From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id 7D9656B025E for ; Wed, 24 Aug 2016 16:42:14 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id w128so52233689pfd.3 for ; Wed, 24 Aug 2016 13:42:14 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id j8si11267480paj.168.2016.08.24.13.42.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 Aug 2016 13:42:13 -0700 (PDT) Date: Wed, 24 Aug 2016 13:42:12 -0700 From: Andrew Morton Subject: Re: [PATCH] mm: silently skip readahead for DAX inodes Message-Id: <20160824134212.e9b50aa36523fbfcbcfe2f55@linux-foundation.org> In-Reply-To: <20160824203712.4580-1-ross.zwisler@linux.intel.com> References: <20160824203712.4580-1-ross.zwisler@linux.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: 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 , stable@vger.kernel.org On Wed, 24 Aug 2016 14:37:12 -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. > > --- a/mm/readahead.c > +++ b/mm/readahead.c > @@ -8,6 +8,7 @@ > */ > > #include > +#include > #include > #include > #include > @@ -544,6 +545,9 @@ do_readahead(struct address_space *mapping, struct file *filp, > if (!mapping || !mapping->a_ops) > return -EINVAL; > > + if (dax_mapping(mapping)) > + return 0; > + Please don't force readers to go spend minutes putzing around in the git tree trying to understand your code. /* these things considered useful! */ -- 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