linux-kernel - Re: [RFC/PATCH 1/8]: CGroup Files: Add locking mode to cgroups control files

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Message-ID: <6599ad830805131407y3d94016cn773ba21a42b6098c@mail.gmail.com>
Date:	Tue, 13 May 2008 14:07:40 -0700
From:	"Paul Menage" <menage@...gle.com>
To:	"Li Zefan" <lizf@...fujitsu.com>
Cc:	pj@....com, xemul@...nvz.org, balbir@...ibm.com, serue@...ibm.com,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org
Subject: Re: [RFC/PATCH 1/8]: CGroup Files: Add locking mode to cgroups control files

On Tue, May 13, 2008 at 2:23 AM, Li Zefan <lizf@...fujitsu.com> wrote:
>  > +
>  > +/**
>  > + * cgroup_file_lock(). Helper for cgroup read/write methods.
>  > + * @cgrp:  the cgroup being acted on
>  > + * @cft:   the control file being written to or read from
>  > + * *write: true if the access is a write access.
>
>  s/*write/@...te
>

Fixed.

>  > @@ -1518,16 +1580,21 @@ static ssize_t cgroup_file_read(struct f
>  >       struct cftype *cft = __d_cft(file->f_dentry);
>  >       struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
>  >
>  > -     if (!cft || cgroup_is_removed(cgrp))
>  > +     if (cgroup_is_removed(cgrp))
>  >               return -ENODEV;
>  >
>
>  This check seems redundant now.
>

It's not needed for safety, but it doesn't seem to hurt to check
cgroup_is_removed() prior to doing any copying, since we'll fail after
copying anyway if cgroup_is_removed() returns true (once we've taken
any relevant locks).

Paul
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