xfs: avoid taking the ilock unnessecarily in xfs_qm_dqattach

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>

1 files changed, 21 insertions, 5 deletions

diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
index 55c6afedc879..18ba438386ab 100644
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -483,6 +483,23 @@ done:
         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
@@ -500,11 +517,7 @@ 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));
@@ -575,6 +588,9 @@ 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);