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libbtrfsutil: add btrfs_util_create_snapshot() 

Thanks to subvolume iterators, we can also implement recursive snapshot
fairly easily.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
master
Omar Sandoval 2018-01-18 14:23:23 -08:00 committed by David Sterba
parent 0b8512b7f5
commit cfa89b3082
7 changed files with 352 additions and 0 deletions
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59
libbtrfsutil/btrfsutil.h
View File

@ -391,6 +391,65 @@ enum btrfs_util_error btrfs_util_create_subvolume_fd(int parent_fd,
uint64_t *async_transid,
struct btrfs_util_qgroup_inherit *qgroup_inherit);
/**
* BTRFS_UTIL_CREATE_SNAPSHOT_RECURSIVE - Also snapshot subvolumes beneath the
* source subvolume onto the same location on the new snapshot.
*
* Note that this is currently implemented in userspace non-atomically. Because
* it modifies the newly-created snapshot, it cannot be combined with
* %BTRFS_UTIL_CREATE_SNAPSHOT_READ_ONLY. It requires appropriate privilege
* (CAP_SYS_ADMIN).
*/
#define BTRFS_UTIL_CREATE_SNAPSHOT_RECURSIVE (1 << 0)
/**
* BTRFS_UTIL_CREATE_SNAPSHOT_READ_ONLY - Create a read-only snapshot.
*/
#define BTRFS_UTIL_CREATE_SNAPSHOT_READ_ONLY (1 << 1)
#define BTRFS_UTIL_CREATE_SNAPSHOT_MASK ((1 << 2) - 1)
/**
* btrfs_util_create_snapshot() - Create a new snapshot from a source subvolume
* path.
* @source: Path of the existing subvolume to snapshot.
* @path: Where to create the snapshot.
* @flags: Bitmask of BTRFS_UTIL_CREATE_SNAPSHOT_* flags.
* @async_transid: See btrfs_util_create_subvolume(). If
* %BTRFS_UTIL_CREATE_SNAPSHOT_RECURSIVE was in @flags, then this will contain
* the largest transaction ID of all created subvolumes.
* @qgroup_inherit: See btrfs_util_create_subvolume().
*
* Return: %BTRFS_UTIL_OK on success, non-zero error code on failure.
*/
enum btrfs_util_error btrfs_util_create_snapshot(const char *source,
const char *path, int flags,
uint64_t *async_transid,
struct btrfs_util_qgroup_inherit *qgroup_inherit);
/**
* btrfs_util_create_snapshot_fd() - See btrfs_util_create_snapshot().
*/
enum btrfs_util_error btrfs_util_create_snapshot_fd(int fd, const char *path,
int flags,
uint64_t *async_transid,
struct btrfs_util_qgroup_inherit *qgroup_inherit);
/**
* btrfs_util_create_snapshot_fd2() - Create a new snapshot from a source
* subvolume file descriptor and a target parent file descriptor and name.
* @fd: File descriptor of the existing subvolume to snapshot.
* @parent_fd: File descriptor of the parent directory where the snapshot should
* be created.
* @name: Name of the snapshot to create.
* @flags: See btrfs_util_create_snapshot().
* @async_transid: See btrfs_util_create_snapshot().
* @qgroup_inherit: See btrfs_util_create_snapshot().
*/
enum btrfs_util_error btrfs_util_create_snapshot_fd2(int fd, int parent_fd,
const char *name,
int flags,
uint64_t *async_transid,
struct btrfs_util_qgroup_inherit *qgroup_inherit);
struct btrfs_util_subvolume_iterator;
/**

1
libbtrfsutil/python/btrfsutilpy.h
View File

@ -73,6 +73,7 @@ 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);
PyObject *create_snapshot(PyObject *self, PyObject *args, PyObject *kwds);
void add_module_constants(PyObject *m);

11
libbtrfsutil/python/module.c
View File

@ -216,6 +216,17 @@ static PyMethodDef btrfsutil_methods[] = {
"path -- string, bytes, or path-like object\n"
"async -- create the subvolume without waiting for it to commit to\n"
"disk and return the transaction ID"},
{"create_snapshot", (PyCFunction)create_snapshot,
METH_VARARGS | METH_KEYWORDS,
"create_snapshot(source, path, recursive=False, read_only=False, async=False)\n\n"
"Create a new snapshot.\n\n"
"Arguments:\n"
"source -- string, bytes, path-like object, or open file descriptor\n"
"path -- string, bytes, or path-like object\n"
"recursive -- also snapshot child subvolumes\n"
"read_only -- create a read-only snapshot\n"
"async -- create the subvolume without waiting for it to commit to\n"
"disk and return the transaction ID"},
{},
};

49
libbtrfsutil/python/subvolume.c
View File

@ -349,6 +349,55 @@ PyObject *create_subvolume(PyObject *self, PyObject *args, PyObject *kwds)
Py_RETURN_NONE;
}
PyObject *create_snapshot(PyObject *self, PyObject *args, PyObject *kwds)
{
static char *keywords[] = {
"source", "path", "recursive", "read_only", "async",
"qgroup_inherit", NULL,
};
struct path_arg src = {.allow_fd = true}, dst = {.allow_fd = false};
enum btrfs_util_error err;
int recursive = 0, read_only = 0, async = 0;
int flags = 0;
QgroupInherit *inherit = NULL;
uint64_t transid;
if (!PyArg_ParseTupleAndKeywords(args, kwds, "O&O&|pppO!:create_snapshot",
keywords, &path_converter, &src,
&path_converter, &dst, &recursive,
&read_only, &async,
&QgroupInherit_type, &inherit))
return NULL;
if (recursive)
flags |= BTRFS_UTIL_CREATE_SNAPSHOT_RECURSIVE;
if (read_only)
flags |= BTRFS_UTIL_CREATE_SNAPSHOT_READ_ONLY;
if (src.path) {
err = btrfs_util_create_snapshot(src.path, dst.path, flags,
async ? &transid : NULL,
inherit ? inherit->inherit : NULL);
} else {
err = btrfs_util_create_snapshot_fd(src.fd, dst.path, flags,
async ? &transid : NULL,
inherit ? inherit->inherit : NULL);
}
if (err) {
SetFromBtrfsUtilErrorWithPaths(err, &src, &dst);
path_cleanup(&src);
path_cleanup(&dst);
return NULL;
}
path_cleanup(&src);
path_cleanup(&dst);
if (async)
return PyLong_FromUnsignedLongLong(transid);
else
Py_RETURN_NONE;
}
typedef struct {
PyObject_HEAD
struct btrfs_util_subvolume_iterator *iter;

10
libbtrfsutil/python/tests/test_qgroup.py
View File

@ -31,6 +31,16 @@ class TestQgroup(BtrfsTestCase):
btrfsutil.create_subvolume(subvol, qgroup_inherit=inherit)
def test_snapshot_inherit(self):
subvol = os.path.join(self.mountpoint, 'subvol')
snapshot = os.path.join(self.mountpoint, 'snapshot')
inherit = btrfsutil.QgroupInherit()
inherit.add_group(5)
btrfsutil.create_subvolume(subvol)
btrfsutil.create_snapshot(subvol, snapshot, qgroup_inherit=inherit)
class TestQgroupInherit(unittest.TestCase):
def test_new(self):

55
libbtrfsutil/python/tests/test_subvolume.py
View File

@ -129,6 +129,13 @@ class TestSubvolume(BtrfsTestCase):
self.assertEqual(info.stime, 0)
self.assertEqual(info.rtime, 0)
subvol_uuid = info.uuid
snapshot = os.path.join(self.mountpoint, 'snapshot')
btrfsutil.create_snapshot(subvol, snapshot)
info = btrfsutil.subvolume_info(snapshot)
self.assertEqual(info.parent_uuid, subvol_uuid)
# TODO: test received_uuid, stransid, rtransid, stime, and rtime
for arg in self.path_or_fd(self.mountpoint):
@ -215,6 +222,54 @@ class TestSubvolume(BtrfsTestCase):
self.assertTrue(os.WIFEXITED(wstatus))
self.assertEqual(os.WEXITSTATUS(wstatus), 0)
def test_create_snapshot(self):
subvol = os.path.join(self.mountpoint, 'subvol')
btrfsutil.create_subvolume(subvol)
os.mkdir(os.path.join(subvol, 'dir'))
for i, arg in enumerate(self.path_or_fd(subvol)):
with self.subTest(type=type(arg)):
snapshots_dir = os.path.join(self.mountpoint, 'snapshots{}'.format(i))
os.mkdir(snapshots_dir)
snapshot = os.path.join(snapshots_dir, 'snapshot')
btrfsutil.create_snapshot(subvol, snapshot + '1')
self.assertTrue(btrfsutil.is_subvolume(snapshot + '1'))
self.assertTrue(os.path.exists(os.path.join(snapshot + '1', 'dir')))
btrfsutil.create_snapshot(subvol, (snapshot + '2').encode())
self.assertTrue(btrfsutil.is_subvolume(snapshot + '2'))
self.assertTrue(os.path.exists(os.path.join(snapshot + '2', 'dir')))
if HAVE_PATH_LIKE:
btrfsutil.create_snapshot(subvol, PurePath(snapshot + '3'))
self.assertTrue(btrfsutil.is_subvolume(snapshot + '3'))
self.assertTrue(os.path.exists(os.path.join(snapshot + '3', 'dir')))
nested_subvol = os.path.join(subvol, 'nested')
more_nested_subvol = os.path.join(nested_subvol, 'more_nested')
btrfsutil.create_subvolume(nested_subvol)
btrfsutil.create_subvolume(more_nested_subvol)
os.mkdir(os.path.join(more_nested_subvol, 'nested_dir'))
snapshot = os.path.join(self.mountpoint, 'snapshot')
btrfsutil.create_snapshot(subvol, snapshot + '1')
# Dummy subvolume.
self.assertEqual(os.stat(os.path.join(snapshot + '1', 'nested')).st_ino, 2)
self.assertFalse(os.path.exists(os.path.join(snapshot + '1', 'nested', 'more_nested')))
btrfsutil.create_snapshot(subvol, snapshot + '2', recursive=True)
self.assertTrue(os.path.exists(os.path.join(snapshot + '2', 'nested/more_nested/nested_dir')))
transid = btrfsutil.create_snapshot(subvol, snapshot + '3', recursive=True, async=True)
self.assertTrue(os.path.exists(os.path.join(snapshot + '3', 'nested/more_nested/nested_dir')))
self.assertGreater(transid, 0)
btrfsutil.create_snapshot(subvol, snapshot + '4', read_only=True)
self.assertTrue(btrfsutil.get_subvolume_read_only(snapshot + '4'))
def test_subvolume_iterator(self):
pwd = os.getcwd()
try:

167
libbtrfsutil/subvolume.c
View File

@ -838,6 +838,173 @@ out_iter:
return err;
}
static enum btrfs_util_error snapshot_subvolume_children(int fd, int parent_fd,
const char *name,
uint64_t *async_transid)
{
struct btrfs_util_subvolume_iterator *iter;
enum btrfs_util_error err;
int dstfd;
dstfd = openat(parent_fd, name, O_RDONLY);
if (dstfd == -1)
return BTRFS_UTIL_ERROR_OPEN_FAILED;
err = btrfs_util_create_subvolume_iterator_fd(fd, 0, 0, &iter);
if (err)
goto out;
for (;;) {
char child_name[BTRFS_SUBVOL_NAME_MAX + 1];
char *child_path;
int child_fd, new_parent_fd;
uint64_t tmp_transid;
err = btrfs_util_subvolume_iterator_next(iter, &child_path,
NULL);
if (err) {
if (err == BTRFS_UTIL_ERROR_STOP_ITERATION)
err = BTRFS_UTIL_OK;
break;
}
/* Remove the placeholder directory. */
if (unlinkat(dstfd, child_path, AT_REMOVEDIR) == -1) {
free(child_path);
err = BTRFS_UTIL_ERROR_RMDIR_FAILED;
break;
}
child_fd = openat(fd, child_path, O_RDONLY);
if (child_fd == -1) {
free(child_path);
err = BTRFS_UTIL_ERROR_OPEN_FAILED;
break;
}
err = openat_parent_and_name(dstfd, child_path, child_name,
sizeof(child_name),
&new_parent_fd);
free(child_path);
if (err) {
SAVE_ERRNO_AND_CLOSE(child_fd);
break;
}
err = btrfs_util_create_snapshot_fd2(child_fd, new_parent_fd,
child_name, 0,
async_transid ? &tmp_transid : NULL,
NULL);
SAVE_ERRNO_AND_CLOSE(child_fd);
SAVE_ERRNO_AND_CLOSE(new_parent_fd);
if (err)
break;
if (async_transid && tmp_transid > *async_transid)
*async_transid = tmp_transid;
}
btrfs_util_destroy_subvolume_iterator(iter);
out:
SAVE_ERRNO_AND_CLOSE(dstfd);
return err;
}
PUBLIC enum btrfs_util_error btrfs_util_create_snapshot(const char *source,
const char *path,
int flags,
uint64_t *async_transid,
struct btrfs_util_qgroup_inherit *qgroup_inherit)
{
enum btrfs_util_error err;
int fd;
fd = open(source, O_RDONLY);
if (fd == -1)
return BTRFS_UTIL_ERROR_OPEN_FAILED;
err = btrfs_util_create_snapshot_fd(fd, path, flags, async_transid,
qgroup_inherit);
SAVE_ERRNO_AND_CLOSE(fd);
return err;
}
PUBLIC enum btrfs_util_error btrfs_util_create_snapshot_fd(int fd,
const char *path,
int flags,
uint64_t *async_transid,
struct btrfs_util_qgroup_inherit *qgroup_inherit)
{
char name[BTRFS_SUBVOL_NAME_MAX + 1];
enum btrfs_util_error err;
int parent_fd;
err = openat_parent_and_name(AT_FDCWD, path, name, sizeof(name),
&parent_fd);
if (err)
return err;
err = btrfs_util_create_snapshot_fd2(fd, parent_fd, name, flags,
async_transid, qgroup_inherit);
SAVE_ERRNO_AND_CLOSE(parent_fd);
return err;
}
PUBLIC enum btrfs_util_error btrfs_util_create_snapshot_fd2(int fd,
int parent_fd,
const char *name,
int flags,
uint64_t *async_transid,
struct btrfs_util_qgroup_inherit *qgroup_inherit)
{
struct btrfs_ioctl_vol_args_v2 args = {.fd = fd};
enum btrfs_util_error err;
size_t len;
int ret;
if ((flags & ~BTRFS_UTIL_CREATE_SNAPSHOT_MASK) ||
((flags & BTRFS_UTIL_CREATE_SNAPSHOT_READ_ONLY) &&
(flags & BTRFS_UTIL_CREATE_SNAPSHOT_RECURSIVE))) {
errno = EINVAL;
return BTRFS_UTIL_ERROR_INVALID_ARGUMENT;
}
if (flags & BTRFS_UTIL_CREATE_SNAPSHOT_READ_ONLY)
args.flags |= BTRFS_SUBVOL_RDONLY;
if (async_transid)
args.flags |= BTRFS_SUBVOL_CREATE_ASYNC;
if (qgroup_inherit) {
args.flags |= BTRFS_SUBVOL_QGROUP_INHERIT;
args.qgroup_inherit = (struct btrfs_qgroup_inherit *)qgroup_inherit;
args.size = (sizeof(*args.qgroup_inherit) +
args.qgroup_inherit->num_qgroups *
sizeof(args.qgroup_inherit->qgroups[0]));
}
len = strlen(name);
if (len >= sizeof(args.name)) {
errno = ENAMETOOLONG;
return BTRFS_UTIL_ERROR_INVALID_ARGUMENT;
}
memcpy(args.name, name, len);
args.name[len] = '\0';
ret = ioctl(parent_fd, BTRFS_IOC_SNAP_CREATE_V2, &args);
if (ret == -1)
return BTRFS_UTIL_ERROR_SUBVOL_CREATE_FAILED;
if (async_transid)
*async_transid = args.transid;
if (flags & BTRFS_UTIL_CREATE_SNAPSHOT_RECURSIVE) {
err = snapshot_subvolume_children(fd, parent_fd, name,
async_transid);
if (err)
return err;
}
return BTRFS_UTIL_OK;
}
PUBLIC void btrfs_util_destroy_subvolume_iterator(struct btrfs_util_subvolume_iterator *iter)
{
if (iter) {