From: Al Viro <viro@ZenIV.linux.org.uk>
To: Greg KH <greg@kroah.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Jiri Slaby <jslaby@suse.cz>, LKML <linux-kernel@vger.kernel.org>,
systemd-devel@lists.freedesktop.org
Subject: Re: sysfs regression: wrong link counts
Date: Mon, 30 Jan 2012 22:56:38 +0000 [thread overview]
Message-ID: <20120130225638.GO23916@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20120130224350.GN23916@ZenIV.linux.org.uk>
On Mon, Jan 30, 2012 at 10:43:50PM +0000, Al Viro wrote:
> On Mon, Jan 30, 2012 at 02:27:17PM -0800, Greg KH wrote:
> > On Mon, Jan 30, 2012 at 10:10:59PM +0000, Alan Cox wrote:
> > > > Isn't there some other "proper" way of doing this in userspace, or is
> > > > this really the correct way?
> > >
> > > You can look at the S_IFMT bits and stuff however link count indicating
> > > number of subdirectories is a standard Unix thing and used by many quite
> > > mundane tools as an optimisation.
> >
> > Ah, yeah, that is easier.
> >
> > Eric, care to fix this or want me to revert it?
>
> Fix _what_? Userland shite quoted upthread? Because that's where the bug
> is - the mundane tools mentioned by Alan treat 1 in st_nlink as "no
> information about the number of subdirectories". And shite might be too
> mild a term for the little gem in question, really...
To repeat this piece of bogosity for those who might've missed it:
/* returns !0 if sysfs filesystem was found, 0 otherwise */
int sensors_init_sysfs(void)
{
struct stat statbuf;
snprintf(sensors_sysfs_mount, NAME_MAX, "%s", "/sys");
if (stat(sensors_sysfs_mount, &statbuf) < 0
|| statbuf.st_nlink <= 2) /* Empty directory */
return 0;
return 1;
}
which is completely bogus - contrary to what it says in comments, it does
*not* check anything about sysfs (or directories being empty). Checking
that sysfs is mounted on /sys could be done by statfs(2) and checking
->f_type, or, considering what the code in lib/sysfs.c is doing, just
checking that /sys/class is readable and failing otherwise.
Sigh...
next prev parent reply other threads:[~2012-01-30 22:56 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 [this message]
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
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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