xfs: xfs_showargs() reports group *and* project quotas enabled

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: a67d7c5f



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.

Signed-off-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>