On Tue, Sep 11, 2012 at 09:31:40AM +0800, Dave Young wrote:
> On 09/10/2012 10:40 PM, Vivek Goyal wrote:
>
> > On Mon, Sep 10, 2012 at 04:10:46PM +0800, Dave Young wrote:
> >> kdump module also need to convert dev name to udev symlinks.
> >> So better to move function get_persistent_dev() to dracut-functions.sh
> >>
> >> Also in this patch improvement and fix the original function:
> >> a) use udevadm info --query=name to get the kernel name.
> >> This will fix the issue caused by passing symbolic link of a device.
> >> b) fix a bug to compare $_tmp instead of $i with $_dev. Really sorry,
> >> should have tested more carefully.
> >>
> >> Signed-off-by: Dave Young <dyoung@xxxxxxxxxx>
> >> ---
> >> dracut-functions.sh | 14 ++++++++++++++
> >> modules.d/99base/module-setup.sh | 13 -------------
> >> 2 files changed, 14 insertions(+), 13 deletions(-)
> >>
> >> --- dracut.orig/dracut-functions.sh
> >> +++ dracut/dracut-functions.sh
> >> @@ -239,6 +239,21 @@ else
> >> }
> >> fi
> >>
> >> +get_persistent_dev() {
> >> + local i _tmp _dev
> >> +
> >> + _dev=$(udevadm info --query=name --name="$1" 2>/dev/null)
> >> + [ -z "$_dev" ] && return
> >> +
> >> + for i in /dev/disk/by-id/*; do
> >> + _tmp=$(udevadm info --query=name --name="$i" 2>/dev/null)
> >> + if [ "$_tmp" = "$_dev" ]; then
> >> + echo $i
> >> + return
> >> + fi
> >> + done
> >> +}
> >> +
> >
> > Can't we just compare the maj:min number of device and come up with udev
> > name? I think that would be simpler and we will not have to call into
> > udevadm.
>
>
> Hi,
>
> /dev/disk/by-id/* are symlinks, $1 could be soft link as well, using
> udevadm will be simpler because we do not need follow symlinks and
> handle the string prefix.
dracut function get_maj_min() uses "stat" with -L option which will
automatically following symlinks if need be. Calling into udevadm
for every possible device (/dev/disk/by-id/*) seems overkill to me. Anyway,
harald has already committed this patch. So we will simplify it some
other time.
One advantage of converting to kernel names is that looking into
/proc/mounts will give us the mount point. I was converting device
name into maj:min and looking into /proc/self/mountinfo to determine
the mount point.
So converting to kernel name does seem to have this little advantage
of being able to find device name and associated mountpoint in
/proc/mounts.
Thanks
Vivek
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