F15: ugly behavior of "df"

[Karel Zak]

On Fri, Jul 22, 2011 at 12:55:54AM +0200, Reindl Harald wrote:
> Am 22.07.2011 00:39, schrieb Karel Zak:
> 
> > * bind mounts are represented as /A -> /B dependence, reality is
> > /A -> device, /B -> device (and /A could be umounted, moved, ...)
> 
> this is not generally true

 # mount /dev/sdb1 /mnt/A
 # mount --bind /mnt/A /mnt/B

 # findmnt /dev/sdb1
 TARGET SOURCE    FSTYPE OPTIONS
 /mnt/A /dev/sdb1 ext4   rw,relatime,barrier=1,stripe=32,data=ordered
 /mnt/B /dev/sdb1 ext4   rw,relatime,barrier=1,stripe=32,data=ordered

 # umount /mnt/A

 # findmnt /dev/sdb1
 TARGET SOURCE    FSTYPE OPTIONS
 /mnt/B /dev/sdb1 ext4   rw,relatime,barrier=1,stripe=32,data=ordered


> [root at srv-rhsoft:~]$ umount /Volumes/dune/www-servers
> umount: /Volumes/dune/www-servers: device is busy.
>         (In some cases useful info about processes that use
>          the device is found by lsof(8) or fuser(1))
> [root at srv-rhsoft:~]$ umount /Volumes/dune/www-servers/phpincludes
> [root at srv-rhsoft:~]$ umount /Volumes/dune/www-servers
> [root at srv-rhsoft:~]$ mount /Volumes/dune/www-servers/phpincludes
> mount: Einhängepunkt /Volumes/dune/www-servers/phpincludes existiert nicht
> [root at srv-rhsoft:~]$ mount /Volumes/dune/www-servers
> [root at srv-rhsoft:~]$ mount /Volumes/dune/www-servers/phpincludes
> 
> [root at srv-rhsoft:~]$ cat /etc/fstab | grep www-servers
> /mnt/data/www/thelounge.net  /Volumes/dune/www-servers               none  bind
> /mnt/data/www/phpincludes    /Volumes/dune/www-servers/phpincludes   none  bind
> 
> so something, somewhere knows that one bind-mount is inside another

 Oh... this is generic thing, you cannot umount any part of VFS if
 there is active submount. This is not related to bind mounts.

 # mount /dev/sdb1 /mnt/A
 # mkdir /mnt/A/subdir

 # mount /dev/sda1 /mnt/A/subdir

 # umount /mnt/A
 umount: /mnt/A: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))

 I hope that umount(8) in Fedora-17 will support --recursive option.

    Karel

-- 
 Karel Zak  <kzak at redhat.com>
 http://karelzak.blogspot.com