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libbtrfsutil: add btrfs_util_[gs]et_default_subvolume() 

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 <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Omar Sandoval 2018-01-18 13:51:16 -08:00 committed by David Sterba
parent 172c0d1a12
commit 624e0233e0
6 changed files with 236 additions and 0 deletions
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43
libbtrfsutil/btrfsutil.h
View File

@ -300,6 +300,8 @@ 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,
@ -312,6 +314,47 @@ 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.
*
* 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_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;
/**

2
libbtrfsutil/python/btrfsutilpy.h
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@ -69,6 +69,8 @@ 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);

14
libbtrfsutil/python/module.c
View File

@ -194,6 +194,20 @@ 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"

50
libbtrfsutil/python/subvolume.c
View File

@ -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};

14
libbtrfsutil/python/tests/test_subvolume.py
View File

@ -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')

113
libbtrfsutil/subvolume.c
View File

@ -465,6 +465,119 @@ 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)