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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 C3CF0C433DF for ; Wed, 3 Jun 2020 04:58:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 699592072F for ; Wed, 3 Jun 2020 04:58:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="PX8/AEo7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725780AbgFCE62 (ORCPT ); Wed, 3 Jun 2020 00:58:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52368 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725275AbgFCE62 (ORCPT ); Wed, 3 Jun 2020 00:58:28 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D0BEC05BD43; Tue, 2 Jun 2020 21:58:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=4hilE/7L5QlGGOsWg+8etgv/113+iSUSl6TGtC/AcDQ=; b=PX8/AEo7bHIzGr1KmB4+ay+aB3 8I21/1neIEfA/E+ANgo7ymdeT4BMPYcyXt0gNairBfGVvD60ABXHeL2LovBIAoHbaEPoWGOCcinVa knfN9pZvH7LURV9bRrSx/SBINQZxv0dAV36UEpv1I1vm3D8iitkVzcgHI/u7vFJV7Xa8tWzdiijxG mvEt4+U2NSwaexg1+2hv8gQLRg0P+VN5tsLf3WxsYFXlWInMV1/SDWlz1xCk2zbOPnSpHLhVEKEJH GTlQ5PSzIf1/R2mH2DeSd8swKrOl+yLIxAc7r80CQgxbnmfXf3nL5tsbQ5au88bL7XodyWSJ2Xeia HxFSAjVw==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jgLTq-0004Uf-2w; Wed, 03 Jun 2020 04:58:22 +0000 Date: Tue, 2 Jun 2020 21:58:22 -0700 From: Christoph Hellwig To: Konstantin Khlebnikov Cc: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, dm-devel@redhat.com, linux-raid@vger.kernel.org, Jens Axboe , Christoph Hellwig Subject: Re: [PATCH RFC 1/3] block: add flag 'nowait_requests' into queue limits Message-ID: <20200603045822.GA17137@infradead.org> References: <159101473169.180989.12175693728191972447.stgit@buzz> <159101502963.180989.6228080995222059011.stgit@buzz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <159101502963.180989.6228080995222059011.stgit@buzz> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, Jun 01, 2020 at 03:37:09PM +0300, Konstantin Khlebnikov wrote: > Add flag for marking bio-based queues which support REQ_NOWAIT. > Set for all request based (mq) devices. > > Stacking device should set it after blk_set_stacking_limits() if method > make_request() itself doesn't delay requests or handles REQ_NOWAIT. I don't think this belongs into the queue limits. For example a stacking driver that always defers requests to a workqueue can support REQ_NOWAIT entirely independent of the underlying devices. I think this just needs to be a simple queue flag.