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SubjectRe: [PATCH] disk quotas fail when /etc/mtab is symlinked to /proc/mounts
Mark Bellon wrote:

> Andrew Morton wrote:
>
>> Mark Bellon <mbellon@mvista.com> wrote:
>>
>>
>>> If /etc/mtab is a regular file all of the mount options (of a file
>>> system) are written to /etc/mtab by the mount command. The quota
>>> tools look there for the quota strings for their operation. If,
>>> however, /etc/mtab is a symlink to /proc/mounts (a "good thing" in
>>> some environments) the tools don't write anything - they assume the
>>> kernel will take care of things.
>>>
>>> While the quota options are sent down to the kernel via the mount
>>> system call and the file system codes handle them properly
>>> unfortunately there is no code to echo the quota strings into
>>> /proc/mounts and the quota tools fail in the symlink case.
>>>
>>
>>
>> hm. Perhaps others with operational experience in that area can
>> comment.
>>
>>
> OK.
>
>>
>>
>>> The attached patchs modify the EXT[2|3] and [X|J]FS codes to add the
>>> necessary hooks. The show_options function of each file system in
>>> these patches currently deal with only those things that seemed
>>> related to quotas; especially in the EXT3 case more can be done
>>> (later?).
>>>
>>
>>
>> It seems sad to do it in each filesystem. Is there no way in which
>> we can
>> do this for all filesystems, in a single place in the VFS?
>>
>>
> Each file system must be able to echo it's own FS specific options,
> hence the show_options hook (XFS is a good example). EXT3 has it's own
> form of journalled quota file options, hence the need for the specific
> hook.
>
> The "older style" (e.g. "usrquota", "grpquota", "quota") could be done
> generically but a FS might want any number of quota options. The few
> lines of code in each file system didn't seem so bad especially if the
> show_function start echoing more.

Followup comment/through...

If we want /proc/mounts to really replace /etc/mtab in the general case,
always using it as a symlink, the file system codes will all need the
show_options hook - they will need to echo all of their private options
duplicating, as closely as possible, what would have been written to the
/etc/mtab regular file.

mark

mark

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