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blk-mq: remove REQ_ATOM_COMPLETE usages from blk-mq 

After the recent updates to use generation number and state based
synchronization, blk-mq no longer depends on REQ_ATOM_COMPLETE except
to avoid firing the same timeout multiple times.

Remove all REQ_ATOM_COMPLETE usages and use a new rq_flags flag
RQF_MQ_TIMEOUT_EXPIRED to avoid firing the same timeout multiple
times.  This removes atomic bitops from hot paths too.

v2: Removed blk_clear_rq_complete() from blk_mq_rq_timed_out().

v3: Added RQF_MQ_TIMEOUT_EXPIRED flag.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: "jianchao.wang" <jianchao.w.wang@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
hifive-unleashed-5.1
Tejun Heo 2018-01-09 08:29:51 -08:00 committed by Jens Axboe
parent 358f70da49
commit 634f9e4631
3 changed files with 10 additions and 8 deletions
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15
block/blk-mq.c
View File

@ -634,8 +634,7 @@ void blk_mq_complete_request(struct request *rq)
* hctx_lock() covers both issue and completion paths.
*/
hctx_lock(hctx, &srcu_idx);
if (blk_mq_rq_aborted_gstate(rq) != rq->gstate &&
!blk_mark_rq_complete(rq))
if (blk_mq_rq_aborted_gstate(rq) != rq->gstate)
__blk_mq_complete_request(rq);
hctx_unlock(hctx, srcu_idx);
}
@ -685,8 +684,6 @@ void blk_mq_start_request(struct request *rq)
preempt_enable();
set_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
if (test_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags))
clear_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags);
if (q->dma_drain_size && blk_rq_bytes(rq)) {
/*
@ -837,6 +834,8 @@ static void blk_mq_rq_timed_out(struct request *req, bool reserved)
if (!test_bit(REQ_ATOM_STARTED, &req->atomic_flags))
return;
req->rq_flags |= RQF_MQ_TIMEOUT_EXPIRED;
if (ops->timeout)
ret = ops->timeout(req, reserved);
@ -852,7 +851,6 @@ static void blk_mq_rq_timed_out(struct request *req, bool reserved)
*/
blk_mq_rq_update_aborted_gstate(req, 0);
blk_add_timer(req);
blk_clear_rq_complete(req);
break;
case BLK_EH_NOT_HANDLED:
break;
@ -871,7 +869,8 @@ static void blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
might_sleep();
if (!test_bit(REQ_ATOM_STARTED, &rq->atomic_flags))
if ((rq->rq_flags & RQF_MQ_TIMEOUT_EXPIRED) ||
!test_bit(REQ_ATOM_STARTED, &rq->atomic_flags))
return;
/* read coherent snapshots of @rq->state_gen and @rq->deadline */
@ -906,8 +905,8 @@ static void blk_mq_terminate_expired(struct blk_mq_hw_ctx *hctx,
* now guaranteed to see @rq->aborted_gstate and yield. If
* @rq->aborted_gstate still matches @rq->gstate, @rq is ours.
*/
if (READ_ONCE(rq->gstate) == rq->aborted_gstate &&
!blk_mark_rq_complete(rq))
if (!(rq->rq_flags & RQF_MQ_TIMEOUT_EXPIRED) &&
READ_ONCE(rq->gstate) == rq->aborted_gstate)
blk_mq_rq_timed_out(rq, reserved);
}

1
block/blk-timeout.c
View File

@ -214,6 +214,7 @@ void blk_add_timer(struct request *req)
req->timeout = q->rq_timeout;
req->deadline = jiffies + req->timeout;
req->rq_flags &= ~RQF_MQ_TIMEOUT_EXPIRED;
/*
* Only the non-mq case needs to add the request to a protected list.

2
include/linux/blkdev.h
View File

@ -125,6 +125,8 @@ typedef __u32 __bitwise req_flags_t;
#define RQF_SPECIAL_PAYLOAD ((__force req_flags_t)(1 << 18))
/* The per-zone write lock is held for this request */
#define RQF_ZONE_WRITE_LOCKED ((__force req_flags_t)(1 << 19))
/* timeout is expired */
#define RQF_MQ_TIMEOUT_EXPIRED ((__force req_flags_t)(1 << 20))
/* flags that prevent us from merging requests: */
#define RQF_NOMERGE_FLAGS \