xfs: use separate lock classes for realtime metadata inode ILOCKs

Realtime metadata files are not quite regular files because userspace
can't access the realtime bitmap directly, and because we take the ILOCK
of the rt bitmap file while holding the ILOCK of a realtime file.  The
double nature of inodes confuses lockdep, so up until now we've created
lockdep subclasses to help lockdep keep things straight.

We've gotten away with using lockdep subclasses because there's only two
rt metadata files, but with the coming addition of realtime rmap and
refcounting, we'd need two more subclasses, which is a lot of class bits
to burn on a side feature.

Therefore, switch to manually setting the lockdep class of the rt
metadata ILOCKs.  In the next patch we'll remove the rt-related ILOCK
subclasses.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>

1 files changed, 34 insertions, 2 deletions

diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
index 11c42ebfa0a5..674ca3dab72e 100644
--- a/fs/xfs/xfs_rtalloc.c
+++ b/fs/xfs/xfs_rtalloc.c
@@ -27,6 +27,16 @@
 #include "xfs_rtbitmap.h"
 
 /*
+ * Realtime metadata files are not quite regular files because userspace can't
+ * access the realtime bitmap directly, and because we take the ILOCK of the rt
+ * bitmap file while holding the ILOCK of a regular realtime file.  This double
+ * locking confuses lockdep, so create different lockdep classes here to help
+ * it keep things straight.
+ */
+static struct lock_class_key xfs_rbmip_key;
+static struct lock_class_key xfs_rsumip_key;
+
+/*
  * Read and return the summary information for a given extent size,
  * bitmap block combination.
  * Keeps track of a current summary block, so we don't keep reading
@@ -1342,6 +1352,28 @@ xfs_rtalloc_reinit_frextents(
 	return 0;
 }
 
+static inline int
+__xfs_rt_iget(
+	struct xfs_mount	*mp,
+	xfs_ino_t		ino,
+	struct lock_class_key	*lockdep_key,
+	const char		*lockdep_key_name,
+	struct xfs_inode	**ipp)
+{
+	int			error;
+
+	error = xfs_imeta_iget(mp, ino, XFS_DIR3_FT_REG_FILE, ipp);
+	if (error)
+		return error;
+
+	lockdep_set_class_and_name(&(*ipp)->i_lock.mr_lock, lockdep_key,
+			lockdep_key_name);
+	return 0;
+}
+
+#define xfs_rt_iget(mp, ino, lockdep_key, ipp) \
+	__xfs_rt_iget((mp), (ino), (lockdep_key), #lockdep_key, (ipp))
+
 /*
  * Read in the bmbt of an rt metadata inode so that we never have to load them
  * at runtime.  This enables the use of shared ILOCKs for rtbitmap scans.  Use
@@ -1389,7 +1421,7 @@ xfs_rtmount_inodes(
 	xfs_sb_t	*sbp;
 
 	sbp = &mp->m_sb;
-	error = xfs_imeta_iget(mp, mp->m_sb.sb_rbmino, XFS_DIR3_FT_REG_FILE,
+	error = xfs_rt_iget(mp, mp->m_sb.sb_rbmino, &xfs_rbmip_key,
 			&mp->m_rbmip);
 	if (xfs_metadata_is_sick(error))
 		xfs_rt_mark_sick(mp, XFS_SICK_RT_BITMAP);
@@ -1401,7 +1433,7 @@ xfs_rtmount_inodes(
 	if (error)
 		goto out_rele_bitmap;
 
-	error = xfs_imeta_iget(mp, mp->m_sb.sb_rsumino, XFS_DIR3_FT_REG_FILE,
+	error = xfs_rt_iget(mp, mp->m_sb.sb_rsumino, &xfs_rsumip_key,
 			&mp->m_rsumip);
 	if (xfs_metadata_is_sick(error))
 		xfs_rt_mark_sick(mp, XFS_SICK_RT_SUMMARY);