aoe: end barrier bios with EOPNOTSUPP

BugLink: http://bugzilla.kernel.org/show_bug.cgi?id=13942
Bruno Premont noticed that aoe throws a BUG during umount of an XFS in
2.6.31:

[ 5259.349897] aoe: bi_io_vec is NULL
[ 5259.349940] ------------[ cut here ]------------
[ 5259.349958] kernel BUG at /usr/src/linux-2.6/drivers/block/aoe/aoeblk.c:177!
[ 5259.349990] invalid opcode: 0000 [#1]

The bio in question is a barrier.  Jens Axboe suggested that such bios
need to be recognized and ended with -EOPNOTSUPP by any driver that
provides its own ->make_request_fn handler and does not handle
barriers.

In testing the changes below eliminate the BUG.

(Better would be real barrier support, something that Ed says he'll add
for later in the .32 cycle. For now, this at least gets rid of a bug
with crashing on an empty barrier. Jens)

Signed-off-by: Ed L. Cashin <ecashin@coraid.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/drivers/block/aoe/aoeblk.c b/drivers/block/aoe/aoeblk.c
index 1e15889c4b9819f837076c1b17df34fc8ef881c2..bf7ceba1878870b9b9131fde538dd3217d2160af 100644 (file)
--- a/drivers/block/aoe/aoeblk.c
+++ b/drivers/block/aoe/aoeblk.c
@@ -172,6 +172,9 @@ aoeblk_make_request(struct request_queue *q, struct bio *bio)
                BUG();
                bio_endio(bio, -ENXIO);
                return 0;
+       } else if (bio_rw_flagged(bio, BIO_RW_BARRIER)) {
+               bio_endio(bio, -EOPNOTSUPP);
+               return 0;
        } else if (bio->bi_io_vec == NULL) {
                printk(KERN_ERR "aoe: bi_io_vec is NULL\n");
                BUG();