[PATCH v12 1/4] xfs: Refactor xfs_isilocked()

[Pavel Reichl <preichl@xxxxxxxxxx>]

Refactor xfs_isilocked() to use newly introduced __xfs_rwsem_islocked().
__xfs_rwsem_islocked() is a helper function which encapsulates checking
state of rw_semaphores hold by inode.

Signed-off-by: Pavel Reichl <preichl@xxxxxxxxxx>
Suggested-by: Dave Chinner <dchinner@xxxxxxxxxx>
Suggested-by: Eric Sandeen <sandeen@xxxxxxxxxx>
Suggested-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
---
 fs/xfs/xfs_inode.c | 39 +++++++++++++++++++++++++++++++--------
 fs/xfs/xfs_inode.h | 21 ++++++++++++++-------
 2 files changed, 45 insertions(+), 15 deletions(-)

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index c06129cffba9..1fdf8c7eb990 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -345,9 +345,34 @@ xfs_ilock_demote(
 }
 
 #if defined(DEBUG) || defined(XFS_WARN)
-int
+static inline bool
+__xfs_rwsem_islocked(
+	struct rw_semaphore	*rwsem,
+	int			lock_flags,
+	int			shift)
+{
+	lock_flags >>= shift;
+
+	if (!debug_locks)
+		return rwsem_is_locked(rwsem);
+	/*
+	 * If the shared flag is not set, pass 0 to explicitly check for
+	 * exclusive access to the lock. If the shared flag is set, we typically
+	 * want to make sure the lock is at least held in shared mode
+	 * (i.e., shared | excl) but we don't necessarily care that it might
+	 * actually be held exclusive. Therefore, pass -1 to check whether the
+	 * lock is held in any mode rather than one of the explicit shared mode
+	 * values (1 or 2)."
+	 */
+	if (lock_flags & (1 << XFS_SHARED_LOCK_SHIFT)) {
+		return lockdep_is_held_type(rwsem, -1);
+	}
+	return lockdep_is_held_type(rwsem, 0);
+}
+
+bool
 xfs_isilocked(
-	xfs_inode_t		*ip,
+	struct xfs_inode	*ip,
 	uint			lock_flags)
 {
 	if (lock_flags & (XFS_ILOCK_EXCL|XFS_ILOCK_SHARED)) {
@@ -362,15 +387,13 @@ xfs_isilocked(
 		return rwsem_is_locked(&ip->i_mmaplock.mr_lock);
 	}
 
-	if (lock_flags & (XFS_IOLOCK_EXCL|XFS_IOLOCK_SHARED)) {
-		if (!(lock_flags & XFS_IOLOCK_SHARED))
-			return !debug_locks ||
-				lockdep_is_held_type(&VFS_I(ip)->i_rwsem, 0);
-		return rwsem_is_locked(&VFS_I(ip)->i_rwsem);
+	if (lock_flags & (XFS_IOLOCK_EXCL | XFS_IOLOCK_SHARED)) {
+		return __xfs_rwsem_islocked(&VFS_I(ip)->i_rwsem, lock_flags,
+				XFS_IOLOCK_FLAG_SHIFT);
 	}
 
 	ASSERT(0);
-	return 0;
+	return false;
 }
 #endif
 
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index e9a8bb184d1f..9cecd6c9c90c 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -268,12 +268,19 @@ static inline void xfs_ifunlock(struct xfs_inode *ip)
  * Bit ranges:	1<<1  - 1<<16-1 -- iolock/ilock modes (bitfield)
  *		1<<16 - 1<<32-1 -- lockdep annotation (integers)
  */
-#define	XFS_IOLOCK_EXCL		(1<<0)
-#define	XFS_IOLOCK_SHARED	(1<<1)
-#define	XFS_ILOCK_EXCL		(1<<2)
-#define	XFS_ILOCK_SHARED	(1<<3)
-#define	XFS_MMAPLOCK_EXCL	(1<<4)
-#define	XFS_MMAPLOCK_SHARED	(1<<5)
+
+#define XFS_IOLOCK_FLAG_SHIFT	0
+#define XFS_ILOCK_FLAG_SHIFT	2
+#define XFS_MMAPLOCK_FLAG_SHIFT	4
+
+#define XFS_SHARED_LOCK_SHIFT	1
+
+#define XFS_IOLOCK_EXCL		(1 << XFS_IOLOCK_FLAG_SHIFT)
+#define XFS_IOLOCK_SHARED	(XFS_IOLOCK_EXCL << XFS_SHARED_LOCK_SHIFT)
+#define XFS_ILOCK_EXCL		(1 << XFS_ILOCK_FLAG_SHIFT)
+#define XFS_ILOCK_SHARED	(XFS_ILOCK_EXCL << XFS_SHARED_LOCK_SHIFT)
+#define XFS_MMAPLOCK_EXCL	(1 << XFS_MMAPLOCK_FLAG_SHIFT)
+#define XFS_MMAPLOCK_SHARED	(XFS_MMAPLOCK_EXCL << XFS_SHARED_LOCK_SHIFT)
 
 #define XFS_LOCK_MASK		(XFS_IOLOCK_EXCL | XFS_IOLOCK_SHARED \
 				| XFS_ILOCK_EXCL | XFS_ILOCK_SHARED \
@@ -412,7 +419,7 @@ void		xfs_ilock(xfs_inode_t *, uint);
 int		xfs_ilock_nowait(xfs_inode_t *, uint);
 void		xfs_iunlock(xfs_inode_t *, uint);
 void		xfs_ilock_demote(xfs_inode_t *, uint);
-int		xfs_isilocked(xfs_inode_t *, uint);
+bool		xfs_isilocked(struct xfs_inode *, uint);
 uint		xfs_ilock_data_map_shared(struct xfs_inode *);
 uint		xfs_ilock_attr_map_shared(struct xfs_inode *);
 
-- 
2.26.2