[PATCH] Fix failure paths in modules init in umem.c

If register_blkdev() or alloc-disk fail in mm_init() after
pci_register_driver() succeeds, then mm_pci_driver is not unregistered
properly:

Cc: Philip Guo <pg@cs.stanford.edu>
Signed-off-by: NNeil Brown <neilb@suse.de>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/block/umem.c

@@ -1179,8 +1179,10 @@ static int __init mm_init(void)
 		return -ENOMEM;
 
 	err = major_nr = register_blkdev(0, "umem");
-	if (err < 0)
+	if (err < 0) {
+		pci_unregister_driver(&mm_pci_driver);
 		return -EIO;
+	}
 
 	for (i = 0; i < num_cards; i++) {
 		mm_gendisk[i] = alloc_disk(1 << MM_SHIFT);
@@ -1207,6 +1209,7 @@ static int __init mm_init(void)
 	return 0;
 
 out:
+	pci_unregister_driver(&mm_pci_driver);
 	unregister_blkdev(major_nr, "umem");
 	while (i--)
 		put_disk(mm_gendisk[i]);