Since Ceph version Infernalis (9.2.0) the new fast-diff mechanism
of RBD allows for querying actual rbd image usage.
Prior to this version there was no easy and fast way to query how
much allocation a RBD image had inside a Ceph cluster.
To use the fast-diff feature it needs to be enabled per RBD image
and is only supported by Ceph cluster running version Infernalis
(9.2.0) or newer.
Without the fast-diff feature enabled qemu-img will report an allocation
identical to the image capacity.
'qemu-img info rbd:cepharm/liyi-rbd' might output for example:
image: json:{"driver": "raw", "file": {"pool": "cepharm",
"image": "liyi-rbd", "driver": "rbd"}}
file format: raw
virtual size: 20 GiB (21474836480 bytes)
disk size: 0 B
cluster_size: 4194304
Newly created rbds will have the fast-diff feature enabled.
Signed-off-by: Yi Li <y...@winhong.com>
---
block/rbd.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 60 insertions(+)
diff --git a/block/rbd.c b/block/rbd.c
index 617553b022..f231653f7b 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -1107,6 +1107,65 @@ static int64_t qemu_rbd_getlength(BlockDriverState *bs)
return info.size;
}
+#if LIBRBD_VERSION_CODE > 265
+static int disk_usage_callback(uint64_t offset, size_t len, int exists,
+ void *arg)
+{
+ uint64_t *used_size = (uint64_t *)(arg);
+ if (exists) {
+ (*used_size) += len;
+ }
+ return 0;
+}
+#endif
+
+static int64_t qemu_rbd_allocated_file_size(BlockDriverState *bs)
+{
+ BDRVRBDState *s = bs->opaque;
+ rbd_image_info_t info;
+ int r;
+ uint64_t used_size = 0;
+ uint64_t features = 0;
+
+ r = rbd_stat(s->image, &info, sizeof(info));
+ if (r < 0) {
+ return r;
+ }
+
+ r = rbd_get_features(s->image, &features);
+ if (r < 0) {
+ return r;
+ }
+
+ /*
+ * rbd_diff_iterate2() is available in versions above Ceph 0.94 (Hammer)
+ * It uses a object map inside Ceph which is faster than rbd_diff_iterate()
+ * which iterates all objects.
+ * LIBRBD_VERSION_CODE for Ceph 0.94 is 265. In 266 and upwards
diff_iterate2
+ * is available
+ */
+#if LIBRBD_VERSION_CODE > 265
+ if (features & RBD_FEATURE_FAST_DIFF) {
+
+ /*
+ * RBD image fast-diff feature enabled
+ * Querying for actual allocation.
+ */
+ r = rbd_diff_iterate2(s->image, NULL, 0, info.size, 0, 1,
+ &disk_usage_callback,
+ &used_size);
+ if (r < 0) {
+ return r;
+ }
+ } else {
+ used_size = info.size;
+ }
+#else
+ used_size = info.size;
+#endif
+ return used_size;
+}
+
static int coroutine_fn qemu_rbd_co_truncate(BlockDriverState *bs,
int64_t offset,
bool exact,
@@ -1316,6 +1375,7 @@ static BlockDriver bdrv_rbd = {
.bdrv_get_info = qemu_rbd_getinfo,
.create_opts = &qemu_rbd_create_opts,
.bdrv_getlength = qemu_rbd_getlength,
+ .bdrv_get_allocated_file_size = qemu_rbd_allocated_file_size,
.bdrv_co_truncate = qemu_rbd_co_truncate,
.protocol_name = "rbd",
--
2.25.3
