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authorKonstantin Khlebnikov <khlebnikov@yandex-team.ru>2019-07-08 18:29:57 +0300
committerJens Axboe <axboe@kernel.dk>2019-07-10 18:00:57 +0300
commit3a10f999ffd464d01c5a05592a15470a3c4bbc36 (patch)
tree84008b527c89f973b57d8f8a9fb1721a7004e4e7 /block/blk-throttle.c
parent113ab72ed4794c193509a97d7c6d32a6886e1682 (diff)
downloadlinux-3a10f999ffd464d01c5a05592a15470a3c4bbc36.tar.xz
blk-throttle: fix zero wait time for iops throttled group
After commit 991f61fe7e1d ("Blk-throttle: reduce tail io latency when iops limit is enforced") wait time could be zero even if group is throttled and cannot issue requests right now. As a result throtl_select_dispatch() turns into busy-loop under irq-safe queue spinlock. Fix is simple: always round up target time to the next throttle slice. Fixes: 991f61fe7e1d ("Blk-throttle: reduce tail io latency when iops limit is enforced") Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Cc: stable@vger.kernel.org # v4.19+ Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-throttle.c')
-rw-r--r--block/blk-throttle.c9
1 files changed, 3 insertions, 6 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 9ea7c0ecad10..8ab6c8153223 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -881,13 +881,10 @@ static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio,
unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
u64 tmp;
- jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
-
- /* Slice has just started. Consider one slice interval */
- if (!jiffy_elapsed)
- jiffy_elapsed_rnd = tg->td->throtl_slice;
+ jiffy_elapsed = jiffies - tg->slice_start[rw];
- jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
+ /* Round up to the next throttle slice, wait time must be nonzero */
+ jiffy_elapsed_rnd = roundup(jiffy_elapsed + 1, tg->td->throtl_slice);
/*
* jiffy_elapsed_rnd should not be a big value as minimum iops can be