From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f69.google.com (mail-pa0-f69.google.com [209.85.220.69]) by kanga.kvack.org (Postfix) with ESMTP id 94AD26B0038 for ; Sun, 11 Sep 2016 23:35:51 -0400 (EDT) Received: by mail-pa0-f69.google.com with SMTP id fu12so42949918pac.1 for ; Sun, 11 Sep 2016 20:35:51 -0700 (PDT) Received: from mail-pf0-x241.google.com (mail-pf0-x241.google.com. [2607:f8b0:400e:c00::241]) by mx.google.com with ESMTPS id h2si13550880pah.243.2016.09.11.20.35.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 11 Sep 2016 20:35:50 -0700 (PDT) Received: by mail-pf0-x241.google.com with SMTP id x24so7416735pfa.3 for ; Sun, 11 Sep 2016 20:35:46 -0700 (PDT) Date: Mon, 12 Sep 2016 13:35:36 +1000 From: Nicholas Piggin Subject: Re: [RFC PATCH 1/2] mm, mincore2(): retrieve dax and tlb-size attributes of an address range Message-ID: <20160912133536.1bdb57a9@roar.ozlabs.ibm.com> In-Reply-To: <147361509579.17004.5258725187329709824.stgit@dwillia2-desk3.amr.corp.intel.com> References: <147361509579.17004.5258725187329709824.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams Cc: linux-mm@kvack.org, Andrea Arcangeli , Xiao Guangrong , Arnd Bergmann , linux-nvdimm@lists.01.org, linux-api@vger.kernel.org, Dave Hansen , linux-kernel@vger.kernel.org, Andrew Morton , "Kirill A. Shutemov" , linux-arch@vger.kernel.org On Sun, 11 Sep 2016 10:31:35 -0700 Dan Williams wrote: > As evidenced by this bug report [1], userspace libraries are interested > in whether a mapping is DAX mapped, i.e. no intervening page cache. > Rather than using the ambiguous VM_MIXEDMAP flag in smaps, provide an > explicit "is dax" indication as a new flag in the page vector populated > by mincore. Can you cc linux-arch when adding new syscalls (or other such things that need arch enablement). I wonder if the changelog for a new syscall should have a bit more grandeur. Without seeing patch 2, you might not know this was a new syscall just by reading the subject and changelog. mincore() defines other bits to be reserved, but I guess it probably breaks things if you suddenly started using them. It's a bit sad to introduce a new syscall for this and immediately use up all bits that can be returned. Would it be a serious problem to return a larger mask per page? Thanks, Nick -- 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