[libvirt] [PATCH] qemu: Shared or readonly disks are always safe wrt migration

[Jiri Denemark]

No matter what cache mode is used, readonly disks are always safe wrt
migration. Shared disks are required to be readonly or to disable
host-side cache, which makes them safe as well.
---
 src/qemu/qemu_migration.c |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index 84037e4..5c4297c 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -828,10 +828,12 @@ qemuMigrationIsSafe(virDomainDefPtr def)
     for (i = 0 ; i < def->ndisks ; i++) {
         virDomainDiskDefPtr disk = def->disks[i];
 
-        /* shared && !readonly implies cache=none */
+        /* Our code elsewhere guarantees shared disks are either readonly (in
+         * which case cache mode doesn't matter) or used with cache=none */
         if (disk->src &&
-            disk->cachemode != VIR_DOMAIN_DISK_CACHE_DISABLE &&
-            (disk->cachemode || !disk->shared || disk->readonly)) {
+            !disk->shared &&
+            !disk->readonly &&
+            disk->cachemode != VIR_DOMAIN_DISK_CACHE_DISABLE) {
             int cfs;
             if ((cfs = virStorageFileIsClusterFS(disk->src)) == 1)
                 continue;
-- 
1.7.8.5