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=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 4EE29C83008 for ; Tue, 28 Apr 2020 18:48:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2B40120575 for ; Tue, 28 Apr 2020 18:48:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="N+WnqWVX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730963AbgD1Ss0 (ORCPT ); Tue, 28 Apr 2020 14:48:26 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:53212 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730962AbgD1Sk6 (ORCPT ); Tue, 28 Apr 2020 14:40:58 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588099257; 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=4IhIJ7/e3VDH321W4uVTvr/gfrTSIY3xCZQuvN2kwiA=; b=N+WnqWVX+5qtBzKsJm8mWzS57E/AXUXsTl+JXKpehG+oyklcwaPx5LWKkv+Fvk3xecyK2d 57Mb4blpMW94qDkx1rQR2Gd+EZK3cshfnBHD97KYON70dkfx6bccAn3pTVq0D76vIg/ZM5 0l9oYwzr8mdmkuaGrk8ZJmNmGNpKajs= 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-152-4RG9HmGTOEun38Rst9DCTA-1; Tue, 28 Apr 2020 14:40:53 -0400 X-MC-Unique: 4RG9HmGTOEun38Rst9DCTA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1CF3C462; Tue, 28 Apr 2020 18:40:52 +0000 (UTC) Received: from localhost (unknown [10.18.25.174]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D80941C950; Tue, 28 Apr 2020 18:40:48 +0000 (UTC) Date: Tue, 28 Apr 2020 14:40:47 -0400 From: Mike Snitzer To: Christoph Hellwig Cc: Jens Axboe , linux-block@vger.kernel.org, dm-devel@redhat.com, linux-bcache@vger.kernel.org Subject: Re: [PATCH 3/3] block: bypass ->make_request_fn for blk-mq drivers Message-ID: <20200428184047.GB17609@redhat.com> References: <20200425075336.721021-1-hch@lst.de> <20200425075336.721021-4-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200425075336.721021-4-hch@lst.de> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Sat, Apr 25 2020 at 3:53am -0400, Christoph Hellwig wrote: > Call blk_mq_make_request when no ->make_request_fn is set. This is > safe now that blk_alloc_queue always sets up the pointer for make_request > based drivers. This avoids an indirect call in the blk-mq driver I/O > fast path, which is rather expensive due to spectre mitigations. > > Signed-off-by: Christoph Hellwig Makes me cringe thinking about all the indirect calls sprinkled throughout DM... Acked-by: Mike Snitzer