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From: Greg KH <gregkh@linuxfoundation.org>
To: Yi Tao <escape@linux.alibaba.com>
Cc: tj@kernel.org, lizefan.x@bytedance.com, hannes@cmpxchg.org,
	mcgrof@kernel.org, keescook@chromium.org, yzaikin@google.com,
	linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, shanpeic@linux.alibaba.com
Subject: Re: [RFC PATCH 1/2] add pinned flags for kernfs node
Date: Wed, 8 Sep 2021 14:35:17 +0200	[thread overview]
Message-ID: <YTiuBaiVZhe3db9O@kroah.com> (raw)
In-Reply-To: <e753e449240bfc43fcb7aa26dca196e2f51e0836.1631102579.git.escape@linux.alibaba.com>

On Wed, Sep 08, 2021 at 08:15:12PM +0800, Yi Tao wrote:
> This patch is preparing for the implementation of cgroup pool. If a
> kernfs node is set to pinned. the data of this node will no longer be
> protected by kernfs internally. When it performs the following actions,
> the area protected by kernfs_rwsem will be protected by the specific
> spinlock:
> 	1.rename this node
> 	2.remove this node
> 	3.create child node
> 
> Suggested-by: Shanpei Chen <shanpeic@linux.alibaba.com>
> Signed-off-by: Yi Tao <escape@linux.alibaba.com>
> ---
>  fs/kernfs/dir.c        | 74 ++++++++++++++++++++++++++++++++++++--------------
>  include/linux/kernfs.h | 14 ++++++++++
>  2 files changed, 68 insertions(+), 20 deletions(-)

Ugh, this is going to get messy fast.

Why are kernfs changes needed for this?  kernfs creation is not
necessarily supposed to be "fast", what benchmark needs this type of
change to require the addition of this complexity?

And how are we going to audit things to ensure the "pinning" is working
properly?

thanks,

greg k-h

WARNING: multiple messages have this Message-ID (diff)
From: Greg KH <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>
To: Yi Tao <escape-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org>
Cc: tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
	lizefan.x-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org,
	hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org,
	mcgrof-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
	keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org,
	yzaikin-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	shanpeic-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org
Subject: Re: [RFC PATCH 1/2] add pinned flags for kernfs node
Date: Wed, 8 Sep 2021 14:35:17 +0200	[thread overview]
Message-ID: <YTiuBaiVZhe3db9O@kroah.com> (raw)
In-Reply-To: <e753e449240bfc43fcb7aa26dca196e2f51e0836.1631102579.git.escape-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org>

On Wed, Sep 08, 2021 at 08:15:12PM +0800, Yi Tao wrote:
> This patch is preparing for the implementation of cgroup pool. If a
> kernfs node is set to pinned. the data of this node will no longer be
> protected by kernfs internally. When it performs the following actions,
> the area protected by kernfs_rwsem will be protected by the specific
> spinlock:
> 	1.rename this node
> 	2.remove this node
> 	3.create child node
> 
> Suggested-by: Shanpei Chen <shanpeic-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org>
> Signed-off-by: Yi Tao <escape-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org>
> ---
>  fs/kernfs/dir.c        | 74 ++++++++++++++++++++++++++++++++++++--------------
>  include/linux/kernfs.h | 14 ++++++++++
>  2 files changed, 68 insertions(+), 20 deletions(-)

Ugh, this is going to get messy fast.

Why are kernfs changes needed for this?  kernfs creation is not
necessarily supposed to be "fast", what benchmark needs this type of
change to require the addition of this complexity?

And how are we going to audit things to ensure the "pinning" is working
properly?

thanks,

greg k-h

  parent reply	other threads:[~2021-09-08 12:35 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-08 12:15 [RFC PATCH 0/2] support cgroup pool in v1 Yi Tao
2021-09-08 12:15 ` Yi Tao
2021-09-08 12:15 ` [RFC PATCH 1/2] add pinned flags for kernfs node Yi Tao
2021-09-08 12:15   ` [RFC PATCH 2/2] support cgroup pool in v1 Yi Tao
2021-09-08 12:15     ` Yi Tao
2021-09-08 12:35     ` Greg KH
2021-09-08 12:35       ` Greg KH
     [not found]       ` <084930d2-057a-04a7-76d1-b2a7bd37deb0@linux.alibaba.com>
2021-09-09 13:27         ` Greg KH
2021-09-10  2:20           ` taoyi.ty
2021-09-10  2:15       ` taoyi.ty
2021-09-10  2:15         ` taoyi.ty
2021-09-10  6:01         ` Greg KH
2021-09-10  6:01           ` Greg KH
2021-09-08 15:30     ` kernel test robot
2021-09-08 16:52     ` kernel test robot
2021-09-08 17:39     ` kernel test robot
2021-09-08 17:39     ` [RFC PATCH] cgroup_pool_mutex can be static kernel test robot
2021-09-08 12:35   ` Greg KH [this message]
2021-09-08 12:35     ` [RFC PATCH 1/2] add pinned flags for kernfs node Greg KH
2021-09-10  2:14     ` taoyi.ty
2021-09-10  6:00       ` Greg KH
2021-09-10  6:00         ` Greg KH
2021-09-08 16:26   ` kernel test robot
2021-09-08 12:37 ` [RFC PATCH 0/2] support cgroup pool in v1 Greg KH
2021-09-10  2:11   ` taoyi.ty
2021-09-10  6:01     ` Greg KH
2021-09-10  6:01       ` Greg KH
2021-09-10 16:49     ` Tejun Heo
2021-09-10 16:49       ` Tejun Heo
2021-09-13 14:20       ` Christian Brauner
2021-09-13 14:20         ` Christian Brauner
2021-09-13 16:24         ` Tejun Heo
2021-09-13 16:24           ` Tejun Heo
2021-09-08 16:35 ` Tejun Heo
2021-09-10  2:12   ` taoyi.ty

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