From 52b042ab9948cc367b61f9ca9c18603aa7813c3a Mon Sep 17 00:00:00 2001 From: Yihao Wu Date: Wed, 22 May 2019 01:57:10 +0800 Subject: 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 Reviewed-by: Jeff Layton Signed-off-by: Anna Schumaker --- fs/nfs/nfs4proc.c | 24 +++++++----------------- 1 file changed, 7 insertions(+), 17 deletions(-) (limited to 'fs/nfs') 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); -- cgit v1.2.3 From ba851a39c9703f09684a541885ed176f8fb7c868 Mon Sep 17 00:00:00 2001 From: Yihao Wu Date: Mon, 13 May 2019 14:58:22 +0800 Subject: NFSv4.1: Fix bug only first CB_NOTIFY_LOCK is handled When a waiter is waked by CB_NOTIFY_LOCK, it will retry nfs4_proc_setlk(). The waiter may fail to nfs4_proc_setlk() and sleep again. However, the waiter is already removed from clp->cl_lock_waitq when handling CB_NOTIFY_LOCK in nfs4_wake_lock_waiter(). So any subsequent CB_NOTIFY_LOCK won't wake this waiter anymore. We should put the waiter back to clp->cl_lock_waitq before retrying. Cc: stable@vger.kernel.org #4.9+ Signed-off-by: Yihao Wu Reviewed-by: Jeff Layton Signed-off-by: Anna Schumaker --- fs/nfs/nfs4proc.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'fs/nfs') diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index 5f89bbd177c6..e38f4af20950 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -6987,20 +6987,22 @@ nfs4_retry_setlk(struct nfs4_state *state, int cmd, struct file_lock *request) init_wait(&wait); wait.private = &waiter; wait.func = nfs4_wake_lock_waiter; - add_wait_queue(q, &wait); while(!signalled()) { + add_wait_queue(q, &wait); status = nfs4_proc_setlk(state, cmd, request); - if ((status != -EAGAIN) || IS_SETLK(cmd)) + if ((status != -EAGAIN) || IS_SETLK(cmd)) { + finish_wait(q, &wait); break; + } status = -ERESTARTSYS; freezer_do_not_count(); wait_woken(&wait, TASK_INTERRUPTIBLE, NFS4_LOCK_MAXTIMEOUT); freezer_count(); + finish_wait(q, &wait); } - finish_wait(q, &wait); return status; } #else /* !CONFIG_NFS_V4_1 */ -- cgit v1.2.3