Commit 37f9579f authored by Bart Van Assche's avatar Bart Van Assche Committed by Jens Axboe
Browse files

blk-mq: Avoid that submitting a bio concurrently with device removal triggers a crash 



Because blkcg_exit_queue() is now called from inside blk_cleanup_queue()
it is no longer safe to access cgroup information during or after the
blk_cleanup_queue() call. Hence protect the generic_make_request_checks()
call with blk_queue_enter() / blk_queue_exit().

Reported-by: default avatarMing Lei <ming.lei@redhat.com>
Fixes: a063057d ("block: Fix a race between request queue removal and the block cgroup controller")
Signed-off-by: default avatarBart Van Assche <bart.vanassche@wdc.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent a93f00b3

block/blk-core.c

+29 −6
Original line number Diff line number Diff line
@@ -2385,8 +2385,20 @@ blk_qc_t generic_make_request(struct bio *bio) 
	 * yet.

	 */

	struct bio_list bio_list_on_stack[2];

	blk_mq_req_flags_t flags = 0;

	struct request_queue *q = bio->bi_disk->queue;

	blk_qc_t ret = BLK_QC_T_NONE;



	if (bio->bi_opf & REQ_NOWAIT)

		flags = BLK_MQ_REQ_NOWAIT;

	if (blk_queue_enter(q, flags) < 0) {

		if (!blk_queue_dying(q) && (bio->bi_opf & REQ_NOWAIT))

			bio_wouldblock_error(bio);

		else

			bio_io_error(bio);

		return ret;

	}



	if (!generic_make_request_checks(bio))

		goto out;
@@ -2423,11 +2435,22 @@ blk_qc_t generic_make_request(struct bio *bio) 
	bio_list_init(&bio_list_on_stack[0]);

	current->bio_list = bio_list_on_stack;

	do {

		struct request_queue *q = bio->bi_disk->queue;

		blk_mq_req_flags_t flags = bio->bi_opf & REQ_NOWAIT ?

			BLK_MQ_REQ_NOWAIT : 0;

		bool enter_succeeded = true;



		if (likely(blk_queue_enter(q, flags) == 0)) {

		if (unlikely(q != bio->bi_disk->queue)) {

			if (q)

				blk_queue_exit(q);

			q = bio->bi_disk->queue;

			flags = 0;

			if (bio->bi_opf & REQ_NOWAIT)

				flags = BLK_MQ_REQ_NOWAIT;

			if (blk_queue_enter(q, flags) < 0) {

				enter_succeeded = false;

				q = NULL;

			}

		}



		if (enter_succeeded) {

			struct bio_list lower, same;



			/* Create a fresh bio_list for all subordinate requests */
@@ -2435,8 +2458,6 @@ blk_qc_t generic_make_request(struct bio *bio) 
			bio_list_init(&bio_list_on_stack[0]);

			ret = q->make_request_fn(q, bio);



			blk_queue_exit(q);



			/* sort new bios into those for a lower level

			 * and those for the same level

			 */
@@ -2463,6 +2484,8 @@ blk_qc_t generic_make_request(struct bio *bio) 
	current->bio_list = NULL; /* deactivate */



out:

	if (q)

		blk_queue_exit(q);

	return ret;

}

EXPORT_SYMBOL(generic_make_request);

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