Add a readonly flag open_ctree to force RO opens

Author: chrismason-xx

btrfsck.c

@@ -746,7 +746,7 @@ int main(int ac, char **av) {
 	cache_tree_init(&nodes);
 	cache_tree_init(&reada);
 
-	root = open_ctree(av[1], 0);
+	root = open_ctree(av[1], 0, 0);
 
 	bits_nr = 1024;
 	bits = malloc(bits_nr * sizeof(struct block_info));

convert.c

@@ -2189,7 +2189,7 @@ int do_convert(const char *devname, int datacsum, int packing, int noxattr)
 		fprintf(stderr, "unable to update system chunk\n");
 		goto fail;
 	}
-	root = open_ctree_fd(fd, devname, super_bytenr);
+	root = open_ctree_fd(fd, devname, super_bytenr, O_RDWR);
 	if (!root) {
 		fprintf(stderr, "unable to open ctree\n");
 		goto fail;
@@ -2251,7 +2251,7 @@ int do_convert(const char *devname, int datacsum, int packing, int noxattr)
 		goto fail;
 	}
 
-	root = open_ctree_fd(fd, devname, 0);
+	root = open_ctree_fd(fd, devname, 0, O_RDWR);
 	if (!root) {
 		fprintf(stderr, "unable to open ctree\n");
 		goto fail;
@@ -2349,7 +2349,7 @@ int do_rollback(const char *devname, int force)
 		fprintf(stderr, "unable to open %s\n", devname);
 		goto fail;
 	}
-	root = open_ctree_fd(fd, devname, 0);
+	root = open_ctree_fd(fd, devname, 0, O_RDWR);
 	if (!root) {
 		fprintf(stderr, "unable to open ctree\n");
 		goto fail;

ctree.h

@@ -515,6 +515,7 @@ struct btrfs_fs_info {
 	struct btrfs_fs_devices *fs_devices;
 	struct list_head space_info;
 	int system_allocs;
+	int readonly;
 };
 
 /*

debug-tree.c

@@ -130,7 +130,7 @@ int main(int ac, char **av)
 	if (ac != 1)
 		print_usage();
 
-	root = open_ctree(av[optind], 0);
+	root = open_ctree(av[optind], 0, 0);
 	if (!root) {
 		fprintf(stderr, "unable to open %s\n", av[optind]);
 		exit(1);

dir-test.c

@@ -435,7 +435,7 @@ int main(int ac, char **av)
 	struct btrfs_trans_handle *trans;
 	radix_tree_init();
 
-	root = open_ctree(av[ac-1], &super);
+	root = open_ctree(av[ac-1], &super, 0);
 	trans = btrfs_start_transaction(root, 1);
 
 	dir_oid = btrfs_super_root_dir(&super);
@@ -478,7 +478,7 @@ int main(int ac, char **av)
 				btrfs_header_level(&root->node->node.header),
 				btrfs_header_nritems(&root->node->node.header));
 			close_ctree(root, &super);
-			root = open_ctree("dbfile", &super);
+			root = open_ctree("dbfile", &super, 0);
 		}
 		while(count--) {
 			ret = ops[op](trans, root, &radix);

disk-io.c

@@ -454,22 +454,27 @@ struct btrfs_root *btrfs_read_fs_root(struct btrfs_fs_info *fs_info,
 	return root;
 }
 
-struct btrfs_root *open_ctree(const char *filename, u64 sb_bytenr)
+struct btrfs_root *open_ctree(const char *filename, u64 sb_bytenr, int writes)
 {
 	int fp;
 	struct btrfs_root *root;
+	int flags = O_CREAT | O_RDWR;
 
-	fp = open(filename, O_CREAT | O_RDWR, 0600);
+	if (!writes)
+		flags = O_RDONLY;
+
+	fp = open(filename, flags, 0600);
 	if (fp < 0) {
 		return NULL;
 	}
-	root = open_ctree_fd(fp, filename, sb_bytenr);
+	root = open_ctree_fd(fp, filename, sb_bytenr, writes);
 	close(fp);
 
 	return root;
 }
 
-struct btrfs_root *open_ctree_fd(int fp, const char *path, u64 sb_bytenr)
+struct btrfs_root *open_ctree_fd(int fp, const char *path, u64 sb_bytenr,
+				 int writes)
 {
 	u32 sectorsize;
 	u32 nodesize;
@@ -510,6 +515,9 @@ struct btrfs_root *open_ctree_fd(int fp, const char *path, u64 sb_bytenr)
 	fs_info->chunk_root = chunk_root;
 	fs_info->dev_root = dev_root;
 
+	if (!writes)
+		fs_info->readonly = 1;
+
 	extent_io_tree_init(&fs_info->extent_cache);
 	extent_io_tree_init(&fs_info->free_space_cache);
 	extent_io_tree_init(&fs_info->block_group_cache);
@@ -527,7 +535,10 @@ struct btrfs_root *open_ctree_fd(int fp, const char *path, u64 sb_bytenr)
 	__setup_root(4096, 4096, 4096, 4096, tree_root,
 		     fs_info, BTRFS_ROOT_TREE_OBJECTID);
 
-	ret = btrfs_open_devices(fs_devices, O_RDWR);
+	if (writes)
+		ret = btrfs_open_devices(fs_devices, O_RDWR);
+	else
+		ret = btrfs_open_devices(fs_devices, O_RDONLY);
 	BUG_ON(ret);
 
 	ret = btrfs_bootstrap_super_map(&fs_info->mapping_tree, fs_devices);
@@ -656,6 +667,10 @@ int write_ctree_super(struct btrfs_trans_handle *trans,
 	int ret;
 	struct btrfs_root *tree_root = root->fs_info->tree_root;
 	struct btrfs_root *chunk_root = root->fs_info->chunk_root;
+
+	if (root->fs_info->readonly)
+		return 0;
+
 	btrfs_set_super_generation(&root->fs_info->super_copy,
 				   trans->transid);
 	btrfs_set_super_root(&root->fs_info->super_copy,

disk-io.h

@@ -31,8 +31,9 @@ struct extent_buffer *btrfs_find_create_tree_block(struct btrfs_root *root,
 						   u64 bytenr, u32 blocksize);
 int clean_tree_block(struct btrfs_trans_handle *trans,
 		     struct btrfs_root *root, struct extent_buffer *buf);
-struct btrfs_root *open_ctree(const char *filename, u64 sb_bytenr);
-struct btrfs_root *open_ctree_fd(int fp, const char *path, u64 sb_bytenr);
+struct btrfs_root *open_ctree(const char *filename, u64 sb_bytenr, int writes);
+struct btrfs_root *open_ctree_fd(int fp, const char *path, u64 sb_bytenr,
+				 int writes);
 int close_ctree(struct btrfs_root *root);
 int write_ctree_super(struct btrfs_trans_handle *trans,
 		      struct btrfs_root *root);

mkfs.c

@@ -77,7 +77,7 @@ static int make_root_dir(int fd, const char *device_name) {
 	u64 chunk_size = 0;
 	int ret;
 
-	root = open_ctree_fd(fd, device_name, 0);
+	root = open_ctree_fd(fd, device_name, 0, O_RDWR);
 
 	if (!root) {
 		fprintf(stderr, "ctree init failed\n");
@@ -408,7 +408,7 @@ int main(int ac, char **av)
 		fprintf(stderr, "failed to setup the root directory\n");
 		exit(1);
 	}
-	root = open_ctree(file, 0);
+	root = open_ctree(file, 0, O_RDWR);
 	root->fs_info->alloc_start = alloc_start;
 	trans = btrfs_start_transaction(root, 1);
 

quick-test.c

@@ -50,7 +50,7 @@ int main(int ac, char **av) {
 
 	radix_tree_init();
 
-	root = open_ctree(av[1], BTRFS_SUPER_INFO_OFFSET);
+	root = open_ctree(av[1], BTRFS_SUPER_INFO_OFFSET, O_RDWR);
 	trans = btrfs_start_transaction(root, 1);
 	srand(55);
 	btrfs_set_key_type(&ins, BTRFS_STRING_ITEM_KEY);
@@ -73,7 +73,7 @@ int main(int ac, char **av) {
 	btrfs_commit_transaction(trans, root);
 	close_ctree(root);
 	exit(1);
-	root = open_ctree(av[1], BTRFS_SUPER_INFO_OFFSET);
+	root = open_ctree(av[1], BTRFS_SUPER_INFO_OFFSET, O_RDWR);
 	printf("starting search\n");
 	srand(55);
 	for (i = 0; i < run_size; i++) {
@@ -92,7 +92,7 @@ int main(int ac, char **av) {
 	}
 	close_ctree(root);
 
-	root = open_ctree(av[1], BTRFS_SUPER_INFO_OFFSET);
+	root = open_ctree(av[1], BTRFS_SUPER_INFO_OFFSET, O_RDWR);
 	printf("node %p level %d total ptrs %d free spc %lu\n", root->node,
 	        btrfs_header_level(root->node),
 		btrfs_header_nritems(root->node),
@@ -120,7 +120,7 @@ int main(int ac, char **av) {
 	btrfs_commit_transaction(trans, root);
 	close_ctree(root);
 
-	root = open_ctree(av[1], BTRFS_SUPER_INFO_OFFSET);
+	root = open_ctree(av[1], BTRFS_SUPER_INFO_OFFSET, O_RDWR);
 	trans = btrfs_start_transaction(root, 1);
 	srand(128);
 	for (i = 0; i < run_size; i++) {
@@ -136,7 +136,7 @@ int main(int ac, char **av) {
 	btrfs_commit_transaction(trans, root);
 	close_ctree(root);
 
-	root = open_ctree(av[1], BTRFS_SUPER_INFO_OFFSET);
+	root = open_ctree(av[1], BTRFS_SUPER_INFO_OFFSET, O_RDWR);
 	srand(128);
 	printf("starting search2\n");
 	for (i = 0; i < run_size; i++) {