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Commit 689c3db4 authored by Pavel Shilovsky's avatar Pavel Shilovsky Committed by Steve French
Browse files

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: default avatarPavel Shilovsky <pshilovsky@samba.org>
Acked-by: default avatarJeff Layton <jlayton@redhat.com>
Signed-off-by: default avatarSteve French <smfrench@gmail.com>
parent b33fcf1c

fs/cifs/file.c

+4 −5
Original line number Diff line number Diff line
@@ -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;

}