Btrfs: ctree: reduce args where only fs_info used

This patch is part of a larger project to cleanup btrfs's internal usage
of struct btrfs_root. Many functions take btrfs_root only to grab a
pointer to fs_info.

This causes programmers to ponder which root can be passed. Since only
the fs_info is read affected functions can accept any root, except this
is only obvious upon inspection.

This patch reduces the specificty of such functions to accept the
fs_info directly.

This patch does not address the two functions in ctree.c (insert_ptr,
and split_item) which only use root for BUG_ONs in ctree.c

This patch affects the following functions:
  1) fixup_low_keys
  2) btrfs_set_item_key_safe
Signed-off-by: Daniel Dressler <danieru.dressler@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.cz>

fs/btrfs/ctree.c

@@ -3126,7 +3126,8 @@ int btrfs_search_slot_for_read(struct btrfs_root *root,
  * higher levels
  *
  */
-static void fixup_low_keys(struct btrfs_root *root, struct btrfs_path *path,
+static void fixup_low_keys(struct btrfs_fs_info *fs_info,
+			   struct btrfs_path *path,
 			   struct btrfs_disk_key *key, int level)
 {
 	int i;
@@ -3137,7 +3138,7 @@ static void fixup_low_keys(struct btrfs_root *root, struct btrfs_path *path,
 		if (!path->nodes[i])
 			break;
 		t = path->nodes[i];
-		tree_mod_log_set_node_key(root->fs_info, t, tslot, 1);
+		tree_mod_log_set_node_key(fs_info, t, tslot, 1);
 		btrfs_set_node_key(t, key, tslot);
 		btrfs_mark_buffer_dirty(path->nodes[i]);
 		if (tslot != 0)
@@ -3151,7 +3152,8 @@ static void fixup_low_keys(struct btrfs_root *root, struct btrfs_path *path,
  * This function isn't completely safe. It's the caller's responsibility
  * that the new key won't break the order
  */
-void btrfs_set_item_key_safe(struct btrfs_root *root, struct btrfs_path *path,
+void btrfs_set_item_key_safe(struct btrfs_fs_info *fs_info,
+			     struct btrfs_path *path,
 			     struct btrfs_key *new_key)
 {
 	struct btrfs_disk_key disk_key;
@@ -3173,7 +3175,7 @@ void btrfs_set_item_key_safe(struct btrfs_root *root, struct btrfs_path *path,
 	btrfs_set_item_key(eb, &disk_key, slot);
 	btrfs_mark_buffer_dirty(eb);
 	if (slot == 0)
-		fixup_low_keys(root, path, &disk_key, 1);
+		fixup_low_keys(fs_info, path, &disk_key, 1);
 }
 
 /*
@@ -3931,7 +3933,7 @@ static noinline int __push_leaf_left(struct btrfs_trans_handle *trans,
 		clean_tree_block(trans, root, right);
 
 	btrfs_item_key(right, &disk_key, 0);
-	fixup_low_keys(root, path, &disk_key, 1);
+	fixup_low_keys(root->fs_info, path, &disk_key, 1);
 
 	/* then fixup the leaf pointer in the path */
 	if (path->slots[0] < push_items) {
@@ -4168,6 +4170,7 @@ static noinline int split_leaf(struct btrfs_trans_handle *trans,
 	int mid;
 	int slot;
 	struct extent_buffer *right;
+	struct btrfs_fs_info *fs_info = root->fs_info;
 	int ret = 0;
 	int wret;
 	int split;
@@ -4271,10 +4274,10 @@ static noinline int split_leaf(struct btrfs_trans_handle *trans,
 	btrfs_set_header_backref_rev(right, BTRFS_MIXED_BACKREF_REV);
 	btrfs_set_header_owner(right, root->root_key.objectid);
 	btrfs_set_header_level(right, 0);
-	write_extent_buffer(right, root->fs_info->fsid,
+	write_extent_buffer(right, fs_info->fsid,
 			    btrfs_header_fsid(), BTRFS_FSID_SIZE);
 
-	write_extent_buffer(right, root->fs_info->chunk_tree_uuid,
+	write_extent_buffer(right, fs_info->chunk_tree_uuid,
 			    btrfs_header_chunk_tree_uuid(right),
 			    BTRFS_UUID_SIZE);
 
@@ -4297,7 +4300,7 @@ static noinline int split_leaf(struct btrfs_trans_handle *trans,
 			path->nodes[0] = right;
 			path->slots[0] = 0;
 			if (path->slots[1] == 0)
-				fixup_low_keys(root, path, &disk_key, 1);
+				fixup_low_keys(fs_info, path, &disk_key, 1);
 		}
 		btrfs_mark_buffer_dirty(right);
 		return ret;
@@ -4615,7 +4618,7 @@ void btrfs_truncate_item(struct btrfs_root *root, struct btrfs_path *path,
 		btrfs_set_disk_key_offset(&disk_key, offset + size_diff);
 		btrfs_set_item_key(leaf, &disk_key, slot);
 		if (slot == 0)
-			fixup_low_keys(root, path, &disk_key, 1);
+			fixup_low_keys(root->fs_info, path, &disk_key, 1);
 	}
 
 	item = btrfs_item_nr(slot);
@@ -4716,7 +4719,7 @@ void setup_items_for_insert(struct btrfs_root *root, struct btrfs_path *path,
 
 	if (path->slots[0] == 0) {
 		btrfs_cpu_key_to_disk(&disk_key, cpu_key);
-		fixup_low_keys(root, path, &disk_key, 1);
+		fixup_low_keys(root->fs_info, path, &disk_key, 1);
 	}
 	btrfs_unlock_up_safe(path, 1);
 
@@ -4888,7 +4891,7 @@ static void del_ptr(struct btrfs_root *root, struct btrfs_path *path,
 		struct btrfs_disk_key disk_key;
 
 		btrfs_node_key(parent, &disk_key, 0);
-		fixup_low_keys(root, path, &disk_key, level + 1);
+		fixup_low_keys(root->fs_info, path, &disk_key, level + 1);
 	}
 	btrfs_mark_buffer_dirty(parent);
 }
@@ -4990,7 +4993,7 @@ int btrfs_del_items(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 			struct btrfs_disk_key disk_key;
 
 			btrfs_item_key(leaf, &disk_key, 0);
-			fixup_low_keys(root, path, &disk_key, 1);
+			fixup_low_keys(root->fs_info, path, &disk_key, 1);
 		}
 
 		/* delete the leaf if it is mostly empty */

fs/btrfs/ctree.h

@@ -3483,7 +3483,8 @@ int btrfs_previous_item(struct btrfs_root *root,
 			int type);
 int btrfs_previous_extent_item(struct btrfs_root *root,
 			struct btrfs_path *path, u64 min_objectid);
-void btrfs_set_item_key_safe(struct btrfs_root *root, struct btrfs_path *path,
+void btrfs_set_item_key_safe(struct btrfs_fs_info *fs_info,
+			     struct btrfs_path *path,
 			     struct btrfs_key *new_key);
 struct extent_buffer *btrfs_root_node(struct btrfs_root *root);
 struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root);

fs/btrfs/file-item.c

@@ -553,7 +553,7 @@ static noinline void truncate_one_csum(struct btrfs_root *root,
 		btrfs_truncate_item(root, path, new_size, 0);
 
 		key->offset = end_byte;
-		btrfs_set_item_key_safe(root, path, key);
+		btrfs_set_item_key_safe(root->fs_info, path, key);
 	} else {
 		BUG();
 	}

fs/btrfs/file.c

@@ -868,7 +868,7 @@ int __btrfs_drop_extents(struct btrfs_trans_handle *trans,
 
 			memcpy(&new_key, &key, sizeof(new_key));
 			new_key.offset = end;
-			btrfs_set_item_key_safe(root, path, &new_key);
+			btrfs_set_item_key_safe(root->fs_info, path, &new_key);
 
 			extent_offset += end - key.offset;
 			btrfs_set_file_extent_offset(leaf, fi, extent_offset);
@@ -1126,7 +1126,7 @@ int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,
 				     ino, bytenr, orig_offset,
 				     &other_start, &other_end)) {
 			new_key.offset = end;
-			btrfs_set_item_key_safe(root, path, &new_key);
+			btrfs_set_item_key_safe(root->fs_info, path, &new_key);
 			fi = btrfs_item_ptr(leaf, path->slots[0],
 					    struct btrfs_file_extent_item);
 			btrfs_set_file_extent_generation(leaf, fi,
@@ -1160,7 +1160,7 @@ int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,
 							 trans->transid);
 			path->slots[0]++;
 			new_key.offset = start;
-			btrfs_set_item_key_safe(root, path, &new_key);
+			btrfs_set_item_key_safe(root->fs_info, path, &new_key);
 
 			fi = btrfs_item_ptr(leaf, path->slots[0],
 					    struct btrfs_file_extent_item);
@@ -2169,7 +2169,7 @@ static int fill_holes(struct btrfs_trans_handle *trans, struct inode *inode,
 		u64 num_bytes;
 
 		key.offset = offset;
-		btrfs_set_item_key_safe(root, path, &key);
+		btrfs_set_item_key_safe(root->fs_info, path, &key);
 		fi = btrfs_item_ptr(leaf, path->slots[0],
 				    struct btrfs_file_extent_item);
 		num_bytes = btrfs_file_extent_num_bytes(leaf, fi) + end -