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authorYu Kuai <yukuai3@huawei.com>2022-08-29 10:22:37 +0800
committerJens Axboe <axboe@kernel.dk>2022-09-12 00:19:48 -0600
commit320fb0f91e55ba248d4bad106b408e59099cfa89 (patch)
treef9662d4a2aef4a0f3d133e6343c5eaf44b722bd0 /include/linux/bio.h
parent4acb83417cadfdcbe64215f9d0ddcf3132af808e (diff)
blk-throttle: fix that io throttle can only work for single bio
Test scripts: cd /sys/fs/cgroup/blkio/ echo "8:0 1024" > blkio.throttle.write_bps_device echo $$ > cgroup.procs dd if=/dev/zero of=/dev/sda bs=10k count=1 oflag=direct & dd if=/dev/zero of=/dev/sda bs=10k count=1 oflag=direct & Test result: 10240 bytes (10 kB, 10 KiB) copied, 10.0134 s, 1.0 kB/s 10240 bytes (10 kB, 10 KiB) copied, 10.0135 s, 1.0 kB/s The problem is that the second bio is finished after 10s instead of 20s. Root cause: 1) second bio will be flagged: __blk_throtl_bio while (true) { ... if (sq->nr_queued[rw]) -> some bio is throttled already break }; bio_set_flag(bio, BIO_THROTTLED); -> flag the bio 2) flagged bio will be dispatched without waiting: throtl_dispatch_tg tg_may_dispatch tg_with_in_bps_limit if (bps_limit == U64_MAX || bio_flagged(bio, BIO_THROTTLED)) *wait = 0; -> wait time is zero return true; commit 9f5ede3c01f9 ("block: throttle split bio in case of iops limit") support to count split bios for iops limit, thus it adds flagged bio checking in tg_with_in_bps_limit() so that split bios will only count once for bps limit, however, it introduce a new problem that io throttle won't work if multiple bios are throttled. In order to fix the problem, handle iops/bps limit in different ways: 1) for iops limit, there is no flag to record if the bio is throttled, and iops is always applied. 2) for bps limit, original bio will be flagged with BIO_BPS_THROTTLED, and io throttle will ignore bio with the flag. Noted this patch also remove the code to set flag in __bio_clone(), it's introduced in commit 111be8839817 ("block-throttle: avoid double charge"), and author thinks split bio can be resubmited and throttled again, which is wrong because split bio will continue to dispatch from caller. Fixes: 9f5ede3c01f9 ("block: throttle split bio in case of iops limit") Cc: <stable@vger.kernel.org> Signed-off-by: Yu Kuai <yukuai3@huawei.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20220829022240.3348319-2-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include/linux/bio.h')
-rw-r--r--include/linux/bio.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/bio.h b/include/linux/bio.h
index ca22b06700a9..2c5806997bbf 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -509,7 +509,7 @@ static inline void bio_set_dev(struct bio *bio, struct block_device *bdev)
{
bio_clear_flag(bio, BIO_REMAPPED);
if (bio->bi_bdev != bdev)
- bio_clear_flag(bio, BIO_THROTTLED);
+ bio_clear_flag(bio, BIO_BPS_THROTTLED);
bio->bi_bdev = bdev;
bio_associate_blkg(bio);
}