Re: [PATCH net-next v3 10/18] nvme/host: Use sendmsg(MSG_SPLICE_PAGES) rather then sendpage

Jakub Kicinski
2023-06-30T16:15:36Z

On Fri, 30 Jun 2023 09:10:43 -0700 Nathan Chancellor wrote:
> > Let me CC llvm@ in case someone's there is willing to make
> > the compiler warn about this.
>
> Turns out clang already has a warning for this, -Wcomma:
>
> drivers/nvme/host/tcp.c:1017:38: error: possible misuse of comma operator here [-Werror,-Wcomma]
> 1017 | msg.msg_flags &= ~MSG_SPLICE_PAGES,
> | ^
> drivers/nvme/host/tcp.c:1017:4: note: cast expression to void to silence warning
> 1017 | msg.msg_flags &= ~MSG_SPLICE_PAGES,
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> | (void)( )
> 1 error generated.
>
> Let me do some wider build testing to see if it is viable to turn this
> on for the whole kernel because it seems worth it, at least in this
> case. There are a lot of cases where a warning won't be emitted (see the
> original upstream review for a list: https://reviews.llvm.org/D3976) but
> something is better than nothing, right? :)

Ah, neat. Misleading indentation is another possible angle, I reckon,
but not sure if that's enabled/possible to enable for the entire kernel
either :( We test-build with W=1 in networking, FWIW, so W=1 would be
enough for us.