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

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Message-ID: <78d464bd-94db-a1bc-d864-d85f2751dca3@bytedance.com>
Date:   Mon, 22 Aug 2022 09:58:22 +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 for-6.1] kernfs, cgroup: implement kernfs_deactivate()
 and cgroup_file_show()

On 2022/8/20 08:05, Tejun Heo wrote:
> Hello,
> 
> 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 make kernfs [de]activation generic so that it can be used
> anytime to deactivate (hide and drain) and activate (show) kernfs nodes,
> and, on top, implement 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.

Hello,

It's so nice of you for implementing this! I will rebase on your work to
do per-cgroup PSI disable/re-enable and test it today.

Thanks!

> 
> This patchset contains the following seven 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-Make-kernfs_drain-skip-draining-more-aggressi.patch
>  0006-kernfs-Allow-kernfs-nodes-to-be-deactivated-and-re-a.patch
>  0007-cgroup-Implement-cgroup_file_show.patch
> 
> 0001-0003 are misc prep patches. 0004-0006 implement kernsf_deactivate().
> 0008 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-deactivate
> 
> diffstat follows. Thanks.
> 
>  fs/kernfs/dir.c             |  120 +++++++++++++++++++++++++++++++++++++++++-------------------
>  fs/kernfs/file.c            |  139 +++++++++++++++++++++++++++++++---------------------------------------
>  fs/kernfs/kernfs-internal.h |    1
>  include/linux/cgroup.h      |    1
>  include/linux/kernfs.h      |    2 +
>  kernel/cgroup/cgroup.c      |   23 +++++++++++
>  6 files changed, 172 insertions(+), 114 deletions(-)
> 
> --
> tejun
> 
>