[PATCH 1/3] Blk-iolatency: warn on negative inflight IO counter

[Liu Bo]

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

Signed-off-by: Liu Bo <bo....@linux.alibaba.com>
---
 block/blk-iolatency.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index fc714ef402a6..7200f3189a84 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -591,6 +591,7 @@ 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))
@@ -609,7 +610,8 @@ 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 (!enabled || iolat->min_lat_nsec == 0)
                        goto next;
                iolatency_record_time(iolat, &bio->bi_issue, now,
-- 
2.20.1.2.gb21ebb6