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CIFS: Fix a deadlock when a file is reopened 

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.

CC: <stable@vger.kernel.org>
Signed-off-by: Pavel Shilovsky <pshilovsky@samba.org>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
This commit is contained in:
Pavel Shilovsky 2013-07-11 11:17:45 +04:00 committed by Steve French
parent b33fcf1c9d
commit 689c3db4d5
1 changed files with 4 additions and 5 deletions
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9
fs/cifs/file.c
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@ -561,11 +561,10 @@ 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;
}
@ -576,7 +575,7 @@ 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;
}