btrfs: root->fs_info cleanup, add fs_info convenience variables

In routines where someptr->fs_info is referenced multiple times, we
introduce a convenience variable.  This makes the code considerably
more readable.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index 60e711a..f7f6cb7d 100644
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -132,6 +132,7 @@
 		      *root, struct btrfs_key *key, struct btrfs_root_item
 		      *item)
 {
+	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct btrfs_path *path;
 	struct extent_buffer *l;
 	int ret;
@@ -151,8 +152,7 @@
 
 	if (ret != 0) {
 		btrfs_print_leaf(root, path->nodes[0]);
-		btrfs_crit(root->fs_info,
-			   "unable to update root key %llu %u %llu",
+		btrfs_crit(fs_info, "unable to update root key %llu %u %llu",
 			   key->objectid, key->type, key->offset);
 		BUG_ON(1);
 	}
@@ -228,7 +228,7 @@
 	int ret;
 	bool can_recover = true;
 
-	if (tree_root->fs_info->sb->s_flags & MS_RDONLY)
+	if (fs_info->sb->s_flags & MS_RDONLY)
 		can_recover = false;
 
 	path = btrfs_alloc_path();
@@ -276,8 +276,7 @@
 		 * in turn reads and inserts fs roots while doing backref
 		 * walking.
 		 */
-		root = btrfs_lookup_fs_root(tree_root->fs_info,
-					    root_key.objectid);
+		root = btrfs_lookup_fs_root(fs_info, root_key.objectid);
 		if (root) {
 			WARN_ON(!test_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED,
 					  &root->state));
@@ -298,7 +297,7 @@
 			trans = btrfs_join_transaction(tree_root);
 			if (IS_ERR(trans)) {
 				err = PTR_ERR(trans);
-				btrfs_handle_fs_error(tree_root->fs_info, err,
+				btrfs_handle_fs_error(fs_info, err,
 					    "Failed to start trans to delete orphan item");
 				break;
 			}
@@ -306,7 +305,7 @@
 						    root_key.objectid);
 			btrfs_end_transaction(trans, tree_root);
 			if (err) {
-				btrfs_handle_fs_error(tree_root->fs_info, err,
+				btrfs_handle_fs_error(fs_info, err,
 					    "Failed to delete root orphan item");
 				break;
 			}
@@ -321,7 +320,7 @@
 
 		set_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state);
 
-		err = btrfs_insert_fs_root(root->fs_info, root);
+		err = btrfs_insert_fs_root(fs_info, root);
 		if (err) {
 			BUG_ON(err == -EEXIST);
 			btrfs_free_fs_root(root);