linux-ext4 - Re: DRAFT Design Spec for 1st Class Quota Support in Ext4

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Message-ID: <20100426184746.GC21179@atrey.karlin.mff.cuni.cz>
Date:	Mon, 26 Apr 2010 20:47:47 +0200
From:	Jan Kara <jack@...e.cz>
To:	Theodore Ts'o <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: DRAFT Design Spec for 1st Class Quota Support in Ext4

  Hi Ted,

  The proposal looks fine. A couple of comments / questions:

> 6) Tune2fs will have a facility for adding and removing user and group
> quotas inodes while the file system is mounted.  The quota usage will
> not be correct after the quota inodes are newly added, however, so quota
> will not be enabled by default,  If the quota inodes are removed, quota
> will be disabled first.
  I suppose you will make quota file mtime not match last mounted time so
that e2fsck updating the usage will be triggered, right?

> 7) There will be a new interface so that bulk quota information can be
> fetched from the file system.  This needs to be negotiated with Jan
> Kara.  It can either be a new system call, or a magic file in /proc that
> can be opened and the repquota data extracted.
  Traditionally, quota interaction happens via quotactl() syscall. I'm not
against adding a syscall for this but then it would be a logical thing to
transition all the quotactl interface to standard syscalls... I'll try to
come up with some proposal during this week.
  Using /proc/ file looks like an ugly hack to me.

  And one more question: You don't speak in your document, when quotas
will be enabled. I expect accounting will be enabled during mount time, how
about quota enforcement? I think it might be useful if admin can disable
the quota limit enforcement and QUOTAON / QUOTAOFF sysctl is a natural
way to do this. Generic quota code supports this so it comes basically
for free.

								Honza
-- 
Jan Kara <jack@...e.cz>
SuSE CR Labs
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