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blk-mq: recover from stale cached request in blk_mq_submit_bio #767

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blk-mq: recover from stale cached request in blk_mq_submit_bio #767

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24 changes: 15 additions & 9 deletions block/blk-mq.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3096,22 +3096,23 @@ static struct request *blk_mq_peek_cached_request(struct blk_plug *plug,
return rq;
}

static void blk_mq_use_cached_rq(struct request *rq, struct blk_plug *plug,
static bool blk_mq_use_cached_rq(struct request *rq, struct blk_plug *plug,
struct bio *bio)
{
if (rq_list_pop(&plug->cached_rqs) != rq)
WARN_ON_ONCE(1);

/*
* If any qos ->throttle() end up blocking, we will have flushed the
* plug and hence killed the cached_rq list as well. Pop this entry
* before we throttle.
* We will have flushed the plug and hence killed the cached_rq list as
* well if anything had blocked. Pop this entry before we throttle if
* the entry is still valid.
*/
if (rq_list_pop(&plug->cached_rqs) != rq)
return false;

rq_qos_throttle(rq->q, bio);

blk_mq_rq_time_init(rq, blk_time_get_ns());
rq->cmd_flags = bio->bi_opf;
INIT_LIST_HEAD(&rq->queuelist);
return true;
}

static bool bio_unaligned(const struct bio *bio, struct request_queue *q)
Expand Down Expand Up @@ -3211,8 +3212,13 @@ void blk_mq_submit_bio(struct bio *bio)

new_request:
if (rq) {
blk_mq_use_cached_rq(rq, plug, bio);
} else {
if (!blk_mq_use_cached_rq(rq, plug, bio)) {
rq = NULL;
if (unlikely(bio_queue_enter(bio)))
return;
}
}
if (!rq) {
rq = blk_mq_get_new_requests(q, plug, bio);
if (unlikely(!rq)) {
if (bio->bi_opf & REQ_NOWAIT)
Expand Down