scsi time out and error handler are based on an assumption that
normal completion mustn't do anything on an timeout request.
After 12f5b931 (blk-mq: Remove generation seqeunce), we lost this.
To regain it, introduce blk_mq_mark_rq_complete which change state
from IN-FLIGHT to COMPLETE atomically. It will be added to
blk_mq_complete_request and blk_mq_check_expired to avoid the race
between timeout and normal io completion path.
Because we have hand over the task to complete a timeout request to
LLDD timeout path by invoking blk_mq_complete_request, export
__blk_mq_complete_request for LLDD to complete the timeout request.
Signed-off-by: Jianchao Wang <jianchao.w.wang@xxxxxxxxxx>
---
block/blk-mq.c | 22 +++++++++++++++-------
include/linux/blk-mq.h | 1 +
include/linux/blkdev.h | 6 ++++++
3 files changed, 22 insertions(+), 7 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 70c65bb..a73acbd 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -473,6 +473,7 @@ static void __blk_mq_free_request(struct request *rq)
struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
const int sched_tag = rq->internal_tag;
+ WRITE_ONCE(rq->state, MQ_RQ_IDLE);
if (rq->tag != -1)
blk_mq_put_tag(hctx, hctx->tags, ctx, rq->tag);
if (sched_tag != -1)
@@ -509,7 +510,6 @@ void blk_mq_free_request(struct request *rq)
if (blk_rq_rl(rq))
blk_put_rl(blk_rq_rl(rq));
- WRITE_ONCE(rq->state, MQ_RQ_IDLE);
if (refcount_dec_and_test(&rq->ref))
__blk_mq_free_request(rq);
}
@@ -552,15 +552,17 @@ static void __blk_mq_complete_request_remote(void *data)
rq->q->softirq_done_fn(rq);
}
-static void __blk_mq_complete_request(struct request *rq)
+/*
+ * The LLDD timeout path must invoke this interface to complete
+ * the request.
+ */
+void __blk_mq_complete_request(struct request *rq)
{
struct blk_mq_ctx *ctx = rq->mq_ctx;
bool shared = false;
int cpu;
- if (cmpxchg(&rq->state, MQ_RQ_IN_FLIGHT, MQ_RQ_COMPLETE) !=
- MQ_RQ_IN_FLIGHT)
- return;
+ WARN_ON(blk_mq_rq_state(rq) != MQ_RQ_COMPLETE);
if (rq->internal_tag != -1)
blk_mq_sched_completed_request(rq);
@@ -584,6 +586,7 @@ static void __blk_mq_complete_request(struct request *rq)
}
put_cpu();
}
+EXPORT_SYMBOL(__blk_mq_complete_request);
static void hctx_unlock(struct blk_mq_hw_ctx *hctx, int srcu_idx)
__releases(hctx->srcu)
@@ -617,7 +620,9 @@ void blk_mq_complete_request(struct request *rq)
{
if (unlikely(blk_should_fake_timeout(rq->q)))
return;
- __blk_mq_complete_request(rq);
+
+ if (blk_mq_mark_rq_complete(rq))
+ __blk_mq_complete_request(rq);
}
EXPORT_SYMBOL(blk_mq_complete_request);
@@ -783,6 +788,7 @@ static void blk_mq_rq_timed_out(struct request *req, bool reserved)
req->rq_flags &= ~RQF_TIMED_OUT;
blk_add_timer(req);
+ WRITE_ONCE(req->state, MQ_RQ_IN_FLIGHT);
}
static bool blk_mq_req_expired(struct request *rq, unsigned long *next)
@@ -835,8 +841,10 @@ static void blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
* expired; if it is not expired, then the request was completed and
* reallocated as a new request.
*/
- if (blk_mq_req_expired(rq, next))
+ if (blk_mq_req_expired(rq, next) &&
+ blk_mq_mark_rq_complete(rq)) {
blk_mq_rq_timed_out(rq, reserved);
+ }
if (refcount_dec_and_test(&rq->ref))
__blk_mq_free_request(rq);
}
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index e3147eb..0a509ae 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -259,6 +259,7 @@ void blk_mq_add_to_requeue_list(struct request *rq, bool at_head,
void blk_mq_kick_requeue_list(struct request_queue *q);
void blk_mq_delay_kick_requeue_list(struct request_queue *q, unsigned long msecs);
void blk_mq_complete_request(struct request *rq);
+void __blk_mq_complete_request(struct request *rq);
bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
struct bio *bio);
bool blk_mq_queue_stopped(struct request_queue *q);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 9154570..37511c4 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -272,6 +272,12 @@ struct request {
#endif
};
+static inline bool blk_mq_mark_rq_complete(struct request *rq)
+{
+ return (cmpxchg(&rq->state, MQ_RQ_IN_FLIGHT, MQ_RQ_COMPLETE) ==
+ MQ_RQ_IN_FLIGHT);
+}
+
static inline bool blk_op_is_scsi(unsigned int op)
{
return op == REQ_OP_SCSI_IN || op == REQ_OP_SCSI_OUT;
--
2.7.4
