linstor: add QemuImg 3-param constructor for skip-zero copy optimization

Add QemuImg(timeout, skipZeroIfSupported, noCache) constructor that
detects --target-is-zero support in qemu-img and uses it during convert
to skip writing zeroes on pre-zeroed block devices. This significantly
improves copy performance on thin-provisioned LINSTOR volumes.

Update LinstorStorageAdaptor.copyPhysicalDisk and
LinstorRevertBackupSnapshotCommandWrapper to use the new constructor
with zeroedDevice detection via LinstorUtil.resourceSupportZeroBlocks.

Author: rp-

plugins/hypervisors/kvm/src/main/java/org/apache/cloudstack/utils/qemu/QemuImg.java

@@ -38,11 +38,14 @@ public class QemuImg {
     public final static String FILE_FORMAT = "file_format";
     public final static String IMAGE = "image";
     public final static String VIRTUAL_SIZE = "virtual_size";
+    public static final String TARGET_ZERO_FLAG = "--target-is-zero";
 
     /* The qemu-img binary. We expect this to be in $PATH */
     public String _qemuImgPath = "qemu-img";
     private String cloudQemuImgPath = "cloud-qemu-img";
     private int timeout;
+    private boolean skipZero = false;
+    private boolean noCache = false;
 
     private String getQemuImgPathScript = String.format("which %s >& /dev/null; " +
                     "if [ $? -gt 0 ]; then echo \"%s\"; else echo \"%s\"; fi",
@@ -97,6 +100,38 @@ public QemuImg(final int timeout) {
         this.timeout = timeout;
     }
 
+    /**
+     * Create a QemuImg object that supports skipping target zeroes.
+     * We detect this support via qemu-img help since support can
+     * be backported rather than found in a specific version.
+     *
+     * @param timeout script timeout, default 0
+     * @param skipZeroIfSupported Don't write zeroes to target device during convert, if supported by qemu-img
+     * @param noCache Ensure we flush writes to target disk (useful for block device targets)
+     */
+    public QemuImg(final int timeout, final boolean skipZeroIfSupported, final boolean noCache) {
+        if (skipZeroIfSupported) {
+            final Script s = new Script(_qemuImgPath, timeout);
+            s.add("--help");
+
+            final OutputInterpreter.AllLinesParser parser = new OutputInterpreter.AllLinesParser();
+            final String result = s.execute(parser);
+
+            // Older Qemu returns output in result due to --help reporting error status
+            if (result != null) {
+                if (result.contains(TARGET_ZERO_FLAG)) {
+                    this.skipZero = true;
+                }
+            } else {
+                if (parser.getLines().contains(TARGET_ZERO_FLAG)) {
+                    this.skipZero = true;
+                }
+            }
+        }
+        this.timeout = timeout;
+        this.noCache = noCache;
+    }
+
     public void setTimeout(final int timeout) {
         this.timeout = timeout;
     }
@@ -254,6 +289,16 @@ public void convert(final QemuImgFile srcFile, final QemuImgFile destFile,
         }
 
         script.add("convert");
+
+        if (skipZero) {
+            script.add("-n");
+            script.add(TARGET_ZERO_FLAG);
+            script.add("-W");
+            // with target-is-zero we skip zeros in 1M chunks for compatibility
+            script.add("-S");
+            script.add("1M");
+        }
+
         Long version  = LibvirtConnection.getConnection().getVersion();
         if (version >= 2010000) {
             script.add("-U");
@@ -281,6 +326,11 @@ public void convert(final QemuImgFile srcFile, final QemuImgFile destFile,
 
         addSnapshotToConvertCommand(srcFile.getFormat().toString(), snapshotName, forceSourceFormat, script, version);
 
+        if (noCache) {
+            script.add("-t");
+            script.add("none");
+        }
+
         script.add(srcFile.getFileName());
         script.add(destFile.getFileName());
 

plugins/storage/volume/linstor/src/main/java/com/cloud/hypervisor/kvm/resource/wrapper/LinstorRevertBackupSnapshotCommandWrapper.java

@@ -60,7 +60,7 @@ private void convertQCow2ToRAW(
             blkDiscardScript.add(dstPath);
             blkDiscardScript.execute();
         }
-        final QemuImg qemu = new QemuImg(waitMilliSeconds);
+        final QemuImg qemu = new QemuImg(waitMilliSeconds, zeroedDevice, true);
         final QemuImgFile dstFile = new QemuImgFile(dstPath, QemuImg.PhysicalDiskFormat.RAW);
         qemu.convert(srcQemuFile, dstFile);
     }

plugins/storage/volume/linstor/src/main/java/com/cloud/hypervisor/kvm/storage/LinstorStorageAdaptor.java

@@ -619,7 +619,6 @@ public KVMPhysicalDisk copyPhysicalDisk(KVMPhysicalDisk disk, String name, KVMSt
         s_logger.debug(String.format("Linstor.copyPhysicalDisk: %s -> %s", disk.getPath(), name));
         final QemuImg.PhysicalDiskFormat sourceFormat = disk.getFormat();
         final String sourcePath = disk.getPath();
-        final QemuImg qemu = new QemuImg(timeout);
 
         final QemuImgFile srcFile = new QemuImgFile(sourcePath, sourceFormat);
 
@@ -634,7 +633,9 @@ public KVMPhysicalDisk copyPhysicalDisk(KVMPhysicalDisk disk, String name, KVMSt
         destFile.setFormat(dstDisk.getFormat());
         destFile.setSize(disk.getVirtualSize());
 
+        boolean zeroedDevice = LinstorUtil.resourceSupportZeroBlocks(destPools, getLinstorRscName(name));
         try {
+            final QemuImg qemu = new QemuImg(timeout, zeroedDevice, true);
             qemu.convert(srcFile, destFile);
         } catch (QemuImgException | LibvirtException e) {
             s_logger.error(e);