Commit 52b042ab authored by Yihao Wu's avatar Yihao Wu Committed by Anna Schumaker
Browse files

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



Commit b7dbcc0e "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: a1d617d8 ("nfs: allow blocking locks to be awoken by lock callbacks")
Cc: stable@vger.kernel.org #4.9+
Signed-off-by: default avatarYihao Wu <wuyihao@linux.alibaba.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
parent 7987b694

fs/nfs/nfs4proc.c

+7 −17
Original line number Diff line number Diff line
@@ -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);

CRA Git | Maintained and supported by SUSTech CRA and CCSE