[libvirt] [PATCH libvirt] qemu: show a warning when using aio=native without cache=none
Qemu will fallback to aio=threads when the cache mode doesn't use
O_DIRECT, even if aio=native was explictly set.
Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1086704
Signed-off-by: Giuseppe Scrivano <gscrivan(a)redhat.com>
---
src/qemu/qemu_command.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index fb64cda..92a6c9a 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -3477,6 +3477,13 @@ qemuBuildDriveStr(virConnectPtr conn,
mode = qemuDiskCacheV1TypeToString(disk->cachemode);
}
+ if (disk->iomode == VIR_DOMAIN_DISK_IO_NATIVE &&
+ disk->cachemode != VIR_DOMAIN_DISK_CACHE_DIRECTSYNC) {
+ VIR_WARN("native I/O needs either no disk cache "
+ "or directsync cache mode, QEMU will fallback "
+ "to aio=threads");
+ }
+
virBufferAsprintf(&opt, ",cache=%s", mode);
} else if (disk->shared && !disk->readonly) {
virBufferAddLit(&opt, ",cache=off");
--
1.9.3