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

["Zhong, Xin" <xin.zhong@intel.com>]

> -----Original Message-----
> From: Andreas Philipp [mailto:philipp.andreas@gmail.com]
> Sent: Monday, July 11, 2011 10:11 PM
> To: Zhong, Xin
> Cc: linux-btrfs@vger.kernel.org; Hugo Mills
> Subject: Re: [PATCH V2] Btrfs-progs: add "btrfs subvolume get-default"
> subcommand
> 
> 
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> 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.

Ok. I will update my patch. Thanks!

> 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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