[PATCH storage] fix #7598: qemu-img resize: tolerate timeout if resize succeeded

[PATCH storage] fix #7598: qemu-img resize: tolerate timeout if resize succeeded

[Jakob Klocker]

On slow storages there is a chance the 10 second timeout is triggered
when resizing a volume. If the timeout fires while the resize is in a
certain state near the end, the operation can still complete
successfully even though a timeout error is thrown. In that case the
config is never updated and keeps the old, wrong size.

Because the config is out of sync, the volume is then displayed with
the wrong size in the web interface.

Link: https://bugzilla.proxmox.com/show_bug.cgi?id=7598
Signed-off-by: Jakob Klocker <j.klocker@proxmox.com>
---
 src/PVE/Storage/Common.pm | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/PVE/Storage/Common.pm b/src/PVE/Storage/Common.pm
index 3932aee..ee2ea00 100644
--- a/src/PVE/Storage/Common.pm
+++ b/src/PVE/Storage/Common.pm
@@ -277,7 +277,17 @@ sub qemu_img_resize {
     push $cmd->@*, '-f', $format, $path, $size;
 
     $timeout = 10 if !$timeout;
-    run_command($cmd, timeout => $timeout);
+    eval { run_command($cmd, timeout => $timeout); };
+    if (my $err = $@) {
+
+        die $err if $err !~ /got timeout/;
+
+        my $info = JSON::decode_json(qemu_img_info($path, $format));
+        die $err if !$info;
+
+        my $actual_size = $info->{'virtual-size'};
+        die $err if !defined($actual_size) || $actual_size < $size;
+    }
 }
 
 1;
-- 
2.47.3

Re: [PATCH storage] fix #7598: qemu-img resize: tolerate timeout if resize succeeded

[Fabian Grünbichler]

On June 3, 2026 10:25 am, Jakob Klocker wrote:
> On slow storages there is a chance the 10 second timeout is triggered
> when resizing a volume. If the timeout fires while the resize is in a
> certain state near the end, the operation can still complete
> successfully even though a timeout error is thrown. In that case the
> config is never updated and keeps the old, wrong size.
> 
> Because the config is out of sync, the volume is then displayed with
> the wrong size in the web interface.
> 
> Link: https://bugzilla.proxmox.com/show_bug.cgi?id=7598
> Signed-off-by: Jakob Klocker <j.klocker@proxmox.com>
> ---
>  src/PVE/Storage/Common.pm | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/src/PVE/Storage/Common.pm b/src/PVE/Storage/Common.pm
> index 3932aee..ee2ea00 100644
> --- a/src/PVE/Storage/Common.pm
> +++ b/src/PVE/Storage/Common.pm
> @@ -277,7 +277,17 @@ sub qemu_img_resize {
>      push $cmd->@*, '-f', $format, $path, $size;
>  
>      $timeout = 10 if !$timeout;

I think making this worker-task aware and bumping the timeout in that
case would make more sense - storage performance varies wildy, and like
I noted in the bug, this only seems to be called from a worker context
where the additional time hurts way less than risking running into the
timeout just because something is slow.

e.g., in the RBD plugin we have a default connect timeout of 60s in
workers, in the ZFS plugin we bump ZFS requests to 300s if a smaller
timeout is set, and default to a timeout of one hour if none is set.

> -    run_command($cmd, timeout => $timeout);
> +    eval { run_command($cmd, timeout => $timeout); };
> +    if (my $err = $@) {
> +
> +        die $err if $err !~ /got timeout/;
> +
> +        my $info = JSON::decode_json(qemu_img_info($path, $format));
> +        die $err if !$info;
> +
> +        my $actual_size = $info->{'virtual-size'};
> +        die $err if !defined($actual_size) || $actual_size < $size;
> +    }

IMHO this doesn't fix the actual bug mentioned.. I guess what you see
here if running into this behaviour is that the resize was done, but
syncing then takes long and hits the timeout?

because what `qemu-img resize` does for raw images is basically just

ftruncate(..)
fdatasync(..)

and just because you read back the updated size in the timeout case
(from local, cached metadata), does not necessarily mean it got
persisted to the storage (which might be on a different system) - that's
what the sync is for after all..

>  }
>  
>  1;
> -- 
> 2.47.3
> 
> 
> 
> 
>