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rbd: Use RBD fast-diff for querying actual volume allocation

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Since Ceph version Infernalis (9.2.0) the new fast-diff mechanism
of RBD allows for querying actual volume usage.

Prior to this version there was no easy and fast way to query how
much allocation a RBD volume 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 libvirt will report an allocation
identical to the image capacity. This is how libvirt behaves currently.

'virsh vol-info rbd/image2' might output for example:

  Name:           image2
  Type:           network
  Capacity:       1,00 GiB
  Allocation:     124,00 MiB

Newly created volumes will have the fast-diff feature enabled if the
backing Ceph cluster supports it.

Signed-off-by: Wido den Hollander <wido@widodh.nl>
This commit is contained in:
Wido den Hollander 2016-02-11 17:04:17 +01:00 committed by John Ferlan
parent ab342e99f6
commit 98782f8899
1 changed files with 81 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

85
src/storage/storage_backend_rbd.c
View File

@ -297,6 +297,68 @@ volStorageBackendRBDGetFeatures(rbd_image_t image,
return ret;
}
#if LIBRBD_VERSION_CODE > 265
static bool
volStorageBackendRBDUseFastDiff(uint64_t features)
{
return features & RBD_FEATURE_FAST_DIFF;
}
static int
virStorageBackendRBDRefreshVolInfoCb(uint64_t offset ATTRIBUTE_UNUSED,
size_t len,
int exists,
void *arg)
{
uint64_t *used_size = (uint64_t *)(arg);
if (exists)
(*used_size) += len;
return 0;
}
static int
virStorageBackendRBDSetAllocation(virStorageVolDefPtr vol,
rbd_image_t *image,
rbd_image_info_t *info)
{
int r, ret = -1;
uint64_t allocation = 0;
if ((r = rbd_diff_iterate2(image, NULL, 0, info->size, 0, 1,
&virStorageBackendRBDRefreshVolInfoCb,
&allocation)) < 0) {
virReportSystemError(-r, _("failed to iterate RBD image '%s'"),
vol->name);
goto cleanup;
}
VIR_DEBUG("Found %zu bytes allocated for RBD image %s",
allocation, vol->name);
vol->target.allocation = allocation;
ret = 0;
cleanup:
return ret;
}
#else
static int
volStorageBackendRBDUseFastDiff(uint64_t features ATTRIBUTE_UNUSED)
{
return false;
}
static int
virStorageBackendRBDSetAllocation(virStorageVolDefPtr vol ATTRIBUTE_UNUSED,
rbd_image_t *image ATTRIBUTE_UNUSED,
rbd_image_info_t *info ATTRIBUTE_UNUSED)
{
return false;
}
#endif
static int
volStorageBackendRBDRefreshVolInfo(virStorageVolDefPtr vol,
virStoragePoolObjPtr pool,
@ -306,6 +368,7 @@ volStorageBackendRBDRefreshVolInfo(virStorageVolDefPtr vol,
int r = 0;
rbd_image_t image = NULL;
rbd_image_info_t info;
uint64_t features;
if ((r = rbd_open_read_only(ptr->ioctx, vol->name, &image, NULL)) < 0) {
ret = -r;
@ -321,15 +384,29 @@ volStorageBackendRBDRefreshVolInfo(virStorageVolDefPtr vol,
goto cleanup;
}
VIR_DEBUG("Refreshed RBD image %s/%s (size: %zu obj_size: %zu num_objs: %zu)",
pool->def->source.name, vol->name, info.size, info.obj_size,
info.num_objs);
if (volStorageBackendRBDGetFeatures(image, vol->name, &features) < 0)
goto cleanup;
vol->target.capacity = info.size;
vol->target.allocation = info.obj_size * info.num_objs;
vol->type = VIR_STORAGE_VOL_NETWORK;
vol->target.format = VIR_STORAGE_FILE_RAW;
if (volStorageBackendRBDUseFastDiff(features)) {
VIR_DEBUG("RBD image %s/%s has fast-diff feature enabled. "
"Querying for actual allocation",
pool->def->source.name, vol->name);
if (virStorageBackendRBDSetAllocation(vol, image, &info) < 0)
goto cleanup;
} else {
vol->target.allocation = info.obj_size * info.num_objs;
}
VIR_DEBUG("Refreshed RBD image %s/%s (capacity: %llu allocation: %llu "
"obj_size: %zu num_objs: %zu)",
pool->def->source.name, vol->name, vol->target.capacity,
vol->target.allocation, info.obj_size, info.num_objs);
VIR_FREE(vol->target.path);
if (virAsprintf(&vol->target.path, "%s/%s",
pool->def->source.name,