From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id 98D1D6B0390 for ; Tue, 4 Apr 2017 03:46:22 -0400 (EDT) Received: by mail-wr0-f197.google.com with SMTP id q19so27369612wra.6 for ; Tue, 04 Apr 2017 00:46:22 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com. [148.163.158.5]) by mx.google.com with ESMTPS id a16si2903210wme.143.2017.04.04.00.46.20 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 04 Apr 2017 00:46:21 -0700 (PDT) Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v347i0Z7091085 for ; Tue, 4 Apr 2017 03:46:19 -0400 Received: from e06smtp15.uk.ibm.com (e06smtp15.uk.ibm.com [195.75.94.111]) by mx0b-001b2d01.pphosted.com with ESMTP id 29m1yp6wj3-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 04 Apr 2017 03:46:19 -0400 Received: from localhost by e06smtp15.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 4 Apr 2017 08:46:17 +0100 Date: Tue, 4 Apr 2017 10:46:13 +0300 From: Mike Rapoport Subject: Re: [PATCH for 4.11] userfaultfd: report actual registered features in fdinfo References: <1491140181-22121-1-git-send-email-rppt@linux.vnet.ibm.com> <20170403143523.GC5107@redhat.com> <20170403151024.GA14802@rapoport-lnx> <20170403163034.GD5107@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170403163034.GD5107@redhat.com> Message-Id: <20170404074612.GA6082@rapoport-lnx> Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: Andrew Morton , Pavel Emelyanov , linux-mm@kvack.org Hello Andrea, On Mon, Apr 03, 2017 at 06:30:34PM +0200, Andrea Arcangeli wrote: > 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. > Well, by the time CRIU checkpoints open file descriptors, the process is already stopped, hence we are not racing with anything here. -- 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