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=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 76FA3C2D0DB for ; Tue, 21 Jan 2020 14:43:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 43CB524653 for ; Tue, 21 Jan 2020 14:43:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="BSnRsEVM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729336AbgAUOn1 (ORCPT ); Tue, 21 Jan 2020 09:43:27 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:38168 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727817AbgAUOn1 (ORCPT ); Tue, 21 Jan 2020 09:43:27 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1579617805; 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=P/kFNLOn149gl4f8L/s6aC62LAQxTpZ4AIKpdDtErUw=; b=BSnRsEVMcJ9ILo5jIKBEaHvb7JSyMBdnnEunDaI7cvl1bXzhaTHf0Wt3OrrADpVGifQ1S+ adxtwM0vnHf0oBAFU25ea3OtjQkp0HXF0nLlK8IfqbtOXvx5GbMT8SZpY5l6bZMFAZ6RvA nPslHiOuU0se3p4c7WdQyjhqNKz2yFA= 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-115-nMbHgjLMPE6MiAMlKZu2_Q-1; Tue, 21 Jan 2020 09:43:21 -0500 X-MC-Unique: nMbHgjLMPE6MiAMlKZu2_Q-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BA0168018AE; Tue, 21 Jan 2020 14:43:16 +0000 (UTC) Received: from localhost (unknown [10.18.25.174]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6A0EC8BE1B; Tue, 21 Jan 2020 14:43:11 +0000 (UTC) Date: Tue, 21 Jan 2020 09:43:10 -0500 From: Mike Snitzer To: Kirill Tkhai Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, martin.petersen@oracle.com, bob.liu@oracle.com, axboe@kernel.dk, agk@redhat.com, dm-devel@redhat.com, song@kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca, Chaitanya.Kulkarni@wdc.com, darrick.wong@oracle.com, ming.lei@redhat.com, osandov@fb.com, jthumshirn@suse.de, minwoo.im.dev@gmail.com, damien.lemoal@wdc.com, andrea.parri@amarulasolutions.com, hare@suse.com, tj@kernel.org, ajay.joshi@wdc.com, sagi@grimberg.me, dsterba@suse.com, bvanassche@acm.org, dhowells@redhat.com, asml.silence@gmail.com Subject: Re: [PATCH v4 6/7] dm: Directly disable max_allocate_sectors for now Message-ID: <20200121144310.GA10055@redhat.com> References: <157960325642.108120.13626623438131044304.stgit@localhost.localdomain> <157960337238.108120.18048939587162465175.stgit@localhost.localdomain> <20200121122458.GA9365@redhat.com> <619a7a14-44e6-eca7-c1ea-3f04abeee53d@virtuozzo.com> <20200121134840.GA9944@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Tue, Jan 21 2020 at 9:20am -0500, Kirill Tkhai wrote: > On 21.01.2020 16:48, Mike Snitzer wrote: > > On Tue, Jan 21 2020 at 8:33am -0500, > > Kirill Tkhai wrote: > > > >> On 21.01.2020 15:36, Kirill Tkhai wrote: > >>> On 21.01.2020 15:24, Mike Snitzer wrote: > >>>> On Tue, Jan 21 2020 at 5:42am -0500, > >>>> Kirill Tkhai wrote: > >>>> > >>>>> Since dm inherits limits from underlining block devices, > >>>>> this patch directly disables max_allocate_sectors for dm > >>>>> till full allocation support is implemented. > >>>>> > >>>>> This prevents high-level primitives (generic_make_request_checks(), > >>>>> __blkdev_issue_write_zeroes(), ...) from sending REQ_ALLOCATE > >>>>> requests. > >>>>> > >>>>> Signed-off-by: Kirill Tkhai > >>>>> --- > >>>>> drivers/md/dm-table.c | 2 ++ > >>>>> drivers/md/md.h | 1 + > >>>>> 2 files changed, 3 insertions(+) > >>>> > >>>> You're mixing DM and MD changes in the same patch. > >>>> > >>>> But I'm wondering if it might be best to set this default for stacking > >>>> devices in blk_set_stacking_limits()? > >>>> > >>>> And then it is up to each stacking driver to override as needed. > >>> > >>> Hm. Sound like a good idea. This "lim->max_allocate_sectors = 0" in blk_set_stacking_limits() > >>> should work for dm's dm_calculate_queue_limits(), since it calls blk_stack_limits(), which is: > >>> > >>> t->max_allocate_sectors = min(t->max_allocate_sectors, > >>> b->max_allocate_sectors); > >>> > >>> Could you please tell is this fix is also enough for md? > >> > >> It looks like it's enough since queue defaults are set in md_alloc()->blk_set_stacking_limits(). > >> In case of we set "max_allocate_sectors = 0", in further it can be changed only manually, > >> but nobody does this. > > > > Yes, it will work to disable this capability for MD and DM. > > > > But if/when a stacked device _dooes_ want to support this then it'll be > > awkward to override this stacking default to allow blk_stack_limits() > > to properly stack up this limit. blk_limits are extremely fiddley so > > this isn't necessarily new. But by explicitly defaulting to 0 and then > > having blk_stack_limits use min() for this limit: it results in stacking > > drivers needing to clumsily unwind the default. E.g. DM will need to > > tweak its blk_stack_limits() related code to allow override that > > actually _does_ stack up the underlying devices' capability (and not > > just impose its own limit that ignores the underlying devices). > > > > So I'm not convinced this is the right way to go (be it the v4 approach > > you took or the cleaner use of blk_set_stacking_limits I suggested). > > Is there a strong vision about the way we should go? Or you leave this choose > up to me? I don't have time to work through it at the moment (e.g. implementing dm-thinp support to know what the block core code should be) so I'll just defer to you on a disabling it for now. > > And to be clear, I'm interested in having DM thinp support this > > capability to preallocate blocks. > > My opinion is it would be better to not mix several subsystem related > support in a single patch set. Both of the approaches (v4 or that you > suggested) do not prevents us to implement allocation support in next > patch series. After we have the base functionality enabled, we may add > support in other subsystems and drivers one by one with more focus > on the subsystem specificities and with the best possible attention. Yeah, I'm aware nothing is ever set in stone. Setting to 0 in blk_set_stacking_limits() is OK for now. Thanks, Mike