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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 B769AC433E2 for ; Mon, 14 Sep 2020 15:04:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7308520829 for ; Mon, 14 Sep 2020 15:04:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="FDHLUC5B" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726022AbgINPEI (ORCPT ); Mon, 14 Sep 2020 11:04:08 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:25746 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726285AbgINPEF (ORCPT ); Mon, 14 Sep 2020 11:04:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600095843; 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=kFVrrrfRjT3a23tm074wxzjtFdymZ366A9Lx0WOWK70=; b=FDHLUC5B4osvt5k6kI3XiEogFJyn0hSDlQ6bGiF/X36aZgTqB+gm8MrrWOzUwOD2BNjcE7 hxvrQqAEDmPQFmmJp1h9MH1XBiL1F5oYs0SZN2HmNX+1XtzVtfw121oChIPJQmMrDUC+4W CnFAwO2QLstte6pJuuyUAli07pe7o1o= 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-410-GCWNhFdoM6yySkwJjRDAuA-1; Mon, 14 Sep 2020 11:04:00 -0400 X-MC-Unique: GCWNhFdoM6yySkwJjRDAuA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8E2A9100747E; Mon, 14 Sep 2020 15:03:59 +0000 (UTC) Received: from localhost (unknown [10.18.25.174]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9C7655DC06; Mon, 14 Sep 2020 15:03:53 +0000 (UTC) Date: Mon, 14 Sep 2020 11:03:52 -0400 From: Mike Snitzer To: Damien Le Moal Cc: Ming Lei , Vijayendra Suman , "dm-devel@redhat.com" , "linux-block@vger.kernel.org" Subject: Re: [PATCH 1/3] block: fix blk_rq_get_max_sectors() to flow more carefully Message-ID: <20200914150352.GC14410@redhat.com> References: <20200911215338.44805-1-snitzer@redhat.com> <20200911215338.44805-2-snitzer@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 10.5.11.14 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Sun, Sep 13 2020 at 8:46pm -0400, Damien Le Moal wrote: > On 2020/09/12 6:53, Mike Snitzer wrote: > > blk_queue_get_max_sectors() has been trained for REQ_OP_WRITE_SAME and > > REQ_OP_WRITE_ZEROES yet blk_rq_get_max_sectors() didn't call it for > > those operations. > > > > Also, there is no need to avoid blk_max_size_offset() if > > 'chunk_sectors' isn't set because it falls back to 'max_sectors'. > > > > Signed-off-by: Mike Snitzer > > --- > > include/linux/blkdev.h | 19 +++++++++++++------ > > 1 file changed, 13 insertions(+), 6 deletions(-) > > > > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > > index bb5636cc17b9..453a3d735d66 100644 > > --- a/include/linux/blkdev.h > > +++ b/include/linux/blkdev.h > > @@ -1070,17 +1070,24 @@ static inline unsigned int blk_rq_get_max_sectors(struct request *rq, > > sector_t offset) > > { > > struct request_queue *q = rq->q; > > + int op; > > + unsigned int max_sectors; > > > > if (blk_rq_is_passthrough(rq)) > > return q->limits.max_hw_sectors; > > > > - if (!q->limits.chunk_sectors || > > - req_op(rq) == REQ_OP_DISCARD || > > - req_op(rq) == REQ_OP_SECURE_ERASE) > > - return blk_queue_get_max_sectors(q, req_op(rq)); > > + op = req_op(rq); > > + max_sectors = blk_queue_get_max_sectors(q, op); > > > > - return min(blk_max_size_offset(q, offset), > > - blk_queue_get_max_sectors(q, req_op(rq))); > > + switch (op) { > > + case REQ_OP_DISCARD: > > + case REQ_OP_SECURE_ERASE: > > + case REQ_OP_WRITE_SAME: > > + case REQ_OP_WRITE_ZEROES: > > + return max_sectors; > > + } > > Doesn't this break md devices ? (I think does use chunk_sectors for stride size, > no ?) > > As mentioned in my reply to Ming's email, this will allow these commands to > potentially cross over zone boundaries on zoned block devices, which would be an > immediate command failure. Depending on the implementation it is beneficial to get a large discard (one not constrained by chunk_sectors, e.g. dm-stripe.c's optimization for handling large discards and issuing N discards, one per stripe). Same could apply for other commands. Like all devices, zoned devices should impose command specific limits in the queue_limits (and not lean on chunk_sectors to do a one-size-fits-all). But that aside, yes I agree I didn't pay close enough attention to the implications of deferring the splitting of these commands until they were issued to underlying storage. This chunk_sectors early splitting override is a bit of a mess... not quite following the logic given we were supposed to be waiting to split bios as late as possible. Mike