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block: cover another queue enter recursion via BIO_QUEUE_ENTERED

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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 cd4a4ae468 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: cd4a4ae468 ("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>
This commit is contained in:
Ming Lei 2019-01-22 16:20:17 +08:00 committed by Jens Axboe
parent 8b9433eb4d
commit 698cef1739
2 changed files with 11 additions and 10 deletions
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11
block/blk-core.c
View File

@ -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

10
block/blk-merge.c
View File

@ -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);