Re: [PATCH V2] Btrfs-progs: add "btrfs subvolume get-default" subcommand

[Andreas Philipp <philipp.andreas@gmail.com>]

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Would you mind rebasing your patch on Hugo Mills' integration-branch for
btrfs progs at
http://git.darksatanic.net/repo/btrfs-progs-unstable.git
integration-20110705
since it does not apply on top of all changes which are already there.
Additionally, I spotted one whitespace error in the patch and marked it
below.
 
Thanks,
Andreas Philipp
 
On 11.07.2011 10:56, Zhong, Xin wrote:
> Add subcommand to get the default subvolume of btrfs filesystem
>
> Reported-by: Yang, Yi <yi.y.yang@intel.com>
> Signed-off-by: Zhong, Xin <xin.zhong@intel.com>
> ---
> btrfs-list.c | 57
+++++++++++++++++++++++++++++++++++++++++++++++++++++++--
> btrfs.c | 3 +++
> btrfs_cmds.c | 31 ++++++++++++++++++++++++++++++-
> btrfs_cmds.h | 3 ++-
> 4 files changed, 90 insertions(+), 4 deletions(-)
>
> diff --git a/btrfs-list.c b/btrfs-list.c
> index 93766a8..aa6a9b4 100644
> --- a/btrfs-list.c
> +++ b/btrfs-list.c
> @@ -536,7 +536,7 @@ build:
> return full;
> }
>
> -int list_subvols(int fd)
> +int list_subvols(int fd, int get_default)
> {
> struct root_lookup root_lookup;
> struct rb_node *n;
> @@ -545,10 +545,12 @@ int list_subvols(int fd)
> struct btrfs_ioctl_search_key *sk = &args.key;
> struct btrfs_ioctl_search_header *sh;
> struct btrfs_root_ref *ref;
> + struct btrfs_dir_item *di;
> unsigned long off = 0;
> int name_len;
> char *name;
> u64 dir_id;
> + u64 subvol_id = 0;
> int i;
>
> root_lookup_init(&root_lookup);
> @@ -642,6 +644,52 @@ int list_subvols(int fd)
> n = rb_next(n);
> }
>
> + memset(&args, 0, sizeof(args));
> +
> + /* search in the tree of tree roots */
> + sk->tree_id = BTRFS_ROOT_TREE_OBJECTID;
> +
> + /* search dir item */
> + sk->max_type = BTRFS_DIR_ITEM_KEY;
> + sk->min_type = BTRFS_DIR_ITEM_KEY;
> +
> + sk->max_objectid = BTRFS_ROOT_TREE_DIR_OBJECTID;
> + sk->min_objectid = BTRFS_ROOT_TREE_DIR_OBJECTID;
> + sk->max_offset = (u64)-1;
> + sk->max_transid = (u64)-1;
> +
> + /* just a big number, doesn't matter much */
> + sk->nr_items = 4096;
> +
> + /* try to get the objectid of default subvolume */
> + if(get_default) {
> + ret = ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args);
> + if (ret < 0) {
> + fprintf(stderr, "ERROR: can't perform the search\n");
> + return ret;
> + }
> +
> + off = 0;
> + /* go through each item to find dir item named "default" */
> + for (i = 0; i < sk->nr_items; i++) {
> + sh = (struct btrfs_ioctl_search_header *)(args.buf +
> + off);
> + off += sizeof(*sh);
> + if (sh->type == BTRFS_DIR_ITEM_KEY) {
> + di = (struct btrfs_dir_item *)(args.buf + off);
> + name_len = le16_to_cpu(di->name_len);
> + name = (char *)di + sizeof(struct btrfs_dir_item);
> + if (!strncmp("default", name, name_len)) {
> + subvol_id = btrfs_disk_key_objectid(
> + &di->location);
> + break;
> + }
> + }
> +
> + off += sh->len;
> + }
> + }
> +
> /* now that we have all the subvol-relative paths filled in,
> * we have to string the subvols together so that we can get
> * a path all the way back to the FS root
> @@ -650,7 +698,12 @@ int list_subvols(int fd)
> while (n) {
> struct root_info *entry;
> entry = rb_entry(n, struct root_info, rb_node);
> - resolve_root(&root_lookup, entry);
> + if(!get_default)
> + resolve_root(&root_lookup, entry);
> + /* we only want the default subvolume */
> + else if(subvol_id == entry->root_id)
> + resolve_root(&root_lookup, entry);
> +
This line adds a whitespace error.
> n = rb_prev(n);
> }
>
> diff --git a/btrfs.c b/btrfs.c
> index 46314cf..6b73f88 100644
> --- a/btrfs.c
> +++ b/btrfs.c
> @@ -73,6 +73,9 @@ static struct Command commands[] = {
> "Set the subvolume of the filesystem <path> which will be mounted\n"
> "as default."
> },
> + { do_get_default_subvol, 1, "subvolume get-default", "<path>\n"
> + "Get the default subvolume of a filesystem."
> + },
> { do_fssync, 1,
> "filesystem sync", "<path>\n"
> "Force a sync on the filesystem <path>."
> diff --git a/btrfs_cmds.c b/btrfs_cmds.c
> index 8031c58..11c56f6 100644
> --- a/btrfs_cmds.c
> +++ b/btrfs_cmds.c
> @@ -301,7 +301,7 @@ int do_subvol_list(int argc, char **argv)
> fprintf(stderr, "ERROR: can't access '%s'\n", subvol);
> return 12;
> }
> - ret = list_subvols(fd);
> + ret = list_subvols(fd, 0);
> if (ret)
> return 19;
> return 0;
> @@ -834,6 +834,35 @@ int do_set_default_subvol(int nargs, char **argv)
> return 0;
> }
>
> +int do_get_default_subvol(int nargs, char **argv)
> +{
> + int fd;
> + int ret;
> + char *subvol;
> +
> + subvol = argv[1];
> +
> + ret = test_issubvolume(subvol);
> + if (ret < 0) {
> + fprintf(stderr, "ERROR: error accessing '%s'\n", subvol);
> + return 12;
> + }
> + if (!ret) {
> + fprintf(stderr, "ERROR: '%s' is not a subvolume\n", subvol);
> + return 13;
> + }
> +
> + fd = open_file_or_dir(subvol);
> + if (fd < 0) {
> + fprintf(stderr, "ERROR: can't access '%s'\n", subvol);
> + return 12;
> + }
> + ret = list_subvols(fd, 1);
> + if (ret)
> + return 19;
> + return 0;
> +}
> +
> int do_df_filesystem(int nargs, char **argv)
> {
> struct btrfs_ioctl_space_args *sargs;
> diff --git a/btrfs_cmds.h b/btrfs_cmds.h
> index 7bde191..9cf1ca1 100644
> --- a/btrfs_cmds.h
> +++ b/btrfs_cmds.h
> @@ -28,7 +28,8 @@ int do_scan(int nargs, char **argv);
> int do_resize(int nargs, char **argv);
> int do_subvol_list(int nargs, char **argv);
> int do_set_default_subvol(int nargs, char **argv);
> -int list_subvols(int fd);
> +int do_get_default_subvol(int nargs, char **argv);
> +int list_subvols(int fd, int get_default);
> int do_df_filesystem(int nargs, char **argv);
> int find_updated_files(int fd, u64 root_id, u64 oldest_gen);
> int do_find_newer(int argc, char **argv);
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