linux-kernel - Re: [PATCH] Remove some pointless conditionals before kfree() in kernel/cgroup.c

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Date:	Mon, 23 Feb 2009 11:17:57 +0300
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Paul Menage <menage@...gle.com>
Cc:	Jesper Juhl <jj@...osbits.net>, linux-kernel@...r.kernel.org,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	Paul Jackson <pj@....com>, Simon Derr <simon.derr@...l.net>
Subject: Re: [PATCH] Remove some pointless conditionals before kfree() in
	kernel/cgroup.c

[Paul Menage - Mon, Feb 23, 2009 at 12:12:51AM -0800]
| On Sun, Feb 22, 2009 at 2:05 PM, Jesper Juhl <jj@...osbits.net> wrote:
| > Hi,
| >
| > Here's a small patch for kernel/cgroup.c
| >
| > Removes a few pointless tests of pointer == 0 before kfree() in
| > kernel/cgroup.c.
| > If the pointer we hand to kfree() is 0, then kfree() is a noop, so there
| > is no need to test.
| >
| > Reduces object file size a bit :
| >
| > Before:
| > $ size kernel/cgroup.o
| >   text    data     bss     dec     hex filename
| >  21593    7804    4924   34321    8611 kernel/cgroup.o
| > After:
| > $ size kernel/cgroup.o
| >   text    data     bss     dec     hex filename
| >  21537    7744    4924   34205    859d kernel/cgroup.o
| 
| Thanks. I'm a bit surprised that it also shrunk the data segment size
| (and in fact, by more than the text segment size). Any idea how that
| came about?

Maybe kfree was inlined by gcc for some reason?

| 
| >
| > Signed-off-by: Jesper Juhl <jj@...osbits.net>
| 
| Acked-by: Paul Menage <menage@...gle.com>
| 
| Paul
| 
| > ---
| >
| > diff --git a/kernel/cgroup.c b/kernel/cgroup.c
| > index 9edb5c4..1c0a9b5 100644
| > --- a/kernel/cgroup.c
| > +++ b/kernel/cgroup.c
| > @@ -865,8 +865,7 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
| >        if (opts.release_agent)
| >                strcpy(root->release_agent_path, opts.release_agent);
| >  out_unlock:
| > -       if (opts.release_agent)
| > -               kfree(opts.release_agent);
| > +       kfree(opts.release_agent);
| >        mutex_unlock(&cgroup_mutex);
| >        mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
| >        return ret;
| > @@ -969,15 +968,13 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
| >        /* First find the desired set of subsystems */
| >        ret = parse_cgroupfs_options(data, &opts);
| >        if (ret) {
| > -               if (opts.release_agent)
| > -                       kfree(opts.release_agent);
| > +               kfree(opts.release_agent);
| >                return ret;
| >        }
| >
| >        root = kzalloc(sizeof(*root), GFP_KERNEL);
| >        if (!root) {
| > -               if (opts.release_agent)
| > -                       kfree(opts.release_agent);
| > +               kfree(opts.release_agent);
| >                return -ENOMEM;
| >        }
| >
| >
| >
| > --
| > Jesper Juhl <jj@...osbits.net>             http://www.chaosbits.net/
| > Plain text mails only, please      http://www.expita.com/nomime.html
| > Don't top-post  http://www.catb.org/~esr/jargon/html/T/top-post.html
| >
| >
| 
	- Cyrill -
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