From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Jiri Slaby <jslaby@suse.cz>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
LKML <linux-kernel@vger.kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Linus Torvalds <torvalds@linux-foundation.org>,
Maciej Rutecki <maciej.rutecki@gmail.com>
Subject: Re: [PATCH] sysfs: Optionally count subdirectories to support buggy applications
Date: Wed, 1 Feb 2012 14:49:18 -0800 [thread overview]
Message-ID: <20120201224918.GA2868@kroah.com> (raw)
In-Reply-To: <m139auxjfz.fsf@fess.ebiederm.org>
On Wed, Feb 01, 2012 at 02:44:32PM -0800, Eric W. Biederman wrote:
> Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes:
>
> > On Wed, Feb 01, 2012 at 02:21:59PM -0800, Eric W. Biederman wrote:
> >>
> >> lm_sensors and possibly other applications get confused if all sysfs
> >> directories return nlink == 1. The lm_sensors code that got confused
> >> was just wrong and a fixed version of lm_sensors should be released
> >> shortly.
> >>
> >> There may be other applications that have problems with sysfs return
> >> nlink == 1 for directories. To allow people to continue to use old
> >> versions of userspace with new kernels add to sysfs a compile time
> >> option to maintain mostly precise directory counts for those people who
> >> don't mind the cost.
> >>
> >> I have moved where we keep nlink in sysfs_dirent as compared to previous
> >> versions of subdirectory counting to a location that packs better.
> >>
> >> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
> >> ---
> >> fs/sysfs/Kconfig | 15 +++++++++++++++
> >> fs/sysfs/dir.c | 8 ++++++++
> >> fs/sysfs/inode.c | 2 ++
> >> fs/sysfs/sysfs.h | 38 ++++++++++++++++++++++++++++++++++++++
> >> 4 files changed, 63 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/fs/sysfs/Kconfig b/fs/sysfs/Kconfig
> >> index 8c41fea..9b403e9 100644
> >> --- a/fs/sysfs/Kconfig
> >> +++ b/fs/sysfs/Kconfig
> >> @@ -21,3 +21,18 @@ config SYSFS
> >> example, "root=03:01" for /dev/hda1.
> >>
> >> Designers of embedded systems may wish to say N here to conserve space.
> >> +
> >> +config SYSFS_COUNT_LINKS
> >> + bool "sysfs count subdirectoires to support buggy applications"
> >> + default n
> >
> > As we don't want to break things, this should be default y, right?
>
> The new behavior is backwards compatible. What the new behavior is not
> is bug compatible. So nothing *should* break.
"should", but you really don't know, as all we have is one report so
far.
> Furthermore the breaking we have seen so far is limited to just
> lm_sensors. That is exactly one program that is not a server failing to
> start. That seems pretty minor in the worst case.
>
> So I really don't expect anyone who ships 3.4 to enable this option.
What about users who use a new kernel on old userspace, which happens
all the time (i.e. all the kernel developers themselves)?
> I have written the option solely so that in case my assessment turns out
> to be wrong there is already a tested solution. I have been through the
> pain of not being able to upgrade/test a new kernel because of a
> backwards incompatible change and it can be very unpleasant.
I'd really prefer this to be default 'y', and if a distro knows it can
turn it off to save time/space, it can.
thanks,
greg k-h
next prev parent reply other threads:[~2012-02-01 22:58 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 [this message]
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
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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