Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751833AbcDOSYQ (ORCPT ); Fri, 15 Apr 2016 14:24:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:32919 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751075AbcDOSYN (ORCPT ); Fri, 15 Apr 2016 14:24:13 -0400 From: Jeff Moyer To: Dan Williams Cc: "Verma\, Vishal L" , "hch\@infradead.org" , "jack\@suse.cz" , "axboe\@fb.com" , "linux-nvdimm\@ml01.01.org" , "david\@fromorbit.com" , "linux-kernel\@vger.kernel.org" , "xfs\@oss.sgi.com" , "linux-block\@vger.kernel.org" , "linux-mm\@kvack.org" , "viro\@zeniv.linux.org.uk" , "linux-fsdevel\@vger.kernel.org" , "akpm\@linux-foundation.org" , "linux-ext4\@vger.kernel.org" , "Wilcox\, Matthew R" Subject: Re: [PATCH v2 5/5] dax: handle media errors in dax_do_io 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> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Fri, 15 Apr 2016 14:24:10 -0400 In-Reply-To: (Dan Williams's message of "Fri, 15 Apr 2016 11:17:39 -0700") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1171 Lines: 33 Dan Williams writes: > On Fri, Apr 15, 2016 at 11:06 AM, Jeff Moyer wrote: >> Dan Williams writes: >> >>>>> 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. 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)? I'm not sure that's >> a great plan, either. >> > > If errors are rare how much are we actually losing in practice? How long is a piece of string? > Moreover, we're going to do the full badblocks lookup anyway when we > call ->direct_access(). If we had that information earlier we can > avoid this fallback dance. None of the proposed approaches looks clean to me. I'll go along with whatever you guys think is best. I am in favor of wrapping up all that duplicated code, though. Cheers, Jeff