Re: [PATCH 21/32] VFS: Implement fsmount() to effect a pre-configured mount [ver #8]
From: David Howells
Date: Mon Jun 04 2018 - 11:24:31 EST
Arnd Bergmann <arnd@xxxxxxxx> wrote:
> The prototype in the header doesn't match the one in the implementation,
> which should cause a compile-time error, at least if syscalls.h is included
> in namespace.c
I've fixed that sort of thing up from kbuild warnings.
> Do you have a particular use case in mind for the spare_4/spare_5 arguments?
> If not, we can probably skip them. If we end up needing them after all, we
> can always add a new syscall entry point, or use one of the flag bits to
> decide whether the additional arguments are valid or not.
Whilst that is true, these aren't really (or probably shouldn't be) hot path
syscalls, so I would contend that just clearing the extra arguments shouldn't
be much of a performance loss. On the other hand, syscall numbers are to some
extent precious. If we hit ~512 syscalls we start to have an issue as we
start to get overlaps.
And, yes, I do have ideas for them involving ID mapping on mounts (ie. killing
off shiftfs).
> > COND_SYSCALL(sys_fsopen);
> > +COND_SYSCALL(sys_fsmount);
>
> This should only be needed if the syscall is optional, which it doesn't
> seem to be (same for the other ones here).
Al removed them.
David