linux-kernel - Re: [RFC/PATCH 2/8]: CGroup Files: Add a cgroup write

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Date:	Tue, 13 May 2008 14:01:01 -0700
From:	"Paul Menage" <menage@...gle.com>
To:	"Andrew Morton" <akpm@...ux-foundation.org>
Cc:	pj@....com, xemul@...nvz.org, balbir@...ibm.com, serue@...ibm.com,
	linux-kernel@...r.kernel.org, containers@...ts.linux-foundation.org
Subject: Re: [RFC/PATCH 2/8]: CGroup Files: Add a cgroup write_string control file method

On Tue, May 13, 2008 at 1:07 PM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
>  >
>  > +     /* If non-zero, defines the maximum length of string that can
>  > +      * be passed to write_string; defaults to 64 */
>  > +     int max_write_len;
>
>  would size_t be a more appropriate type?
>

Probably overkill, but I guess it's technically more correct. Updated
for the next version of these patches.

>
>  s/) (/)(/ would be more conventional.
>

OK, I've updated this and the other extraneous spaces in a separate patch.

>
>  > +     /*
>  > +      * write_string() is passed a nul-terminated kernelspace
>  > +      * buffer of maximum length determined by max_write_len
>  > +      */
>  > +     int (*write_string) (struct cgroup *cgrp, struct cftype *cft,
>  > +                          char *buffer);
>
>  Should these return size_t?

No, it returns 0 or a -ve error code. I've added a comment to this effect.
>  >       char *buffer = static_buffer;
>  > -     ssize_t max_bytes = sizeof(static_buffer) - 1;
>  > +     ssize_t max_bytes =  cft->max_write_len ?: sizeof(static_buffer) - 1;
>
>  A blank line between end-of-locals and start-of-code is conventional
>  and, IMO, easier on the eye.
>
>  Does gcc actually generate better code with that x?:y thing?

I doubt it - but I felt that it made the code a bit clearer since it
reduces repetition. I can change it to

	size_t max_bytes =  cft->max_write_len;

	if (!max_bytes)
		max_bytes = sizeof(static_buffer) - 1;

Paul
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