From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F20EFC4BA13 for ; Wed, 26 Feb 2020 16:58:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CC8CA2467F for ; Wed, 26 Feb 2020 16:58:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Z5HqPk7R" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727112AbgBZQ6G (ORCPT ); Wed, 26 Feb 2020 11:58:06 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:49232 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727141AbgBZQ6F (ORCPT ); Wed, 26 Feb 2020 11:58:05 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582736284; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=sgFRQgERnZWSeTCYUsPGjYde4JUbCe/DftIr4ctMkfU=; b=Z5HqPk7RJNoP+Rc30O9vQpEQuaeAj1rdu/1n/6L8WW59XCFlB2keycTqvFU+0+kZtAjl8q scWf6wKp8wpQDgGYX4SjjUp95d6ykSohs7guPRNv//T9lvWCiBsjEvhkQvzbsLwis/2n1I lRigFNMahOlR29ev/THcNuJmMTmSZLE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-77-gR2VWTs9ONWsOjFxXq7p1A-1; Wed, 26 Feb 2020 11:58:01 -0500 X-MC-Unique: gR2VWTs9ONWsOjFxXq7p1A-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 869FE107ACC4; Wed, 26 Feb 2020 16:57:59 +0000 (UTC) Received: from horse.redhat.com (unknown [10.18.25.35]) by smtp.corp.redhat.com (Postfix) with ESMTP id DE30660BE1; Wed, 26 Feb 2020 16:57:56 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 76F622257D2; Wed, 26 Feb 2020 11:57:56 -0500 (EST) Date: Wed, 26 Feb 2020 11:57:56 -0500 From: Vivek Goyal To: Dan Williams Cc: Dave Chinner , Jeff Moyer , linux-fsdevel , linux-nvdimm , Christoph Hellwig , device-mapper development Subject: Re: [PATCH v5 2/8] drivers/pmem: Allow pmem_clear_poison() to accept arbitrary offset and len Message-ID: <20200226165756.GB30329@redhat.com> References: <20200221201759.GF25974@redhat.com> <20200223230330.GE10737@dread.disaster.area> <20200224201346.GC14651@redhat.com> <20200224211553.GD14651@redhat.com> <20200225133653.GA7488@redhat.com> <20200225200824.GB7488@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Feb 25, 2020 at 02:49:30PM -0800, Dan Williams wrote: [..] > > > I'm ok with replacing blkdev_issue_zeroout() with a dax operation > > > callback that deals with page aligned entries. That change at least > > > makes the error boundary symmetric across copy_from_iter() and the > > > zeroing path. > > > > IIUC, you are suggesting that modify dax_zero_page_range() to take page > > aligned start and size and call this interface from > > __dax_zero_page_range() and get rid of blkdev_issue_zeroout() in that > > path? > > > > Something like. > > > > __dax_zero_page_range() { > > if(page_aligned_io) > > call_dax_page_zero_range() > > else > > use_direct_access_and_memcpy; > > } > > > > And other callers of blkdev_issue_zeroout() in filesystems can migrate > > to calling dax_zero_page_range() instead. > > > > If yes, I am not seeing what advantage do we get by this change. > > > > - __dax_zero_page_range() seems to be called by only partial block > > zeroing code. So dax_zero_page_range() call will remain unused. > > > > > > - dax_zero_page_range() will be exact replacement of > > blkdev_issue_zeroout() so filesystems will not gain anything. Just that > > it will create a dax specific hook. > > > > In that case it might be simpler to just get rid of blkdev_issue_zeroout() > > call from __dax_zero_page_range() and make sure there are no callers of > > full block zeroing from this path. > > I think you're right. The path I'm concerned about not regressing is > the error clearing on new block allocation and we get that already via > xfs_zero_extent() and sb_issue_zeroout(). Well I was wrong. I found atleast one user which uses __dax_zero_page_range() to zero full PAGE_SIZE blocks. xfs_io -c "allocsp 32K 0" foo.txt In that case, I will add a new dax method say dax_zero_page_range() which will only take PAGE_SIZE aligned range will clear known poison and call that from __dax_zero_page_range() if I/O is PAGE_SIZE aligned. For now I will limit this interface to take only single page at a time because otherwise implementation becomes complex in dm/md stack where range has to be broken across multiple devices and there are no users because current iomap API passes one page at a time. So once we have grown users, then one can also tackle the complexity of modifying dm/md to break a page range across multiple devices. Will post a patch series for this. Thanks Vivek