squashfs seems nfs-incompatible

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Jan Engelhardt

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Aug 2, 2005, 11:17:02 AM8/2/05
to plou...@users.sourceforge.net, Linux Kernel Mailing List
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
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Phillip Lougher

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Aug 4, 2005, 11:43:19 AM8/4/05
to Jan Engelhardt, plou...@users.sourceforge.net, Linux Kernel Mailing List
On 8/2/05, Jan Engelhardt <jen...@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

Jan Engelhardt

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Aug 5, 2005, 2:10:08 AM8/5/05
to Phillip Lougher, plou...@users.sourceforge.net, Linux Kernel Mailing List
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
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| Alphagate Systems, http://alphagate.hopto.org/

Phillip Lougher

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Aug 5, 2005, 3:33:55 AM8/5/05
to Jan Engelhardt, Phillip Lougher, plou...@users.sourceforge.net, Linux Kernel Mailing List
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

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