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Commit 698cef17 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

block: cover another queue enter recursion via BIO_QUEUE_ENTERED 



Except for blk_queue_split(), bio_split() is used for splitting bio too,
then the remained bio is often resubmit to queue via generic_make_request().
So the same queue enter recursion exits in this case too. Unfortunatley
commit cd4a4ae4 doesn't help this case.

This patch covers the above case by setting BIO_QUEUE_ENTERED before calling
q->make_request_fn.

In theory the per-bio flag is used to simulate one stack variable, it is
just fine to clear it after q->make_request_fn is returned. Especially
the same bio can't be submitted from another context.

Fixes: cd4a4ae4 ("block: don't use blocking queue entered for recursive bio submits")
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: NeilBrown <neilb@suse.com>
Reviewed-by: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 8b9433eb

block/blk-core.c

+11 −0
Original line number Diff line number Diff line
@@ -1083,7 +1083,18 @@ blk_qc_t generic_make_request(struct bio *bio) 
			/* Create a fresh bio_list for all subordinate requests */

			bio_list_on_stack[1] = bio_list_on_stack[0];

			bio_list_init(&bio_list_on_stack[0]);



			/*

			 * Since we're recursing into make_request here, ensure

			 * that we mark this bio as already having entered the queue.

			 * If not, and the queue is going away, we can get stuck

			 * forever on waiting for the queue reference to drop. But

			 * that will never happen, as we're already holding a

			 * reference to it.

			 */

			bio_set_flag(bio, BIO_QUEUE_ENTERED);

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

			bio_clear_flag(bio, BIO_QUEUE_ENTERED);



			/* sort new bios into those for a lower level

			 * and those for the same level

block/blk-merge.c

+0 −10
Original line number Diff line number Diff line
@@ -272,16 +272,6 @@ void blk_queue_split(struct request_queue *q, struct bio **bio) 
		/* there isn't chance to merge the splitted bio */

		split->bi_opf |= REQ_NOMERGE;



		/*

		 * Since we're recursing into make_request here, ensure

		 * that we mark this bio as already having entered the queue.

		 * If not, and the queue is going away, we can get stuck

		 * forever on waiting for the queue reference to drop. But

		 * that will never happen, as we're already holding a

		 * reference to it.

		 */

		bio_set_flag(*bio, BIO_QUEUE_ENTERED);



		bio_chain(split, *bio);

		trace_block_split(q, split, (*bio)->bi_iter.bi_sector);

		generic_make_request(*bio);