From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756479AbcHXWPs (ORCPT ); Wed, 24 Aug 2016 18:15:48 -0400 Received: from mga01.intel.com ([192.55.52.88]:49650 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755703AbcHXWPr (ORCPT ); Wed, 24 Aug 2016 18:15:47 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,572,1464678000"; d="scan'208";a="1041026595" From: Ross Zwisler To: linux-kernel@vger.kernel.org Cc: Ross Zwisler , Andrew Morton , Dan Williams , Dave Chinner , Dave Hansen , Jan Kara , linux-mm@kvack.org, linux-nvdimm@ml01.01.org, Jeff Moyer Subject: [PATCH v2] mm: silently skip readahead for DAX inodes Date: Wed, 24 Aug 2016 16:14:29 -0600 Message-Id: <20160824221429.21158-1-ross.zwisler@linux.intel.com> X-Mailer: git-send-email 2.9.0 In-Reply-To: <20160824134212.e9b50aa36523fbfcbcfe2f55@linux-foundation.org> References: <20160824134212.e9b50aa36523fbfcbcfe2f55@linux-foundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- Changes from v1: - Added a comment so readers don't have to go putzing around in the git tree to understand why we're doing what we're doing. :) (akpm) --- mm/readahead.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/mm/readahead.c b/mm/readahead.c index 65ec288..c8a955b 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -8,6 +8,7 @@ */ #include +#include #include #include #include @@ -544,6 +545,14 @@ do_readahead(struct address_space *mapping, struct file *filp, if (!mapping || !mapping->a_ops) return -EINVAL; + /* + * 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. + */ + if (dax_mapping(mapping)) + return 0; + return force_page_cache_readahead(mapping, filp, index, nr); } -- 2.9.0