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....@redhat.com>
[ 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-ker...@i-love.sakura.ne.jp>
Cc: NeilBrown <ne...@suse.com>
Reviewed-by: Mike Snitzer <snit...@redhat.com>
Signed-off-by: Ming Lei <ming....@redhat.com>
Signed-off-by: Jens Axboe <ax...@kernel.dk>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
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);
--
2.19.1
This one should be dropped, given it has been reverted.
Dropped, thank you.
--
Thanks,
Sasha
