squashfs seems nfs-incompatible

squashfs seems nfs-incompatible

[Jan Engelhardt]

Hi,


I found out that you cannot mount an exported squash fs. The exports(5) fsid= 
parameter does not help it [like it did with unionfs].


Jan Engelhardt
-- 

Re: squashfs seems nfs-incompatible

[Phillip Lougher]

On 8/2/05, Jan Engelhardt <jengelh@linux01.gwdg.de> wrote:
>
> I found out that you cannot mount an exported squash fs. The exports(5) fsid=
> parameter does not help it [like it did with unionfs].
> 


The exports(5) man page says fsid=num is necessary for filesystems on
non-block devices - I don't know whether this includes loopback
filesystems.  Have you tried exporting a Squashfs filesystem mounted
on a real block device?

I've never tried to export a Squashfs filesystem, and so I don't know
if it works.  If it doesn't, I would say it is because Squashfs (like
Cramfs) doesn't store correct nlink information for directories.

The next release does store nlink information, has support for > 4GB
files/filesystems, and other nice improvements.  I'm hoping to release
an alpha release soon.

Phillip

Re: squashfs seems nfs-incompatible

[Phillip Lougher]

Jan Engelhardt wrote:
> After a short flash of 
> idea and comparison, it turns out that squashfs is missing 
> sb->s_export->get_parent (the only requirement as it seems). Includes that you 
> have sb->s_export non-null, of course. sb->s_export can be set within 
> fill_super().
> 
> 

Ok, thanks.  I'll try and get a fix for it in the next release.

Regards

Phillip

Re: squashfs seems nfs-incompatible

[Jan Engelhardt]

Hi,

>> I found out that you cannot mount an exported squash fs. The exports(5) fsid=
>> parameter does not help it [like it did with unionfs].
>
>The exports(5) man page says fsid=num is necessary for filesystems on
>non-block devices - I don't know whether this includes loopback
>filesystems.  Have you tried exporting a Squashfs filesystem mounted
>on a real block device?

Loopback is a real block device, and no, fsid= does not help it. I have talked 
with the unionfs people, because it works for them. After a short flash of 
idea and comparison, it turns out that squashfs is missing 
sb->s_export->get_parent (the only requirement as it seems). Includes that you 
have sb->s_export non-null, of course. sb->s_export can be set within 
fill_super().

>I've never tried to export a Squashfs filesystem, and so I don't know
>if it works.  If it doesn't, I would say it is because Squashfs (like
>Cramfs) doesn't store correct nlink information for directories.
>
>The next release does store nlink information, has support for > 4GB
>files/filesystems, and other nice improvements.  I'm hoping to release
>an alpha release soon.

FTR, I currently cheated by using
`mount -t unionfs -o dirs=/squash=ro none /squash` to get the export working.



Jan Engelhardt
-- 
| Alphagate Systems, http://alphagate.hopto.org/