btrfs: introduce BTRFS_MAX_ITEM_SIZE

We use BTRFS_LEAF_DATA_SIZE - sizeof(struct btrfs_item) in
several places.  This introduces a BTRFS_MAX_ITEM_SIZE macro to do the
same.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -150,13 +150,13 @@ struct btrfs_header {
 				     sizeof(struct btrfs_key_ptr))
 #define __BTRFS_LEAF_DATA_SIZE(bs) ((bs) - sizeof(struct btrfs_header))
 #define BTRFS_LEAF_DATA_SIZE(r) (__BTRFS_LEAF_DATA_SIZE(r->nodesize))
+#define BTRFS_MAX_ITEM_SIZE(r) \
+	(BTRFS_LEAF_DATA_SIZE(r) - sizeof(struct btrfs_item))
 #define BTRFS_FILE_EXTENT_INLINE_DATA_START		\
 		(offsetof(struct btrfs_file_extent_item, disk_bytenr))
-#define BTRFS_MAX_INLINE_DATA_SIZE(r) (BTRFS_LEAF_DATA_SIZE(r) - \
-					sizeof(struct btrfs_item) - \
+#define BTRFS_MAX_INLINE_DATA_SIZE(r) (BTRFS_MAX_ITEM_SIZE(r) - \
 					BTRFS_FILE_EXTENT_INLINE_DATA_START)
-#define BTRFS_MAX_XATTR_SIZE(r)	(BTRFS_LEAF_DATA_SIZE(r) - \
-				 sizeof(struct btrfs_item) -\
+#define BTRFS_MAX_XATTR_SIZE(r)	(BTRFS_MAX_ITEM_SIZE(r) - \
 				 sizeof(struct btrfs_dir_item))
 
 

fs/btrfs/extent-tree.c

@@ -2779,7 +2779,7 @@ u64 btrfs_csum_bytes_to_leaves(struct btrfs_root *root, u64 csum_bytes)
 	u64 num_csums_per_leaf;
 	u64 num_csums;
 
-	csum_size = BTRFS_LEAF_DATA_SIZE(root) - sizeof(struct btrfs_item);
+	csum_size = BTRFS_MAX_ITEM_SIZE(root);
 	num_csums_per_leaf = div64_u64(csum_size,
 			(u64)btrfs_super_csum_size(root->fs_info->super_copy));
 	num_csums = div64_u64(csum_bytes, root->sectorsize);

fs/btrfs/file-item.c

@@ -27,9 +27,8 @@
 #include "print-tree.h"
 #include "compression.h"
 
-#define __MAX_CSUM_ITEMS(r, size) ((unsigned long)(((BTRFS_LEAF_DATA_SIZE(r) - \
-				   sizeof(struct btrfs_item) * 2) / \
-				  size) - 1))
+#define __MAX_CSUM_ITEMS(r, size) \
+	((unsigned long)(((BTRFS_MAX_ITEM_SIZE(r) * 2) / size) - 1))
 
 #define MAX_CSUM_ITEMS(r, size) (min_t(u32, __MAX_CSUM_ITEMS(r, size), \
 				       PAGE_SIZE))

fs/btrfs/volumes.c

@@ -4573,8 +4573,7 @@ static void check_raid56_incompat_flag(struct btrfs_fs_info *info, u64 type)
 	btrfs_set_fs_incompat(info, RAID56);
 }
 
-#define BTRFS_MAX_DEVS(r) ((BTRFS_LEAF_DATA_SIZE(r)		\
-			- sizeof(struct btrfs_item)		\
+#define BTRFS_MAX_DEVS(r) ((BTRFS_MAX_ITEM_SIZE(r)		\
 			- sizeof(struct btrfs_chunk))		\
 			/ sizeof(struct btrfs_stripe) + 1)