> -----Original Message-----
> From: Goffredo Baroncelli <kreij...@libero.it>
> [mailto:kreij...@libero.it]
> Sent: Monday, July 11, 2011 8:03 PM
> To: Zhong, Xin
> Cc: linux-btrfs@vger.kernel.org
> Subject: R: [PATCH V2] Btrfs-progs: add "btrfs subvolume get-default"
> subcommand
>
> >----Messaggio originale----
> >Da: xin.zh...@intel.com
> >Data: 11/07/2011 10.56
> >A: <linux-btrfs@vger.kernel.org>
> >Cc: <xin.zh...@intel.com>
> >Ogg: [PATCH V2] Btrfs-progs: add "btrfs subvolume get-
> default"
> subcommand
> >
> >Add subcommand to get the default subvolume of btrfs filesystem
> >
> >Reported-by: Yang, Yi <yi.y.y...@intel.com>
> >Signed-off-by: Zhong, Xin <xin.zh...@intel.com>
> >---
> > btrfs-list.c | 57
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++--
> > btrfs.c | 3 +++
> > btrfs_cmds.c | 31 ++++++++++++++++++++++++++++++-
> > btrfs_cmds.h | 3 ++-
> > 4 files changed, 90 insertions(+), 4 deletions(-)
>
> please update the man page too.
>
> >
> >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;
> [...]
> >+ /* 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;
> >+
> [...]
> >+ /* 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;
> >+ }
>
> I am not familiar with the "default subvolume key", but are you sure
> that the
> key is always in the first set of returned keys ?
>
It seems there's not too much dir item in the root tree. In fact, I only see it
used for for default subvolume in the root tree.
So it should be enough.
> >+ }
> >+
> > /* 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);
> >+
>
> What happens if there no is a default subvolume (for example a very old
> btrfs
> filesystem, and/or after removing the "default" subvolume) ?
> I suggest to handle this case printing something like "No default
> subvolume
> found"
>
If there's no default subvolume, the output is empty. Just the same as when you
use "btrfs subvolume list" and there's no subvolume at all.
Thanks for all the review!
>
> BR
> G.Baroncelli
>
> > 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);
> >--
> >1.7.0.4
> >
> >--
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