Re: [PATCH 0/3] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2

[Askar Safin <safinaskar@gmail.com>]

Andrei Vagin <avagin@gmail.com>:
> The CRIU fifo test fails with this change. The problem is that vmsplice
> with SPLICE_F_NONBLOCK to a fifo file descriptor fails with -EOPNOTSUPP.
> 
> It seems we need a fix like this one:
> 
> diff --git a/fs/pipe.c b/fs/pipe.c
> index 429b0714ec57..6fc49e933727 100644
> --- a/fs/pipe.c
> +++ b/fs/pipe.c
> @@ -1253,6 +1253,7 @@ static int fifo_open(struct inode *inode, struct
> file *filp)
> 
>         /* We can only do regular read/write on fifos */
>         stream_open(inode, filp);
> +       filp->f_mode |= FMODE_NOWAIT;
> 
>         switch (filp->f_mode & (FMODE_READ | FMODE_WRITE)) {
>         case FMODE_READ:

Does CRIU actually rely on ability to do SPLICE_F_NONBLOCK vmsplice into
named fifos? Or this is merely a test?

If this is just a test, I think we need not to preserve this behavior.

I did debian code search with regex "vmsplice.*SPLICE_F_NONBLOCK" and I
found very few packages. And it seems all them use pipes, not named fifos.

(On speed: I still think that my vmsplice patches are good thing,
despite performance regressions in CRIU.)

-- 
Askar Safin