btrfs: remove BTRFS_LEAF_DATA_OFFSET

This is simply the same thing as btrfs_item_nr_offset(leaf, 0), so
remove this helper and replace it's usage with the above statement.

Signed-off-by: Josef Bacik <[e-mail]>
Signed-off-by: David Sterba <[e-mail]>

fs/btrfs/accessors.h

···
 	unsigned long offset;
 };
 
-#define BTRFS_LEAF_DATA_OFFSET		offsetof(struct btrfs_leaf, items)
-
 void btrfs_init_map_token(struct btrfs_map_token *token, struct extent_buffer *eb);
 
 /*
···
 
 /* Cast into the data area of the leaf. */
 #define btrfs_item_ptr(leaf, slot, type)				\
-	((type *)(BTRFS_LEAF_DATA_OFFSET + btrfs_item_offset(leaf, slot)))
+	((type *)(btrfs_item_nr_offset(leaf, 0) + btrfs_item_offset(leaf, slot)))
 
 #define btrfs_item_ptr_offset(leaf, slot)				\
-	((unsigned long)(BTRFS_LEAF_DATA_OFFSET + btrfs_item_offset(leaf, slot)))
+	((unsigned long)(btrfs_item_nr_offset(leaf, 0) + btrfs_item_offset(leaf, slot)))
 
 #endif

fs/btrfs/ctree.c

···
 				     unsigned long src_offset,
 				     unsigned long len)
 {
-	memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET + dst_offset,
-			      BTRFS_LEAF_DATA_OFFSET + src_offset, len);
+	memmove_extent_buffer(leaf, btrfs_item_nr_offset(leaf, 0) + dst_offset,
+			      btrfs_item_nr_offset(leaf, 0) + src_offset, len);
 }
 
 /*
···
 				  unsigned long dst_offset,
 				  unsigned long src_offset, unsigned long len)
 {
-	copy_extent_buffer(dst, src, BTRFS_LEAF_DATA_OFFSET + dst_offset,
-			   BTRFS_LEAF_DATA_OFFSET + src_offset, len);
+	copy_extent_buffer(dst, src, btrfs_item_nr_offset(dst, 0) + dst_offset,
+			   btrfs_item_nr_offset(src, 0) + src_offset, len);
 }
 
 /*

fs/btrfs/extent_io.c

···
 		 * header 0 1 2 .. N ... data_N .. data_2 data_1 data_0
 		 */
 		start = btrfs_item_nr_offset(eb, nritems);
-		end = BTRFS_LEAF_DATA_OFFSET;
+		end = btrfs_item_nr_offset(eb, 0);
 		if (nritems == 0)
 			end += BTRFS_LEAF_DATA_SIZE(eb->fs_info);
 		else