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authorOmar Sandoval <osandov@fb.com>2018-02-14 22:16:33 -0800
committerDavid Sterba <dsterba@suse.com>2018-03-06 11:28:36 +0100
commit8b87811f945bec2a0681334030ed51af1e4828f6 (patch)
tree217417d7eeddb7eb5704908ae8991c4b5158187d /libbtrfsutil
parentf676a8ad118ecba7fbf4edc77b91f788c6fa7e7c (diff)
libbtrfsutil: add btrfs_util_subvolume_path()
We can just walk up root backrefs with BTRFS_IOC_TREE_SEARCH and inode paths with BTRFS_IOC_INO_LOOKUP. Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'libbtrfsutil')
-rw-r--r--libbtrfsutil/btrfsutil.h21
-rw-r--r--libbtrfsutil/python/btrfsutilpy.h1
-rw-r--r--libbtrfsutil/python/module.c8
-rw-r--r--libbtrfsutil/python/subvolume.c30
-rw-r--r--libbtrfsutil/python/tests/test_subvolume.py31
-rw-r--r--libbtrfsutil/subvolume.c125
6 files changed, 216 insertions, 0 deletions
diff --git a/libbtrfsutil/btrfsutil.h b/libbtrfsutil/btrfsutil.h
index 654dd99..1cedc8d 100644
--- a/libbtrfsutil/btrfsutil.h
+++ b/libbtrfsutil/btrfsutil.h
@@ -147,6 +147,27 @@ enum btrfs_util_error btrfs_util_subvolume_id(const char *path,
*/
enum btrfs_util_error btrfs_util_subvolume_id_fd(int fd, uint64_t *id_ret);
+/**
+ * btrfs_util_subvolume_path() - Get the path of the subvolume with a given ID
+ * relative to the filesystem root.
+ * @path: Path on a Btrfs filesystem.
+ * @id: ID of subvolume to set as the default. If zero is given, the subvolume
+ * ID of @path is used.
+ * @path_ret: Returned path.
+ *
+ * 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_subvolume_path(const char *path, uint64_t id,
+ char **path_ret);
+
+/**
+ * btrfs_util_subvolume_path_fd() - See btrfs_util_subvolume_path().
+ */
+enum btrfs_util_error btrfs_util_subvolume_path_fd(int fd, uint64_t id,
+ char **path_ret);
+
struct btrfs_util_qgroup_inherit;
/**
diff --git a/libbtrfsutil/python/btrfsutilpy.h b/libbtrfsutil/python/btrfsutilpy.h
index 19ba71f..1fd475b 100644
--- a/libbtrfsutil/python/btrfsutilpy.h
+++ b/libbtrfsutil/python/btrfsutilpy.h
@@ -63,6 +63,7 @@ PyObject *start_sync(PyObject *self, PyObject *args, PyObject *kwds);
PyObject *wait_sync(PyObject *self, PyObject *args, PyObject *kwds);
PyObject *is_subvolume(PyObject *self, PyObject *args, PyObject *kwds);
PyObject *subvolume_id(PyObject *self, PyObject *args, PyObject *kwds);
+PyObject *subvolume_path(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 deb2687..455e909 100644
--- a/libbtrfsutil/python/module.c
+++ b/libbtrfsutil/python/module.c
@@ -165,6 +165,14 @@ static PyMethodDef btrfsutil_methods[] = {
"Get the ID of the subvolume containing a file.\n\n"
"Arguments:\n"
"path -- string, bytes, path-like object, or open file descriptor"},
+ {"subvolume_path", (PyCFunction)subvolume_path,
+ METH_VARARGS | METH_KEYWORDS,
+ "subvolume_path(path, id=0) -> int\n\n"
+ "Get the path of a subvolume relative to the filesystem root.\n\n"
+ "Arguments:\n"
+ "path -- string, bytes, path-like object, or open file descriptor\n"
+ "id -- if not zero, instead of returning the subvolume path of the\n"
+ "given path, return the path of the subvolume with this ID"},
{"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 6f2080e..6382d29 100644
--- a/libbtrfsutil/python/subvolume.c
+++ b/libbtrfsutil/python/subvolume.c
@@ -72,6 +72,36 @@ PyObject *subvolume_id(PyObject *self, PyObject *args, PyObject *kwds)
return PyLong_FromUnsignedLongLong(id);
}
+PyObject *subvolume_path(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;
+ char *subvol_path;
+ PyObject *ret;
+
+ if (!PyArg_ParseTupleAndKeywords(args, kwds, "O&|K:subvolume_path",
+ keywords, &path_converter, &path, &id))
+ return NULL;
+
+ if (path.path)
+ err = btrfs_util_subvolume_path(path.path, id, &subvol_path);
+ else
+ err = btrfs_util_subvolume_path_fd(path.fd, id, &subvol_path);
+ if (err) {
+ SetFromBtrfsUtilErrorWithPath(err, &path);
+ path_cleanup(&path);
+ return NULL;
+ }
+
+ path_cleanup(&path);
+
+ ret = PyUnicode_DecodeFSDefault(subvol_path);
+ free(subvol_path);
+ return ret;
+}
+
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 f6c5958..57ba27b 100644
--- a/libbtrfsutil/python/tests/test_subvolume.py
+++ b/libbtrfsutil/python/tests/test_subvolume.py
@@ -56,6 +56,37 @@ class TestSubvolume(BtrfsTestCase):
with self.subTest(type=type(arg)):
self.assertEqual(btrfsutil.subvolume_id(arg), 5)
+ def test_subvolume_path(self):
+ btrfsutil.create_subvolume(os.path.join(self.mountpoint, 'subvol1'))
+ os.mkdir(os.path.join(self.mountpoint, 'dir1'))
+ os.mkdir(os.path.join(self.mountpoint, 'dir1/dir2'))
+ btrfsutil.create_subvolume(os.path.join(self.mountpoint, 'dir1/dir2/subvol2'))
+ btrfsutil.create_subvolume(os.path.join(self.mountpoint, 'dir1/dir2/subvol2/subvol3'))
+ os.mkdir(os.path.join(self.mountpoint, 'subvol1/dir3'))
+ btrfsutil.create_subvolume(os.path.join(self.mountpoint, 'subvol1/dir3/subvol4'))
+
+ for arg in self.path_or_fd(self.mountpoint):
+ with self.subTest(type=type(arg)):
+ self.assertEqual(btrfsutil.subvolume_path(arg), '')
+ self.assertEqual(btrfsutil.subvolume_path(arg, 5), '')
+ self.assertEqual(btrfsutil.subvolume_path(arg, 256), 'subvol1')
+ self.assertEqual(btrfsutil.subvolume_path(arg, 257), 'dir1/dir2/subvol2')
+ self.assertEqual(btrfsutil.subvolume_path(arg, 258), 'dir1/dir2/subvol2/subvol3')
+ self.assertEqual(btrfsutil.subvolume_path(arg, 259), 'subvol1/dir3/subvol4')
+
+ pwd = os.getcwd()
+ try:
+ os.chdir(self.mountpoint)
+ path = ''
+ for i in range(26):
+ name = chr(ord('a') + i) * 255
+ path = os.path.join(path, name)
+ btrfsutil.create_subvolume(name)
+ os.chdir(name)
+ self.assertEqual(btrfsutil.subvolume_path('.'), path)
+ finally:
+ os.chdir(pwd)
+
def test_create_subvolume(self):
subvol = os.path.join(self.mountpoint, 'subvol')
diff --git a/libbtrfsutil/subvolume.c b/libbtrfsutil/subvolume.c
index 6ac372c..86d1519 100644
--- a/libbtrfsutil/subvolume.c
+++ b/libbtrfsutil/subvolume.c
@@ -126,6 +126,131 @@ PUBLIC enum btrfs_util_error btrfs_util_subvolume_id_fd(int fd,
return BTRFS_UTIL_OK;
}
+PUBLIC enum btrfs_util_error btrfs_util_subvolume_path(const char *path,
+ uint64_t id,
+ char **path_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_subvolume_path_fd(fd, id, path_ret);
+ SAVE_ERRNO_AND_CLOSE(fd);
+ return err;
+}
+
+PUBLIC enum btrfs_util_error btrfs_util_subvolume_path_fd(int fd, uint64_t id,
+ char **path_ret)
+{
+ char *path, *p;
+ size_t capacity = 4096;
+
+ if (id == 0) {
+ enum btrfs_util_error err;
+
+ err = btrfs_util_is_subvolume_fd(fd);
+ if (err)
+ return err;
+
+ err = btrfs_util_subvolume_id_fd(fd, &id);
+ if (err)
+ return err;
+ }
+
+ path = malloc(capacity);
+ if (!path)
+ return BTRFS_UTIL_ERROR_NO_MEMORY;
+ p = path + capacity - 1;
+ p[0] = '\0';
+
+ while (id != BTRFS_FS_TREE_OBJECTID) {
+ struct btrfs_ioctl_search_args search = {
+ .key = {
+ .tree_id = BTRFS_ROOT_TREE_OBJECTID,
+ .min_objectid = id,
+ .max_objectid = id,
+ .min_type = BTRFS_ROOT_BACKREF_KEY,
+ .max_type = BTRFS_ROOT_BACKREF_KEY,
+ .min_offset = 0,
+ .max_offset = UINT64_MAX,
+ .min_transid = 0,
+ .max_transid = UINT64_MAX,
+ .nr_items = 1,
+ },
+ };
+ struct btrfs_ioctl_ino_lookup_args lookup;
+ const struct btrfs_ioctl_search_header *header;
+ const struct btrfs_root_ref *ref;
+ const char *name;
+ uint16_t name_len;
+ size_t lookup_len;
+ size_t total_len;
+ int ret;
+
+ ret = ioctl(fd, BTRFS_IOC_TREE_SEARCH, &search);
+ if (ret == -1) {
+ free(path);
+ return BTRFS_UTIL_ERROR_SEARCH_FAILED;
+ }
+
+ if (search.key.nr_items == 0) {
+ free(path);
+ errno = ENOENT;
+ return BTRFS_UTIL_ERROR_SUBVOLUME_NOT_FOUND;
+ }
+
+ header = (struct btrfs_ioctl_search_header *)search.buf;
+ ref = (struct btrfs_root_ref *)(header + 1);
+ name = (char *)(ref + 1);
+ name_len = le16_to_cpu(ref->name_len);
+
+ id = header->offset;
+
+ lookup.treeid = id;
+ lookup.objectid = le64_to_cpu(ref->dirid);
+ ret = ioctl(fd, BTRFS_IOC_INO_LOOKUP, &lookup);
+ if (ret == -1) {
+ free(path);
+ return BTRFS_UTIL_ERROR_SEARCH_FAILED;
+ }
+ lookup_len = strlen(lookup.name);
+
+ total_len = name_len + lookup_len + (id != BTRFS_FS_TREE_OBJECTID);
+ if (p - total_len < path) {
+ char *new_path, *new_p;
+ size_t new_capacity = capacity * 2;
+
+ new_path = malloc(new_capacity);
+ if (!new_path) {
+ free(path);
+ return BTRFS_UTIL_ERROR_NO_MEMORY;
+ }
+ new_p = new_path + new_capacity - (path + capacity - p);
+ memcpy(new_p, p, path + capacity - p);
+ free(path);
+ path = new_path;
+ p = new_p;
+ capacity = new_capacity;
+ }
+ p -= name_len;
+ memcpy(p, name, name_len);
+ p -= lookup_len;
+ memcpy(p, lookup.name, lookup_len);
+ if (id != BTRFS_FS_TREE_OBJECTID)
+ *--p = '/';
+ }
+
+ if (p != path)
+ memmove(path, p, path + capacity - p);
+
+ *path_ret = path;
+
+ 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)