[pve-devel] [PATCH qemu-server] virtiofs: prevent issue with Windows OS and too many files

[Fiona Ebner]

Am 02.05.25 um 13:52 schrieb Markus Frank:
> On 2025-04-28 12:17, Fiona Ebner wrote:
>> As reported in the community forum [0] and the virtio-win project [1],
>> virtiofsd will run into its open file limit when used with a Windows
>> guest that reads too many files. It's also reported that the issue
>> does not occur with Linux guests and a workaround is using
>> '--inode-file-handles=mandatory' on virtiofsd command line.
> I was able to reproduce the issue with a directory containing a million
> files.
> The virtiofs share became unusable when I tried to list the files with
> 'ls'.
> This patch allows to list all the files without problems.
>>
>> The option is described as follows in the vritiofsd help:
> typo: virtiofsd

Will fix!

>>
>>> When to use file handles to reference inodes instead of O_PATH file
>>> descriptors (never, prefer, mandatory)
>>
>> and the default is 'never'.
>>
>> Fix the above issue by using 'prefer' rather than 'mandatory', because
>> that should not break other edge cases:
>>
>>> prefer: Attempt to generate file handles, but fall back to O_PATH
>>> file descriptors where the underlying filesystem does not support
>>> file handles. Useful when there are various different filesystems
>>> under the shared directory and some of them do not support file
>>> handles.
>>
>> [0]: https://forum.proxmox.com/threads/165565/
>> [1]: https://github.com/virtio-win/kvm-guest-drivers-windows/issues/1136
>>
>> Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
> Tested-by: Markus Frank <m.frank at proxmox.com>
>> ---
>>
>> Didn't get around to measure the performance impact yet, so feel free
>> to check that if you test this patch. While not being broken is more
>> important than good performance, it would still be good to know for
>> completeness.
> I made a few read/write tests with fio in a Windows 11 guest.

Since the option affects file handles, it would be more interesting to
test something that involves handling many files rather than just IO.