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[PATCH] xfs: provide a inode iolock lockdep class

To: xfs@xxxxxxxxxxx
Subject: [PATCH] xfs: provide a inode iolock lockdep class
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Mon, 13 Dec 2010 12:07:11 +1100
From: Dave Chinner <dchinner@xxxxxxxxxx>

The XFS iolock needs to be re-initialised to a new lock class before
it enters reclaim to prevent lockdep false positives. Unfortunately,
this is not sufficient protection as inodes in the XFS_IRECLAIMABLE
state can be recycled and not re-initialised before being reused.

We need to re-initialise the lock state when transfering out of
XFS_IRECLAIMABLE state to XFS_INEW, but we need to keep the same
class as if the inode was just allocated. Hence we need a specific
lockdep class variable for the iolock so that both initialisations
use the same class.

While there, add a specific class for inodes in the reclaim state so
that it is easy to tell from lockdep reports what state the inode
was in that generated the report.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
 fs/xfs/linux-2.6/xfs_super.c |    2 ++
 fs/xfs/xfs_iget.c            |   19 +++++++++++++++++++
 fs/xfs/xfs_inode.h           |    2 ++
 3 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index 064f964..c45b323 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -1118,6 +1118,8 @@ xfs_fs_evict_inode(
         */
        ASSERT(!rwsem_is_locked(&ip->i_iolock.mr_lock));
        mrlock_init(&ip->i_iolock, MRLOCK_BARRIER, "xfsio", ip->i_ino);
+       lockdep_set_class_and_name(&ip->i_iolock.mr_lock,
+                       &xfs_iolock_reclaimable, "xfs_iolock_reclaimable");
 
        xfs_inactive(ip);
 }
diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c
index 0cdd269..cdb1c25 100644
--- a/fs/xfs/xfs_iget.c
+++ b/fs/xfs/xfs_iget.c
@@ -43,6 +43,17 @@
 
 
 /*
+ * Define xfs inode iolock lockdep classes. We need to ensure that all active
+ * inodes are considered the same for lockdep purposes, including inodes that
+ * are recycled through the XFS_IRECLAIMABLE state. This is the the only way to
+ * guarantee the locks are considered the same when there are multiple lock
+ * initialisation siteѕ. Also, define a reclaimable inode class so it is
+ * obvious in lockdep reports which class the report is against.
+ */
+static struct lock_class_key xfs_iolock_active;
+struct lock_class_key xfs_iolock_reclaimable;
+
+/*
  * Allocate and initialise an xfs_inode.
  */
 STATIC struct xfs_inode *
@@ -71,6 +82,8 @@ xfs_inode_alloc(
        ASSERT(completion_done(&ip->i_flush));
 
        mrlock_init(&ip->i_iolock, MRLOCK_BARRIER, "xfsio", ip->i_ino);
+       lockdep_set_class_and_name(&ip->i_iolock.mr_lock,
+                       &xfs_iolock_active, "xfs_iolock_active");
 
        /* initialise the xfs inode */
        ip->i_ino = ino;
@@ -218,6 +231,12 @@ xfs_iget_cache_hit(
                ip->i_flags |= XFS_INEW;
                __xfs_inode_clear_reclaim_tag(mp, pag, ip);
                inode->i_state = I_NEW;
+
+               ASSERT(!rwsem_is_locked(&ip->i_iolock.mr_lock));
+               mrlock_init(&ip->i_iolock, MRLOCK_BARRIER, "xfsio", ip->i_ino);
+               lockdep_set_class_and_name(&ip->i_iolock.mr_lock,
+                               &xfs_iolock_active, "xfs_iolock_active");
+
                spin_unlock(&ip->i_flags_lock);
                write_unlock(&pag->pag_ici_lock);
        } else {
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index fb2ca2e..1c6514d 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -438,6 +438,8 @@ static inline void xfs_ifunlock(xfs_inode_t *ip)
 #define XFS_IOLOCK_DEP(flags)  (((flags) & XFS_IOLOCK_DEP_MASK) >> 
XFS_IOLOCK_SHIFT)
 #define XFS_ILOCK_DEP(flags)   (((flags) & XFS_ILOCK_DEP_MASK) >> 
XFS_ILOCK_SHIFT)
 
+extern struct lock_class_key xfs_iolock_reclaimable;
+
 /*
  * Flags for xfs_itruncate_start().
  */
-- 
1.7.2.3

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