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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 86948EB64D9 for ; Thu, 15 Jun 2023 11:41:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344322AbjFOLlz (ORCPT ); Thu, 15 Jun 2023 07:41:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52818 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344270AbjFOLlV (ORCPT ); Thu, 15 Jun 2023 07:41:21 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6DDF6212C; Thu, 15 Jun 2023 04:39:16 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 985A4639DD; Thu, 15 Jun 2023 11:38:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F35FFC433BC; Thu, 15 Jun 2023 11:38:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1686829134; bh=pC9I6e0OWmAUP6vgtjaR7+ZgsLgeZHz9GxRxlURUdvs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WlXEJo+CzNj6Ai3idWQrgZRGPSrOC5Yp0jST/fGosBNNUn/YfinqLNxJgHeCt8Xac J0P0T+q74gFqPzoOjYQj8DlyS8YR41zh1VYmnKuGLtnuCNdrhlTxPiKsbKuZtx77sy cDxjk1l1FipPXudd28FY4yHLrI/6W9nMETjAzS23iR9NkXc4lMFdgVZca2A20ck0OW p1POzMflHisqzi2hILJFISF1NCNef0j/o7wErqYAxbuEekH1xREO1zAvRb1It+yAIc 5bxOZk4/t963Gb8dfz858O13NkAfK73XfinSHhGtOISyBkhDbrkDUV4wH67/2oikxt l2rPrYSFC1dPg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Uday Shankar , Costa Sapuntzakis , Randy Jennings , Hannes Reinecke , Christoph Hellwig , Keith Busch , Sasha Levin , sagi@grimberg.me, linux-nvme@lists.infradead.org Subject: [PATCH AUTOSEL 6.1 16/16] nvme: improve handling of long keep alives Date: Thu, 15 Jun 2023 07:38:16 -0400 Message-Id: <20230615113816.649135-16-sashal@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230615113816.649135-1-sashal@kernel.org> References: <20230615113816.649135-1-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.1.34 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Uday Shankar [ Upstream commit c7275ce6a5fd32ca9f5a6294ed89cf0523181af9 ] Upon keep alive completion, nvme_keep_alive_work is scheduled with the same delay every time. If keep alive commands are completing slowly, this may cause a keep alive timeout. The following trace illustrates the issue, taking KATO = 8 and TBKAS off for simplicity: 1. t = 0: run nvme_keep_alive_work, send keep alive 2. t = ε: keep alive reaches controller, controller restarts its keep alive timer 3. t = 4: host receives keep alive completion, schedules nvme_keep_alive_work with delay 4 4. t = 8: run nvme_keep_alive_work, send keep alive Here, a keep alive having RTT of 4 causes a delay of at least 8 - ε between the controller receiving successive keep alives. With ε small, the controller is likely to detect a keep alive timeout. Fix this by calculating the RTT of the keep alive command, and adjusting the scheduling delay of the next keep alive work accordingly. Reported-by: Costa Sapuntzakis Reported-by: Randy Jennings Signed-off-by: Uday Shankar Reviewed-by: Hannes Reinecke Reviewed-by: Christoph Hellwig Signed-off-by: Keith Busch Signed-off-by: Sasha Levin --- drivers/nvme/host/core.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index 06dd1c0780bfc..4e4203c327114 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -1234,6 +1234,20 @@ static enum rq_end_io_ret nvme_keep_alive_end_io(struct request *rq, struct nvme_ctrl *ctrl = rq->end_io_data; unsigned long flags; bool startka = false; + unsigned long rtt = jiffies - (rq->deadline - rq->timeout); + unsigned long delay = nvme_keep_alive_work_period(ctrl); + + /* + * Subtract off the keepalive RTT so nvme_keep_alive_work runs + * at the desired frequency. + */ + if (rtt <= delay) { + delay -= rtt; + } else { + dev_warn(ctrl->device, "long keepalive RTT (%u ms)\n", + jiffies_to_msecs(rtt)); + delay = 0; + } blk_mq_free_request(rq); @@ -1252,7 +1266,7 @@ static enum rq_end_io_ret nvme_keep_alive_end_io(struct request *rq, startka = true; spin_unlock_irqrestore(&ctrl->lock, flags); if (startka) - nvme_queue_keep_alive_work(ctrl); + queue_delayed_work(nvme_wq, &ctrl->ka_work, delay); return RQ_END_IO_NONE; } -- 2.39.2