btrfs-progs: add --default-subvol option to mkfs.btrfs

Adds a --default-subvol option to mkfs.btrfs, which works the same way as --subvol but also marks the subvolume as the default. Signed-off-by: Mark Harmstone <[email protected]>
kdave · Aug 14, 2024 · e0dfe20 · e0dfe20
1 parent 58663fa
commit e0dfe20
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Showing 4 changed files with 96 additions and 5 deletions.
diff --git a/Documentation/mkfs.btrfs.rst b/Documentation/mkfs.btrfs.rst
@@ -160,6 +160,10 @@ OPTIONS
         directory.  The option *--rootdir* must also be specified, and *subdir* must be an
         existing subdirectory within it.  This option can be specified multiple times.
 
+-D|--default-subvol <subdir>
+        As *--subvol*, except that it also sets the subvolume as the default for the
+        filesystem.  This option can only be specified once.
+
 --shrink
         Shrink the filesystem to its minimal size, only works with *--rootdir* option.
 

diff --git a/mkfs/main.c b/mkfs/main.c
@@ -441,6 +441,7 @@ static const char * const mkfs_usage[] = {
 	OPTLINE("-b|--byte-count SIZE", "set size of each device to SIZE (filesystem size is sum of all device sizes)"),
 	OPTLINE("-r|--rootdir DIR", "copy files from DIR to the image root directory"),
 	OPTLINE("-u|--subvol SUBDIR", "create SUBDIR as subvolume rather than normal directory"),
+	OPTLINE("-D|--default-subvol SUBDIR", "create SUBDIR as subvolume rather than normal directory, and set it as the default"),
 	OPTLINE("--shrink", "(with --rootdir) shrink the filled filesystem to minimal size"),
 	OPTLINE("-K|--nodiscard", "do not perform whole device TRIM"),
 	OPTLINE("-f|--force", "force overwrite of existing filesystem"),
@@ -1058,6 +1059,7 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
 	char *source_dir = NULL;
 	size_t source_dir_len = 0;
 	struct rootdir_subvol *rds;
+	bool has_default_subvol = false;
 	LIST_HEAD(subvols);
 
 	cpu_detect_flags();
@@ -1090,6 +1092,7 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
 			{ "version", no_argument, NULL, 'V' },
 			{ "rootdir", required_argument, NULL, 'r' },
 			{ "subvol", required_argument, NULL, 'u' },
+			{ "default-subvol", required_argument, NULL, 'D' },
 			{ "nodiscard", no_argument, NULL, 'K' },
 			{ "features", required_argument, NULL, 'O' },
 			{ "runtime-features", required_argument, NULL, 'R' },
@@ -1107,7 +1110,7 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
 			{ NULL, 0, NULL, 0}
 		};
 
-		c = getopt_long(argc, argv, "A:b:fl:n:s:m:d:L:R:O:r:U:VvMKqu:",
+		c = getopt_long(argc, argv, "A:b:fl:n:s:m:d:L:R:O:r:U:VvMKqu:D:",
 				long_options, NULL);
 		if (c < 0)
 			break;
@@ -1213,7 +1216,8 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
 				free(source_dir);
 				source_dir = strdup(optarg);
 				break;
-			case 'u': {
+			case 'u':
+			case 'D': {
 				struct rootdir_subvol *s;
 
 				s = malloc(sizeof(struct rootdir_subvol));
@@ -1226,6 +1230,19 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
 				s->dir = strdup(optarg);
 				s->full_path = NULL;
 
+				if (c == 'D') {
+					if (has_default_subvol) {
+						error("--default-subvol can only be specified once");
+						ret = 1;
+						goto error;
+					}
+
+					has_default_subvol = true;
+					s->is_default = true;
+				} else {
+					s->is_default = false;
+				}
+
 				list_add_tail(&s->list, &subvols);
 				break;
 				}
@@ -1928,6 +1945,8 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
 	}
 
 	if (source_dir) {
+		u64 default_subvol_id;
+
 		pr_verbose(LOG_DEFAULT, "Rootdir from:       %s\n", source_dir);
 
 		trans = btrfs_start_transaction(root, 1);
@@ -1938,7 +1957,7 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
 		}
 
 		ret = btrfs_mkfs_fill_dir(trans, source_dir, root,
-					  &subvols);
+					  &subvols, &default_subvol_id);
 		if (ret) {
 			error("error while filling filesystem: %d", ret);
 			btrfs_abort_transaction(trans, ret);
@@ -1969,6 +1988,15 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
 		} else {
 			pr_verbose(LOG_DEFAULT, "  Shrink:           no\n");
 		}
+
+		if (has_default_subvol) {
+			ret = btrfs_set_default_subvolume(fs_info,
+							  default_subvol_id);
+			if (ret < 0) {
+				error("error setting default subvolume: %d", ret);
+				goto out;
+			}
+		}
 	}
 
 	ret = btrfs_rebuild_uuid_tree(fs_info);

diff --git a/mkfs/rootdir.c b/mkfs/rootdir.c
@@ -95,6 +95,7 @@ static struct rootdir_path current_path = {
 
 static struct btrfs_trans_handle *g_trans = NULL;
 static struct list_head *g_subvols;
+static u64 *g_default_subvol_id;
 static u64 next_subvol_id = BTRFS_FIRST_FREE_OBJECTID;
 
 static inline struct inode_entry *rootdir_path_last(struct rootdir_path *path)
@@ -435,6 +436,9 @@ static int ftw_add_subvol(const char *full_path, const struct stat *st,
 		return ret;
 	}
 
+	if (s->is_default)
+		*g_default_subvol_id = subvol_id;
+
 	key.objectid = subvol_id;
 	key.type = BTRFS_ROOT_ITEM_KEY;
 	key.offset = (u64)-1;
@@ -697,7 +701,8 @@ static int ftw_add_inode(const char *full_path, const struct stat *st,
 };
 
 int btrfs_mkfs_fill_dir(struct btrfs_trans_handle *trans, const char *source_dir,
-			struct btrfs_root *root, struct list_head *subvols)
+			struct btrfs_root *root, struct list_head *subvols,
+			u64 *default_subvol_id)
 {
 	int ret;
 	struct stat root_st;
@@ -710,6 +715,7 @@ int btrfs_mkfs_fill_dir(struct btrfs_trans_handle *trans, const char *source_dir
 
 	g_trans = trans;
 	g_subvols = subvols;
+	g_default_subvol_id = default_subvol_id;
 	INIT_LIST_HEAD(&current_path.inode_list);
 
 	ret = nftw(source_dir, ftw_add_inode, 32, FTW_PHYS);
@@ -992,3 +998,53 @@ int btrfs_mkfs_shrink_fs(struct btrfs_fs_info *fs_info, u64 *new_size_ret,
 	}
 	return ret;
 }
+
+int btrfs_set_default_subvolume(struct btrfs_fs_info *fs_info, u64 objectid)
+{
+	struct btrfs_trans_handle *trans;
+	struct btrfs_path path = { 0 };
+	struct btrfs_dir_item *di;
+	struct btrfs_key location;
+	struct extent_buffer *leaf;
+	struct btrfs_disk_key disk_key;
+	u64 features;
+	int ret;
+
+	trans = btrfs_start_transaction(fs_info->tree_root, 1);
+	if (IS_ERR(trans))
+		return -PTR_ERR(trans);
+
+	di = btrfs_lookup_dir_item(trans, fs_info->tree_root, &path,
+				   btrfs_super_root_dir(fs_info->super_copy),
+				   "default", 7, 1);
+	if (!di || IS_ERR(di)) {
+		btrfs_release_path(&path);
+
+		if (di)
+			ret = PTR_ERR(di);
+		else
+			ret = -ENOENT;
+
+		btrfs_abort_transaction(trans, ret);
+		return ret;
+	}
+
+	leaf = path.nodes[0];
+
+	location.objectid = objectid;
+	location.type = BTRFS_ROOT_ITEM_KEY;
+	location.offset = 0;
+
+	btrfs_cpu_key_to_disk(&disk_key, &location);
+	btrfs_set_dir_item_key(leaf, di, &disk_key);
+
+	btrfs_mark_buffer_dirty(leaf);
+
+	btrfs_release_path(&path);
+
+	features = btrfs_super_incompat_flags(fs_info->super_copy);
+	features |= BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL;
+	btrfs_set_super_incompat_flags(fs_info->super_copy, features);
+
+	return btrfs_commit_transaction(trans, fs_info->tree_root);
+}
diff --git a/mkfs/rootdir.h b/mkfs/rootdir.h
@@ -32,13 +32,16 @@ struct rootdir_subvol {
 	struct list_head list;
 	char *dir;
 	char *full_path;
+	bool is_default;
 };
 
 int btrfs_mkfs_fill_dir(struct btrfs_trans_handle *trans, const char *source_dir,
-			struct btrfs_root *root, struct list_head *subvols);
+			struct btrfs_root *root, struct list_head *subvols,
+			u64 *default_subvol_id);
 u64 btrfs_mkfs_size_dir(const char *dir_name, u32 sectorsize, u64 min_dev_size,
 			u64 meta_profile, u64 data_profile);
 int btrfs_mkfs_shrink_fs(struct btrfs_fs_info *fs_info, u64 *new_size_ret,
 			 bool shrink_file_size);
+int btrfs_set_default_subvolume(struct btrfs_fs_info *fs_info, u64 objectid);
 
 #endif