block: fix an oops on BLKPREP_KILL

Doing a bit of torture testing, I ran across a BUG in the block
subsystem (at blk-core.c:2048): the test for if the request is queued.

It turns out the trigger was a BLKPREP_KILL coming out of the SCSI prep
function.  Currently for BLKPREP_KILL requests, we send them straight
into __blk_end_request_all() with an error, but they've never been
dequeued, so they trip the bug.  Fix this by starting requests before
killing them.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 8b3b74e69184..7ae83a1e2acf 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1789,6 +1789,11 @@ struct request *blk_peek_request(struct request_queue *q)
                         break;
                 } else if (ret == BLKPREP_KILL) {
                         rq->cmd_flags |= REQ_QUIET;
+                        /*
+                         * Mark this request as started so we don't trigger
+                         * any debug logic in the end I/O path.
+                         */
+                        blk_start_request(rq);
                         __blk_end_request_all(rq, -EIO);
                 } else {
                         printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);