From: Yu Kuai <yukuai@fygo.io>

This set fix some problems that are reported long time ago with minimal changes,
the blkcg_mutex refactor I'm working on can fix these problems as well, but it's
complicated and may not land in this merge window. So I think this set should land
in this merge window first.

Patch 1 protects blkg_destroy_all()'s q->blkg_list walk with
blkcg_mutex.

Patches 2-3 fix races between blkcg_activate_policy() and concurrent
blkg destruction.

Patch 4 factors the policy data teardown loop into a helper after the
race fixes.

Changes since v3:
- Rebase on the latest for-7.3/block branch.

Changes since v2:
- Rebase on the latest block-7.2 branch.

Changes since v1:
- Drop the BFQ q->blkg_list patch because the current block tree already
  has a stronger fix in commit 17b2d950a3c0 ("block, bfq: protect async
  queue reset with blkcg locks").
- Add Reviewed-by tags from Tang Yizhou.

Yu Kuai (1):
  blk-cgroup: protect q->blkg_list iteration in blkg_destroy_all() with
    blkcg_mutex

Zheng Qixing (3):
  blk-cgroup: fix race between policy activation and blkg destruction
  blk-cgroup: skip dying blkg in blkcg_activate_policy()
  blk-cgroup: factor policy pd teardown loop into helper

 block/blk-cgroup.c | 65 +++++++++++++++++++++++++---------------------
 1 file changed, 35 insertions(+), 30 deletions(-)

-- 
2.51.0

From: Yu Kuai <yukuai@fygo.io>

This set fix some problems that are reported long time ago with minimal changes,
the blkcg_mutex refactor I'm working on can fix these problems as well, but it's
complicated and may not land in this merge window. So I think this set should land
in this merge window first.

Patch 1 protects blkg_destroy_all()'s q->blkg_list walk with
blkcg_mutex.

Patches 2-3 fix races between blkcg_activate_policy() and concurrent
blkg destruction.

Patch 4 factors the policy data teardown loop into a helper after the
race fixes.

Changes since v3:
- Rebase on the latest for-7.3/block branch.

Changes since v2:
- Rebase on the latest block-7.2 branch.

Changes since v1:
- Drop the BFQ q->blkg_list patch because the current block tree already
  has a stronger fix in commit 17b2d950a3c0 ("block, bfq: protect async
  queue reset with blkcg locks").
- Add Reviewed-by tags from Tang Yizhou.

Yu Kuai (1):
  blk-cgroup: protect q->blkg_list iteration in blkg_destroy_all() with
    blkcg_mutex

Zheng Qixing (3):
  blk-cgroup: fix race between policy activation and blkg destruction
  blk-cgroup: skip dying blkg in blkcg_activate_policy()
  blk-cgroup: factor policy pd teardown loop into helper

 block/blk-cgroup.c | 65 +++++++++++++++++++++++++---------------------
 1 file changed, 35 insertions(+), 30 deletions(-)

-- 
2.51.0

On 8/2/26 4:55 PM, Yu Kuai wrote:
> From: Yu Kuai <yukuai@fygo.io>
> 
> This set fix some problems that are reported long time ago with minimal changes,
> the blkcg_mutex refactor I'm working on can fix these problems as well, but it's
> complicated and may not land in this merge window. So I think this set should land
> in this merge window first.
> 
> Patch 1 protects blkg_destroy_all()'s q->blkg_list walk with
> blkcg_mutex.
> 
> Patches 2-3 fix races between blkcg_activate_policy() and concurrent
> blkg destruction.
> 
> Patch 4 factors the policy data teardown loop into a helper after the
> race fixes.
> 

This series looks good to me, however as I recall, we discussed about
protecting blkg_create() as well using ->blkcg_mutex. I remember the
blkg_create() is not protected with ->blkcg_mutex under each call path,
so would you to also cover that change in this patchset?

Thanks,
--Nilay

Hi,

在 2026/8/3 14:51, Nilay Shroff 写道:
> On 8/2/26 4:55 PM, Yu Kuai wrote:
>> From: Yu Kuai <yukuai@fygo.io>
>>
>> This set fix some problems that are reported long time ago with 
>> minimal changes,
>> the blkcg_mutex refactor I'm working on can fix these problems as 
>> well, but it's
>> complicated and may not land in this merge window. So I think this 
>> set should land
>> in this merge window first.
>>
>> Patch 1 protects blkg_destroy_all()'s q->blkg_list walk with
>> blkcg_mutex.
>>
>> Patches 2-3 fix races between blkcg_activate_policy() and concurrent
>> blkg destruction.
>>
>> Patch 4 factors the policy data teardown loop into a helper after the
>> race fixes.
>>
>
> This series looks good to me, however as I recall, we discussed about
> protecting blkg_create() as well using ->blkcg_mutex. I remember the
> blkg_create() is not protected with ->blkcg_mutex under each call path,
> so would you to also cover that change in this patchset?

I can't do this for now without a big refactor, because it's possible that
blkg_create() can be called from bio_set_dev(), and bio_set_dev() can be
called from many atomic contexts, examples are patch 1,2,3,5,8,9,10 from the
following RFC v1 set:

[RFC PATCH v1 00/17] blk-cgroup: protect blkgs with blkcg_mutex - Yu Kuai <https://lore.kernel.org/all/20260704195124.1375075-1-yukuai@kernel.org/>

>
> Thanks,
> --Nilay
>
-- 
Thanks,
Kuai

On 8/3/26 1:50 PM, yu kuai wrote:
> Hi,
> 
> 在 2026/8/3 14:51, Nilay Shroff 写道:
>> On 8/2/26 4:55 PM, Yu Kuai wrote:
>>> From: Yu Kuai <yukuai@fygo.io>
>>>
>>> This set fix some problems that are reported long time ago with
>>> minimal changes,
>>> the blkcg_mutex refactor I'm working on can fix these problems as
>>> well, but it's
>>> complicated and may not land in this merge window. So I think this
>>> set should land
>>> in this merge window first.
>>>
>>> Patch 1 protects blkg_destroy_all()'s q->blkg_list walk with
>>> blkcg_mutex.
>>>
>>> Patches 2-3 fix races between blkcg_activate_policy() and concurrent
>>> blkg destruction.
>>>
>>> Patch 4 factors the policy data teardown loop into a helper after the
>>> race fixes.
>>>
>>
>> This series looks good to me, however as I recall, we discussed about
>> protecting blkg_create() as well using ->blkcg_mutex. I remember the
>> blkg_create() is not protected with ->blkcg_mutex under each call path,
>> so would you to also cover that change in this patchset?
> 
> I can't do this for now without a big refactor, because it's possible that
> blkg_create() can be called from bio_set_dev(), and bio_set_dev() can be
> called from many atomic contexts, examples are patch 1,2,3,5,8,9,10 from the
> following RFC v1 set:
> 
> [RFC PATCH v1 00/17] blk-cgroup: protect blkgs with blkcg_mutex - Yu Kuai <https://lore.kernel.org/all/20260704195124.1375075-1-yukuai@kernel.org/>
> 
Okay understood. With that, for this entire patchset:

Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>

On Sun, 02 Aug 2026 19:25:16 +0800, Yu Kuai wrote:
> This set fix some problems that are reported long time ago with minimal changes,
> the blkcg_mutex refactor I'm working on can fix these problems as well, but it's
> complicated and may not land in this merge window. So I think this set should land
> in this merge window first.
> 
> Patch 1 protects blkg_destroy_all()'s q->blkg_list walk with
> blkcg_mutex.
> 
> [...]

Applied, thanks!

[1/4] blk-cgroup: protect q->blkg_list iteration in blkg_destroy_all() with blkcg_mutex
      (no commit info)
[2/4] blk-cgroup: fix race between policy activation and blkg destruction
      (no commit info)
[3/4] blk-cgroup: skip dying blkg in blkcg_activate_policy()
      (no commit info)
[4/4] blk-cgroup: factor policy pd teardown loop into helper
      (no commit info)

Best regards,
-- 
Jens Axboe