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    SubjectRe: sysfs root link count broken in 2.6.22-git5
    Hi Kay,

    On Thu, 19 Jul 2007 02:44:54 +0200, Kay Sievers wrote:
    > On 7/18/07, Jean Delvare <khali@linux-fr.org> wrote:
    > > On Tue, 17 Jul 2007 20:38:28 -0700, Greg KH wrote:
    > > > On Tue, Jul 17, 2007 at 11:05:30PM +0200, Jean Delvare wrote:
    > > > > The code looks like:
    > > > >
    > > > > if (sysfs_get_mnt_path(sensors_sysfs_mount, NAME_MAX)
    > > > > || stat(sensors_sysfs_mount, &statbuf) < 0
    > > > > || statbuf.st_nlink <= 2) /* Empty directory */
    > > > > return 0; /* Failure */
    > > > >
    > > > > This works OK with 2.6.22.1, but the last test fails with the current
    > > > > git kernel even when sysfs is mounted.
    > > >
    > > > Yeah, but is checking the number of hard links in the directory a safe
    > > > way to always verify that it isn't empty?
    > >
    > > I think so, yes. To the best of my knowledge, it has worked on all
    > > Unix-like systems for decades. There are other ways, but this is by far
    > > the less expensive.
    >
    > Well, just check if /sys/devices/ exists, that should be cheap enough. :)

    Yes, this is a possibility, and one I had considered at first. But I
    wasn't sure which subdirectory to check. sysfs isn't well known for its
    stability, and I didn't know which directories exist since the
    early days of sysfs, and which do not. For example, fs, kernel and
    module were not present in 2.6.5. I am also not sure if directories
    which exist today are guaranteed to exist forever. This is the reason
    why I decided to check the link count instead, basically checking that
    at least one subdirectory exists, without having to name it.

    --
    Jean Delvare
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