From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f200.google.com (mail-qk0-f200.google.com [209.85.220.200]) by kanga.kvack.org (Postfix) with ESMTP id A170B6B0038 for ; Mon, 3 Apr 2017 12:30:37 -0400 (EDT) Received: by mail-qk0-f200.google.com with SMTP id d66so48542332qkb.0 for ; Mon, 03 Apr 2017 09:30:37 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id 33si12336118qth.121.2017.04.03.09.30.36 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 03 Apr 2017 09:30:36 -0700 (PDT) Date: Mon, 3 Apr 2017 18:30:34 +0200 From: Andrea Arcangeli Subject: Re: [PATCH for 4.11] userfaultfd: report actual registered features in fdinfo Message-ID: <20170403163034.GD5107@redhat.com> References: <1491140181-22121-1-git-send-email-rppt@linux.vnet.ibm.com> <20170403143523.GC5107@redhat.com> <20170403151024.GA14802@rapoport-lnx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170403151024.GA14802@rapoport-lnx> Sender: owner-linux-mm@kvack.org List-ID: To: Mike Rapoport Cc: Andrew Morton , Pavel Emelyanov , linux-mm@kvack.org Hello Mike, On Mon, Apr 03, 2017 at 06:10:24PM +0300, Mike Rapoport wrote: > Actually, I've found these details in /proc useful when I was experimenting > with checkpoint-restore of an application that uses userfaultfd. With > interface in /proc// we know exactly which process use userfaultfd and > can act appropriately. You've to be somewhat serialized by other means though, because "exactly" has a limit with fdinfo. For example by the time read() returns, the uffd may have been closed already by the app (just the uffd isn't ->release()d yet as the last fput has yet to run, the fdinfo runs the last fput in such case). As long as you can cope with this and you've a stable fdinfo it's ok. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org