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blk-mq: fix race in IO start accounting

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Commit c6d600c6 opened up a small race where we could attempt to
account IO completion on a request, racing with IO start accounting.
Fix this up by ensuring that we've accounted for IO start before
inserting the request.

Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jens Axboe 2014-05-09 14:54:08 -06:00
parent 4bb659b156
commit cf4b50afc2
1 changed files with 2 additions and 4 deletions
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6
block/blk-mq.c
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@ -1088,17 +1088,15 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
}
if (!(hctx->flags & BLK_MQ_F_SHOULD_MERGE)) {
init_request_from_bio(rq, bio);
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);
blk_mq_bio_to_request(rq, bio);
goto insert_rq;
}