[pve-devel] [PATCH qemu-server 2/3] virtiofs: drop writeback option

[Fiona Ebner]

VirtIO-fs using writeback cache seems very broken at the moment. If a
guest accesses a file (even just using 'touch'), that the host is
currently writing, the guest can permanently end up with a truncated
version of that file. Even subsequent operations like moving the file,
will not result in the correct file being visible, but just rename the
truncated one.

Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
---
 PVE/QemuServer/Virtiofs.pm | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/PVE/QemuServer/Virtiofs.pm b/PVE/QemuServer/Virtiofs.pm
index 13035c9b..cfde92c9 100644
--- a/PVE/QemuServer/Virtiofs.pm
+++ b/PVE/QemuServer/Virtiofs.pm
@@ -45,13 +45,6 @@ my $virtiofs_fmt = {
 	default => 0,
 	optional => 1,
     },
-    writeback => {
-	type => 'boolean',
-	description => "Enable writeback cache. If enabled, writes may be cached in the guest until"
-	    ." the file is closed or an fsync is performed.",
-	default => 0,
-	optional => 1,
-    },
     'expose-xattr' => {
 	type => 'boolean',
 	description => "Enable support for extended attributes for this mount.",
@@ -182,7 +175,6 @@ sub start_virtiofsd {
 	    push @$cmd, '--announce-submounts';
 	    push @$cmd, '--allow-direct-io' if $virtiofs->{'direct-io'};
 	    push @$cmd, '--cache='.$virtiofs->{cache} if $virtiofs->{cache};
-	    push @$cmd, '--writeback' if $virtiofs->{'writeback'};
 	    push @$cmd, '--syslog';
 	    exec(@$cmd);
 	} elsif (!defined($pid2)) {
-- 
2.39.5