From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boaz Harrosh Subject: Re: regression introduced by "block: Add support for DAX reads/writes to block devices" Date: Thu, 13 Aug 2015 08:32:10 +0300 Message-ID: <55CC2BDA.3080906@plexistor.com> References: <100D68C7BA14664A8938383216E40DE04091408C@FMSMSX114.amr.corp.intel.com> <100D68C7BA14664A8938383216E40DE0409144D9@FMSMSX114.amr.corp.intel.com> <55C855D5.1070001@plexistor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: "Wilcox, Matthew R" , "linda.knippers@hp.com" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" To: Jeff Moyer Return-path: Received: from mail-wi0-f178.google.com ([209.85.212.178]:36663 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751041AbbHMFcN (ORCPT ); Thu, 13 Aug 2015 01:32:13 -0400 Received: by wicja10 with SMTP id ja10so137321155wic.1 for ; Wed, 12 Aug 2015 22:32:12 -0700 (PDT) In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 08/13/2015 12:11 AM, Jeff Moyer wrote: > Boaz Harrosh writes: > >> On 08/07/2015 11:41 PM, Jeff Moyer wrote: >> <> >>> >>>> We need to cope with the case where the end of a partition isn't on a >>>> page boundary though. >>> >>> Well, that's usually done by falling back to buffered I/O. I gave that >>> a try and panicked the box. :) I'll keep looking into it, but probably >>> won't have another patch until next week. >>> >> >> lets slow down for a sec, please. >> >> We have all established that an unaligned partition start is BAD and not supported? > > No. Unaligned partitions on RAID arrays or 512e devices are bad because > they result in suboptimal performance. They are most certainly still > supported, though. > What ? I meant for dax on pmem or brd. I meant that we *do not* support dax access on an unaligned partition start. (None dax is perfectly supported) We did it this way because of the direct_access API that returns a pfn with is PAGE_SIZE. We could introduce a pfn+offset but we thought it is not worth it, and that dax should be page aligned for code simplicity Cheers Boaz > -Jeff >