[PATCH] aoe: end barrier bios with EOPNOTSUPP

[Ed Cashin <ecashin@coraid.com>]

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.

Signed-off-by: Ed L. Cashin <ecashin@coraid.com>
---
After this patch has been reviewed I plan to add this patch to
the aoe quilt tree for linux-next.

 drivers/block/aoe/aoeblk.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/block/aoe/aoeblk.c b/drivers/block/aoe/aoeblk.c
index 2307a27..d6806fb 100644
--- 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_barrier(bio)) {
+                bio_endio(bio, -EOPNOTSUPP);
+                return 0;
 	} else if (bio->bi_io_vec == NULL) {
 		printk(KERN_ERR "aoe: bi_io_vec is NULL\n");
 		BUG();
-- 
1.5.6.5


-- 
  Ed Cashin
  http://noserose.net/e/
  http://www.coraid.com/