xfs: simplify xfs_qm_dqattach_grouphint

No need to play games with the qlock now that the freelist lock nests inside
it.  Also clean up various outdated comments.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

1 files changed, 16 insertions, 48 deletions

diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
index 22360bb26af9..3c553454443c 100644
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -650,11 +650,7 @@ xfs_qm_dqattach_one(
 
 /*
  * Given a udquot and gdquot, attach a ptr to the group dquot in the
- * udquot as a hint for future lookups. The idea sounds simple, but the
- * execution isn't, because the udquot might have a group dquot attached
- * already and getting rid of that gets us into lock ordering constraints.
- * The process is complicated more by the fact that the dquots may or may not
- * be locked on entry.
+ * udquot as a hint for future lookups.
  */
 STATIC void
 xfs_qm_dqattach_grouphint(
@@ -665,45 +661,21 @@ xfs_qm_dqattach_grouphint(
 
         xfs_dqlock(udq);
 
-        if ((tmp = udq->q_gdquot)) {
-                if (tmp == gdq) {
-                        xfs_dqunlock(udq);
-                        return;
-                }
+        tmp = udq->q_gdquot;
+        if (tmp) {
+                if (tmp == gdq)
+                        goto done;
 
                 udq->q_gdquot = NULL;
-                /*
-                 * We can't keep any dqlocks when calling dqrele,
-                 * because the freelist lock comes before dqlocks.
-                 */
-                xfs_dqunlock(udq);
-                /*
-                 * we took a hard reference once upon a time in dqget,
-                 * so give it back when the udquot no longer points at it
-                 * dqput() does the unlocking of the dquot.
-                 */
                 xfs_qm_dqrele(tmp);
-
-                xfs_dqlock(udq);
-                xfs_dqlock(gdq);
-
-        } else {
-                ASSERT(XFS_DQ_IS_LOCKED(udq));
-                xfs_dqlock(gdq);
-        }
-
-        ASSERT(XFS_DQ_IS_LOCKED(udq));
-        ASSERT(XFS_DQ_IS_LOCKED(gdq));
-        /*
-         * Somebody could have attached a gdquot here,
-         * when we dropped the uqlock. If so, just do nothing.
-         */
-        if (udq->q_gdquot == NULL) {
-                XFS_DQHOLD(gdq);
-                udq->q_gdquot = gdq;
         }
 
+        xfs_dqlock(gdq);
+        XFS_DQHOLD(gdq);
         xfs_dqunlock(gdq);
+
+        udq->q_gdquot = gdq;
+done:
         xfs_dqunlock(udq);
 }
 
@@ -770,17 +742,13 @@ xfs_qm_dqattach_locked(
                 ASSERT(ip->i_gdquot);
 
                 /*
-                 * We may or may not have the i_udquot locked at this point,
-                 * but this check is OK since we don't depend on the i_gdquot to
-                 * be accurate 100% all the time. It is just a hint, and this
-                 * will succeed in general.
-                 */
-                if (ip->i_udquot->q_gdquot == ip->i_gdquot)
-                        goto done;
-                /*
-                 * Attach i_gdquot to the gdquot hint inside the i_udquot.
+                 * We do not have i_udquot locked at this point, but this check
+                 * is OK since we don't depend on the i_gdquot to be accurate
+                 * 100% all the time. It is just a hint, and this will
+                 * succeed in general.
                  */
-                xfs_qm_dqattach_grouphint(ip->i_udquot, ip->i_gdquot);
+                if (ip->i_udquot->q_gdquot != ip->i_gdquot)
+                        xfs_qm_dqattach_grouphint(ip->i_udquot, ip->i_gdquot);
         }
 
  done: