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=-5.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 7E943C43441 for ; Mon, 19 Nov 2018 08:58:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4695320823 for ; Mon, 19 Nov 2018 08:58:18 +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="JLTbinaN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4695320823 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-block-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727122AbeKSTVP (ORCPT ); Mon, 19 Nov 2018 14:21:15 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:37666 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726289AbeKSTVP (ORCPT ); Mon, 19 Nov 2018 14:21:15 -0500 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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=C9EBn/npVuPiYxeMHCBFKi7NQeM9Vn4qO/S4Q+Wg4IY=; b=JLTbinaNQWYJWkdew8/qUHATH f2h5Rq6EB1N1NBv6rzUWGM7KCZMN4alVcbYXmBPG3xsFToV47MlqDjV8SiTABD0sIiZYCFOu0lQtk HklZlyROnjUqzf6892sT6ZDJnLUk9aVhRrY7moSWnq5wNQFFXHypHSRSEiBNS83v17Zfa8srnHtcf mxHPtC9EGuhMkZWl9JDnXMFv6QVHJVJS3XN3J1LOwaR/ifQCxxwgM6MvuTtsat16o1SdujbIzkDzy q8rumJ4mZcxYaBkD6g5Bqe8kK2C3yCFUkCtbNPW2JEz8rA6ONr0WG/a2nji93dk7YRhe2pF8e0Pns o6/NTKVDQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gOfNn-0000G8-N6; Mon, 19 Nov 2018 08:58:15 +0000 Date: Mon, 19 Nov 2018 00:58:15 -0800 From: Christoph Hellwig To: Keith Busch Cc: linux-scsi@vger.kernel.org, linux-block@vger.kernel.org, Jens Axboe , Martin Petersen , Bart Van Assche Subject: Re: [PATCHv3 2/3] scsi: Do not rely on blk-mq for double completions Message-ID: <20181119085815.GB29626@infradead.org> References: <20181115175820.13391-1-keith.busch@intel.com> <20181115175820.13391-3-keith.busch@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181115175820.13391-3-keith.busch@intel.com> User-Agent: Mutt/1.9.2 (2017-12-15) 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 > index 5d83a162d03b..c1d5e4e36125 100644 > --- a/drivers/scsi/scsi_lib.c > +++ b/drivers/scsi/scsi_lib.c > @@ -1635,8 +1635,11 @@ static blk_status_t scsi_mq_prep_fn(struct request *req) > > static void scsi_mq_done(struct scsi_cmnd *cmd) > { > + if (unlikely(test_and_set_bit(__SCMD_COMPLETE, &cmd->flags))) > + return; > trace_scsi_dispatch_cmd_done(cmd); > - blk_mq_complete_request(cmd->request); > + if (unlikely(!blk_mq_complete_request(cmd->request))) > + clear_bit(__SCMD_COMPLETE, &cmd->flags); > } This looks a little odd to me. If we didn't complete the command someone else did. Why would we clear the bit in this case? > static void scsi_mq_put_budget(struct blk_mq_hw_ctx *hctx) > @@ -1701,6 +1704,7 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx, > goto out_dec_host_busy; > req->rq_flags |= RQF_DONTPREP; > } else { > + cmd->flags &= ~SCMD_COMPLETE; > blk_mq_start_request(req); > } > > diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h > index d6fd2aba0380..ded7c7194a28 100644 > --- a/include/scsi/scsi_cmnd.h > +++ b/include/scsi/scsi_cmnd.h > @@ -58,6 +58,9 @@ struct scsi_pointer { > #define SCMD_TAGGED (1 << 0) > #define SCMD_UNCHECKED_ISA_DMA (1 << 1) > #define SCMD_INITIALIZED (1 << 2) > + > +#define __SCMD_COMPLETE 3 > +#define SCMD_COMPLETE (1 << __SCMD_COMPLETE) This mixing of atomic and non-atomic bitops looks rather dangerous to me. Can you add a new atomic_flags just for the completed flag, and always use the bitops on it for now? I think we can eventually kill most of the existing flags except for SCMD_TAGGED over the next merge window or two and then move that over as well. Otherwise the concept looks fine to me.