From: ebiederm@xmission.com (Eric W. Biederman)
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.cz>,
Linus Torvalds <torvalds@linux-foundation.org>,
Jiri Slaby <jirislaby@gmail.com>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
LKML <linux-kernel@vger.kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Maciej Rutecki <maciej.rutecki@gmail.com>
Subject: Re: [PATCH 1/3] sysfs: Compact sysfs_dirent s_flags into a byte.
Date: Thu, 08 Mar 2012 18:49:51 -0800 [thread overview]
Message-ID: <m1eht2trn4.fsf@fess.ebiederm.org> (raw)
In-Reply-To: <20120308222843.GB32001@kroah.com> (Greg Kroah-Hartman's message of "Thu, 8 Mar 2012 14:28:43 -0800")
Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes:
> On Thu, Mar 08, 2012 at 01:34:22PM -0800, Eric W. Biederman wrote:
>>
>> In an effort to keep sysfs_dirent small used the smallest
>> basic type I can for sysfs s_flags.
>>
>> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
>> ---
>> fs/sysfs/sysfs.h | 10 +++++-----
>> 1 files changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
>> index 6289a00..c76c932 100644
>> --- a/fs/sysfs/sysfs.h
>> +++ b/fs/sysfs/sysfs.h
>> @@ -76,7 +76,7 @@ struct sysfs_dirent {
>> struct sysfs_elem_bin_attr s_bin_attr;
>> };
>>
>> - unsigned short s_flags;
>> + unsigned char s_flags;
>> umode_t s_mode;
>> unsigned int s_ino;
>> struct sysfs_inode_attrs *s_iattr;
>
> Are you sure this saved you any real space here? Have you use pahole (I
> think that's the tool name) to determine if there are holes in the
> structure? Given that you moved this to a smaller variable, yet there
> are pointers later on, odds are nothing changed at all overall.
>
> Verification would be good to have, to see if this work was really worth
> it, right?
The next patch stuffs an 8bit nlink in the hole. I was making room so
we don't have to grow sysfs_dirent.
Eric
next prev parent reply other threads:[~2012-03-09 2:46 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-30 21:56 sysfs regression: wrong link counts Jiri Slaby
2012-01-30 22:06 ` Greg KH
2012-01-30 22:10 ` Alan Cox
2012-01-30 22:27 ` Greg KH
2012-01-30 22:43 ` Al Viro
2012-01-30 22:56 ` Al Viro
2012-01-31 1:27 ` Eric W. Biederman
2012-01-31 10:48 ` Jiri Slaby
2012-01-31 12:44 ` Eric W. Biederman
2012-01-31 16:45 ` Linus Torvalds
2012-01-31 19:18 ` Al Viro
2012-02-01 5:06 ` Eric W. Biederman
2012-02-01 22:21 ` [PATCH] sysfs: Optionally count subdirectories to support buggy applications Eric W. Biederman
2012-02-01 22:24 ` Greg Kroah-Hartman
2012-02-01 22:44 ` Eric W. Biederman
2012-02-01 22:49 ` Greg Kroah-Hartman
2012-02-01 22:31 ` Dave Jones
2012-02-01 22:35 ` Jiri Slaby
2012-02-01 23:15 ` Linus Torvalds
2012-02-01 23:18 ` Linus Torvalds
2012-02-02 1:22 ` Al Viro
2012-02-02 21:24 ` [RFC] killing boilerplate checks in ->link/->mkdir/->rename Al Viro
2012-02-02 23:46 ` Linus Torvalds
2012-02-03 1:16 ` Al Viro
2012-02-03 1:45 ` Al Viro
2012-02-03 2:00 ` Linus Torvalds
2012-02-03 14:57 ` Chris Mason
2012-02-03 17:08 ` Al Viro
2012-02-03 19:34 ` Artem Bityutskiy
2012-02-06 8:50 ` Artem Bityutskiy
2012-02-06 13:56 ` Al Viro
2012-02-06 17:05 ` Artem Bityutskiy
2012-02-06 17:11 ` Al Viro
2012-02-07 7:21 ` Artem Bityutskiy
2012-02-06 22:49 ` Dave Chinner
2012-02-03 8:25 ` Andreas Dilger
2012-02-03 17:03 ` Al Viro
2012-02-04 7:42 ` Andreas Dilger
2012-03-05 13:30 ` [PATCH] sysfs: Optionally count subdirectories to support buggy applications Jiri Slaby
2012-03-05 16:09 ` Greg Kroah-Hartman
2012-03-05 16:47 ` Linus Torvalds
2012-03-08 21:05 ` Greg Kroah-Hartman
2012-03-08 22:18 ` Eric W. Biederman
2012-03-08 23:40 ` Linus Torvalds
2012-03-08 21:28 ` Eric W. Biederman
2012-03-08 21:34 ` [PATCH 1/3] sysfs: Compact sysfs_dirent s_flags into a byte Eric W. Biederman
2012-03-08 21:36 ` [PATCH 2/3] sysfs: Maintain usable nlink directory counts Eric W. Biederman
2012-03-08 21:37 ` [PATCH 3/3] sysfs: Remove SYSFS_FLAG_REMOVED and use sd->s_nlink == 0 instead Eric W. Biederman
2012-03-09 3:40 ` Linus Torvalds
2012-03-08 22:28 ` [PATCH 1/3] sysfs: Compact sysfs_dirent s_flags into a byte Greg Kroah-Hartman
2012-03-09 2:49 ` Eric W. Biederman [this message]
2012-01-31 3:45 ` sysfs regression: wrong link counts Eric W. Biederman
2012-01-31 11:54 ` Alan Cox
2012-01-30 22:52 ` Kay Sievers
2012-01-31 10:41 ` network regression: cannot rename netdev twice Jiri Slaby
2012-01-31 10:52 ` Kay Sievers
2012-01-31 11:00 ` Jiri Slaby
2012-01-31 11:13 ` Kay Sievers
2012-01-31 11:17 ` Jiri Slaby
2012-01-31 11:58 ` Kay Sievers
2012-01-31 14:18 ` Eric W. Biederman
2012-01-31 14:40 ` [PATCH] sysfs: Update the name hash when renaming sysfs entries Eric W. Biederman
2012-01-31 14:41 ` Jiri Slaby
2012-01-31 14:55 ` Greg KH
2012-02-04 2:14 ` network regression: cannot rename netdev twice Henrique de Moraes Holschuh
2012-02-06 20:03 ` Kay Sievers
2012-02-08 2:00 ` Henrique de Moraes Holschuh
2012-02-08 3:50 ` Kay Sievers
2012-02-08 6:42 ` Valdis.Kletnieks
2012-02-08 10:57 ` Kay Sievers
2012-02-08 20:06 ` Valdis.Kletnieks
2012-02-08 20:27 ` Stephen Hemminger
2012-02-08 23:48 ` Kay Sievers
2012-01-31 1:32 ` sysfs regression: wrong link counts Eric W. Biederman
2012-02-01 18:29 ` Maciej Rutecki
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