[PATCH] fs: Check if automount actually mounts something

[Sascha Hauer]

On Tue, Aug 09, 2022 at 03:05:19PM +0200, Uwe Kleine-König wrote:
> Hello,
> 
> On Tue, Aug 09, 2022 at 12:06:38PM +0200, Sascha Hauer wrote:
> > On Thu, Jul 14, 2022 at 11:12:38PM +0200, Uwe Kleine-König wrote:
> > > On Thu, Jul 14, 2022 at 09:35:09PM +0200, Sascha Hauer wrote:
> > > > An automount command that returns successfully but doesn't mount
> > > > anything makes barebox hang as can be reproduced with:
> > > > 
> > > > automount -d /mnt/foo true
> > > > ls /mnt/foo
> > > > 
> > > > Check if the current dentry is a mountpoint after running the automount
> > > > command, otherwise return with an error from automount_mount().
> > > 
> > > While I think the intention of this patch is fine, I have little doubts
> > > if that breaks some workflows, e.g. something like:
> > > 
> > > 	automount -d /mnt/tralala 'for p in 0 1 2; do mkdir ${automount_path}/${p} && mount /dev/disk0.${p} ${automount_path}/${p} || break; done'
> > 
> > You would create 3 automountpoints for that.
> 
> Yeah, if you go one step further and create a directory for each
> partition of the thumb drive, this is a dynamic thing though and solving
> that with an automount might make sense, so something like:
> 
> 	automount -d /mnt/tralala "for p in /dev/disk0.*; do mp=$(\${automount_path}/\$(basename $p)); automount -d \$mp 'mount \$p \$mp'"
> 
> (don't know if that would work, but you get the idea I guess).

It won't work. The outer automount is for mounting /mnt/tralala/. You
can't access anything inside /mnt/tralala/ before that has been
completed.

Similarly the following doesn't work:

# automount -d /mnt/tralala 'echo -o ${automount_path}/foo bar'
# ls /mnt/tralala/
open: Invalid argument
running automount command 'echo -o ${automount_path}/foo bar' failed
ls: /mnt/tralala/: No such device

Sascha

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |