From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f197.google.com (mail-ob0-f197.google.com [209.85.214.197]) by kanga.kvack.org (Postfix) with ESMTP id AA2D56B0005 for ; Fri, 15 Apr 2016 15:10:24 -0400 (EDT) Received: by mail-ob0-f197.google.com with SMTP id th5so42948472obc.1 for ; Fri, 15 Apr 2016 12:10:24 -0700 (PDT) Received: from g4t3426.houston.hp.com (g4t3426.houston.hp.com. [15.201.208.54]) by mx.google.com with ESMTPS id jx3si17038386oeb.82.2016.04.15.12.10.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 15 Apr 2016 12:10:24 -0700 (PDT) Message-ID: <1460746909.4597.7.camel@hpe.com> Subject: Re: [PATCH v2 5/5] dax: handle media errors in dax_do_io From: Toshi Kani Date: Fri, 15 Apr 2016 13:01:49 -0600 In-Reply-To: References: <1459303190-20072-1-git-send-email-vishal.l.verma@intel.com> <1459303190-20072-6-git-send-email-vishal.l.verma@intel.com> <1460739288.3012.3.camel@intel.com> <1460741821.3012.11.camel@intel.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams , Jeff Moyer Cc: "axboe@fb.com" , "jack@suse.cz" , "david@fromorbit.com" , "linux-kernel@vger.kernel.org" , "xfs@oss.sgi.com" , "hch@infradead.org" , "linux-mm@kvack.org" , "linux-block@vger.kernel.org" , "viro@zeniv.linux.org.uk" , "linux-nvdimm@ml01.01.org" , "linux-fsdevel@vger.kernel.org" , "akpm@linux-foundation.org" , "linux-ext4@vger.kernel.org" , "Wilcox, Matthew R" On Fri, 2016-04-15 at 11:17 -0700, Dan Williams wrote: > On Fri, Apr 15, 2016 at 11:06 AM, Jeff Moyer wrote: > > > > Dan Williams writes: > >A > > > > > There's a lot of special casing here, so you might consider > > > > > adding comments. > > > > Correct - maybe we should reconsider wrapper-izing this? :) > > > Another option is just to skip dax_do_io() and this special casing > > > fallback entirely if errors are present.A A I.e. only attempt dax_do_io > > > when: IS_DAX() && gendisk->bb && bb->count == 0. > > > > So, if there's an error anywhere on the device, penalize all I/O (not > > just writes, and not just on sectors that are bad)?A A I'm not sure > > that's a great plan, either. > > > If errors are rare how much are we actually losing in practice? > Moreover, we're going to do the full badblocks lookup anyway when we > call ->direct_access().A A If we had that information earlier we can > avoid this fallback dance. A system running with DAX may have active data set in NVDIMM lager than RAM size. A In this case, falling back to non-DAX will allocate page cache for the data, which will saturate the system with memory pressure. Thanks, -Toshi A -- 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