Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag

[Christoph Hellwig]

On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
> Said that, why not provide a variant that would take an explicit
> "is it compat" argument and use it there?  And have the normal
> one pass in_compat_syscall() to that...

That would help to not introduce a regression with this series yes.
But it wouldn't fix existing bugs when io_uring is used to access
read or write methods that use in_compat_syscall().  One example that
I recently ran into is drivers/scsi/sg.c.