diff options
| author | Konstantin Khlebnikov <khlebnikov@yandex-team.ru> | 2019-07-08 18:29:57 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-07-26 10:13:07 +0300 |
| commit | 2df91af73fd4f28c6ba39dd1c49f42e244d9f667 (patch) | |
| tree | a5826dbe8795dc1d57b951425eb38fc7e03b58b8 | |
| parent | 24d22d774481e7d586534937b0f24d0a0dfb7e40 (diff) | |
| download | linux-2df91af73fd4f28c6ba39dd1c49f42e244d9f667.tar.xz | |
blk-throttle: fix zero wait time for iops throttled group
commit 3a10f999ffd464d01c5a05592a15470a3c4bbc36 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | block/blk-throttle.c | 9 |
1 files changed, 3 insertions, 6 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 1b97a73d2fb1..61e990867a5d 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 |