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

[Andrei Vagin]

On Wed, Jun 17, 2026 at 4:08 AM Christian Brauner <brauner@xxxxxxxxxx> wrote:
>
> > After this patch, step b) is a straight copy which means step d)'s
> > fixup doesn't modify what's in the pipe. This could be fixed up in
> > libfuse to not depend on modify-after-vmsplice, but I don't think this
> > helps for applications using already-released libfuse versions. I
> > think this patch needs to be reverted.
>
> Note, nothing was merged. I deliberately kept in -next though for a long
> time to see how quickly we'd see regressions.

The bait worked. CRIU wins a prize in this lottery.

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: