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>

1 files changed, 3 insertions, 1 deletions

diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index 1893686a9c1f..2620baa1f699 100644
--- 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,