = nfs4_alloc_state_owner();
        spin_lock(&clp->cl_lock);
        sp = nfs4_find_state_owner(clp, cred);
        if (sp == NULL)
                sp = nfs4_client_grab_unused(clp, cred);
        if (sp == NULL && new != NULL) {
                list_add(&new->so_list, &clp->cl_state_owners);
                new->so_client = clp;
                new->so_id = nfs4_alloc_lockowner_id(clp);
                new->so_cred = cred;
                sp = new;
                new = NULL;
        }
        spin_unlock(&clp->cl_lock);
        if (new)
                kfree(new);
        if (sp != NULL)
                return sp;
        put_rpccred(cred);
        return NULL;
}

/*
 * Must be called with clp->cl_sem held in order to avoid races
 * with state recovery...
 */
void nfs4_put_state_owner(struct nfs4_state_owner *sp)
{
        struct nfs4_client *clp = sp->so_client;
        struct rpc_cred *cred = sp->so_cred;

        if (!atomic_dec_and_lock(&sp->so_count, &clp->cl_lock))
                return;
        if (clp->cl_nunused >= OPENOWNER_POOL_SIZE)
                goto out_free;
        if (list_empty(&sp->so_list))
                goto out_free;
        list_move(&sp->so_list, &clp->cl_unused);
        clp->cl_nunused++;
        spin_unlock(&clp->cl_lock);
        put_rpccred(cred);
        cred = NULL;
        return;
out_free:
        list_del(&sp->so_list);
        spin_unlock(&clp->cl_lock);
        put_rpccred(cred);
        kfree(sp);
}

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

        state = kmalloc(sizeof(*state), GFP_KERNEL);
        if (!state)
                return NULL;
        state->state = 0;
        state->nreaders = 0;
        state->nwriters = 0;
        state->flags = 0;
        memset(state->stateid.data, 0, sizeof(state->stateid.data));
        atomic_set(&state->count, 1);
        INIT_LIST_HEAD(&state->lock_states);
        spin_lock_init(&state->state_lock);
        return state;
}

static struct nfs4_state *
__nfs4_find_state(struct inode *inode, struct rpc_cred *cred, mode_t mode)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        struct nfs4_state *state;

        mode &= (FMODE_READ|FMODE_WRITE);
        list_for_each_entry(state, &nfsi->open_states, inode_states) {
                if (state->owner->so_cred != cred)
                        continue;
                if ((mode & FMODE_READ) != 0 && state->nreaders == 0)
                        continue;
                if ((mode & FMODE_WRITE) != 0 && state->nwriters == 0)
                        continue;
                if ((state->state & mode) != mode)
                        continue;
                atomic_inc(&state->count);
                if (mode & FMODE_READ)
                        state->nreaders++;
                if (mode & FMODE_WRITE)
                        state->nwriters++;
                return state;
        }
        return NULL;
}

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(state, &nfsi->open_states, inode_states) {
                /* Is this in the process of being freed? */
                if (state->nreaders == 0 && state->nwriters == 0)
                        continue;
                if (state->owner == owner) {
                        atomic_inc(&state->count);
                        return state;
                }
        }
        return NULL;
}

struct nfs4_state *
nfs4_find_state(struct inode *inode, struct rpc_cred *cred, mode_t mode)
{
        struct nfs4_state *state;

        spin_lock(&inode->i_lock);
        state = __nfs4_find_state(inode, cred, mode);
        spin_unlock(&inode->i_lock);
        return state;
}

static void
nfs4_free_open_state(struct nfs4_state *state)
{
        kfree(state);
}

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);

        spin_lock(&inode->i_lock);
        state = __nfs4_find_state_byowner(inode, owner);
        spin_unlock(&inode->i_lock);
        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);
                list_add(&state->inode_states, &nfsi->open_states);
                state->inode = igrab(inode);
                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;
}

/*
 * Beware! Caller must be holding exactly one
 * reference to clp->cl_sem!
 */
void nfs4_put_open_state(struct nfs4_state *state)
{
        struct inode *inode = state->inode;
        struct nfs4_state_owner *owner = state->owner;

        if (!atomic_dec_and_lock(&state->count, &owner->so_lock))
                return;
        spin_lock(&inode->i_lock);
        if (!list_empty(&state->inode_states))
                list_del(&state->inode_states);
        list_del(&state->open_states);
        spin_unlock(&inode->i_lock);
        spin_unlock(&owner->so_lock);
        iput(inode);
        BUG_ON (state->state != 0);
        nfs4_free_open_state(state);
        nfs4_put_state_owner(owner);
}

/*
 * Close the current file.
 */
void nfs4_close_state(struct nfs4_state *state, mode_t mode)
{
        struct inode *inode = state->inode;
        struct nfs4_state_owner *owner = state->owner;
        int newstate;

        atomic_inc(&owner->so_count);
        /* Protect against nfs4_find_state() */
        spin_lock(&owner->so_lock);
        spin_lock(&inode->i_lock);
        if (mode & FMODE_READ)
                state->nreaders--;
        if (mode & FMODE_WRITE)
                state->nwriters--;
        if (state->nwriters == 0) {
                if (state->nreaders == 0)
                        list_del_init(&state->inode_states);
                /* See reclaim code */
                list_move_tail(&state->open_states, &owner->so_states);
        }
        spin_unlock(&inode->i_lock);
        spin_unlock(&owner->so_lock);
        newstate = 0;
        if (state->state != 0) {
                if (state->nreaders)
                        newstate |= FMODE_READ;
                if (state->nwriters)
                        newstate |= FMODE_WRITE;
                if (state->state == newstate)
                        goto out;
                if (test_bit(NFS_DELEGATED_STATE, &state->flags)) {
                        state->state = newstate;
                        goto out;
                }
                if (nfs4_do_close(inode, state, newstate) == 0)
                        return;
        }
out:
        nfs4_put_open_state(state);
        nfs4_put_state_owner(owner);
}

/*
 * Search the state->lock_states for an existing lock_owner
 * that is compatible with current->files
 */
static struct nfs4_lock_state *
__nfs4_find_lock_state(struct nfs4_state *state, fl_owner_t fl_owner)
{
        struct nfs4_lock_state *pos;
        list_for_each_entry(pos, &state->lock_states, ls_locks) {
                if (pos->ls_owner != fl_owner)
                        continue;
                atomic_inc(&pos->ls_count);
                return pos;
        }
        return NULL;
}

/*
 * 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 nfs4_client *clp = state->owner->so_client;

        lsp = kzalloc(sizeof(*lsp), GFP_KERNEL);
        if (lsp == NULL)
                return NULL;
        lsp->ls_seqid.sequence = &state->owner->so_sequence;
        atomic_set(&lsp->ls_count, 1);
        lsp->ls_owner = fl_owner;
        spin_lock(&clp->cl_lock);
        lsp->ls_id = nfs4_alloc_lockowner_id(clp);
        spin_unlock(&clp->cl_lock);
        INIT_LIST_HEAD(&lsp->ls_locks);
        return lsp;
}

/*
 * Return a compatible lock_state. If no initialized lock_state structure
 * exists, return an uninitialized one.
 *
 * The caller must be holding clp->cl_sem
 */
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);
                if (lsp != NULL)
                        break;
                if (new != NULL) {
                        new->ls_state = state;
                        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);
        kfree(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 nfs4_state *state;

        if (lsp == NULL)
                return;
        state = lsp->ls_state;
        if (!atomic_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);
        kfree(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;
        atomic_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 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;
}

/*
 * Byte-range lock aware utility to initialize the stateid of read/write
 * requests.
 */
void nfs4_copy_stateid(nfs4_stateid *dst, struct nfs4_state *state, fl_owner_t fl_owner)
{
        struct nfs4_lock_state *lsp;

        memcpy(dst, &state->stateid, sizeof(*dst));
        if (test_bit(LK_STATE_IN_USE, &state->flags) == 0)
                return;

        spin_lock(&state->state_lock);
        lsp = __nfs4_find_lock_state(state, fl_owner);
        if (lsp != NULL && (lsp->ls_flags & NFS_LOCK_INITIALIZED) != 0)
                memcpy(dst, &lsp->ls_stateid, sizeof(*dst));
        spin_unlock(&state->state_lock);
        nfs4_put_lock_state(lsp);
}

struct nfs_seqid *nfs_alloc_seqid(struct nfs_seqid_counter *counter)
{
        struct nfs_seqid *new;

        new = kmalloc(sizeof(*new), GFP_KERNEL);
        if (new != NULL) {
                new->sequence = counter;
                INIT_LIST_HEAD(&new->list);
        }
        return new;
}

void nfs_free_seqid(struct nfs_seqid *seqid)
{
        struct rpc_sequence *sequence = seqid->sequence->sequence;

        if (!list_empty(&seqid->list)) {
                spin_lock(&sequence->lock);
                list_del(&seqid->list);
                spin_unlock(&sequence->lock);
        }
        rpc_wake_up_next(&sequence->wait);
        kfree(seqid);
}

/*
 * Increment the seqid if the OPEN/OPEN_DOWNGRADE/CLOSE succeeded, or
 * failed with a seqid incrementing error -
 * see comments nfs_fs.h:seqid_mutating_error()
 */
static inline void nfs_increment_seqid(int status, struct nfs_seqid *seqid)
{
        switch (status) {
                case 0:
                        break;
                case -NFS4ERR_BAD_SEQID:
                case -NFS4ERR_STALE_CLIENTID:
                case -NFS4ERR_STALE_STATEID:
                case -NFS4ERR_BAD_STATEID:
                case -NFS4ERR_BADXDR:
                case -NFS4ERR_RESOURCE:
                case -NFS4ERR_NOFILEHANDLE:
                        /* 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)
{
        if (status == -NFS4ERR_BAD_SEQID) {
                struct nfs4_state_owner *sp = container_of(seqid->sequence,
                                struct nfs4_state_owner, so_seqid);
                nfs4_drop_state_owner(sp);
        }
        return nfs_increment_seqid(status, seqid);
}

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

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

        if (sequence->list.next == &seqid->list)
                goto out;
        spin_lock(&sequence->lock);
        if (!list_empty(&sequence->list)) {
                rpc_sleep_on(&sequence->wait, task, NULL, NULL);
                status = -EAGAIN;
        } else
                list_add(&seqid->list, &sequence->list);
        spin_unlock(&sequence->lock);
out:
        return status;
}

static int reclaimer(void *);
struct reclaimer_args {
        struct nfs4_client *clp;
        struct completion complete;
};

/*
 * State recovery routine
 */
void
nfs4_recover_state(void *data)
{
        struct nfs4_client *clp = (struct nfs4_client *)data;
        struct reclaimer_args args = {
                .clp = clp,
        };
        might_sleep();

        init_completion(&args.complete);

        if (kernel_thread(reclaimer, &args, CLONE_KERNEL) < 0)
                goto out_failed_clear;
        wait_for_completion(&args.complete);
        return;
out_failed_clear:
        set_bit(NFS4CLNT_OK, &clp->cl_state);
        wake_up_all(&clp->cl_waitq);
        rpc_wake_up(&clp->cl_rpcwaitq);
}

/*
 * Schedule a state recovery attempt
 */
void
nfs4_schedule_state_recovery(struct nfs4_client *clp)
{
        if (!clp)
                return;
        if (test_and_clear_bit(NFS4CLNT_OK, &clp->cl_state))
                schedule_work(&clp->cl_recoverd);
}

static int nfs4_reclaim_locks(struct nfs4_state_recovery_ops *ops, struct nfs4_state *state)
{
        struct inode *inode = state->inode;
        struct file_lock *fl;
        int status = 0;

        for (fl = inode->i_flock; fl != 0; fl = fl->fl_next) {
                if (!(fl->fl_flags & FL_POSIX))
                        continue;
                if (((struct nfs_open_context *)fl->fl_file->private_data)->state != state)
                        continue;
                status = ops->recover_lock(state, fl);
                if (status >= 0)
                        continue;
                switch (status) {
                        default:
                                printk(KERN_ERR "%s: unhandled error %d. Zeroing state\n",
                                                __FUNCTION__, status);
                        case -NFS4ERR_EXPIRED:
                        case -NFS4ERR_NO_GRACE:
                        case -NFS4ERR_RECLAIM_BAD:
                        case -NFS4ERR_RECLAIM_CONFLICT:
                                /* kill_proc(fl->fl_owner, SIGLOST, 1); */
                                break;
                        case -NFS4ERR_STALE_CLIENTID:
                                goto out_err;
                }
        }
        return 0;
out_err:
        return status;
}

static int nfs4_reclaim_open_state(struct nfs4_state_recovery_ops *ops, struct nfs4_state_owner *sp)
{
        struct nfs4_state *state;
        struct nfs4_lock_state *lock;
        int status = 0;

        /* 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.
         */
        list_for_each_entry(state, &sp->so_states, open_states) {
                if (state->state == 0)
                        continue;
                status = ops->recover_open(sp, state);
                if (status >= 0) {
                        status = nfs4_reclaim_locks(ops, state);
                        if (status < 0)
                                goto out_err;
                        list_for_each_entry(lock, &state->lock_states, ls_locks) {
                                if (!(lock->ls_flags & NFS_LOCK_INITIALIZED))
                                        printk("%s: Lock reclaim failed!\n",
                                                        __FUNCTION__);
                        }
                        continue;
                }
                switch (status) {
                        default:
                                printk(KERN_ERR "%s: unhandled error %d. Zeroing state\n",
                                                __FUNCTION__, status);
                        case -ENOENT:
                        case -NFS4ERR_RECLAIM_BAD:
                        case -NFS4ERR_RECLAIM_CONFLICT:
                                /*
                                 * Open state on this file cannot be recovered
                                 * All we can do is revert to using the zero stateid.
                                 */
                                memset(state->stateid.data, 0,
                                        sizeof(state->stateid.data));
                                /* Mark the file as being 'closed' */
                                state->state = 0;
                                break;
                        case -NFS4ERR_EXPIRED:
                        case -NFS4ERR_NO_GRACE:
                        case -NFS4ERR_STALE_CLIENTID:
                                goto out_err;
                }
        }
        return 0;
out_err:
        return status;
}

static void nfs4_state_mark_reclaim(struct nfs4_client *clp)
{
        struct nfs4_state_owner *sp;
        struct nfs4_state *state;
        struct nfs4_lock_state *lock;

        /* Reset all sequence ids to zero */
        list_for_each_entry(sp, &clp->cl_state_owners, so_list) {
                sp->so_seqid.counter = 0;
                sp->so_seqid.flags = 0;
                spin_lock(&sp->so_lock);
                list_for_each_entry(state, &sp->so_states, open_states) {
                        list_for_each_entry(lock, &state->lock_states, ls_locks) {
                                lock->ls_seqid.counter = 0;
                                lock->ls_seqid.flags = 0;
                                lock->ls_flags &= ~NFS_LOCK_INITIALIZED;
                        }
                }
                spin_unlock(&sp->so_lock);
        }
}

static int reclaimer(void *ptr)
{
        struct reclaimer_args *args = (struct reclaimer_args *)ptr;
        struct nfs4_client *clp = args->clp;
        struct nfs4_state_owner *sp;
        struct nfs4_state_recovery_ops *ops;
        int status = 0;

        daemonize("%u.%u.%u.%u-reclaim", NIPQUAD(clp->cl_addr));
        allow_signal(SIGKILL);

        atomic_inc(&clp->cl_count);
        complete(&args->complete);

        /* Ensure exclusive access to NFSv4 state */
        lock_kernel();
        down_write(&clp->cl_sem);
        /* Are there any NFS mounts out there? */
        if (list_empty(&clp->cl_superblocks))
                goto out;
restart_loop:
        status = nfs4_proc_renew(clp);
        switch (status) {
                case 0:
                case -NFS4ERR_CB_PATH_DOWN:
                        goto out;
                case -NFS4ERR_STALE_CLIENTID:
                case -NFS4ERR_LEASE_MOVED:
                        ops = &nfs4_reboot_recovery_ops;
                        break;
                default:
                        ops = &nfs4_network_partition_recovery_ops;
        };
        nfs4_state_mark_reclaim(clp);
        status = __nfs4_init_client(clp);
        if (status)
                goto out_error;
        /* Mark all delegations for reclaim */
        nfs_delegation_mark_reclaim(clp);
        /* Note: list is protected by exclusive lock on cl->cl_sem */
        list_for_each_entry(sp, &clp->cl_state_owners, so_list) {
                status = nfs4_reclaim_open_state(ops, sp);
                if (status < 0) {
                        if (status == -NFS4ERR_NO_GRACE) {
                                ops = &nfs4_network_partition_recovery_ops;
                                status = nfs4_reclaim_open_state(ops, sp);
                        }
                        if (status == -NFS4ERR_STALE_CLIENTID)
                                goto restart_loop;
                        if (status == -NFS4ERR_EXPIRED)
                                goto restart_loop;
                }
        }
        nfs_delegation_reap_unclaimed(clp);
out:
        set_bit(NFS4CLNT_OK, &clp->cl_state);
        up_write(&clp->cl_sem);
        unlock_kernel();
        wake_up_all(&clp->cl_waitq);
        rpc_wake_up(&clp->cl_rpcwaitq);
        if (status == -NFS4ERR_CB_PATH_DOWN)
                nfs_handle_cb_pathdown(clp);
        nfs4_put_client(clp);
        return 0;
out_error:
        printk(KERN_WARNING "Error: state recovery failed on NFSv4 server %u.%u.%u.%u with error %d\n",
                                NIPQUAD(clp->cl_addr.s_addr), -status);
        goto out;
}

/*
 * Local variables:
 *  c-basic-offset: 8
 * End:
 */