Re: UBIFS quota support

[Richard Weinberger <richard.weinberger@xxxxxxxxx>]

On Thu, Jan 10, 2019 at 12:45 PM Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> wrote:
>
> Hi all,
>
> I'm currently working on resurrecting the UBIFS quota patches posted back in
> 2015 by Dongsheng Yang, last posted here:
>
> http://lists.infradead.org/pipermail/linux-mtd/2015-September/061812.html
>
> First of all I think work stopped there, there is no newer UBIFS quota
> support I am missing, right?
>
> One problem with this series was that the quotactl systemcall expects a
> path to a block device. UBIFS doesn't work on a block device but on a
> character device instead.
> The solution in this series was to pass the path to the cdev in
> quotactl.  A struct cdev * member was added to struct super_block which
> was used to identify the superblock for a given cdev. This approach was
> rejected by Christoph ("I don't think the cdev has any business in core
> VFS code.").  Apart from that UBIFS can not only be mounted with a path
> to the character device (mount -t ubifs /dev/ubix_y /mnt) but also in
> the form ubix:volname (mount -t ubifs ubix:volname /mnt) in which case
> userspace doesn't have any valid path it could pass in quotactl.
>
> An idea out of this would be to allow to pass the mountpoint instead of
> the path to the block device in quotactl which would work with nfs or
> even tmpfs aswell. Would that be acceptable? Any other ideas?

*kind ping*

Jan, another thing Sascha and I are not sure about, what are the consistency
constraints of the quota file?
If I read the code correctly, quota just writes to the quota file and
assumes that
the file system makes sure about consistency. Either by fsck fixing the quota
file or having a data journal for the quota file.
In case of UBIFS where we have a data journal this should be doable.
Is it okay when the quota file has S_SYNC set?

-- 
Thanks,
//richard

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