[PATCH 068/102] xfs: avoid taking the ilock unnessecarily in xfs_qm_dqattach

Dave Chinner
2012-08-23T05:04:19Z

From: Christoph Hellwig <hch@infradead.org>

Upstream commit: b4d05e3019692fc5a8c573fbce60de2d48c5b7a1

Check if we actually need to attach a dquot before taking the ilock in
xfs_qm_dqattach. This avoid superflous lock roundtrips for the common cases
of quota support compiled in but not activated on a filesystem and an
inode that already has the dquots attached.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
---
fs/xfs/quota/xfs_qm.c | 26 +++++++++++++++++++++-----
1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/quota/xfs_qm.c b/fs/xfs/quota/xfs_qm.c
index eacf7e0..fd8ddac 100644
--- a/fs/xfs/quota/xfs_qm.c
+++ b/fs/xfs/quota/xfs_qm.c
@@ -777,6 +777,23 @@ xfs_qm_dqattach_grouphint(
xfs_dqunlock(udq);
}

+static bool
+xfs_qm_need_dqattach(
+ struct xfs_inode *ip)
+{
+ struct xfs_mount *mp = ip->i_mount;
+
+ if (!XFS_IS_QUOTA_RUNNING(mp))
+ return false;
+ if (!XFS_IS_QUOTA_ON(mp))
+ return false;
+ if (!XFS_NOT_DQATTACHED(mp, ip))
+ return false;
+ if (ip->i_ino == mp->m_sb.sb_uquotino ||
+ ip->i_ino == mp->m_sb.sb_gquotino)
+ return false;
+ return true;
+}

/*
* Given a locked inode, attach dquot(s) to it, taking U/G/P-QUOTAON
@@ -794,11 +811,7 @@ xfs_qm_dqattach_locked(
uint nquotas = 0;
int error = 0;

- if (!XFS_IS_QUOTA_RUNNING(mp) ||
- !XFS_IS_QUOTA_ON(mp) ||
- !XFS_NOT_DQATTACHED(mp, ip) ||
- ip->i_ino == mp->m_sb.sb_uquotino ||
- ip->i_ino == mp->m_sb.sb_gquotino)
+ if (!xfs_qm_need_dqattach(ip))
return 0;

ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
@@ -873,6 +886,9 @@ xfs_qm_dqattach(
{
int error;

+ if (!xfs_qm_need_dqattach(ip))
+ return 0;
+
xfs_ilock(ip, XFS_ILOCK_EXCL);
error = xfs_qm_dqattach_locked(ip, flags);
xfs_iunlock(ip, XFS_ILOCK_EXCL);