Re: [PATCH] disk quotas fail when /etc/mtab is symlinked to /proc/mounts

[Mark Bellon <mbellon@mvista.com>]

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