[pve-devel] [PATCH-SERIES manager/qemu-server/docs 0/3] drop writeback cache setting

[pve-devel] [PATCH-SERIES manager/qemu-server/docs 0/3] drop writeback cache setting

[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.

manager:

Fiona Ebner (1):
  ui: virtiofs edit: drop writeback checkbox

 www/manager6/qemu/VirtiofsEdit.js | 5 -----
 1 file changed, 5 deletions(-)


qemu-server:

Fiona Ebner (1):
  virtiofs: drop writeback option

 PVE/QemuServer/Virtiofs.pm | 8 --------
 1 file changed, 8 deletions(-)


docs:

Fiona Ebner (1):
  qm: virtiofs: drop writeback cache

 qm.adoc | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)


Summary over all repositories:
  3 files changed, 2 insertions(+), 15 deletions(-)

-- 
Generated by git-murpp 0.5.0


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[pve-devel] [PATCH manager 1/3] ui: virtiofs edit: drop writeback checkbox

[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@proxmox.com>
---
 www/manager6/qemu/VirtiofsEdit.js | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/www/manager6/qemu/VirtiofsEdit.js b/www/manager6/qemu/VirtiofsEdit.js
index fe8dc930..6983a763 100644
--- a/www/manager6/qemu/VirtiofsEdit.js
+++ b/www/manager6/qemu/VirtiofsEdit.js
@@ -57,11 +57,6 @@ Ext.define('PVE.qemu.VirtiofsInputPanel', {
 		    ['never', 'never'],
 		],
 	    },
-	    {
-		xtype: 'proxmoxcheckbox',
-		name: 'writeback',
-		fieldLabel: gettext('Writeback cache'),
-	    },
 	    {
 		xtype: 'proxmoxcheckbox',
 		name: 'expose-xattr',
-- 
2.39.5



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[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@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



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[pve-devel] [PATCH docs 3/3] qm: virtiofs: drop writeback cache

[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@proxmox.com>
---
 qm.adoc | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/qm.adoc b/qm.adoc
index 539912a..1babb82 100644
--- a/qm.adoc
+++ b/qm.adoc
@@ -1309,7 +1309,7 @@ has been configured in the resource mapping. Additionally, you can set the
 `cache` option to either `always`, `never`, `metadata`, or `auto` (default:
 `auto`), depending on your requirements. How the different caching modes behave
 can be read https://lwn.net/Articles/774495/[here under the "Caching Modes"
-section]. To enable writeback cache set `writeback` to `1`.
+section].
 
 Virtiofsd supports ACL and xattr passthrough (can be enabled with the
 `expose-acl` and `expose-xattr` options), allowing the guest to access ACLs and
@@ -1327,7 +1327,7 @@ applications do their own caching.
 ----
 qm set <vmid> -virtiofs0 dirid=<dirid>,cache=always,direct-io=1
 qm set <vmid> -virtiofs1 <dirid>,cache=never,expose-xattr=1
-qm set <vmid> -virtiofs2 <dirid>,expose-acl=1,writeback=1
+qm set <vmid> -virtiofs2 <dirid>,expose-acl=1
 ----
 
 To temporarily mount virtio-fs in a guest VM with the Linux kernel virtio-fs
-- 
2.39.5



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[pve-devel] applied-series: [PATCH-SERIES manager/qemu-server/docs 0/3] drop writeback cache setting

[Thomas Lamprecht]

Am 08.04.25 um 17:07 schrieb 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.
> 
> manager:
> 
> Fiona Ebner (1):
>   ui: virtiofs edit: drop writeback checkbox
> 
>  www/manager6/qemu/VirtiofsEdit.js | 5 -----
>  1 file changed, 5 deletions(-)
> 
> 
> qemu-server:
> 
> Fiona Ebner (1):
>   virtiofs: drop writeback option
> 
>  PVE/QemuServer/Virtiofs.pm | 8 --------
>  1 file changed, 8 deletions(-)
> 
> 
> docs:
> 
> Fiona Ebner (1):
>   qm: virtiofs: drop writeback cache
> 
>  qm.adoc | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> 
> Summary over all repositories:
>   3 files changed, 2 insertions(+), 15 deletions(-)
> 


applied, thanks!


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