Btrfs-progs: bring 'subvol get-default' back in

Commit bab2c565 accidentally broke 'subvol get-default' command by
removing almost all of the underlying code.  Bring it back with some
fixes and improvements.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/btrfs-list.c b/btrfs-list.c
index cc1dc66..00c428b 100644 (file)
--- a/btrfs-list.c
+++ b/btrfs-list.c
@@ -552,6 +552,60 @@ build:
        return full;
 }
 
+static int get_default_subvolid(int fd, u64 *default_id)
+{
+       struct btrfs_ioctl_search_args args;
+       struct btrfs_ioctl_search_key *sk = &args.key;
+       struct btrfs_ioctl_search_header *sh;
+       u64 found = 0;
+       int ret;
+
+       memset(&args, 0, sizeof(args));
+
+       /*
+        * search for a dir item with a name 'default' in the tree of
+        * tree roots, it should point us to a default root
+        */
+       sk->tree_id = 1;
+
+       /* don't worry about ancient format and request only one item */
+       sk->nr_items = 1;
+
+       sk->max_objectid = BTRFS_ROOT_TREE_DIR_OBJECTID;
+       sk->min_objectid = BTRFS_ROOT_TREE_DIR_OBJECTID;
+       sk->max_type = BTRFS_DIR_ITEM_KEY;
+       sk->min_type = BTRFS_DIR_ITEM_KEY;
+       sk->max_offset = (u64)-1;
+       sk->max_transid = (u64)-1;
+
+       ret = ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args);
+       if (ret < 0)
+               return ret;
+
+       /* the ioctl returns the number of items it found in nr_items */
+       if (sk->nr_items == 0)
+               goto out;
+
+       sh = (struct btrfs_ioctl_search_header *)args.buf;
+
+       if (sh->type == BTRFS_DIR_ITEM_KEY) {
+               struct btrfs_dir_item *di;
+               int name_len;
+               char *name;
+
+               di = (struct btrfs_dir_item *)(sh + 1);
+               name_len = btrfs_stack_dir_name_len(di);
+               name = (char *)(di + 1);
+
+               if (!strncmp("default", name, name_len))
+                       found = btrfs_disk_key_objectid(&di->location);
+       }
+
+out:
+       *default_id = found;
+       return 0;
+}
+
 static int __list_subvol_search(int fd, struct root_lookup *root_lookup)
 {
        int ret;
@@ -663,12 +717,32 @@ static int __list_subvol_fill_paths(int fd, struct root_lookup *root_lookup)
        return 0;
 }
 
-int list_subvols(int fd, int print_parent)
+int list_subvols(int fd, int print_parent, int get_default)
 {
        struct root_lookup root_lookup;
        struct rb_node *n;
+       u64 default_id;
        int ret;
 
+       if (get_default) {
+               ret = get_default_subvolid(fd, &default_id);
+               if (ret) {
+                       fprintf(stderr, "ERROR: can't perform the search - %s\n",
+                               strerror(errno));
+                       return ret;
+               }
+               if (default_id == 0) {
+                       fprintf(stderr, "ERROR: 'default' dir item not found\n");
+                       return ret;
+               }
+
+               /* no need to resolve roots if FS_TREE is default */
+               if (default_id == BTRFS_FS_TREE_OBJECTID) {
+                       printf("ID 5 (FS_TREE)\n");
+                       return ret;
+               }
+       }
+
        ret = __list_subvol_search(fd, &root_lookup);
        if (ret) {
                fprintf(stderr, "ERROR: can't perform the search - %s\n",
@@ -696,6 +770,11 @@ int list_subvols(int fd, int print_parent)
                char *path;
 
                entry = rb_entry(n, struct root_info, rb_node);
+               if (get_default && entry->root_id != default_id) {
+                       n = rb_prev(n);
+                       continue;
+               }
+
                resolve_root(&root_lookup, entry, &parent_id, &level, &path);
                if (print_parent) {
                        printf("ID %llu parent %llu top level %llu path %s\n",

diff --git a/ctree.h b/ctree.h
index 5309059..141ec59 100644 (file)
--- a/ctree.h
+++ b/ctree.h
@@ -1416,6 +1416,8 @@ BTRFS_SETGET_FUNCS(dir_type, struct btrfs_dir_item, type, 8);
 BTRFS_SETGET_FUNCS(dir_name_len, struct btrfs_dir_item, name_len, 16);
 BTRFS_SETGET_FUNCS(dir_transid, struct btrfs_dir_item, transid, 64);
 
+BTRFS_SETGET_STACK_FUNCS(stack_dir_name_len, struct btrfs_dir_item, name_len, 16);
+
 static inline void btrfs_dir_item_key(struct extent_buffer *eb,
                                      struct btrfs_dir_item *item,
                                      struct btrfs_disk_key *key)