The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 52b042ab9948cc367b61f9ca9c18603aa7813c3a Mon Sep 17 00:00:00 2001

From: Yihao Wu wuyihao@linux.alibaba.com Date: Wed, 22 May 2019 01:57:10 +0800 Subject: [PATCH] NFSv4.1: Again fix a race where CB_NOTIFY_LOCK fails to wake a waiter

Commit b7dbcc0e433f "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: a1d617d8f134 ("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

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index c29cbef6b53f..5f89bbd177c6 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -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);