block: cover another queue enter recursion via BIO_QUEUE_ENTERED (698cef17) · Commits · 戴 / test

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 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: ("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:

Mike Snitzer <snitzer@redhat.com> Signed-off-by:

Ming Lei <ming.lei@redhat.com> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

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);

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