[PATCH 1/5] blk-mq: prevent normal completion from entering a timeout request
From: Jianchao Wang <hidden>
Date: 2018-06-20 13:23:15
Also in:
linux-scsi, lkml
Subsystem:
block layer, the rest · Maintainers:
Jens Axboe, Linus Torvalds
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 <redacted> --- 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