[PATCH v2 3/4] qemu: support metadata-cache-size for blockdev

[Nikolay Shirokovskiy <nshirokovskiy@xxxxxxxxxxxxx>]

Just set l2-cache-size to INT64_MAX for all format nodes of
qcow2 type in block node graph.

-drive configuration is not supported because we can not
set l2 cache size down the backing chain in this case.

Note that imlementation sets l2-cache-size and not cache-size.
Unfortunately at time of this patch setting cache-size to INT64_MAX
fails and as guest performance depends only on l2 cache size
and not refcount cache size (which is documented in recent qemu)
we can set l2 directly.

Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@xxxxxxxxxxxxx>
---
 src/qemu/qemu_block.c     |  5 ++++-
 src/qemu/qemu_command.c   | 23 +++++++++++++++++++++++
 src/qemu/qemu_domain.c    |  2 ++
 src/util/virstoragefile.c |  1 +
 src/util/virstoragefile.h |  1 +
 5 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/src/qemu/qemu_block.c b/src/qemu/qemu_block.c
index 5321dda..8771cc1 100644
--- a/src/qemu/qemu_block.c
+++ b/src/qemu/qemu_block.c
@@ -1322,7 +1322,6 @@ qemuBlockStorageSourceGetFormatQcow2Props(virStorageSourcePtr src,
      * 'pass-discard-snapshot'
      * 'pass-discard-other'
      * 'overlap-check'
-     * 'l2-cache-size'
      * 'l2-cache-entry-size'
      * 'refcount-cache-size'
      * 'cache-clean-interval'
@@ -1331,6 +1330,10 @@ qemuBlockStorageSourceGetFormatQcow2Props(virStorageSourcePtr src,
     if (qemuBlockStorageSourceGetFormatQcowGenericProps(src, "qcow2", props) < 0)
         return -1;
 
+    if (src->metadata_cache_size == VIR_DOMAIN_DISK_METADATA_CACHE_SIZE_MAXIMUM &&
+        virJSONValueObjectAdd(props, "I:l2-cache-size", INT64_MAX, NULL) < 0)
+        return -1;
+
     return 0;
 }
 
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index f59cbf5..12b2c8d 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -1330,6 +1330,20 @@ qemuCheckDiskConfig(virDomainDiskDefPtr disk,
         return -1;
     }
 
+    if (disk->metadata_cache_size) {
+        if (disk->src->format != VIR_STORAGE_FILE_QCOW2) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("metadata_cache_size can only be set for qcow2 disks"));
+            return -1;
+        }
+
+        if (disk->metadata_cache_size != VIR_DOMAIN_DISK_METADATA_CACHE_SIZE_MAXIMUM) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("metadata_cache_size can only be set to 'maximum'"));
+            return -1;
+        }
+    }
+
     if (qemuCaps) {
         if (disk->serial &&
             disk->bus == VIR_DOMAIN_DISK_BUS_SCSI &&
@@ -1353,6 +1367,15 @@ qemuCheckDiskConfig(virDomainDiskDefPtr disk,
                            _("detect_zeroes is not supported by this QEMU binary"));
             return -1;
         }
+
+        if (disk->metadata_cache_size &&
+            !(virQEMUCapsGet(qemuCaps, QEMU_CAPS_BLOCKDEV) &&
+              virQEMUCapsGet(qemuCaps, QEMU_CAPS_QCOW2_L2_CACHE_SIZE))) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("setting metadata_cache_size is not supported by "
+                             "this QEMU binary"));
+            return -1;
+        }
     }
 
     if (disk->serial &&
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 045a7b4..23d9348 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -9074,6 +9074,7 @@ qemuDomainDiskChangeSupported(virDomainDiskDefPtr disk,
     /* "snapshot" is a libvirt internal field and thus can be changed */
     /* startupPolicy is allowed to be updated. Therefore not checked here. */
     CHECK_EQ(transient, "transient", true);
+    CHECK_EQ(metadata_cache_size, "metadata_cache_size", true);
 
     /* Note: For some address types the address auto generation for
      * @disk has still not happened at this point (e.g. driver
@@ -13244,6 +13245,7 @@ qemuDomainPrepareDiskSourceData(virDomainDiskDefPtr disk,
     src->iomode = disk->iomode;
     src->cachemode = disk->cachemode;
     src->discard = disk->discard;
+    src->metadata_cache_size = disk->metadata_cache_size;
 
     if (disk->device == VIR_DOMAIN_DISK_DEVICE_FLOPPY)
         src->floppyimg = true;
diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c
index 94c32d8..9089e2f 100644
--- a/src/util/virstoragefile.c
+++ b/src/util/virstoragefile.c
@@ -2210,6 +2210,7 @@ virStorageSourceCopy(const virStorageSource *src,
     ret->cachemode = src->cachemode;
     ret->discard = src->discard;
     ret->detect_zeroes = src->detect_zeroes;
+    ret->metadata_cache_size = src->metadata_cache_size;
 
     /* storage driver metadata are not copied */
     ret->drv = NULL;
diff --git a/src/util/virstoragefile.h b/src/util/virstoragefile.h
index 3ff6c4f..8b57399 100644
--- a/src/util/virstoragefile.h
+++ b/src/util/virstoragefile.h
@@ -331,6 +331,7 @@ struct _virStorageSource {
     int cachemode; /* enum virDomainDiskCache */
     int discard; /* enum virDomainDiskDiscard */
     int detect_zeroes; /* enum virDomainDiskDetectZeroes */
+    int metadata_cache_size; /* enum virDomainDiskImageMetadataCacheSize */
 
     bool floppyimg; /* set to true if the storage source is going to be used
                        as a source for floppy drive */
-- 
1.8.3.1

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