On 2021/3/1 14:50, Ming Lei wrote:
On Sun, Feb 28, 2021 at 09:14:44PM -0500, Yufen Yu wrote:
We just set hctx->tags->rqs[tag] when get driver tag, but will
not set hctx->sched_tags->rqs[tag] when get sched tag.
So, blk_mq_tag_to_rq() always return NULL for sched_tags.
True, also blk_mq_tag_to_rq() seems an awkward API, and it needs
'struct blk_mq_tags *', but which is a block layer internal definition.
Signed-off-by: Yufen Yu <yuyufen@xxxxxxxxxx>
---
block/blk-mq.c | 14 +++-----------
1 file changed, 3 insertions(+), 11 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5362a7958b74..424afe112b58 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -846,6 +846,7 @@ static int blk_mq_test_tag_bit(struct blk_mq_tags *tags, unsigned int tag)
struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
{
+ /* if tags is hctx->sched_tags, it always return NULL */
if (tag < tags->nr_tags && blk_mq_test_tag_bit(tags, tag)) {
prefetch(tags->rqs[tag]);
return tags->rqs[tag];
@@ -3845,17 +3846,8 @@ static bool blk_mq_poll_hybrid(struct request_queue *q,
if (!blk_qc_t_is_internal(cookie))
rq = blk_mq_tag_to_rq(hctx->tags, blk_qc_t_to_tag(cookie));
- else {
- rq = blk_mq_tag_to_rq(hctx->sched_tags, blk_qc_t_to_tag(cookie));
- /*
- * With scheduling, if the request has completed, we'll
- * get a NULL return here, as we clear the sched tag when
- * that happens. The request still remains valid, like always,
- * so we should be safe with just the NULL check.
- */
- if (!rq)
- return false;
- }
+ else
+ return false;
I think the correct fix is to retrieve the request via:
hctx->sched_tags->static_rqs[blk_qc_t_to_tag(cookie)]
since it is nice to run blk_mq_poll_hybrid_sleep() for one
non-started request in case of real scheduler.
Yes, do blk_mq_poll_hybrid_sleep() should be more reasonable here.
I will modify it in next version.
Thanks,
Yufen
