From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757121AbcHXWtU (ORCPT ); Wed, 24 Aug 2016 18:49:20 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:60976 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754171AbcHXWtR (ORCPT ); Wed, 24 Aug 2016 18:49:17 -0400 Date: Wed, 24 Aug 2016 15:47:58 -0700 From: Andrew Morton To: Ross Zwisler Cc: linux-kernel@vger.kernel.org, Dan Williams , Dave Chinner , Dave Hansen , Jan Kara , linux-mm@kvack.org, linux-nvdimm@ml01.01.org, Jeff Moyer Subject: Re: [PATCH v2] mm: silently skip readahead for DAX inodes Message-Id: <20160824154758.3bb6bbf66f8914f0e90c9183@linux-foundation.org> In-Reply-To: <20160824221429.21158-1-ross.zwisler@linux.intel.com> References: <20160824134212.e9b50aa36523fbfcbcfe2f55@linux-foundation.org> <20160824221429.21158-1-ross.zwisler@linux.intel.com> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 24 Aug 2016 16:14:29 -0600 Ross Zwisler wrote: > For DAX inodes we need to be careful to never have page cache pages in the > mapping->page_tree. This radix tree should be composed only of DAX > exceptional entries and zero pages. > > ltp's readahead02 test was triggering a warning because we were trying to > insert a DAX exceptional entry but found that a page cache page had > already been inserted into the tree. This page was being inserted into the > radix tree in response to a readahead(2) call. > > Readahead doesn't make sense for DAX inodes, but we don't want it to report > a failure either. Instead, we just return success and don't do any work. > > Signed-off-by: Ross Zwisler > Reported-by: Jeff Moyer cc:stable [4.5+] ?