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Message-ID: <eead2765ea5e417abe616950b4e5d02f@AcuMS.aculab.com>
Date: Mon, 16 Nov 2020 17:11:24 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Willem de Bruijn' <willemdebruijn.kernel@...il.com>,
Matthew Wilcox <willy@...radead.org>
CC: "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
Al Viro <viro@...iv.linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>,
"Soheil Hassas Yeganeh" <soheil.kdev@...il.com>,
Arnd Bergmann <arnd@...db.de>,
"Shuo Chen" <shuochen@...gle.com>
Subject: RE: [PATCH v2] epoll: add nsec timeout support
From: Willem de Bruijn
> Sent: 16 November 2020 17:01
>
> On Mon, Nov 16, 2020 at 11:19 AM Matthew Wilcox <willy@...radead.org> wrote:
> >
> > On Mon, Nov 16, 2020 at 11:10:01AM -0500, Willem de Bruijn wrote:
> > > diff --git a/include/uapi/linux/eventpoll.h b/include/uapi/linux/eventpoll.h
> > > index 8a3432d0f0dc..f6ef9c9f8ac2 100644
> > > --- a/include/uapi/linux/eventpoll.h
> > > +++ b/include/uapi/linux/eventpoll.h
> > > @@ -21,6 +21,7 @@
> > >
> > > /* Flags for epoll_create1. */
> > > #define EPOLL_CLOEXEC O_CLOEXEC
> > > +#define EPOLL_NSTIMEO 0x1
> > >
> > > /* Valid opcodes to issue to sys_epoll_ctl() */
> > > #define EPOLL_CTL_ADD 1
> >
> > Not a problem with your patch, but this concerns me. O_CLOEXEC is
> > defined differently for each architecture, so we need to stay out of
> > several different bits when we define new flags for EPOLL_*. Maybe
> > this:
> >
> > /*
> > * Flags for epoll_create1. O_CLOEXEC may be different bits, depending
> > * on the CPU architecture. Reserve the known ones.
> > */
> > #define EPOLL_CLOEXEC O_CLOEXEC
> > #define EPOLL_RESERVED_FLAGS 0x00680000
> > #define EPOLL_NSTIMEO 0x00000001
>
> Thanks. Good point, I'll add that in v3.
You could also add a compile assert to check that the flag is reserved.
David
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