| From | Kamal Mostafa <> | Subject | [PATCH 132/145] CIFS: Fix a deadlock when a file is reopened | Date | Wed, 17 Jul 2013 15:47:44 -0700 |
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3.8.13.5 -stable review patch. If anyone has any objections, please let me know.
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From: Pavel Shilovsky <pshilovsky@samba.org>
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 <pshilovsky@samba.org> Acked-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Steve French <smfrench@gmail.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- fs/cifs/file.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/fs/cifs/file.c b/fs/cifs/file.c index 1d93ee8..ae62632 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -551,11 +551,10 @@ 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; } @@ -566,7 +565,7 @@ 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; } -- 1.8.1.2
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