linux-kernel - Re: [PATCHSET v2 for-6.1] kernfs, cgroup: implement kernfs_show() and cgroup_file

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Message-ID: <a81e08ab-090d-0cb3-ec2d-490c5e2719ab@bytedance.com>
Date:   Sun, 28 Aug 2022 16:33:24 +0800
From:   Chengming Zhou <zhouchengming@...edance.com>
To:     Tejun Heo <tj@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Johannes Weiner <hannes@...xchg.org>,
        Imran Khan <imran.f.khan@...cle.com>, kernel-team@...com
Subject: Re: [PATCHSET v2 for-6.1] kernfs, cgroup: implement kernfs_show() and
 cgroup_file_show()

On 2022/8/28 13:04, Tejun Heo wrote:
> Hello,
> 
> Greg: If this looks good to you, can you apply 0001-0008 to your tree? I'll
> likely have more cgroup updates on top, so I think it'd be better if I pull
> your tree and then handle the cgroup part in cgroup tree.
> 
> Currently, deactivated kernfs nodes are used for two purposes - during
> removal to kill and drain nodes and during creation to make multiple
> kernfs_nodes creations to succeed or fail as a group.
> 
> This patchset implements kernfs_show() which can dynamically show and hide
> kernfs_nodes using the [de]activation mechanisms, and, on top, implements
> cgroup_file_show() which allows toggling cgroup file visiblity.
> 
> This is for the following pending patchset to allow disabling PSI on
> per-cgroup basis:
> 
>  https://lore.kernel.org/all/20220808110341.15799-1-zhouchengming@bytedance.com/t/#u
> 
> which requires hiding the corresponding cgroup interface files while
> disabled.
> 
> This patchset contains the following nine patches.
> 
>  0001-kernfs-Simply-by-replacing-kernfs_deref_open_node-wi.patch
>  0002-kernfs-Drop-unnecessary-mutex-local-variable-initial.patch
>  0003-kernfs-Refactor-kernfs_get_open_node.patch
>  0004-kernfs-Skip-kernfs_drain_open_files-more-aggressivel.patch
>  0005-kernfs-Improve-kernfs_drain-and-always-call-on-remov.patch
>  0006-kernfs-Add-KERNFS_REMOVING-flags.patch
>  0007-kernfs-Factor-out-kernfs_activate_one.patch
>  0008-kernfs-Implement-kernfs_show.patch
>  0009-cgroup-Implement-cgroup_file_show.patch
> 
> 0001-0003 are misc prep patches. 0004-0008 implement kernsf_deactivate().
> 0009 implements cgroup_file_show() on top. The patches are also available in
> the following git branch:
> 
>  git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git kernfs-show
> 
> The main difference from the previous version[1] is that while show/hide
> still use the same mechanism as [de]activation, their states are tracked
> separately so that e.g. an unrelated kernfs_activate() higher up in the tree
> doesn't interfere with hidden nodes in the subtree.

Hello,

For this series:
Reviewed-by: Chengming Zhou <zhouchengming@...edance.com>
Tested-by: Chengming Zhou <zhouchengming@...edance.com>

Thanks!

> 
> diffstat follows. Thanks.
> 
>  fs/kernfs/dir.c             |  102 +++++++++++++++++++++++++++++++----------------
>  fs/kernfs/file.c            |  151 +++++++++++++++++++++++++++++++++-------------------------------------
>  fs/kernfs/kernfs-internal.h |    1
>  include/linux/cgroup.h      |    1
>  include/linux/kernfs.h      |    3 +
>  kernel/cgroup/cgroup.c      |   20 +++++++++
>  6 files changed, 166 insertions(+), 112 deletions(-)
> 
> --
> tejun
> 
> [1] http://lkml.kernel.org/r/20220820000550.367085-1-tj@kernel.org
>