linux-kernel - Re: [PATCH 3/3] userfaultfd: non-cooperative: allow synchronous EVENT

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Date:   Wed, 28 Feb 2018 10:26:14 +0200
From:   Mike Rapoport <rppt@...ux.vnet.ibm.com>
To:     Pavel Emelyanov <xemul@...tuozzo.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        linux-mm <linux-mm@...ck.org>,
        linux-api <linux-api@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>, crml <criu@...nvz.org>
Subject: Re: [PATCH 3/3] userfaultfd: non-cooperative: allow synchronous
 EVENT_REMOVE

On Wed, Feb 28, 2018 at 11:21:02AM +0300, Pavel Emelyanov wrote:
> 
> > @@ -52,6 +53,7 @@
> >  #define _UFFDIO_WAKE			(0x02)
> >  #define _UFFDIO_COPY			(0x03)
> >  #define _UFFDIO_ZEROPAGE		(0x04)
> > +#define _UFFDIO_WAKE_SYNC_EVENT		(0x05)
> 
> Excuse my ignorance, but what's the difference between UFFDIO_WAKE and UFFDIO_WAKE_SYNC_EVENT?

UFFDIO_WAKE is used when UFFDIO_COPY/UFFDIO_ZERO page are used with
UFFDIO_*_MODE_DONTWAKE flag set and it presumes 'struct uffdio_range'
argument to the ioctl(). Since waking up a non page fault event requires
different parameters I've add new ioctl to keep backwards compatibility.
 
> -- Pavel
> 

-- 
Sincerely yours,
Mike.