Hi,
Thanks for the comment
On Mon, Sep 17, 2012 at 10:43:22AM +0200, Karel Zak wrote:
> On Mon, Sep 17, 2012 at 04:00:34PM +0800, Dave Young wrote:
> >
> > ismounted handles both find-by-dev and find-by-mnt, but there's two issues:
> > 1. for find-by-dev, it use readlink to get the canonical dev name, but
> > lvm is different with other devices, lvm use the symlinks in /proc/mounts
> > without converting to canonical name.
>
> Well, dm-N are private DM names and should not be used anywhere in
> userspace. The official device name is /dev/mapper/<name> where the
> <name> is exported by /sys/block/dm-<N>/dm/name. You need something
> like:
>
> cn_device=$(cat /sys/block/${device##/dev/}/dm/name)
Good to know.
>
> > 2. for nfs mounting, just use [ -b $dev ] is not enough, it need being handled
> > seperately.
> >
> > grep all current ismounted() user, they are all ismounted <mntdir>, so change
> > to split the ismounted <dev> to another function dev_ismounted. Afterwards
> > ismounted() should be converted to dir_ismounted.
> >
> > in dev_ismounted, fix the dev name issue by using maj:min to comparing with
> > items in /proc/self/mountinfo. OTOH for nfs share just compare with the 1st
> > field of /proc/mounts.
>
> Do you know about findmnt(1)? It's smaller than stat(1) and provides
> all necessary functionality ;-)
great! I never know this findmnt..
findmnt works well with both nfs and lvm, replace these logic with findmnt
looks more elegant. Will update this patch with findmnt.
>
> > -find_mount() {
> > - local dev mnt etc wanted_dev
> > - wanted_dev="$(readlink -e -q $1)"
> > +# get_maj_min <device>
> > +# Prints the major and minor of a device node.
> > +# Example:
> > +# $ get_maj_min /dev/sda2
> > +# 8:2
> > +get_maj_min() {
> > + local _dev
> > + _dev=$(stat -L -c '$((0x%t)):$((0x%T))' "$1" 2>/dev/null)
> > + _dev=$(eval "echo $_dev")
> > + echo $_dev
> > +}
> > +
> > +find_mount_point() {
> > + local _x majmin mnt wanted_majmin
> > + wanted_majmin="$(get_maj_min $1)"
> > + while read _x _x majmin _x mnt _x; do
> > + [ "$majmin" = "$wanted_majmin" ] && echo "$mnt" && return 0
>
> You should not expect that devno returned by stat(1) matches with
> devno in /proc/self/mountinfo. For example btrfs uses some pseudo-devnos
> (don't forget that btrfs is not strictly per-device filesystem):
>
> # ls -la /dev/sdb
> brw-rw---- 1 root disk 8, 16 Sep 17 10:24 /dev/sdb
> ^^^^^
>
> # grep /dev/sdb /proc/self/mountinfo
> 56 21 0:44 / /mnt/test rw,relatime - btrfs /dev/sdb rw,ssd,nospace_cache
> ^^^^
Thanks for reminding, btrfs is special especially with multi devices.
I remember this devnos confuse lilo as well in my slackware so I have to use
a boot partition.
>
> It's probably better to use a canonical device name.
>
> # findmnt /dev/sdb
> TARGET SOURCE FSTYPE OPTIONS
> /mnt/test /dev/sdb btrfs rw,relatime,ssd,nospace_cache
>
>
>
> Karel
>
> --
> Karel Zak <kzak@xxxxxxxxxx>
> http://karelzak.blogspot.com
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