dm: fix memory leak in dm_create_persistent() when starting metadata update thread fails

If, in dm_create_persistent(), the call to create_singlethread_workqueue()
fails then we'll return without freeing the memory allocated to 'ps', thus
leaking sizeof(struct pstore) bytes.  This patch fixes the leak.

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com
Acked-by: NAlasdair G Kergon <agk@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/md/dm-exception-store.c

@@ -623,6 +623,7 @@ int dm_create_persistent(struct exception_store *store)
 
 	ps->metadata_wq = create_singlethread_workqueue("ksnaphd");
 	if (!ps->metadata_wq) {
+		kfree(ps);
 		DMERR("couldn't start header metadata update thread");
 		return -ENOMEM;
 	}