btrfs-progs: introduce btrfs_make_subvolume()

There are two different subvolume/data reloc tree creation routines:

- create_subvol() from convert/main.c
  * calls btrfs_copy_root() to create an empty root
    This is not safe, as it relies on the source root to be empty.
  * calls btrfs_read_fs_root() to add it to the cache and trace it
    properly
  * calls btrfs_make_root_dir() to initialize the empty new root

- create_data_reloc_tree() from mkfs/main.c
  * calls btrfs_create_tree() to create an empty root
  * Manually add the root to fs_root cache
    This is only safe for data reloc tree as it's never updated
    inside btrfs-progs.
    But not safe for other subvolume trees.
  * manually setup the root dir

Both have their good and bad aspects, so here we introduce a new helper,
btrfs_make_subvolume():

- Calls btrfs_create_tree() to create an empty root
- Calls btrfs_read_fs_root() to setup the cache and tracking properly
- Calls btrfs_make_root_dir() to initialize the root dir
- Calls btrfs_update_root() to reflect the rootdir change

So this new helper can replace both create_subvol() and
create_data_reloc_tree().

Signed-off-by: Qu Wenruo <wqu@suse.com>

Makefile

@@ -221,6 +221,7 @@ objects = \
 	common/device-utils.o	\
 	common/extent-cache.o	\
 	common/extent-tree-utils.o	\
+	common/root-tree-utils.o	\
 	common/filesystem-utils.o	\
 	common/format-output.o	\
 	common/fsfeatures.o	\

check/main.c

@@ -59,6 +59,7 @@
 #include "common/open-utils.h"
 #include "common/string-utils.h"
 #include "common/clear-cache.h"
+#include "common/root-tree-utils.h"
 #include "cmds/commands.h"
 #include "mkfs/common.h"
 #include "check/common.h"

common/root-tree-utils.c

@@ -0,0 +1,107 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include <time.h>
+#include "common/root-tree-utils.h"
+#include "common/messages.h"
+#include "kernel-shared/disk-io.h"
+
+int btrfs_make_root_dir(struct btrfs_trans_handle *trans,
+			struct btrfs_root *root, u64 objectid)
+{
+	int ret;
+	struct btrfs_inode_item inode_item;
+	time_t now = time(NULL);
+
+	memset(&inode_item, 0, sizeof(inode_item));
+	btrfs_set_stack_inode_generation(&inode_item, trans->transid);
+	btrfs_set_stack_inode_size(&inode_item, 0);
+	btrfs_set_stack_inode_nlink(&inode_item, 1);
+	btrfs_set_stack_inode_nbytes(&inode_item, root->fs_info->nodesize);
+	btrfs_set_stack_inode_mode(&inode_item, S_IFDIR | 0755);
+	btrfs_set_stack_timespec_sec(&inode_item.atime, now);
+	btrfs_set_stack_timespec_nsec(&inode_item.atime, 0);
+	btrfs_set_stack_timespec_sec(&inode_item.ctime, now);
+	btrfs_set_stack_timespec_nsec(&inode_item.ctime, 0);
+	btrfs_set_stack_timespec_sec(&inode_item.mtime, now);
+	btrfs_set_stack_timespec_nsec(&inode_item.mtime, 0);
+	btrfs_set_stack_timespec_sec(&inode_item.otime, now);
+	btrfs_set_stack_timespec_nsec(&inode_item.otime, 0);
+
+	if (root->fs_info->tree_root == root)
+		btrfs_set_super_root_dir(root->fs_info->super_copy, objectid);
+
+	ret = btrfs_insert_inode(trans, root, objectid, &inode_item);
+	if (ret)
+		goto error;
+
+	ret = btrfs_insert_inode_ref(trans, root, "..", 2, objectid, objectid, 0);
+	if (ret)
+		goto error;
+
+	btrfs_set_root_dirid(&root->root_item, objectid);
+	ret = 0;
+error:
+	return ret;
+}
+
+/*
+ * Create a subvolume and initialize its content with the top inode.
+ *
+ * The created tree root would have its root_ref as 1.
+ * Thus for subvolumes caller needs to properly add ROOT_BACKREF items.
+ */
+int btrfs_make_subvolume(struct btrfs_trans_handle *trans, u64 objectid)
+{
+	struct btrfs_fs_info *fs_info = trans->fs_info;
+	struct btrfs_root *root;
+	struct btrfs_key key = {
+		.objectid = objectid,
+		.type = BTRFS_ROOT_ITEM_KEY,
+	};
+	int ret;
+
+	/* FSTREE is different and can not be created by this function. */
+	UASSERT(objectid != BTRFS_FS_TREE_OBJECTID);
+	UASSERT(is_fstree(objectid) || objectid == BTRFS_DATA_RELOC_TREE_OBJECTID);
+
+	root = btrfs_create_tree(trans, &key);
+	if (IS_ERR(root)) {
+		ret = PTR_ERR(root);
+		goto error;
+	}
+	/*
+	 * Free it for now, and re-read it from disk to setup cache and
+	 * tracking.
+	 */
+	btrfs_free_fs_root(root);
+	root = btrfs_read_fs_root(fs_info, &key);
+	if (IS_ERR(root)) {
+		ret = PTR_ERR(root);
+		goto error;
+	}
+	ret = btrfs_make_root_dir(trans, root, BTRFS_FIRST_FREE_OBJECTID);
+	if (ret < 0)
+		goto error;
+	ret = btrfs_update_root(trans, fs_info->tree_root, &root->root_key,
+				&root->root_item);
+	if (ret < 0)
+		goto error;
+	return 0;
+error:
+	btrfs_abort_transaction(trans, ret);
+	return ret;
+}

common/root-tree-utils.h

@@ -0,0 +1,26 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#ifndef __ROOT_TREE_UTILS_H__
+#define __ROOT_TREE_UTILS_H__
+
+#include "kernel-shared/transaction.h"
+
+int btrfs_make_root_dir(struct btrfs_trans_handle *trans,
+			struct btrfs_root *root, u64 objectid);
+int btrfs_make_subvolume(struct btrfs_trans_handle *trans, u64 objectid);
+
+#endif

convert/main.c

@@ -120,6 +120,7 @@
 #include "common/box.h"
 #include "common/open-utils.h"
 #include "common/extent-tree-utils.h"
+#include "common/root-tree-utils.h"
 #include "common/clear-cache.h"
 #include "cmds/commands.h"
 #include "check/repair.h"
@@ -916,44 +917,6 @@ out:
 	return ret;
 }
 
-static int create_subvol(struct btrfs_trans_handle *trans,
-			 struct btrfs_root *root, u64 root_objectid)
-{
-	struct extent_buffer *tmp;
-	struct btrfs_root *new_root;
-	struct btrfs_key key;
-	struct btrfs_root_item root_item;
-	int ret;
-
-	ret = btrfs_copy_root(trans, root, root->node, &tmp,
-			      root_objectid);
-	if (ret)
-		return ret;
-
-	memcpy(&root_item, &root->root_item, sizeof(root_item));
-	btrfs_set_root_bytenr(&root_item, tmp->start);
-	btrfs_set_root_level(&root_item, btrfs_header_level(tmp));
-	btrfs_set_root_generation(&root_item, trans->transid);
-	free_extent_buffer(tmp);
-
-	key.objectid = root_objectid;
-	key.type = BTRFS_ROOT_ITEM_KEY;
-	key.offset = trans->transid;
-	ret = btrfs_insert_root(trans, root->fs_info->tree_root,
-				&key, &root_item);
-
-	key.offset = (u64)-1;
-	new_root = btrfs_read_fs_root(root->fs_info, &key);
-	if (!new_root || IS_ERR(new_root)) {
-		error("unable to fs read root: %lu", PTR_ERR(new_root));
-		return PTR_ERR(new_root);
-	}
-
-	ret = btrfs_make_root_dir(trans, new_root, BTRFS_FIRST_FREE_OBJECTID);
-
-	return ret;
-}
-
 /*
  * New make_btrfs() has handle system and meta chunks quite well.
  * So only need to add remaining data chunks.
@@ -1059,13 +1022,13 @@ static int init_btrfs(struct btrfs_mkfs_config *cfg, struct btrfs_root *root,
 			     BTRFS_FIRST_FREE_OBJECTID);
 
 	/* subvol for fs image file */
-	ret = create_subvol(trans, root, CONV_IMAGE_SUBVOL_OBJECTID);
+	ret = btrfs_make_subvolume(trans, CONV_IMAGE_SUBVOL_OBJECTID);
 	if (ret < 0) {
 		error("failed to create subvolume image root: %d", ret);
 		goto err;
 	}
 	/* subvol for data relocation tree */
-	ret = create_subvol(trans, root, BTRFS_DATA_RELOC_TREE_OBJECTID);
+	ret = btrfs_make_subvolume(trans, BTRFS_DATA_RELOC_TREE_OBJECTID);
 	if (ret < 0) {
 		error("failed to create DATA_RELOC root: %d", ret);
 		goto err;

mkfs/common.c

@@ -758,45 +758,6 @@ out:
 	return ret;
 }
 
-int btrfs_make_root_dir(struct btrfs_trans_handle *trans,
-			struct btrfs_root *root, u64 objectid)
-{
-	int ret;
-	struct btrfs_inode_item inode_item;
-	time_t now = time(NULL);
-
-	memset(&inode_item, 0, sizeof(inode_item));
-	btrfs_set_stack_inode_generation(&inode_item, trans->transid);
-	btrfs_set_stack_inode_size(&inode_item, 0);
-	btrfs_set_stack_inode_nlink(&inode_item, 1);
-	btrfs_set_stack_inode_nbytes(&inode_item, root->fs_info->nodesize);
-	btrfs_set_stack_inode_mode(&inode_item, S_IFDIR | 0755);
-	btrfs_set_stack_timespec_sec(&inode_item.atime, now);
-	btrfs_set_stack_timespec_nsec(&inode_item.atime, 0);
-	btrfs_set_stack_timespec_sec(&inode_item.ctime, now);
-	btrfs_set_stack_timespec_nsec(&inode_item.ctime, 0);
-	btrfs_set_stack_timespec_sec(&inode_item.mtime, now);
-	btrfs_set_stack_timespec_nsec(&inode_item.mtime, 0);
-	btrfs_set_stack_timespec_sec(&inode_item.otime, now);
-	btrfs_set_stack_timespec_nsec(&inode_item.otime, 0);
-
-	if (root->fs_info->tree_root == root)
-		btrfs_set_super_root_dir(root->fs_info->super_copy, objectid);
-
-	ret = btrfs_insert_inode(trans, root, objectid, &inode_item);
-	if (ret)
-		goto error;
-
-	ret = btrfs_insert_inode_ref(trans, root, "..", 2, objectid, objectid, 0);
-	if (ret)
-		goto error;
-
-	btrfs_set_root_dirid(&root->root_item, objectid);
-	ret = 0;
-error:
-	return ret;
-}
-
 /*
  * Btrfs minimum size calculation is complicated, it should include at least:
  * 1. system group size

mkfs/common.h

@@ -103,8 +103,6 @@ struct btrfs_mkfs_config {
 };
 
 int make_btrfs(int fd, struct btrfs_mkfs_config *cfg);
-int btrfs_make_root_dir(struct btrfs_trans_handle *trans,
-			struct btrfs_root *root, u64 objectid);
 u64 btrfs_min_dev_size(u32 nodesize, bool mixed, u64 zone_size, u64 meta_profile,
 		       u64 data_profile);
 int test_minimum_size(const char *file, u64 min_dev_size);

mkfs/main.c

@@ -58,6 +58,7 @@
 #include "common/units.h"
 #include "common/string-utils.h"
 #include "common/string-table.h"
+#include "common/root-tree-utils.h"
 #include "cmds/commands.h"
 #include "check/qgroup-verify.h"
 #include "mkfs/common.h"
@@ -734,75 +735,6 @@ static void update_chunk_allocation(struct btrfs_fs_info *fs_info,
 	}
 }
 
-static int create_data_reloc_tree(struct btrfs_trans_handle *trans)
-{
-	struct btrfs_fs_info *fs_info = trans->fs_info;
-	struct btrfs_inode_item *inode;
-	struct btrfs_root *root;
-	struct btrfs_path path = { 0 };
-	struct btrfs_key key = {
-		.objectid = BTRFS_DATA_RELOC_TREE_OBJECTID,
-		.type = BTRFS_ROOT_ITEM_KEY,
-	};
-	u64 ino = BTRFS_FIRST_FREE_OBJECTID;
-	char *name = "..";
-	int ret;
-
-	root = btrfs_create_tree(trans, &key);
-	if (IS_ERR(root)) {
-		ret = PTR_ERR(root);
-		goto out;
-	}
-	/* Update dirid as created tree has default dirid 0 */
-	btrfs_set_root_dirid(&root->root_item, ino);
-	ret = btrfs_update_root(trans, fs_info->tree_root, &root->root_key,
-				&root->root_item);
-	if (ret < 0)
-		goto out;
-
-	/* Cache this tree so it can be cleaned up at close_ctree() */
-	ret = rb_insert(&fs_info->fs_root_tree, &root->rb_node,
-			btrfs_fs_roots_compare_roots);
-	if (ret < 0)
-		goto out;
-
-	/* Insert INODE_ITEM */
-	ret = btrfs_new_inode(trans, root, ino, 0755 | S_IFDIR);
-	if (ret < 0)
-		goto out;
-
-	/* then INODE_REF */
-	ret = btrfs_insert_inode_ref(trans, root, name, strlen(name), ino, ino,
-				     0);
-	if (ret < 0)
-		goto out;
-
-	/* Update nlink of that inode item */
-	key.objectid = ino;
-	key.type = BTRFS_INODE_ITEM_KEY;
-	key.offset = 0;
-
-	ret = btrfs_search_slot(trans, root, &key, &path, 0, 1);
-	if (ret > 0) {
-		ret = -ENOENT;
-		btrfs_release_path(&path);
-		goto out;
-	}
-	if (ret < 0) {
-		btrfs_release_path(&path);
-		goto out;
-	}
-	inode = btrfs_item_ptr(path.nodes[0], path.slots[0],
-			       struct btrfs_inode_item);
-	btrfs_set_inode_nlink(path.nodes[0], inode, 1);
-	btrfs_mark_buffer_dirty(path.nodes[0]);
-	btrfs_release_path(&path);
-	return 0;
-out:
-	btrfs_abort_transaction(trans, ret);
-	return ret;
-}
-
 static int btrfs_uuid_tree_add(struct btrfs_trans_handle *trans, u8 *uuid,
 			       u8 type, u64 subvol_id_cpu)
 {
@@ -1939,7 +1871,7 @@ raid_groups:
 		goto out;
 	}
 
-	ret = create_data_reloc_tree(trans);
+	ret = btrfs_make_subvolume(trans, BTRFS_DATA_RELOC_TREE_OBJECTID);
 	if (ret) {
 		error("unable to create data reloc tree: %d", ret);
 		goto out;