[pve-devel] [PATCH guest-common/qemu-server/docs/manager v1 0/11] Virtiofs improvements

[Filip Schauer]

On 29/10/2025 14:39, Filip Schauer wrote:
> Tested read-only: Works as expected.
>
> Tested live migration with both find-paths and file-handles while
> reading a small file:
> 1. Opened file on first node
> 2. Read a few bytes from the open file handle
> 3. Migrated the VM to the second node
> 4. Read some more bytes from the open file handle
> This worked fine.
>
> Tested live migration while copying a 1GiB file within the virtiofs:
> 1. Mounted a CIFS share on all nodes and configured the directory
>    mappings with `file-handles` as the live migration method
> 2. Created a 1GiB file: `dd if=/dev/urandom of=testA bs=4M count=256`
> 3. Started a copy inside the VM:
>    `/mnt/virtiofs# dd if=testA of=testB status=progress`
> 4. Started a live migration
> 5. Immediately after migration dd failed with:
>    ```
>    dd: error reading 'testA': Input/output error
>    dd: closing input file 'testA': Input/output error
>    ```
>    I tried the same with Live Migration Method set to `find-paths`.
>    This also failed upon migration. This time with:
>    ```
>    dd: writing to 'testB': Input/output error
>    dd: closing input file 'testA': Input/output error
>    ``` 


I did some more testing of virtiofs + dd + live migration to see if
reading/writing to virtiofs works after migration.
I tested the following configurations:

virtiofs backing fs on host  live mig. method  write works?  read works?
NFS                          find-paths        yes           yes
NFS                          file-handles      I/O error     yes
CephFS                       find-paths        yes           yes
CephFS                       file-handles      I/O error     I/O error
CIFS                         find-paths        I/O error     I/O error
CIFS                         file-handles      I/O error     yes


CephFS + file-handles target-node journal upon migration:
Nov 03 18:26:41 pve1 virtiofsd[39002]: pve1 virtiofsd[38999]: Invalid 
inode 7 indexed: Opening file handle: Operation not permitted (os error 1)
Nov 03 18:26:41 pve1 virtiofsd[39002]: pve1 virtiofsd[38999]: Invalid 
inode 6 indexed: Opening file handle: Operation not permitted (os error 1)
Nov 03 18:26:41 pve1 virtiofsd[39002]: pve1 virtiofsd[38999]: Invalid 
inode 5 indexed: Opening file handle: Operation not permitted (os error 1)
Nov 03 18:26:41 pve1 virtiofsd[39002]: pve1 virtiofsd[38999]: Invalid 
inode 4 indexed: Opening file handle: Operation not permitted (os error 1)
Nov 03 18:26:41 pve1 virtiofsd[39002]: pve1 virtiofsd[38999]: Invalid 
inode 3 indexed: Opening file handle: Operation not permitted (os error 1)
Nov 03 18:26:41 pve1 virtiofsd[39002]: pve1 virtiofsd[38999]: Invalid 
inode 2 indexed: Opening file handle: Operation not permitted (os error 1)


CIFS + find-paths source-node journal upon migration:
Nov 03 17:34:43 pve1 virtiofsd[26642]: pve1 virtiofsd[26639]: Inode 7: 
Operation not supported (os error 95)
Nov 03 17:34:47 pve1 virtiofsd[26642]: pve1 virtiofsd[26639]: Inode 7: 
Operation not supported (os error 95)
Nov 03 17:34:47 pve1 virtiofsd[26642]: pve1 virtiofsd[26639]: Failed to 
serialize inode 1 (st_dev=45, mnt_id=511, st_ino=34): Failed to 
reconstruct inode location; marking as invalid
Nov 03 17:34:47 pve1 virtiofsd[26642]: pve1 virtiofsd[26639]: Failed to 
serialize inode 7 (st_dev=45, mnt_id=511, st_ino=144): Failed to 
reconstruct inode location; marking as invalid

CIFS + find-paths target-node journal upon migration:
Nov 03 17:34:47 pve2 virtiofsd[26266]: pve2 virtiofsd[26264]: Invalid 
inode 1 indexed: Migration source has lost inode 1
Nov 03 17:34:47 pve2 virtiofsd[26266]: pve2 virtiofsd[26264]: Invalid 
inode 7 indexed: Migration source has lost inode 7