qemu: capabilities: Introduce QEMU_CAPS_QCOW2_DISCARD_NO_UNREF

The qcow2 driver allows passing discards to the storage while keeping
the reference of the block, and just marking it as zeroed. This can
decrease the levels of fragmentation of the qcow2 metadata when
discards are enabled.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index 055248680557117a27f5786f0d32cbbc524bbd24..7dad7231eef97a5482fc8fb6bf59209cc16d6c6c 100644 (file)
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -693,6 +693,7 @@ VIR_ENUM_IMPL(virQEMUCaps,
               "virtio-gpu.blob", /* QEMU_CAPS_VIRTIO_GPU_BLOB */
               "rbd-encryption-layering", /* QEMU_CAPS_RBD_ENCRYPTION_LAYERING */
               "rbd-encryption-luks-any", /* QEMU_CAPS_RBD_ENCRYPTION_LUKS_ANY */
+              "qcow2-discard-no-unref", /* QEMU_CAPS_QCOW2_DISCARD_NO_UNREF */
     );
 
 
@@ -1536,6 +1537,7 @@ static struct virQEMUCapsStringFlags virQEMUCapsQMPSchemaQueries[] = {
     { "blockdev-add/arg-type/+rbd/encrypt/parent", QEMU_CAPS_RBD_ENCRYPTION_LAYERING },
     { "blockdev-add/arg-type/+rbd/encrypt/format/^luks-any", QEMU_CAPS_RBD_ENCRYPTION_LUKS_ANY },
     { "blockdev-add/arg-type/+nbd/tls-hostname", QEMU_CAPS_BLOCKDEV_NBD_TLS_HOSTNAME },
+    { "blockdev-add/arg-type/+qcow2/discard-no-unref", QEMU_CAPS_QCOW2_DISCARD_NO_UNREF },
     { "blockdev-snapshot/$allow-write-only-overlay", QEMU_CAPS_BLOCKDEV_SNAPSHOT_ALLOW_WRITE_ONLY },
     { "chardev-add/arg-type/backend/+socket/data/reconnect", QEMU_CAPS_CHARDEV_RECONNECT },
     { "device_add/$json-cli-hotplug", QEMU_CAPS_DEVICE_JSON },

diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
index 3b55aed07a1fa181fa151b1166cdfecfcee3f168..ce545cb2ccbf2ffde54c5d1251760fe4682acb9d 100644 (file)
--- a/src/qemu/qemu_capabilities.h
+++ b/src/qemu/qemu_capabilities.h
@@ -672,6 +672,7 @@ typedef enum { /* virQEMUCapsFlags grouping marker for syntax-check */
     QEMU_CAPS_VIRTIO_GPU_BLOB, /* -device virtio-gpu-*.blob= */
     QEMU_CAPS_RBD_ENCRYPTION_LAYERING, /* layered encryption support for Ceph RBD */
     QEMU_CAPS_RBD_ENCRYPTION_LUKS_ANY, /* luks-any (LUKS and LUKS2) encryption format for Ceph RBD */
+    QEMU_CAPS_QCOW2_DISCARD_NO_UNREF, /* qcow2 block driver allows discards without unrefing the sector */
 
     QEMU_CAPS_LAST /* this must always be the last item */
 } virQEMUCapsFlags;

diff --git a/tests/qemucapabilitiesdata/caps_8.1.0_x86_64.xml b/tests/qemucapabilitiesdata/caps_8.1.0_x86_64.xml
index 50ed122fa43365b2250a332e7fd29bafdd1074a4..58bb206f793bf9de59dbc466bb894fc7e4dc49e3 100644 (file)
--- a/tests/qemucapabilitiesdata/caps_8.1.0_x86_64.xml
+++ b/tests/qemucapabilitiesdata/caps_8.1.0_x86_64.xml
@@ -206,6 +206,7 @@
   <flag name='virtio-gpu.blob'/>
   <flag name='rbd-encryption-layering'/>
   <flag name='rbd-encryption-luks-any'/>
+  <flag name='qcow2-discard-no-unref'/>
   <version>8000050</version>
   <microcodeVersion>43100245</microcodeVersion>
   <package>v8.0.0-1619-g369081c455</package>