From: Pavel Shilovsky Date: Thu, 11 Jul 2013 07:17:45 +0000 (+0400) Subject: CIFS: Fix a deadlock when a file is reopened X-Git-Tag: firefly_0821_release~6453^2~1588 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=059a1671f28c977fe69a0f86eeb0fa2084fdb3dd;p=firefly-linux-kernel-4.4.55.git CIFS: Fix a deadlock when a file is reopened commit 689c3db4d57a73bee6c5ad7797fce7b54d32a87c upstream. If we request reading or writing on a file that needs to be reopened, it causes the deadlock: we are already holding rw semaphore for reading and then we try to acquire it for writing in cifs_relock_file. Fix this by acquiring the semaphore for reading in cifs_relock_file due to we don't make any changes in locks and don't need a write access. Signed-off-by: Pavel Shilovsky Acked-by: Jeff Layton Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/cifs/file.c b/fs/cifs/file.c index 48b29d24c9f4..c2934f8701da 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -553,11 +553,10 @@ cifs_relock_file(struct cifsFileInfo *cfile) struct cifs_tcon *tcon = tlink_tcon(cfile->tlink); int rc = 0; - /* we are going to update can_cache_brlcks here - need a write access */ - down_write(&cinode->lock_sem); + down_read(&cinode->lock_sem); if (cinode->can_cache_brlcks) { - /* can cache locks - no need to push them */ - up_write(&cinode->lock_sem); + /* can cache locks - no need to relock */ + up_read(&cinode->lock_sem); return rc; } @@ -568,7 +567,7 @@ cifs_relock_file(struct cifsFileInfo *cfile) else rc = tcon->ses->server->ops->push_mand_locks(cfile); - up_write(&cinode->lock_sem); + up_read(&cinode->lock_sem); return rc; }