This is a note to let you know that I've just added the patch titled
blk-throttle: Fix that bps of child could exceed bps limited in parent
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
blk-throttle-fix-that-bps-of-child-could-exceed-bps-limited-in-parent.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 84aca0a7e039c8735abc0f89f3f48e9006c0dfc7 Mon Sep 17 00:00:00 2001
From: Kemeng Shi <shikemeng@xxxxxxxxxx>
Date: Mon, 5 Dec 2022 19:57:02 +0800
Subject: blk-throttle: Fix that bps of child could exceed bps limited in parent
From: Kemeng Shi <shikemeng@xxxxxxxxxx>
commit 84aca0a7e039c8735abc0f89f3f48e9006c0dfc7 upstream.
Consider situation as following (on the default hierarchy):
HDD
|
root (bps limit: 4k)
|
child (bps limit :8k)
|
fio bs=8k
Rate of fio is supposed to be 4k, but result is 8k. Reason is as
following:
Size of single IO from fio is larger than bytes allowed in one
throtl_slice in child, so IOs are always queued in child group first.
When queued IOs in child are dispatched to parent group, BIO_BPS_THROTTLED
is set and these IOs will not be limited by tg_within_bps_limit anymore.
Fix this by only set BIO_BPS_THROTTLED when the bio traversed the entire
tree.
There patch has no influence on situation which is not on the default
hierarchy as each group is a single root group without parent.
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20221205115709.251489-3-shikemeng@xxxxxxxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Cc: Khazhy Kumykov <khazhy@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
block/blk-throttle.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1066,7 +1066,6 @@ static void tg_dispatch_one_bio(struct t
sq->nr_queued[rw]--;
throtl_charge_bio(tg, bio);
- bio_set_flag(bio, BIO_BPS_THROTTLED);
/*
* If our parent is another tg, we just need to transfer @bio to
@@ -1079,6 +1078,7 @@ static void tg_dispatch_one_bio(struct t
throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg);
start_parent_slice_with_credit(tg, parent_tg, rw);
} else {
+ bio_set_flag(bio, BIO_BPS_THROTTLED);
throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw],
&parent_sq->queued[rw]);
BUG_ON(tg->td->nr_queued[rw] <= 0);
Patches currently in stable-queue which might be from shikemeng@xxxxxxxxxx are
queue-6.1/blk-throttle-fix-that-bps-of-child-could-exceed-bps-limited-in-parent.patch
