[Virtio-fs] F_SETLKW not supported

[Virtio-fs] F_SETLKW not supported

[Aa Aa]

Hi

I am trying to run some java apps via virtfs and some of the file locking (java) doesn't work. Here an exception (java) is thrown something about file locking:

Here is the strace output:

 3541 [pid 12461] openat(AT_FDCWD, "/mnt/<redacted> O_WRONLY|O_CREAT|O_APPEND, 0666 <unfinished ...>
 3542 [pid 12461] <... openat resumed>)       = 180
 3543 [pid 12461] fstat(180, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
 3544 [pid 12461] fcntl(180, F_SETLKW, {l_type=F_WRLCK, l_whence=SEEK_SET, l_start=0, l_len=0} <unfinished ...>
 3545 [pid 12461] <... fcntl resumed>)        = -1 EOPNOTSUPP (Operation not supported)

If I run this on the native file system, there is no issue. Should this functl be supported?

Cheers

JT

Re: [Virtio-fs] F_SETLKW not supported

[Miklos Szeredi]

On Mon, Jul 20, 2020 at 10:01 AM Aa Aa <jimbothom@yandex.com> wrote:
>
> Hi
>
> I am trying to run some java apps via virtfs and some of the file locking (java) doesn't work. Here an exception (java) is thrown something about file locking:
>
> Here is the strace output:
>
>  3541 [pid 12461] openat(AT_FDCWD, "/mnt/<redacted> O_WRONLY|O_CREAT|O_APPEND, 0666 <unfinished ...>
>  3542 [pid 12461] <... openat resumed>)       = 180
>  3543 [pid 12461] fstat(180, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
>  3544 [pid 12461] fcntl(180, F_SETLKW, {l_type=F_WRLCK, l_whence=SEEK_SET, l_start=0, l_len=0} <unfinished ...>
>  3545 [pid 12461] <... fcntl resumed>)        = -1 EOPNOTSUPP (Operation not supported)

I think that's due to an incomplete implementation of POSIX locks in virtiofsd.

Try "no_posix_lock" option: that should make locks work, but only
locally (i.e. inside the guest).

Vivek, do we maybe want to turn off remote posix locks by default
until the implementation is complete?

Thanks,
Miklos

Re: [Virtio-fs] F_SETLKW not supported

[Vivek Goyal]

On Mon, Jul 20, 2020 at 11:33:32AM +0200, Miklos Szeredi wrote:
> On Mon, Jul 20, 2020 at 10:01 AM Aa Aa <jimbothom@yandex.com> wrote:
> >
> > Hi
> >
> > I am trying to run some java apps via virtfs and some of the file locking (java) doesn't work. Here an exception (java) is thrown something about file locking:
> >
> > Here is the strace output:
> >
> >  3541 [pid 12461] openat(AT_FDCWD, "/mnt/<redacted> O_WRONLY|O_CREAT|O_APPEND, 0666 <unfinished ...>
> >  3542 [pid 12461] <... openat resumed>)       = 180
> >  3543 [pid 12461] fstat(180, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
> >  3544 [pid 12461] fcntl(180, F_SETLKW, {l_type=F_WRLCK, l_whence=SEEK_SET, l_start=0, l_len=0} <unfinished ...>
> >  3545 [pid 12461] <... fcntl resumed>)        = -1 EOPNOTSUPP (Operation not supported)
> 
> I think that's due to an incomplete implementation of POSIX locks in virtiofsd.
> 
> Try "no_posix_lock" option: that should make locks work, but only
> locally (i.e. inside the guest).
> 
> Vivek, do we maybe want to turn off remote posix locks by default
> until the implementation is complete?

Hi Miklos,

Disabling it by default till we support blocking version of locks is
probably a good idea. That way it will work out of box without
having to specify no_posix_lock. Anyway, we don't support virtiofs
in shared mode yet. I will send a patch.

Thanks
Vivek