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NFSv4.1: Again fix a race where CB_NOTIFY_LOCK fails to wake a waiter

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Commit b7dbcc0e43 "NFSv4.1: Fix a race where CB_NOTIFY_LOCK fails to wake a waiter"
found this bug. However it didn't fix it.

This commit replaces schedule_timeout() with wait_woken() and
default_wake_function() with woken_wake_function() in function
nfs4_retry_setlk() and nfs4_wake_lock_waiter(). wait_woken() uses
memory barriers in its implementation to avoid potential race condition
when putting a process into sleeping state and then waking it up.

Fixes: a1d617d8f1 ("nfs: allow blocking locks to be awoken by lock callbacks")
Cc: stable@vger.kernel.org #4.9+
Signed-off-by: Yihao Wu <wuyihao@linux.alibaba.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Yihao Wu 2019-05-22 01:57:10 +08:00 committed by Anna Schumaker
parent 7987b694ad
commit 52b042ab99
1 changed files with 7 additions and 17 deletions
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24
fs/nfs/nfs4proc.c
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@ -6932,7 +6932,6 @@ struct nfs4_lock_waiter {
struct task_struct *task;
struct inode *inode;
struct nfs_lowner *owner;
bool notified;
};
static int
@ -6954,13 +6953,13 @@ nfs4_wake_lock_waiter(wait_queue_entry_t *wait, unsigned int mode, int flags, vo
/* Make sure it's for the right inode */
if (nfs_compare_fh(NFS_FH(waiter->inode), &cbnl->cbnl_fh))
return 0;
waiter->notified = true;
}
/* override "private" so we can use default_wake_function */
wait->private = waiter->task;
ret = autoremove_wake_function(wait, mode, flags, key);
ret = woken_wake_function(wait, mode, flags, key);
if (ret)
list_del_init(&wait->entry);
wait->private = waiter;
return ret;
}
@ -6969,7 +6968,6 @@ static int
nfs4_retry_setlk(struct nfs4_state *state, int cmd, struct file_lock *request)
{
int status = -ERESTARTSYS;
unsigned long flags;
struct nfs4_lock_state *lsp = request->fl_u.nfs4_fl.owner;
struct nfs_server *server = NFS_SERVER(state->inode);
struct nfs_client *clp = server->nfs_client;
@ -6979,8 +6977,7 @@ nfs4_retry_setlk(struct nfs4_state *state, int cmd, struct file_lock *request)
.s_dev = server->s_dev };
struct nfs4_lock_waiter waiter = { .task = current,
.inode = state->inode,
.owner = &owner,
.notified = false };
.owner = &owner};
wait_queue_entry_t wait;
/* Don't bother with waitqueue if we don't expect a callback */
@ -6993,21 +6990,14 @@ nfs4_retry_setlk(struct nfs4_state *state, int cmd, struct file_lock *request)
add_wait_queue(q, &wait);
while(!signalled()) {
waiter.notified = false;
status = nfs4_proc_setlk(state, cmd, request);
if ((status != -EAGAIN) || IS_SETLK(cmd))
break;
status = -ERESTARTSYS;
spin_lock_irqsave(&q->lock, flags);
if (waiter.notified) {
spin_unlock_irqrestore(&q->lock, flags);
continue;
}
set_current_state(TASK_INTERRUPTIBLE);
spin_unlock_irqrestore(&q->lock, flags);
freezable_schedule_timeout(NFS4_LOCK_MAXTIMEOUT);
freezer_do_not_count();
wait_woken(&wait, TASK_INTERRUPTIBLE, NFS4_LOCK_MAXTIMEOUT);
freezer_count();
}
finish_wait(q, &wait);