From 165b30e06a6d14e8719c82af290d3b20e4cbc462 Mon Sep 17 00:00:00 2001
From: Peter Krempa <pkrempa@redhat.com>
Date: Mon, 30 Sep 2024 14:16:58 +0200
Subject: [PATCH] qemu: migration: Pre-create QCOW2 images for non-shared
 storage with 0 allocation

Specify that the <allocation> parameter for the newly-created qcow2
image is 0 so that only metadata gets preallocated. Otherwise the
storage driver code instructs qemu to use 'fallocate' preallocation mode
and considers the image fully allocated.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
---
 src/qemu/qemu_migration.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index 7f905f8584..b686e42e58 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -361,6 +361,8 @@ qemuMigrationDstPrecreateDisk(virConnectPtr *conn,
     virBufferAddLit(&buf, "<volume>\n");
     virBufferAdjustIndent(&buf, 2);
     virBufferEscapeString(&buf, "<name>%s</name>\n", volName);
+    if (disk->src->format == VIR_STORAGE_FILE_QCOW2)
+        virBufferAddLit(&buf, "<allocation>0</allocation>\n");
     virBufferAsprintf(&buf, "<capacity>%llu</capacity>\n", capacity);
     virBufferAddLit(&buf, "<target>\n");
     virBufferAdjustIndent(&buf, 2);