librbd: add snap_get_name and snap_get_id method API

Signed-off-by: Zheng Yin <zhengyin@cmss.chinamobile.com>

src/include/rbd/librbd.h

@@ -733,6 +733,8 @@ CEPH_RBD_API int rbd_snap_get_timestamp(rbd_image_t image, uint64_t snap_id, str
 
 CEPH_RBD_API int rbd_snap_set(rbd_image_t image, const char *snapname);
 CEPH_RBD_API int rbd_snap_set_by_id(rbd_image_t image, uint64_t snap_id);
+CEPH_RBD_API int rbd_snap_get_name(rbd_image_t image, uint64_t snap_id, char *snapname, size_t *name_len);
+CEPH_RBD_API int rbd_snap_get_id(rbd_image_t image, const char *snapname, uint64_t *snap_id);
 
 CEPH_RBD_API int rbd_snap_get_namespace_type(rbd_image_t image,
                                              uint64_t snap_id,

src/include/rbd/librbd.hpp

@@ -523,6 +523,8 @@ public:
   int snap_is_protected(const char *snap_name, bool *is_protected);
   int snap_set(const char *snap_name);
   int snap_set_by_id(uint64_t snap_id);
+  int snap_get_name(uint64_t snap_id, std::string *snap_name);
+  int snap_get_id(const std::string snap_name, uint64_t *snap_id);
   int snap_rename(const char *srcname, const char *dstname);
   int snap_get_limit(uint64_t *limit);
   int snap_set_limit(uint64_t limit);

src/librbd/api/Snapshot.cc

@@ -190,6 +190,38 @@ int Snapshot<I>::remove(I *ictx, uint64_t snap_id) {
   return r;
 }
 
+template <typename I>
+int Snapshot<I>::get_name(I *ictx, uint64_t snap_id, std::string *snap_name)
+  {
+    ldout(ictx->cct, 20) << "snap_get_name " << ictx << " " << snap_id << dendl;
+
+    int r = ictx->state->refresh_if_required();
+    if (r < 0)
+      return r;
+
+    std::shared_lock image_locker{ictx->image_lock};
+    r = ictx->get_snap_name(snap_id, snap_name);
+
+    return r;
+  }
+
+template <typename I>
+int Snapshot<I>::get_id(I *ictx, const std::string& snap_name, uint64_t *snap_id)
+  {
+    ldout(ictx->cct, 20) << "snap_get_id " << ictx << " " << snap_name << dendl;
+
+    int r = ictx->state->refresh_if_required();
+    if (r < 0)
+      return r;
+
+    std::shared_lock image_locker{ictx->image_lock};
+    *snap_id = ictx->get_snap_id(cls::rbd::UserSnapshotNamespace(), snap_name);
+    if (*snap_id == CEPH_NOSNAP)
+      return -ENOENT;
+
+    return 0;
+  }
+
 } // namespace api
 } // namespace librbd
 

src/librbd/api/Snapshot.h

@@ -27,6 +27,10 @@ struct Snapshot {
 
   static int remove(ImageCtxT *ictx, uint64_t snap_id);
 
+  static int get_name(ImageCtxT *ictx, uint64_t snap_id, std::string *snap_name);
+
+  static int get_id(ImageCtxT *ictx, const std::string& snap_name, uint64_t *snap_id);
+
 };
 
 } // namespace api

src/librbd/librbd.cc

@@ -2135,6 +2135,18 @@ namespace librbd {
     return librbd::api::Image<>::snap_set(ictx, snap_id);
   }
 
+  int Image::snap_get_name(uint64_t snap_id, std::string *snap_name)
+  {
+    ImageCtx *ictx = (ImageCtx *)ctx;
+    return librbd::api::Snapshot<>::get_name(ictx, snap_id, snap_name);
+  }
+
+  int Image::snap_get_id(const std::string snap_name, uint64_t *snap_id)
+  {
+    ImageCtx *ictx = (ImageCtx *)ctx;
+    return librbd::api::Snapshot<>::get_id(ictx, snap_name, snap_id);
+  }
+
   ssize_t Image::read(uint64_t ofs, size_t len, bufferlist& bl)
   {
     ImageCtx *ictx = (ImageCtx *)ctx;
@@ -4818,6 +4830,28 @@ extern "C" int rbd_snap_set_by_id(rbd_image_t image, uint64_t snap_id)
   return librbd::api::Image<>::snap_set(ictx, snap_id);
 }
 
+extern "C" int rbd_snap_get_name(rbd_image_t image, uint64_t snap_id, char *snapname, size_t *name_len)
+{
+  librbd::ImageCtx *ictx = (librbd::ImageCtx *)image;
+  std::string snap_name;
+  int r = librbd::api::Snapshot<>::get_name(ictx, snap_id, &snap_name);
+  size_t expected_size = snap_name.size();
+  if (*name_len <= expected_size) {
+    *name_len = expected_size + 1;
+    return  -ERANGE;
+  }
+  strncpy(snapname, snap_name.c_str(), expected_size);
+  snapname[expected_size] = '\0';
+  *name_len = expected_size + 1;
+  return r;
+}
+
+extern "C" int rbd_snap_get_id(rbd_image_t image, const char *snapname, uint64_t *snap_id)
+{
+  librbd::ImageCtx *ictx = (librbd::ImageCtx *)image;
+  return librbd::api::Snapshot<>::get_id(ictx, snapname, snap_id);
+}
+
 extern "C" ssize_t rbd_list_children(rbd_image_t image, char *pools,
 				     size_t *pools_len, char *images,
 				     size_t *images_len)

src/pybind/rbd/rbd.pyx

@@ -475,6 +475,10 @@ cdef extern from "rbd/librbd.h" nogil:
     int rbd_snap_get_timestamp(rbd_image_t image, uint64_t snap_id, timespec *timestamp)
     int rbd_snap_set(rbd_image_t image, const char *snapname)
     int rbd_snap_set_by_id(rbd_image_t image, uint64_t snap_id)
+    int rbd_snap_get_name(rbd_image_t image, uint64_t snap_id,
+                          char *snapname, size_t *name_len)
+    int rbd_snap_get_id(rbd_image_t image, const char *snapname,
+                                uint64_t *snap_id)
     int rbd_snap_get_namespace_type(rbd_image_t image,
                                     uint64_t snap_id,
                                     rbd_snap_namespace_type_t *namespace_type)
@@ -3749,6 +3753,52 @@ cdef class Image(object):
         if ret != 0:
             raise make_ex(ret, 'error setting image %s to snapshot %d' % (self.name, snap_id))
 
+    def snap_get_name(self, snap_id):
+        """
+        Get snapshot name by id.
+
+        :param snap_id: the snapshot id
+        :type snap_id: int
+        :returns: str - snapshot name
+        :raises: :class:`ImageNotFound`
+        """
+        cdef:
+            int ret = -errno.ERANGE
+            int64_t _snap_id = snap_id
+            size_t size = 512
+            char *image_name = NULL
+        try:
+            while ret == -errno.ERANGE:
+                image_name =  <char *>realloc_chk(image_name, size)
+                with nogil:
+                    ret = rbd_snap_get_name(self.image, _snap_id, image_name, &size)
+
+            if ret != 0:
+                raise make_ex(ret, 'error snap_get_name.')
+            return decode_cstr(image_name)
+        finally:
+            free(image_name)
+
+    def snap_get_id(self, snap_name):
+        """
+        Get snapshot id by name.
+
+        :param snap_name: the snapshot name
+        :type snap_name: str
+        :returns: int - snapshot id
+        :raises: :class:`ImageNotFound`
+        """
+
+        snap_name = cstr(snap_name, 'snap_name')
+        cdef:
+            const char *_snap_name = snap_name
+            uint64_t snap_id
+        with nogil:
+            ret = rbd_snap_get_id(self.image, _snap_name, &snap_id)
+        if ret != 0:
+            raise make_ex(ret, 'error snap_get_id.')
+        return snap_id
+
     def read(self, offset, length, fadvise_flags=0):
         """
         Read data from the image. Raises :class:`InvalidArgument` if