Blk-iolatency: warn on negative inflight IO counter

This is to catch any unexpected negative value of inflight IO counter.

Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index 1893686..2620baa 100644 (file)
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -592,6 +592,7 @@ static void blkcg_iolatency_done_bio(struct rq_qos *rqos, struct bio *bio)
        u64 now = ktime_to_ns(ktime_get());
        bool issue_as_root = bio_issue_as_root_blkg(bio);
        bool enabled = false;
+       int inflight = 0;
 
        blkg = bio->bi_blkg;
        if (!blkg || !bio_flagged(bio, BIO_TRACKED))
@@ -613,7 +614,8 @@ static void blkcg_iolatency_done_bio(struct rq_qos *rqos, struct bio *bio)
                }
                rqw = &iolat->rq_wait;
 
-               atomic_dec(&rqw->inflight);
+               inflight = atomic_dec_return(&rqw->inflight);
+               WARN_ON_ONCE(inflight < 0);
                if (iolat->min_lat_nsec == 0)
                        goto next;
                iolatency_record_time(iolat, &bio->bi_issue, now,