On 2018/02/16 4:04, Omar Sandoval wrote:
> From: Omar Sandoval <osan...@fb.com>
>
> set_default_subvolume() is a trivial ioctl(), but there's no ioctl() for
> get_default_subvolume(), so we need to search the root tree.
>
> Signed-off-by: Omar Sandoval <osan...@fb.com>
> ---
> libbtrfsutil/btrfsutil.h | 41 ++++++++++
> libbtrfsutil/python/btrfsutilpy.h | 2 +
> libbtrfsutil/python/module.c | 14 ++++
> libbtrfsutil/python/subvolume.c | 50 ++++++++++++
> libbtrfsutil/python/tests/test_subvolume.py | 14 ++++
> libbtrfsutil/subvolume.c | 113
> ++++++++++++++++++++++++++++
> 6 files changed, 234 insertions(+)
>
> diff --git a/libbtrfsutil/btrfsutil.h b/libbtrfsutil/btrfsutil.h
> index 8bd2b847..54777f1d 100644
> --- a/libbtrfsutil/btrfsutil.h
> +++ b/libbtrfsutil/btrfsutil.h
> @@ -256,6 +256,8 @@ enum btrfs_util_error
> btrfs_util_get_subvolume_read_only_fd(int fd, bool *ret);
> * @path: Subvolume path.
> * @read_only: New value of read-only flag.
> *
> + * This requires appropriate privilege (CAP_SYS_ADMIN).
> + *
> * Return: %BTRFS_UTIL_OK on success, non-zero error code on failure.
> */
> enum btrfs_util_error btrfs_util_set_subvolume_read_only(const char *path,
> @@ -268,6 +270,45 @@ enum btrfs_util_error
> btrfs_util_set_subvolume_read_only(const char *path,
> enum btrfs_util_error btrfs_util_set_subvolume_read_only_fd(int fd,
> bool read_only);
>
> +/**
> + * btrfs_util_get_default_subvolume() - Get the default subvolume for a
> + * filesystem.
> + * @path: Path on a Btrfs filesystem.
> + * @id_ret: Returned subvolume ID.
> + *
> + * This requires appropriate privilege (CAP_SYS_ADMIN).
> + *
> + * Return: %BTRFS_UTIL_OK on success, non-zero error code on failure.
> + */
> +enum btrfs_util_error btrfs_util_get_default_subvolume(const char *path,
> + uint64_t *id_ret);
> +
> +/**
> + * btrfs_util_get_default_subvolume_fd() - See
> + * btrfs_util_get_default_subvolume().
> + */
> +enum btrfs_util_error btrfs_util_get_default_subvolume_fd(int fd,
> + uint64_t *id_ret);
> +
> +/**
> + * btrfs_util_set_default_subvolume() - Set the default subvolume for a
> + * filesystem.
> + * @path: Path in a Btrfs filesystem. This may be any path in the
> filesystem; it
> + * does not have to refer to a subvolume unless @id is zero.
> + * @id: ID of subvolume to set as the default. If zero is given, the
> subvolume
> + * ID of @path is used.
The line "This requires appropriate privilege (CAP_SYS_ADMIN)." is missing here.
> + *
> + * Return: %BTRFS_UTIL_OK on success, non-zero error code on failure.
> + */
> +enum btrfs_util_error btrfs_util_set_default_subvolume(const char *path,
> + uint64_t id);
> +
> +/**
> + * btrfs_util_set_default_subvolume_fd() - See
> + * btrfs_util_set_default_subvolume().
> + */
> +enum btrfs_util_error btrfs_util_set_default_subvolume_fd(int fd, uint64_t
> id);
> +
> struct btrfs_util_qgroup_inherit;
>
> /**
> diff --git a/libbtrfsutil/python/btrfsutilpy.h
> b/libbtrfsutil/python/btrfsutilpy.h
> index 21253e51..41314d4a 100644
> --- a/libbtrfsutil/python/btrfsutilpy.h
> +++ b/libbtrfsutil/python/btrfsutilpy.h
> @@ -66,6 +66,8 @@ PyObject *subvolume_path(PyObject *self, PyObject *args,
> PyObject *kwds);
> PyObject *subvolume_info(PyObject *self, PyObject *args, PyObject *kwds);
> PyObject *get_subvolume_read_only(PyObject *self, PyObject *args, PyObject
> *kwds);
> PyObject *set_subvolume_read_only(PyObject *self, PyObject *args, PyObject
> *kwds);
> +PyObject *get_default_subvolume(PyObject *self, PyObject *args, PyObject
> *kwds);
> +PyObject *set_default_subvolume(PyObject *self, PyObject *args, PyObject
> *kwds);
> PyObject *create_subvolume(PyObject *self, PyObject *args, PyObject *kwds);
>
> void add_module_constants(PyObject *m);
> diff --git a/libbtrfsutil/python/module.c b/libbtrfsutil/python/module.c
> index 3395fb14..0ac4d63a 100644
> --- a/libbtrfsutil/python/module.c
> +++ b/libbtrfsutil/python/module.c
> @@ -173,6 +173,20 @@ static PyMethodDef btrfsutil_methods[] = {
> "Arguments:\n"
> "path -- string, bytes, path-like object, or open file descriptor\n"
> "read_only -- bool flag value"},
> + {"get_default_subvolume", (PyCFunction)get_default_subvolume,
> + METH_VARARGS | METH_KEYWORDS,
> + "get_default_subvolume(path) -> int\n\n"
> + "Get the ID of the default subvolume of a filesystem.\n\n"
> + "Arguments:\n"
> + "path -- string, bytes, path-like object, or open file descriptor"},
> + {"set_default_subvolume", (PyCFunction)set_default_subvolume,
> + METH_VARARGS | METH_KEYWORDS,
> + "set_default_subvolume(path, id=0)\n\n"
> + "Set the default subvolume of a filesystem.\n\n"
> + "Arguments:\n"
> + "path -- string, bytes, path-like object, or open file descriptor\n"
> + "id -- if not zero, set the default subvolume to the subvolume with\n"
> + "this ID instead of the given path"},
> {"create_subvolume", (PyCFunction)create_subvolume,
> METH_VARARGS | METH_KEYWORDS,
> "create_subvolume(path, async=False)\n\n"
> diff --git a/libbtrfsutil/python/subvolume.c b/libbtrfsutil/python/subvolume.c
> index 76487865..fa3ec4a7 100644
> --- a/libbtrfsutil/python/subvolume.c
> +++ b/libbtrfsutil/python/subvolume.c
> @@ -270,6 +270,56 @@ PyObject *set_subvolume_read_only(PyObject *self,
> PyObject *args, PyObject *kwds
> Py_RETURN_NONE;
> }
>
> +PyObject *get_default_subvolume(PyObject *self, PyObject *args, PyObject
> *kwds)
> +{
> + static char *keywords[] = {"path", NULL};
> + struct path_arg path = {.allow_fd = true};
> + enum btrfs_util_error err;
> + uint64_t id;
> +
> + if (!PyArg_ParseTupleAndKeywords(args, kwds, "O&:get_default_subvolume",
> + keywords, &path_converter, &path))
> + return NULL;
> +
> + if (path.path)
> + err = btrfs_util_get_default_subvolume(path.path, &id);
> + else
> + err = btrfs_util_get_default_subvolume_fd(path.fd, &id);
> + if (err) {
> + SetFromBtrfsUtilErrorWithPath(err, &path);
> + path_cleanup(&path);
> + return NULL;
> + }
> +
> + path_cleanup(&path);
> + return PyLong_FromUnsignedLongLong(id);
> +}
> +
> +PyObject *set_default_subvolume(PyObject *self, PyObject *args, PyObject
> *kwds)
> +{
> + static char *keywords[] = {"path", "id", NULL};
> + struct path_arg path = {.allow_fd = true};
> + enum btrfs_util_error err;
> + uint64_t id = 0;
> +
> + if (!PyArg_ParseTupleAndKeywords(args, kwds,
> "O&|K:set_default_subvolume",
> + keywords, &path_converter, &path, &id))
> + return NULL;
> +
> + if (path.path)
> + err = btrfs_util_set_default_subvolume(path.path, id);
> + else
> + err = btrfs_util_set_default_subvolume_fd(path.fd, id);
> + if (err) {
> + SetFromBtrfsUtilErrorWithPath(err, &path);
> + path_cleanup(&path);
> + return NULL;
> + }
> +
> + path_cleanup(&path);
> + Py_RETURN_NONE;
> +}
> +
> PyObject *create_subvolume(PyObject *self, PyObject *args, PyObject *kwds)
> {
> static char *keywords[] = {"path", "async", "qgroup_inherit", NULL};
> diff --git a/libbtrfsutil/python/tests/test_subvolume.py
> b/libbtrfsutil/python/tests/test_subvolume.py
> index 23871de9..937a4397 100644
> --- a/libbtrfsutil/python/tests/test_subvolume.py
> +++ b/libbtrfsutil/python/tests/test_subvolume.py
> @@ -154,6 +154,20 @@ class TestSubvolume(BtrfsTestCase):
>
> btrfsutil.set_subvolume_read_only(arg, False)
>
> + def test_default_subvolume(self):
> + for arg in self.path_or_fd(self.mountpoint):
> + with self.subTest(type=type(arg)):
> + self.assertEqual(btrfsutil.get_default_subvolume(arg), 5)
> +
> + subvol = os.path.join(self.mountpoint, 'subvol')
> + btrfsutil.create_subvolume(subvol)
> + for arg in self.path_or_fd(subvol):
> + with self.subTest(type=type(arg)):
> + btrfsutil.set_default_subvolume(arg)
> + self.assertEqual(btrfsutil.get_default_subvolume(arg), 256)
> + btrfsutil.set_default_subvolume(arg, 5)
> + self.assertEqual(btrfsutil.get_default_subvolume(arg), 5)
> +
> def test_create_subvolume(self):
> subvol = os.path.join(self.mountpoint, 'subvol')
>
> diff --git a/libbtrfsutil/subvolume.c b/libbtrfsutil/subvolume.c
> index bc5b309e..b3f768ed 100644
> --- a/libbtrfsutil/subvolume.c
> +++ b/libbtrfsutil/subvolume.c
> @@ -467,6 +467,119 @@ PUBLIC enum btrfs_util_error
> btrfs_util_set_subvolume_read_only_fd(int fd,
> return BTRFS_UTIL_OK;
> }
>
> +PUBLIC enum btrfs_util_error btrfs_util_get_default_subvolume(const char
> *path,
> + uint64_t *id_ret)
> +{
> + enum btrfs_util_error err;
> + int fd;
> +
> + fd = open(path, O_RDONLY);
> + if (fd == -1)
> + return BTRFS_UTIL_ERROR_OPEN_FAILED;
> +
> + err = btrfs_util_get_default_subvolume_fd(fd, id_ret);
> + SAVE_ERRNO_AND_CLOSE(fd);
> + return err;
> +}
> +
> +PUBLIC enum btrfs_util_error btrfs_util_get_default_subvolume_fd(int fd,
> + uint64_t
> *id_ret)
> +{
> + struct btrfs_ioctl_search_args search = {
> + .key = {
> + .tree_id = BTRFS_ROOT_TREE_OBJECTID,
> + .min_objectid = BTRFS_ROOT_TREE_DIR_OBJECTID,
> + .max_objectid = BTRFS_ROOT_TREE_DIR_OBJECTID,
> + .min_type = BTRFS_DIR_ITEM_KEY,
> + .max_type = BTRFS_DIR_ITEM_KEY,
> + .min_offset = 0,
> + .max_offset = UINT64_MAX,
> + .min_transid = 0,
> + .max_transid = UINT64_MAX,
> + .nr_items = 0,
> + },
> + };
> + size_t items_pos = 0, buf_off = 0;
> + int ret;
> +
> + for (;;) {
> + const struct btrfs_ioctl_search_header *header;
> +
> + if (items_pos >= search.key.nr_items) {
> + search.key.nr_items = 4096;
> + ret = ioctl(fd, BTRFS_IOC_TREE_SEARCH, &search);
> + if (ret == -1)
> + return BTRFS_UTIL_ERROR_SEARCH_FAILED;
> + items_pos = 0;
> + buf_off = 0;
> +
> + if (search.key.nr_items == 0) {
> + errno = ENOENT;
> + return BTRFS_UTIL_ERROR_SUBVOLUME_NOT_FOUND;
> + }
> + }
> +
> + header = (struct btrfs_ioctl_search_header *)(search.buf +
> buf_off);
> + if (header->type == BTRFS_DIR_ITEM_KEY) {
> + const struct btrfs_dir_item *dir;
> + const char *name;
> + uint16_t name_len;
> +
> + dir = (struct btrfs_dir_item *)(header + 1);
> + name = (const char *)(dir + 1);
> + name_len = le16_to_cpu(dir->name_len);
> + if (strncmp(name, "default", name_len) == 0) {
> + *id_ret = le64_to_cpu(dir->location.objectid);
> + break;
> + }
> + }
> +
> + items_pos++;
> + buf_off += sizeof(*header) + header->len;
> + search.key.min_offset = header->offset + 1;
> + }
> +
> + return BTRFS_UTIL_OK;
> +}
> +
> +PUBLIC enum btrfs_util_error btrfs_util_set_default_subvolume(const char
> *path,
> + uint64_t id)
> +{
> + enum btrfs_util_error err;
> + int fd;
> +
> + fd = open(path, O_RDONLY);
> + if (fd == -1)
> + return BTRFS_UTIL_ERROR_OPEN_FAILED;
> +
> + err = btrfs_util_set_default_subvolume_fd(fd, id);
> + SAVE_ERRNO_AND_CLOSE(fd);
> + return err;
> +}
> +
> +PUBLIC enum btrfs_util_error btrfs_util_set_default_subvolume_fd(int fd,
> + uint64_t id)
> +{
> + enum btrfs_util_error err;
> + int ret;
> +
> + if (id == 0) {
> + err = btrfs_util_is_subvolume_fd(fd);
> + if (err)
> + return err;
> +
> + err = btrfs_util_subvolume_id_fd(fd, &id);
> + if (err)
> + return err;
> + }
> +
> + ret = ioctl(fd, BTRFS_IOC_DEFAULT_SUBVOL, &id);
> + if (ret == -1)
> + return BTRFS_UTIL_ERROR_DEFAULT_SUBVOL_FAILED;
> +
> + return BTRFS_UTIL_OK;
> +}
> +
> static enum btrfs_util_error openat_parent_and_name(int dirfd, const char
> *path,
> char *name, size_t name_len,
> int *fd)
>
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