Merge tag 'block-5.9-2020-08-14' of git://git.kernel.dk/linux-block

[linux/fpc-iii.git] / fs / afs / flock.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* AFS file locking support
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include "internal.h"

#define AFS_LOCK_GRANTED        0
#define AFS_LOCK_PENDING        1
#define AFS_LOCK_YOUR_TRY       2

struct workqueue_struct *afs_lock_manager;

static void afs_next_locker(struct afs_vnode *vnode, int error);
static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl);
static void afs_fl_release_private(struct file_lock *fl);

static const struct file_lock_operations afs_lock_ops = {
        .fl_copy_lock           = afs_fl_copy_lock,
        .fl_release_private     = afs_fl_release_private,
};

static inline void afs_set_lock_state(struct afs_vnode *vnode, enum afs_lock_state state)
{
        _debug("STATE %u -> %u", vnode->lock_state, state);
        vnode->lock_state = state;
}

static atomic_t afs_file_lock_debug_id;

/*
 * if the callback is broken on this vnode, then the lock may now be available
 */
void afs_lock_may_be_available(struct afs_vnode *vnode)
{
        _enter("{%llx:%llu}", vnode->fid.vid, vnode->fid.vnode);

        spin_lock(&vnode->lock);
        if (vnode->lock_state == AFS_VNODE_LOCK_WAITING_FOR_CB)
                afs_next_locker(vnode, 0);
        trace_afs_flock_ev(vnode, NULL, afs_flock_callback_break, 0);
        spin_unlock(&vnode->lock);
}

/*
 * the lock will time out in 5 minutes unless we extend it, so schedule
 * extension in a bit less than that time
 */
static void afs_schedule_lock_extension(struct afs_vnode *vnode)
{
        ktime_t expires_at, now, duration;
        u64 duration_j;

        expires_at = ktime_add_ms(vnode->locked_at, AFS_LOCKWAIT * 1000 / 2);
        now = ktime_get_real();
        duration = ktime_sub(expires_at, now);
        if (duration <= 0)
                duration_j = 0;
        else
                duration_j = nsecs_to_jiffies(ktime_to_ns(duration));

        queue_delayed_work(afs_lock_manager, &vnode->lock_work, duration_j);
}

/*
 * In the case of successful completion of a lock operation, record the time
 * the reply appeared and start the lock extension timer.
 */
void afs_lock_op_done(struct afs_call *call)
{
        struct afs_operation *op = call->op;
        struct afs_vnode *vnode = op->file[0].vnode;

        if (call->error == 0) {
                spin_lock(&vnode->lock);
                trace_afs_flock_ev(vnode, NULL, afs_flock_timestamp, 0);
                vnode->locked_at = call->reply_time;
                afs_schedule_lock_extension(vnode);
                spin_unlock(&vnode->lock);
        }
}

/*
 * grant one or more locks (readlocks are allowed to jump the queue if the
 * first lock in the queue is itself a readlock)
 * - the caller must hold the vnode lock
 */
static void afs_grant_locks(struct afs_vnode *vnode)
{
        struct file_lock *p, *_p;
        bool exclusive = (vnode->lock_type == AFS_LOCK_WRITE);

        list_for_each_entry_safe(p, _p, &vnode->pending_locks, fl_u.afs.link) {
                if (!exclusive && p->fl_type == F_WRLCK)
                        continue;

                list_move_tail(&p->fl_u.afs.link, &vnode->granted_locks);
                p->fl_u.afs.state = AFS_LOCK_GRANTED;
                trace_afs_flock_op(vnode, p, afs_flock_op_grant);
                wake_up(&p->fl_wait);
        }
}

/*
 * If an error is specified, reject every pending lock that matches the
 * authentication and type of the lock we failed to get.  If there are any
 * remaining lockers, try to wake up one of them to have a go.
 */
static void afs_next_locker(struct afs_vnode *vnode, int error)
{
        struct file_lock *p, *_p, *next = NULL;
        struct key *key = vnode->lock_key;
        unsigned int fl_type = F_RDLCK;

        _enter("");

        if (vnode->lock_type == AFS_LOCK_WRITE)
                fl_type = F_WRLCK;

        list_for_each_entry_safe(p, _p, &vnode->pending_locks, fl_u.afs.link) {
                if (error &&
                    p->fl_type == fl_type &&
                    afs_file_key(p->fl_file) == key) {
                        list_del_init(&p->fl_u.afs.link);
                        p->fl_u.afs.state = error;
                        wake_up(&p->fl_wait);
                }

                /* Select the next locker to hand off to. */
                if (next &&
                    (next->fl_type == F_WRLCK || p->fl_type == F_RDLCK))
                        continue;
                next = p;
        }

        vnode->lock_key = NULL;
        key_put(key);

        if (next) {
                afs_set_lock_state(vnode, AFS_VNODE_LOCK_SETTING);
                next->fl_u.afs.state = AFS_LOCK_YOUR_TRY;
                trace_afs_flock_op(vnode, next, afs_flock_op_wake);
                wake_up(&next->fl_wait);
        } else {
                afs_set_lock_state(vnode, AFS_VNODE_LOCK_NONE);
                trace_afs_flock_ev(vnode, NULL, afs_flock_no_lockers, 0);
        }

        _leave("");
}

/*
 * Kill off all waiters in the the pending lock queue due to the vnode being
 * deleted.
 */
static void afs_kill_lockers_enoent(struct afs_vnode *vnode)
{
        struct file_lock *p;

        afs_set_lock_state(vnode, AFS_VNODE_LOCK_DELETED);

        while (!list_empty(&vnode->pending_locks)) {
                p = list_entry(vnode->pending_locks.next,
                               struct file_lock, fl_u.afs.link);
                list_del_init(&p->fl_u.afs.link);
                p->fl_u.afs.state = -ENOENT;
                wake_up(&p->fl_wait);
        }

        key_put(vnode->lock_key);
        vnode->lock_key = NULL;
}

static void afs_lock_success(struct afs_operation *op)
{
        _enter("op=%08x", op->debug_id);
        afs_vnode_commit_status(op, &op->file[0]);
}

static const struct afs_operation_ops afs_set_lock_operation = {
        .issue_afs_rpc  = afs_fs_set_lock,
        .issue_yfs_rpc  = yfs_fs_set_lock,
        .success        = afs_lock_success,
        .aborted        = afs_check_for_remote_deletion,
};

/*
 * Get a lock on a file
 */
static int afs_set_lock(struct afs_vnode *vnode, struct key *key,
                        afs_lock_type_t type)
{
        struct afs_operation *op;

        _enter("%s{%llx:%llu.%u},%x,%u",
               vnode->volume->name,
               vnode->fid.vid,
               vnode->fid.vnode,
               vnode->fid.unique,
               key_serial(key), type);

        op = afs_alloc_operation(key, vnode->volume);
        if (IS_ERR(op))
                return PTR_ERR(op);

        afs_op_set_vnode(op, 0, vnode);

        op->lock.type   = type;
        op->ops         = &afs_set_lock_operation;
        return afs_do_sync_operation(op);
}

static const struct afs_operation_ops afs_extend_lock_operation = {
        .issue_afs_rpc  = afs_fs_extend_lock,
        .issue_yfs_rpc  = yfs_fs_extend_lock,
        .success        = afs_lock_success,
};

/*
 * Extend a lock on a file
 */
static int afs_extend_lock(struct afs_vnode *vnode, struct key *key)
{
        struct afs_operation *op;

        _enter("%s{%llx:%llu.%u},%x",
               vnode->volume->name,
               vnode->fid.vid,
               vnode->fid.vnode,
               vnode->fid.unique,
               key_serial(key));

        op = afs_alloc_operation(key, vnode->volume);
        if (IS_ERR(op))
                return PTR_ERR(op);

        afs_op_set_vnode(op, 0, vnode);

        op->flags       |= AFS_OPERATION_UNINTR;
        op->ops         = &afs_extend_lock_operation;
        return afs_do_sync_operation(op);
}

static const struct afs_operation_ops afs_release_lock_operation = {
        .issue_afs_rpc  = afs_fs_release_lock,
        .issue_yfs_rpc  = yfs_fs_release_lock,
        .success        = afs_lock_success,
};

/*
 * Release a lock on a file
 */
static int afs_release_lock(struct afs_vnode *vnode, struct key *key)
{
        struct afs_operation *op;

        _enter("%s{%llx:%llu.%u},%x",
               vnode->volume->name,
               vnode->fid.vid,
               vnode->fid.vnode,
               vnode->fid.unique,
               key_serial(key));

        op = afs_alloc_operation(key, vnode->volume);
        if (IS_ERR(op))
                return PTR_ERR(op);

        afs_op_set_vnode(op, 0, vnode);

        op->flags       |= AFS_OPERATION_UNINTR;
        op->ops         = &afs_release_lock_operation;
        return afs_do_sync_operation(op);
}

/*
 * do work for a lock, including:
 * - probing for a lock we're waiting on but didn't get immediately
 * - extending a lock that's close to timing out
 */
void afs_lock_work(struct work_struct *work)
{
        struct afs_vnode *vnode =
                container_of(work, struct afs_vnode, lock_work.work);
        struct key *key;
        int ret;

        _enter("{%llx:%llu}", vnode->fid.vid, vnode->fid.vnode);

        spin_lock(&vnode->lock);

again:
        _debug("wstate %u for %p", vnode->lock_state, vnode);
        switch (vnode->lock_state) {
        case AFS_VNODE_LOCK_NEED_UNLOCK:
                afs_set_lock_state(vnode, AFS_VNODE_LOCK_UNLOCKING);
                trace_afs_flock_ev(vnode, NULL, afs_flock_work_unlocking, 0);
                spin_unlock(&vnode->lock);

                /* attempt to release the server lock; if it fails, we just
                 * wait 5 minutes and it'll expire anyway */
                ret = afs_release_lock(vnode, vnode->lock_key);
                if (ret < 0 && vnode->lock_state != AFS_VNODE_LOCK_DELETED) {
                        trace_afs_flock_ev(vnode, NULL, afs_flock_release_fail,
                                           ret);
                        printk(KERN_WARNING "AFS:"
                               " Failed to release lock on {%llx:%llx} error %d\n",
                               vnode->fid.vid, vnode->fid.vnode, ret);
                }

                spin_lock(&vnode->lock);
                if (ret == -ENOENT)
                        afs_kill_lockers_enoent(vnode);
                else
                        afs_next_locker(vnode, 0);
                spin_unlock(&vnode->lock);
                return;

        /* If we've already got a lock, then it must be time to extend that
         * lock as AFS locks time out after 5 minutes.
         */
        case AFS_VNODE_LOCK_GRANTED:
                _debug("extend");

                ASSERT(!list_empty(&vnode->granted_locks));

                key = key_get(vnode->lock_key);
                afs_set_lock_state(vnode, AFS_VNODE_LOCK_EXTENDING);
                trace_afs_flock_ev(vnode, NULL, afs_flock_work_extending, 0);
                spin_unlock(&vnode->lock);

                ret = afs_extend_lock(vnode, key); /* RPC */
                key_put(key);

                if (ret < 0) {
                        trace_afs_flock_ev(vnode, NULL, afs_flock_extend_fail,
                                           ret);
                        pr_warn("AFS: Failed to extend lock on {%llx:%llx} error %d\n",
                                vnode->fid.vid, vnode->fid.vnode, ret);
                }

                spin_lock(&vnode->lock);

                if (ret == -ENOENT) {
                        afs_kill_lockers_enoent(vnode);
                        spin_unlock(&vnode->lock);
                        return;
                }

                if (vnode->lock_state != AFS_VNODE_LOCK_EXTENDING)
                        goto again;
                afs_set_lock_state(vnode, AFS_VNODE_LOCK_GRANTED);

                if (ret != 0)
                        queue_delayed_work(afs_lock_manager, &vnode->lock_work,
                                           HZ * 10);
                spin_unlock(&vnode->lock);
                _leave(" [ext]");
                return;

        /* If we're waiting for a callback to indicate lock release, we can't
         * actually rely on this, so need to recheck at regular intervals.  The
         * problem is that the server might not notify us if the lock just
         * expires (say because a client died) rather than being explicitly
         * released.
         */
        case AFS_VNODE_LOCK_WAITING_FOR_CB:
                _debug("retry");
                afs_next_locker(vnode, 0);
                spin_unlock(&vnode->lock);
                return;

        case AFS_VNODE_LOCK_DELETED:
                afs_kill_lockers_enoent(vnode);
                spin_unlock(&vnode->lock);
                return;

                /* Fall through */
        default:
                /* Looks like a lock request was withdrawn. */
                spin_unlock(&vnode->lock);
                _leave(" [no]");
                return;
        }
}

/*
 * pass responsibility for the unlocking of a vnode on the server to the
 * manager thread, lest a pending signal in the calling thread interrupt
 * AF_RXRPC
 * - the caller must hold the vnode lock
 */
static void afs_defer_unlock(struct afs_vnode *vnode)
{
        _enter("%u", vnode->lock_state);

        if (list_empty(&vnode->granted_locks) &&
            (vnode->lock_state == AFS_VNODE_LOCK_GRANTED ||
             vnode->lock_state == AFS_VNODE_LOCK_EXTENDING)) {
                cancel_delayed_work(&vnode->lock_work);

                afs_set_lock_state(vnode, AFS_VNODE_LOCK_NEED_UNLOCK);
                trace_afs_flock_ev(vnode, NULL, afs_flock_defer_unlock, 0);
                queue_delayed_work(afs_lock_manager, &vnode->lock_work, 0);
        }
}

/*
 * Check that our view of the file metadata is up to date and check to see
 * whether we think that we have a locking permit.
 */
static int afs_do_setlk_check(struct afs_vnode *vnode, struct key *key,
                              enum afs_flock_mode mode, afs_lock_type_t type)
{
        afs_access_t access;
        int ret;

        /* Make sure we've got a callback on this file and that our view of the
         * data version is up to date.
         */
        ret = afs_validate(vnode, key);
        if (ret < 0)
                return ret;

        /* Check the permission set to see if we're actually going to be
         * allowed to get a lock on this file.
         */
        ret = afs_check_permit(vnode, key, &access);
        if (ret < 0)
                return ret;

        /* At a rough estimation, you need LOCK, WRITE or INSERT perm to
         * read-lock a file and WRITE or INSERT perm to write-lock a file.
         *
         * We can't rely on the server to do this for us since if we want to
         * share a read lock that we already have, we won't go the server.
         */
        if (type == AFS_LOCK_READ) {
                if (!(access & (AFS_ACE_INSERT | AFS_ACE_WRITE | AFS_ACE_LOCK)))
                        return -EACCES;
        } else {
                if (!(access & (AFS_ACE_INSERT | AFS_ACE_WRITE)))
                        return -EACCES;
        }

        return 0;
}

/*
 * request a lock on a file on the server
 */
static int afs_do_setlk(struct file *file, struct file_lock *fl)
{
        struct inode *inode = locks_inode(file);
        struct afs_vnode *vnode = AFS_FS_I(inode);
        enum afs_flock_mode mode = AFS_FS_S(inode->i_sb)->flock_mode;
        afs_lock_type_t type;
        struct key *key = afs_file_key(file);
        bool partial, no_server_lock = false;
        int ret;

        if (mode == afs_flock_mode_unset)
                mode = afs_flock_mode_openafs;

        _enter("{%llx:%llu},%llu-%llu,%u,%u",
               vnode->fid.vid, vnode->fid.vnode,
               fl->fl_start, fl->fl_end, fl->fl_type, mode);

        fl->fl_ops = &afs_lock_ops;
        INIT_LIST_HEAD(&fl->fl_u.afs.link);
        fl->fl_u.afs.state = AFS_LOCK_PENDING;

        partial = (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX);
        type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
        if (mode == afs_flock_mode_write && partial)
                type = AFS_LOCK_WRITE;

        ret = afs_do_setlk_check(vnode, key, mode, type);
        if (ret < 0)
                return ret;

        trace_afs_flock_op(vnode, fl, afs_flock_op_set_lock);

        /* AFS3 protocol only supports full-file locks and doesn't provide any
         * method of upgrade/downgrade, so we need to emulate for partial-file
         * locks.
         *
         * The OpenAFS client only gets a server lock for a full-file lock and
         * keeps partial-file locks local.  Allow this behaviour to be emulated
         * (as the default).
         */
        if (mode == afs_flock_mode_local ||
            (partial && mode == afs_flock_mode_openafs)) {
                no_server_lock = true;
                goto skip_server_lock;
        }

        spin_lock(&vnode->lock);
        list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);

        ret = -ENOENT;
        if (vnode->lock_state == AFS_VNODE_LOCK_DELETED)
                goto error_unlock;

        /* If we've already got a lock on the server then try to move to having
         * the VFS grant the requested lock.  Note that this means that other
         * clients may get starved out.
         */
        _debug("try %u", vnode->lock_state);
        if (vnode->lock_state == AFS_VNODE_LOCK_GRANTED) {
                if (type == AFS_LOCK_READ) {
                        _debug("instant readlock");
                        list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
                        fl->fl_u.afs.state = AFS_LOCK_GRANTED;
                        goto vnode_is_locked_u;
                }

                if (vnode->lock_type == AFS_LOCK_WRITE) {
                        _debug("instant writelock");
                        list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
                        fl->fl_u.afs.state = AFS_LOCK_GRANTED;
                        goto vnode_is_locked_u;
                }
        }

        if (vnode->lock_state == AFS_VNODE_LOCK_NONE &&
            !(fl->fl_flags & FL_SLEEP)) {
                ret = -EAGAIN;
                if (type == AFS_LOCK_READ) {
                        if (vnode->status.lock_count == -1)
                                goto lock_is_contended; /* Write locked */
                } else {
                        if (vnode->status.lock_count != 0)
                                goto lock_is_contended; /* Locked */
                }
        }

        if (vnode->lock_state != AFS_VNODE_LOCK_NONE)
                goto need_to_wait;

try_to_lock:
        /* We don't have a lock on this vnode and we aren't currently waiting
         * for one either, so ask the server for a lock.
         *
         * Note that we need to be careful if we get interrupted by a signal
         * after dispatching the request as we may still get the lock, even
         * though we don't wait for the reply (it's not too bad a problem - the
         * lock will expire in 5 mins anyway).
         */
        trace_afs_flock_ev(vnode, fl, afs_flock_try_to_lock, 0);
        vnode->lock_key = key_get(key);
        vnode->lock_type = type;
        afs_set_lock_state(vnode, AFS_VNODE_LOCK_SETTING);
        spin_unlock(&vnode->lock);

        ret = afs_set_lock(vnode, key, type); /* RPC */

        spin_lock(&vnode->lock);
        switch (ret) {
        case -EKEYREJECTED:
        case -EKEYEXPIRED:
        case -EKEYREVOKED:
        case -EPERM:
        case -EACCES:
                fl->fl_u.afs.state = ret;
                trace_afs_flock_ev(vnode, fl, afs_flock_fail_perm, ret);
                list_del_init(&fl->fl_u.afs.link);
                afs_next_locker(vnode, ret);
                goto error_unlock;

        case -ENOENT:
                fl->fl_u.afs.state = ret;
                trace_afs_flock_ev(vnode, fl, afs_flock_fail_other, ret);
                list_del_init(&fl->fl_u.afs.link);
                afs_kill_lockers_enoent(vnode);
                goto error_unlock;

        default:
                fl->fl_u.afs.state = ret;
                trace_afs_flock_ev(vnode, fl, afs_flock_fail_other, ret);
                list_del_init(&fl->fl_u.afs.link);
                afs_next_locker(vnode, 0);
                goto error_unlock;

        case -EWOULDBLOCK:
                /* The server doesn't have a lock-waiting queue, so the client
                 * will have to retry.  The server will break the outstanding
                 * callbacks on a file when a lock is released.
                 */
                ASSERT(list_empty(&vnode->granted_locks));
                ASSERTCMP(vnode->pending_locks.next, ==, &fl->fl_u.afs.link);
                goto lock_is_contended;

        case 0:
                afs_set_lock_state(vnode, AFS_VNODE_LOCK_GRANTED);
                trace_afs_flock_ev(vnode, fl, afs_flock_acquired, type);
                afs_grant_locks(vnode);
                goto vnode_is_locked_u;
        }

vnode_is_locked_u:
        spin_unlock(&vnode->lock);
vnode_is_locked:
        /* the lock has been granted by the server... */
        ASSERTCMP(fl->fl_u.afs.state, ==, AFS_LOCK_GRANTED);

skip_server_lock:
        /* ... but the VFS still needs to distribute access on this client. */
        trace_afs_flock_ev(vnode, fl, afs_flock_vfs_locking, 0);
        ret = locks_lock_file_wait(file, fl);
        trace_afs_flock_ev(vnode, fl, afs_flock_vfs_lock, ret);
        if (ret < 0)
                goto vfs_rejected_lock;

        /* Again, make sure we've got a callback on this file and, again, make
         * sure that our view of the data version is up to date (we ignore
         * errors incurred here and deal with the consequences elsewhere).
         */
        afs_validate(vnode, key);
        _leave(" = 0");
        return 0;

lock_is_contended:
        if (!(fl->fl_flags & FL_SLEEP)) {
                list_del_init(&fl->fl_u.afs.link);
                afs_next_locker(vnode, 0);
                ret = -EAGAIN;
                goto error_unlock;
        }

        afs_set_lock_state(vnode, AFS_VNODE_LOCK_WAITING_FOR_CB);
        trace_afs_flock_ev(vnode, fl, afs_flock_would_block, ret);
        queue_delayed_work(afs_lock_manager, &vnode->lock_work, HZ * 5);

need_to_wait:
        /* We're going to have to wait.  Either this client doesn't have a lock
         * on the server yet and we need to wait for a callback to occur, or
         * the client does have a lock on the server, but it's shared and we
         * need an exclusive lock.
         */
        spin_unlock(&vnode->lock);

        trace_afs_flock_ev(vnode, fl, afs_flock_waiting, 0);
        ret = wait_event_interruptible(fl->fl_wait,
                                       fl->fl_u.afs.state != AFS_LOCK_PENDING);
        trace_afs_flock_ev(vnode, fl, afs_flock_waited, ret);

        if (fl->fl_u.afs.state >= 0 && fl->fl_u.afs.state != AFS_LOCK_GRANTED) {
                spin_lock(&vnode->lock);

                switch (fl->fl_u.afs.state) {
                case AFS_LOCK_YOUR_TRY:
                        fl->fl_u.afs.state = AFS_LOCK_PENDING;
                        goto try_to_lock;
                case AFS_LOCK_PENDING:
                        if (ret > 0) {
                                /* We need to retry the lock.  We may not be
                                 * notified by the server if it just expired
                                 * rather than being released.
                                 */
                                ASSERTCMP(vnode->lock_state, ==, AFS_VNODE_LOCK_WAITING_FOR_CB);
                                afs_set_lock_state(vnode, AFS_VNODE_LOCK_SETTING);
                                fl->fl_u.afs.state = AFS_LOCK_PENDING;
                                goto try_to_lock;
                        }
                        goto error_unlock;
                case AFS_LOCK_GRANTED:
                default:
                        break;
                }

                spin_unlock(&vnode->lock);
        }

        if (fl->fl_u.afs.state == AFS_LOCK_GRANTED)
                goto vnode_is_locked;
        ret = fl->fl_u.afs.state;
        goto error;

vfs_rejected_lock:
        /* The VFS rejected the lock we just obtained, so we have to discard
         * what we just got.  We defer this to the lock manager work item to
         * deal with.
         */
        _debug("vfs refused %d", ret);
        if (no_server_lock)
                goto error;
        spin_lock(&vnode->lock);
        list_del_init(&fl->fl_u.afs.link);
        afs_defer_unlock(vnode);

error_unlock:
        spin_unlock(&vnode->lock);
error:
        _leave(" = %d", ret);
        return ret;
}

/*
 * unlock on a file on the server
 */
static int afs_do_unlk(struct file *file, struct file_lock *fl)
{
        struct afs_vnode *vnode = AFS_FS_I(locks_inode(file));
        int ret;

        _enter("{%llx:%llu},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);

        trace_afs_flock_op(vnode, fl, afs_flock_op_unlock);

        /* Flush all pending writes before doing anything with locks. */
        vfs_fsync(file, 0);

        ret = locks_lock_file_wait(file, fl);
        _leave(" = %d [%u]", ret, vnode->lock_state);
        return ret;
}

/*
 * return information about a lock we currently hold, if indeed we hold one
 */
static int afs_do_getlk(struct file *file, struct file_lock *fl)
{
        struct afs_vnode *vnode = AFS_FS_I(locks_inode(file));
        struct key *key = afs_file_key(file);
        int ret, lock_count;

        _enter("");

        if (vnode->lock_state == AFS_VNODE_LOCK_DELETED)
                return -ENOENT;

        fl->fl_type = F_UNLCK;

        /* check local lock records first */
        posix_test_lock(file, fl);
        if (fl->fl_type == F_UNLCK) {
                /* no local locks; consult the server */
                ret = afs_fetch_status(vnode, key, false, NULL);
                if (ret < 0)
                        goto error;

                lock_count = READ_ONCE(vnode->status.lock_count);
                if (lock_count != 0) {
                        if (lock_count > 0)
                                fl->fl_type = F_RDLCK;
                        else
                                fl->fl_type = F_WRLCK;
                        fl->fl_start = 0;
                        fl->fl_end = OFFSET_MAX;
                        fl->fl_pid = 0;
                }
        }

        ret = 0;
error:
        _leave(" = %d [%hd]", ret, fl->fl_type);
        return ret;
}

/*
 * manage POSIX locks on a file
 */
int afs_lock(struct file *file, int cmd, struct file_lock *fl)
{
        struct afs_vnode *vnode = AFS_FS_I(locks_inode(file));
        enum afs_flock_operation op;
        int ret;

        _enter("{%llx:%llu},%d,{t=%x,fl=%x,r=%Ld:%Ld}",
               vnode->fid.vid, vnode->fid.vnode, cmd,
               fl->fl_type, fl->fl_flags,
               (long long) fl->fl_start, (long long) fl->fl_end);

        /* AFS doesn't support mandatory locks */
        if (__mandatory_lock(&vnode->vfs_inode) && fl->fl_type != F_UNLCK)
                return -ENOLCK;

        if (IS_GETLK(cmd))
                return afs_do_getlk(file, fl);

        fl->fl_u.afs.debug_id = atomic_inc_return(&afs_file_lock_debug_id);
        trace_afs_flock_op(vnode, fl, afs_flock_op_lock);

        if (fl->fl_type == F_UNLCK)
                ret = afs_do_unlk(file, fl);
        else
                ret = afs_do_setlk(file, fl);

        switch (ret) {
        case 0:         op = afs_flock_op_return_ok; break;
        case -EAGAIN:   op = afs_flock_op_return_eagain; break;
        case -EDEADLK:  op = afs_flock_op_return_edeadlk; break;
        default:        op = afs_flock_op_return_error; break;
        }
        trace_afs_flock_op(vnode, fl, op);
        return ret;
}

/*
 * manage FLOCK locks on a file
 */
int afs_flock(struct file *file, int cmd, struct file_lock *fl)
{
        struct afs_vnode *vnode = AFS_FS_I(locks_inode(file));
        enum afs_flock_operation op;
        int ret;

        _enter("{%llx:%llu},%d,{t=%x,fl=%x}",
               vnode->fid.vid, vnode->fid.vnode, cmd,
               fl->fl_type, fl->fl_flags);

        /*
         * No BSD flocks over NFS allowed.
         * Note: we could try to fake a POSIX lock request here by
         * using ((u32) filp | 0x80000000) or some such as the pid.
         * Not sure whether that would be unique, though, or whether
         * that would break in other places.
         */
        if (!(fl->fl_flags & FL_FLOCK))
                return -ENOLCK;

        fl->fl_u.afs.debug_id = atomic_inc_return(&afs_file_lock_debug_id);
        trace_afs_flock_op(vnode, fl, afs_flock_op_flock);

        /* we're simulating flock() locks using posix locks on the server */
        if (fl->fl_type == F_UNLCK)
                ret = afs_do_unlk(file, fl);
        else
                ret = afs_do_setlk(file, fl);

        switch (ret) {
        case 0:         op = afs_flock_op_return_ok; break;
        case -EAGAIN:   op = afs_flock_op_return_eagain; break;
        case -EDEADLK:  op = afs_flock_op_return_edeadlk; break;
        default:        op = afs_flock_op_return_error; break;
        }
        trace_afs_flock_op(vnode, fl, op);
        return ret;
}

/*
 * the POSIX lock management core VFS code copies the lock record and adds the
 * copy into its own list, so we need to add that copy to the vnode's lock
 * queue in the same place as the original (which will be deleted shortly
 * after)
 */
static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl)
{
        struct afs_vnode *vnode = AFS_FS_I(locks_inode(fl->fl_file));

        _enter("");

        new->fl_u.afs.debug_id = atomic_inc_return(&afs_file_lock_debug_id);

        spin_lock(&vnode->lock);
        trace_afs_flock_op(vnode, new, afs_flock_op_copy_lock);
        list_add(&new->fl_u.afs.link, &fl->fl_u.afs.link);
        spin_unlock(&vnode->lock);
}

/*
 * need to remove this lock from the vnode queue when it's removed from the
 * VFS's list
 */
static void afs_fl_release_private(struct file_lock *fl)
{
        struct afs_vnode *vnode = AFS_FS_I(locks_inode(fl->fl_file));

        _enter("");

        spin_lock(&vnode->lock);

        trace_afs_flock_op(vnode, fl, afs_flock_op_release_lock);
        list_del_init(&fl->fl_u.afs.link);
        if (list_empty(&vnode->granted_locks))
                afs_defer_unlock(vnode);

        _debug("state %u for %p", vnode->lock_state, vnode);
        spin_unlock(&vnode->lock);
}