"loop device recursion avoidance" patch causes difficulties

"loop device recursion avoidance" patch causes difficulties

[Luboš Doležel]

Hello,

I've created a bugreport at http://bugme.osdl.org/show_bug.cgi?id=4472
and I was advised to write to this list.

A patch called "loop device recursion avoidance" which appeared in
2.6.11 kernel has complicated ISO image mounting from another mounted
media.

Example:

# mount /mnt/dvd
# mount -o loop /mnt/dvd/file.iso /somedir

The mount command produces this error: "ioctl: LOOP_SET_FD: Invalid argument".

This operation maybe is a kind of recursion but I think that recursion
should be limited - not disabled.
Now I have to copy the ISO image to my hdd before mounting. I used to
put CD backups on DVDs; now it's more complicated to use.

I am not a "linux-kernel" subscriber so please CC me to: lubosd at gmail com.

Best regards,
Lubos Dolezel

Re: "loop device recursion avoidance" patch causes difficulties

[Andrew Morton]

Lubo_ Dole_el <lubosd@gmail.com> wrote:
>
> I've created a bugreport at http://bugme.osdl.org/show_bug.cgi?id=4472
> and I was advised to write to this list.
> 
> A patch called "loop device recursion avoidance" which appeared in
> 2.6.11 kernel has complicated ISO image mounting from another mounted
> media.

Does this help?


diff -puN drivers/block/loop.c~loop-recusrion-avoidance-fix drivers/block/loop.c
--- 25/drivers/block/loop.c~loop-recusrion-avoidance-fix	Wed May 18 14:03:14 2005
+++ 25-akpm/drivers/block/loop.c	Wed May 18 14:03:14 2005
@@ -765,10 +765,8 @@ static int loop_set_fd(struct loop_devic
 			goto out_putf;
 
 		l = f->f_mapping->host->i_bdev->bd_disk->private_data;
-		if (l->lo_state == Lo_unbound) {
-			error = -EINVAL;
-			goto out_putf;
-		}
+		if (l->lo_state == Lo_unbound)
+			break;
 		f = l->lo_backing_file;
 	}
 
_

Re: "loop device recursion avoidance" patch causes difficulties

[Bill Davidsen]

Luboš Doležel wrote:
> Hello,
> 
> I've created a bugreport at http://bugme.osdl.org/show_bug.cgi?id=4472
> and I was advised to write to this list.
> 
> A patch called "loop device recursion avoidance" which appeared in
> 2.6.11 kernel has complicated ISO image mounting from another mounted
> media.
> 
> Example:
> 
> # mount /mnt/dvd
> # mount -o loop /mnt/dvd/file.iso /somedir
> 
> The mount command produces this error: "ioctl: LOOP_SET_FD: Invalid argument".
> 
> This operation maybe is a kind of recursion but I think that recursion
> should be limited - not disabled.
> Now I have to copy the ISO image to my hdd before mounting. I used to
> put CD backups on DVDs; now it's more complicated to use.

Far worse than complicated, it just doesn't work... I'm glad you found 
this before I did, I have loads of similar things, created when a number 
  of small system were decomissioned and each partition was written raw 
as a file. Like:
   machineA/part1
   machineA/part2
   machineB/part1
and similar. These were all 525MB drives, but the data is moderately 
critical. I've been successful mounting with all older kernel, except 
the SysVR4 images, which have a filesystem Linux can't handle (from 
Dell's brief adventure with SysVR4). Now it appears that I will have to 
copy the data to a drive to use it, which is a minor pain since the 
process is in scripts.

Another case of fixing a problem without completely understanding it, I 
fear. At least one machine had a partition with floppy images, I hope 
they weren't loop mounting them, although it's likely they just burn a 
fresh floppy when needed (boot disks for control PCs).

-- 
    -bill davidsen (davidsen@tmr.com)
"The secret to procrastination is to put things off until the
  last possible moment - but no longer"  -me

Re: "loop device recursion avoidance" patch causes difficulties

[Luboš Doležel]

On 5/18/05, Andrew Morton <akpm@osdl.org> wrote:
> Lubo_ Dole_el <lubosd@gmail.com> wrote:
> >
> > I've created a bugreport at http://bugme.osdl.org/show_bug.cgi?id=4472
> > and I was advised to write to this list.
> >
> > A patch called "loop device recursion avoidance" which appeared in
> > 2.6.11 kernel has complicated ISO image mounting from another mounted
> > media.
> 
> Does this help?
>  

It didn't help. And I've realized a big mistake. I tried to mount the
DVD without supermount. And it worked. So this is a problem in
supermount patch.
Sorry for bothering you :-( and thanks anyway.