libbtrfsutil: add btrfs_util_[gs]et_default_subvolume()
authorOmar Sandoval <osandov@fb.com>
Thu, 18 Jan 2018 21:51:16 +0000 (13:51 -0800)
committerDavid Sterba <dsterba@suse.com>
Tue, 6 Mar 2018 10:28:36 +0000 (11:28 +0100)
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>
libbtrfsutil/btrfsutil.h
libbtrfsutil/python/btrfsutilpy.h
libbtrfsutil/python/module.c
libbtrfsutil/python/subvolume.c
libbtrfsutil/python/tests/test_subvolume.py
libbtrfsutil/subvolume.c

index ab96f44..76ab06b 100644 (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;
 
 /**
index aa17080..a56e41f 100644 (file)
@@ -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);
index 3173ff7..91c4b9b 100644 (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"
index 7648786..fa3ec4a 100644 (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};
index 23871de..937a439 100644 (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')
 
index a8b8a76..965376e 100644 (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)