[PATCH 01/34] xfs: provide a inode iolock lockdep class

Dave Chinner
2010-12-21T07:28:01Z

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@redhat.com>
---
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().