From f2cbab2c844e57725a6807ef7123da0f1ac4838f Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Mon, 19 Jan 2009 02:03:19 +0100
Subject: [PATCH] --- yaml --- r: 129935 b: refs/heads/master c:
 4f2d4ac6e5eb7d72e8df7f3fbf67a78dab8b91cf h: refs/heads/master i:   129933:
 74ad21a20e7d387840a6bcfc000c2982f027ac65   129931:
 118b2fc5aaf75fda6d4364c3683cc8d973f313a9   129927:
 706f236348f2ab72c1a5f26b6dab4e17b2596ead   129919:
 5f575e7c7d7c2e2da0c2eb93c4d3240f9c38f5f8 v: v3

---
 [refs]                         |  2 +-
 trunk/fs/xfs/quota/xfs_dquot.c | 24 ++++++++++++++----------
 trunk/fs/xfs/quota/xfs_dquot.h | 10 ++++++++++
 3 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/[refs] b/[refs]
index 35a551821a2e..a6ba13344626 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 080dda7f5e8e8df95bcd17a5345c276e365a2054
+refs/heads/master: 4f2d4ac6e5eb7d72e8df7f3fbf67a78dab8b91cf
diff --git a/trunk/fs/xfs/quota/xfs_dquot.c b/trunk/fs/xfs/quota/xfs_dquot.c
index 591ca6602bfb..36d1bb6140d1 100644
--- a/trunk/fs/xfs/quota/xfs_dquot.c
+++ b/trunk/fs/xfs/quota/xfs_dquot.c
@@ -1383,6 +1383,12 @@ xfs_dqunlock_nonotify(
 	mutex_unlock(&(dqp->q_qlock));
 }
 
+/*
+ * Lock two xfs_dquot structures.
+ *
+ * To avoid deadlocks we always lock the quota structure with
+ * the lowerd id first.
+ */
 void
 xfs_dqlock2(
 	xfs_dquot_t	*d1,
@@ -1392,18 +1398,16 @@ xfs_dqlock2(
 		ASSERT(d1 != d2);
 		if (be32_to_cpu(d1->q_core.d_id) >
 		    be32_to_cpu(d2->q_core.d_id)) {
-			xfs_dqlock(d2);
-			xfs_dqlock(d1);
+			mutex_lock(&d2->q_qlock);
+			mutex_lock_nested(&d1->q_qlock, XFS_QLOCK_NESTED);
 		} else {
-			xfs_dqlock(d1);
-			xfs_dqlock(d2);
-		}
-	} else {
-		if (d1) {
-			xfs_dqlock(d1);
-		} else if (d2) {
-			xfs_dqlock(d2);
+			mutex_lock(&d1->q_qlock);
+			mutex_lock_nested(&d2->q_qlock, XFS_QLOCK_NESTED);
 		}
+	} else if (d1) {
+		mutex_lock(&d1->q_qlock);
+	} else if (d2) {
+		mutex_lock(&d2->q_qlock);
 	}
 }
 
diff --git a/trunk/fs/xfs/quota/xfs_dquot.h b/trunk/fs/xfs/quota/xfs_dquot.h
index 7e455337e2ba..d443e93b4331 100644
--- a/trunk/fs/xfs/quota/xfs_dquot.h
+++ b/trunk/fs/xfs/quota/xfs_dquot.h
@@ -97,6 +97,16 @@ typedef struct xfs_dquot {
 #define dq_hashlist	q_lists.dqm_hashlist
 #define dq_flags	q_lists.dqm_flags
 
+/*
+ * Lock hierachy for q_qlock:
+ *	XFS_QLOCK_NORMAL is the implicit default,
+ * 	XFS_QLOCK_NESTED is the dquot with the higher id in xfs_dqlock2
+ */
+enum {
+	XFS_QLOCK_NORMAL = 0,
+	XFS_QLOCK_NESTED,
+};
+
 #define XFS_DQHOLD(dqp)		((dqp)->q_nrefs++)
 
 #ifdef DEBUG