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blk-mq: refactor request insertion/merging 

Refactor the logic around adding a new bio to a software queue,
so we nest the ctx->lock where we really need it (merge and
insertion) and don't hold it when we don't (init and IO start
accounting).

Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jens Axboe 2014-04-30 13:43:56 -06:00
parent 98bc1f272a
commit c6d600c65e
1 changed files with 15 additions and 7 deletions
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22
block/blk-mq.c
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@ -1037,17 +1037,25 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
}
}
spin_lock(&ctx->lock);
if (!(hctx->flags & BLK_MQ_F_SHOULD_MERGE)) {
init_request_from_bio(rq, bio);
if ((hctx->flags & BLK_MQ_F_SHOULD_MERGE) &&
blk_mq_attempt_merge(q, ctx, bio))
__blk_mq_free_request(hctx, ctx, rq);
else {
blk_mq_bio_to_request(rq, bio);
spin_lock(&ctx->lock);
insert_rq:
__blk_mq_insert_request(hctx, rq, false);
spin_unlock(&ctx->lock);
blk_account_io_start(rq, 1);
} else {
spin_lock(&ctx->lock);
if (!blk_mq_attempt_merge(q, ctx, bio)) {
init_request_from_bio(rq, bio);
goto insert_rq;
}
spin_unlock(&ctx->lock);
__blk_mq_free_request(hctx, ctx, rq);
}
spin_unlock(&ctx->lock);
/*
* For a SYNC request, send it to the hardware immediately. For an