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Re: [PATCH] xfs_showargs() reports group *and* project quotas enabled

To: "Alex Elder" <aelder@xxxxxxx>
Subject: Re: [PATCH] xfs_showargs() reports group *and* project quotas enabled
From: Felix Blyakher <felixb@xxxxxxx>
Date: Thu, 27 Aug 2009 01:53:28 -0500
Cc: <xfs@xxxxxxxxxxx>
In-reply-to: <1AB9A794DBDDF54A8A81BE2296F7BDFE83ABD9@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
References: <1AB9A794DBDDF54A8A81BE2296F7BDFE83ABD9@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>

On Aug 26, 2009, at 12:46 PM, Alex Elder wrote:

If you enable group or project quotas on an XFS file system, then the
mount table presented through /proc/self/mounts erroneously shows
that both options are in effect for the file system.  The root of
the problem is some bad logic in the xfs_showargs() function, which
is used to format the file system type-specific options in effect
for a file system.

The problem originated in this GIT commit:
   Move platform specific mount option parse out of core XFS code
   Date: 11/22/07
   Author: Dave Chinner
   SHA1 ID: a67d7c5f5d25d0b13a4dfb182697135b014fa478

For XFS quotas, project and group quota management are mutually
exclusive--only one can be in effect at a time.  There are two
parts to managing quotas:  aggregating usage information; and
enforcing limits.  It is possible to have a quota in effect
(aggregating usage) but not enforced.

These features are recorded on an XFS mount point using these flags:
   XFS_PQUOTA_ACCT - Project quotas are aggregated
   XFS_GQUOTA_ACCT - Group quotas are aggregated
   XFS_OQUOTA_ENFD - Project/group quotas are enforced

The code in error is in fs/xfs/linux-2.6/xfs_super.c:

       if (mp->m_qflags & (XFS_PQUOTA_ACCT|XFS_OQUOTA_ENFD))
               seq_puts(m, "," MNTOPT_PRJQUOTA);
       else if (mp->m_qflags & XFS_PQUOTA_ACCT)
               seq_puts(m, "," MNTOPT_PQUOTANOENF);

       if (mp->m_qflags & (XFS_GQUOTA_ACCT|XFS_OQUOTA_ENFD))
               seq_puts(m, "," MNTOPT_GRPQUOTA);
       else if (mp->m_qflags & XFS_GQUOTA_ACCT)
               seq_puts(m, "," MNTOPT_GQUOTANOENF);

The problem is that XFS_OQUOTA_ENFD will be set in mp->m_qflags
if either group or project quotas are enforced, and as a result
both MNTOPT_PRJQUOTA and MNTOPT_GRPQUOTA will be shown as mount
options.

Good catch, Alex.

Signed-off-by: Alex Elder <aelder@xxxxxxx>

Reviewed-by: Felix Blyakher <felixb@xxxxxxx>

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