Re: [PATCH v3 RESEND] fcntl: Add 32bit filesystem mode

[Linus Walleij]

On Tue, Oct 13, 2020 at 11:22 AM Dave Martin <Dave.Martin@arm.com> wrote:

> >       case F_SETFD:
> >               err = 0;
> >               set_close_on_exec(fd, arg & FD_CLOEXEC);
> > +             if (arg & FD_32BIT_MODE)
> > +                     filp->f_mode |= FMODE_32BITHASH;
> > +             else
> > +                     filp->f_mode &= ~FMODE_32BITHASH;
>
> This seems inconsistent?  F_SETFD is for setting flags on a file
> descriptor.  Won't setting a flag on filp here instead cause the
> behaviour to change for all file descriptors across the system that are
> open on this struct file?  Compare set_close_on_exec().
>
> I don't see any discussion on whether this should be an F_SETFL or an
> F_SETFD, though I see F_SETFD was Ted's suggestion originally.

I cannot honestly say I know the semantic difference.

I would ask the QEMU people how a user program would expect
the flag to behave.

Yours,
Linus Walleij