xfs: remove b_last_holder & associated macros

The old lock tracking infrastructure in xfs using the b_last_holder
field seems to only be useful if you can get into the system with a
debugger; it seems that the existing tracepoints would be the way to
go these days, and this old infrastructure can be removed.

Signed-off-by: Eric Sandeen <[e-mail]>
Reviewed-by: Darrick J. Wong <[e-mail]>
Signed-off-by: Darrick J. Wong <[e-mail]>

fs/xfs/xfs.h

···
 
 #ifdef CONFIG_XFS_DEBUG
 #define DEBUG 1
-#define XFS_BUF_LOCK_TRACKING 1
 #endif
 
 #ifdef CONFIG_XFS_ASSERT_FATAL

fs/xfs/xfs_buf.c

···
 
 static kmem_zone_t *xfs_buf_zone;
 
-#ifdef XFS_BUF_LOCK_TRACKING
-# define XB_SET_OWNER(bp)	((bp)->b_last_holder = current->pid)
-# define XB_CLEAR_OWNER(bp)	((bp)->b_last_holder = -1)
-# define XB_GET_OWNER(bp)	((bp)->b_last_holder)
-#else
-# define XB_SET_OWNER(bp)	do { } while (0)
-# define XB_CLEAR_OWNER(bp)	do { } while (0)
-# define XB_GET_OWNER(bp)	do { } while (0)
-#endif
-
 #define xb_to_gfp(flags) \
 	((((flags) & XBF_READ_AHEAD) ? __GFP_NORETRY : GFP_NOFS) | __GFP_NOWARN)
 
···
 	INIT_LIST_HEAD(&bp->b_li_list);
 	sema_init(&bp->b_sema, 0); /* held, no waiters */
 	spin_lock_init(&bp->b_lock);
-	XB_SET_OWNER(bp);
 	bp->b_target = target;
 	bp->b_flags = flags;
 
···
 	int			locked;
 
 	locked = down_trylock(&bp->b_sema) == 0;
-	if (locked) {
-		XB_SET_OWNER(bp);
+	if (locked)
 		trace_xfs_buf_trylock(bp, _RET_IP_);
-	} else {
+	else
 		trace_xfs_buf_trylock_fail(bp, _RET_IP_);
-	}
 	return locked;
 }
 
···
 	if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
 		xfs_log_force(bp->b_target->bt_mount, 0);
 	down(&bp->b_sema);
-	XB_SET_OWNER(bp);
 
 	trace_xfs_buf_lock_done(bp, _RET_IP_);
 }
···
 {
 	ASSERT(xfs_buf_islocked(bp));
 
-	XB_CLEAR_OWNER(bp);
 	up(&bp->b_sema);
-
 	trace_xfs_buf_unlock(bp, _RET_IP_);
 }
 

fs/xfs/xfs_buf.h

···
 	int			b_last_error;
 
 	const struct xfs_buf_ops	*b_ops;
-
-#ifdef XFS_BUF_LOCK_TRACKING
-	int			b_last_holder;
-#endif
 } xfs_buf_t;
 
 /* Finding and Reading Buffers */