[PATCH 4/7] xfs: lockdep annotations for xfs_dqlock2

Christoph Hellwig
2009-01-09T22:13:31Z

[-- Attachment #1: xfs-fix-xfs_dqlock2-lockdep-warning --]
[-- Type: text/plain, Size: 1824 bytes --]

xfs_dqlock2 locks two xfs_dquots, which is fine as it always locks the
dquot with the lower id first. Use mutex_lock_nested to tell lockdep
about this fact.

Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: xfs/fs/xfs/quota/xfs_dquot.c
===================================================================
--- xfs.orig/fs/xfs/quota/xfs_dquot.c 2008-12-29 11:28:54.459613573 +0100
+++ xfs/fs/xfs/quota/xfs_dquot.c 2008-12-29 11:29:31.037738842 +0100
@@ -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,
@@ -1393,10 +1399,10 @@ xfs_dqlock2(
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_nested(&d1->q_qlock, XFS_QLOCK_2ND);
} else {
xfs_dqlock(d1);
- xfs_dqlock(d2);
+ mutex_lock_nested(&d2->q_qlock, XFS_QLOCK_2ND);
}
} else {
if (d1) {
Index: xfs/fs/xfs/quota/xfs_dquot.h
===================================================================
--- xfs.orig/fs/xfs/quota/xfs_dquot.h 2008-12-27 17:55:09.920686659 +0100
+++ xfs/fs/xfs/quota/xfs_dquot.h 2008-12-29 11:29:31.043768451 +0100
@@ -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_DOUBLE is the dquot with the higher id in xfs_dqlock2
+ */
+enum {
+ XFS_QLOCK_NORMAL = 0,
+ XFS_QLOCK_2ND,
+};
+
#define XFS_DQHOLD(dqp) ((dqp)->q_nrefs++)

#ifdef DEBUG