On Fri, Feb 15, 2019 at 10:28:08AM +0800, Ming Lei wrote:
On Thu, Feb 14, 2019 at 09:08:27PM -0500, Sasha Levin wrote:From: Ming Lei <ming.lei@xxxxxxxxxx> [ Upstream commit 698cef173983b086977e633e46476e0f925ca01e ] 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 cd4a4ae4683dc2 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: cd4a4ae4683dc2 ("block: don't use blocking queue entered for recursive bio submits") Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Cc: NeilBrown <neilb@xxxxxxxx> Reviewed-by: Mike Snitzer <snitzer@xxxxxxxxxx> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- block/blk-core.c | 11 +++++++++++ block/blk-merge.c | 10 ---------- 2 files changed, 11 insertions(+), 10 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index deb56932f8c4..22260339f66f 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -2449,7 +2449,18 @@ 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 diff --git a/block/blk-merge.c b/block/blk-merge.c index 7695034f4b87..adfe835ab258 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -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); -- 2.19.1This one should be dropped, given it has been reverted.
Dropped, thank you. -- Thanks, Sasha
