Btrfs-progs: add "btrfs subvolume get-default" subcommand

Add subcommand to get the default subvolume of btrfs filesystem

Reported-by Yang, Yi <[email protected]>

Signed-off-by Zhong, Xin <[email protected]>

---
btrfs-list.c | 57

btrfs.c | 3 +++
btrfs_cmds.c | 31 ++++++++++++++++++++++++++++++-
btrfs_cmds.h | 3 ++-

4 files changed, 90 insertions(+), 4 deletions(-)

btrfs-list.c +49 -1

index 93766a8..aa6a9b4 100644
@@ -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

btrfs-list.c +0 -0

 n = rb_prev(n);
 }
 

btrfs.c +0 -0

index 46314cf..6b73f88 100644
@@ -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>."

btrfs_cmds.c +30 -1

index 8031c58..11c56f6 100644
@@ -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;

btrfs_cmds.h +0 -0

index 7bde191..9cf1ca1 100644

-----Original Message-----
From: Andreas Philipp [mailto:[email protected]]
Sent: Monday, July 11, 2011 10:11 PM
To: Zhong, Xin
Cc: [email protected]; 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.

Thanks,
Andreas Philipp

Quoted 6 lines · Xin

Add subcommand to get the default subvolume of btrfs filesystem

Reported-by Yang, Yi <[email protected]>

Signed-off-by Zhong, Xin <[email protected]>

---
btrfs-list.c | 57

+++++++++++++++++++++++++++++++++++++++++++++++++++++++--

Quoted 85 lines

btrfs.c | 3 +++
btrfs_cmds.c | 31 ++++++++++++++++++++++++++++++-
btrfs_cmds.h | 3 ++-

4 files changed, 90 insertions(+), 4 deletions(-)

btrfs-list.c +49 -1

index 93766a8..aa6a9b4 100644
@@ -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

btrfs-list.c int list_subvols(int fd) · line 706

Quoted 10 lines

btrfs-list.c +6 -1

@@ -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.

Quoted 71 lines

btrfs-list.c +0 -0

 n = rb_prev(n);
 }
 

btrfs.c +0 -0

index 46314cf..6b73f88 100644
@@ -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>."

btrfs_cmds.c +30 -1

index 8031c58..11c56f6 100644
@@ -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;

btrfs_cmds.h +0 -0

index 7bde191..9cf1ca1 100644

btrfs_cmds.h int do_scan(int nargs, char **argv); · line 35

Quoted 9 lines

btrfs_cmds.h +2 -1

@@ -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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Hi Xin / Hugo,
I am referring to
git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-progs.git

has miss match parameter list for list_subvols
----------

 # cd btrfs-progs
 # egrep list_subvols *
 btrfs_cmds.c:	ret = list_subvols(fd, print_parent, 0);
 btrfs_cmds.c:	ret = list_subvols(fd, 0, 1);
 btrfs_cmds.h:int list_subvols(int fd, int print_parent, int get_default);  <-----
 btrfs-list.c:int list_subvols(int fd, int print_parent)  <-----
 ----------

----------

 # egrep -A 3 list_subvols btrfs-list.c
 int list_subvols(int fd, int print_parent)
 {
	struct root_lookup root_lookup;
	struct rb_node *n;
 ----------
 Looks like the following patch was checked in partially.
   http://www.mail-archive.com/[email protected]/msg11103.html

Could you pls take a look / comment.