From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>,
David Laight <David.Laight@aculab.com>,
Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Soheil Hassas Yeganeh <soheil.kdev@gmail.com>,
Arnd Bergmann <arnd@arndb.de>, Shuo Chen <shuochen@google.com>,
linux-man <linux-man@vger.kernel.org>
Subject: Re: [PATCH v3 1/2] epoll: add nsec timeout support with epoll_pwait2
Date: Mon, 11 Jan 2021 15:06:15 -0500 [thread overview]
Message-ID: <CAF=yD-JskHu0oBBTaRT_v7MZNEdgtYN3BmiexqjAgJV1hBKkEw@mail.gmail.com> (raw)
In-Reply-To: <CAF=yD-LAzjyNRy0vqToWqx5LxeQMYY3fVzV0vr0X7Q70ZAR-AQ@mail.gmail.com>
On Thu, Dec 10, 2020 at 5:59 PM Willem de Bruijn
<willemdebruijn.kernel@gmail.com> wrote:
>
> On Thu, Dec 10, 2020 at 3:34 PM Arnd Bergmann <arnd@kernel.org> wrote:
> >
> > On Thu, Dec 10, 2020 at 6:33 PM Willem de Bruijn
> > <willemdebruijn.kernel@gmail.com> wrote:
> > > On Sat, Nov 21, 2020 at 4:27 AM Arnd Bergmann <arnd@kernel.org> wrote:
> > > > On Fri, Nov 20, 2020 at 11:28 PM Willem de Bruijn <willemdebruijn.kernel@gmail.com> wrote:
> > > > I would imagine this can be done like the way I proposed
> > > > for get_bitmap() in sys_migrate_pages:
> > > >
> > > > https://lore.kernel.org/lkml/20201102123151.2860165-4-arnd@kernel.org/
> > >
> > > Coming back to this. Current patchset includes new select and poll
> > > selftests to verify the changes. I need to send a small kselftest
> > > patch for that first.
> > >
> > > Assuming there's no time pressure, I will finish up and send the main
> > > changes after the merge window, for the next release then.
> > >
> > > Current state against linux-next at
> > > https://github.com/wdebruij/linux-next-mirror/tree/select-compat-1
> >
> > Ok, sounds good to me. I've had a (very brief) look and have one
> > suggestion: instead of open-coding the compat vs native mode
> > in multiple places like
> >
> > if (!in_compat_syscall())
> >  return copy_from_user(fdset, ufdset, FDS_BYTES(nr)) ? -EFAULT : 0;
> > else
> >  return compat_get_bitmap(fdset, ufdset, nr);
> >
> > maybe move this into a separate function and call that where needed.
> >
> > I've done this for the get_bitmap() function in my series at
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git/commit/?h=compat-alloc-user-space-7&id=b1b23ebb12b635654a2060df49455167a142c5d2
> >
> > The definition is slightly differrent for cpumask, nodemask and fd_set,
> > so we'd need to try out the best way to structure the code to end
> > up with the most readable version, but it should be possible when
> > there are only three callers (and duplicating the function would
> > be the end of the world either)
>
> For fd_set there is only a single caller for each direction. Do you
> prefer helpers even so?
>
> For sigmask, with three callers, something along the lines of this?
>
> @@ -1138,10 +1135,7 @@ static int do_ppoll(struct pollfd __user
> *ufds, unsigned int nfds,
> return -EINVAL;
> }
>
> - if (!in_compat_syscall())
> - ret = set_user_sigmask(sigmask, sigsetsize);
> - else
> - ret = set_compat_user_sigmask(sigmask, sigsetsize);
> + ret = set_maybe_compat_user_sigmask(sigmask, sigsetsize);
> if (ret)
> return ret;
>
> --- a/include/linux/compat.h
> +++ b/include/linux/compat.h
> @@ -942,6 +942,17 @@ static inline bool in_compat_syscall(void) {
> return false; }
>
> +static inline int set_maybe_compat_user_sigmask(const void __user *sigmask,
> + size_t sigsetsize)
> +{
> +#if defined CONFIG_COMPAT
> + if (unlikely(in_compat_syscall()))
> + return set_compat_user_sigmask(sigmask, sigsetsize);
> +#endif
> +
> + return set_user_sigmask(sigmask, sigsetsize);
> +}
set_user_sigmask is the only open-coded variant that is used more than once.
Because it is used in both select.c and eventpoll.c, a helper would
have to live in compat.h. This then needs a new dependency on
sched_signal.h.
So given that this is a simple branch, it might just make logic more
complex, instead of less. I can add this change in a separate patch on
top of the original three, to judge whether it is worthwhile.
next prev parent reply other threads:[~2021-01-11 20:07 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-18 14:46 [PATCH v3 0/2] add epoll_pwait2 syscall Willem de Bruijn
2020-11-18 14:46 ` [PATCH v3 1/2] epoll: add nsec timeout support with epoll_pwait2 Willem de Bruijn
2020-11-18 15:00 ` Matthew Wilcox
2020-11-18 15:10 ` Willem de Bruijn
2020-11-18 15:37 ` Arnd Bergmann
2020-11-18 15:59 ` David Laight
2020-11-19 14:19 ` Willem de Bruijn
2020-11-19 14:31 ` Matthew Wilcox
2020-11-19 15:37 ` Willem de Bruijn
2020-11-19 15:45 ` Arnd Bergmann
2020-11-19 20:13 ` Willem de Bruijn
2020-11-20 8:13 ` Arnd Bergmann
2020-11-20 16:01 ` Willem de Bruijn
2020-11-20 19:23 ` Arnd Bergmann
2020-11-20 22:28 ` Willem de Bruijn
2020-11-21 9:27 ` Arnd Bergmann
2020-12-10 17:33 ` Willem de Bruijn
2020-12-10 20:34 ` Arnd Bergmann
2020-12-10 22:59 ` Willem de Bruijn
2021-01-11 20:06 ` Willem de Bruijn [this message]
2020-11-18 16:21 ` Willem de Bruijn
2020-11-18 16:50 ` Arnd Bergmann
2020-11-19 3:22 ` Willem de Bruijn
2020-11-18 14:46 ` [PATCH manpages RFC] epoll_wait.2: add epoll_pwait2 Willem de Bruijn
2020-11-18 14:46 ` [PATCH v3 2/2] selftests/filesystems: expand epoll with epoll_pwait2 Willem de Bruijn
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