btrfs: call functions that overwrite their root parameter with fs_info

There are 11 functions that accept a root parameter and immediately
overwrite it.  We can pass those an fs_info pointer instead.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 5e74178..41c1145 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -590,8 +590,9 @@
  * range of bytes.
  */
 int btrfs_del_csums(struct btrfs_trans_handle *trans,
-		    struct btrfs_root *root, u64 bytenr, u64 len)
+		    struct btrfs_fs_info *fs_info, u64 bytenr, u64 len)
 {
+	struct btrfs_root *root = fs_info->csum_root;
 	struct btrfs_path *path;
 	struct btrfs_key key;
 	u64 end_byte = bytenr + len;
@@ -601,8 +602,6 @@
 	u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 	int blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 
-	root = root->fs_info->csum_root;
-
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;