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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 F41A6C43381 for ; Mon, 11 Jan 2021 13:46:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D3D5322226 for ; Mon, 11 Jan 2021 13:46:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387586AbhAKNqz (ORCPT ); Mon, 11 Jan 2021 08:46:55 -0500 Received: from mail.kernel.org ([198.145.29.99]:57630 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731240AbhAKNKm (ORCPT ); Mon, 11 Jan 2021 08:10:42 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 44D4D22515; Mon, 11 Jan 2021 13:10:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1610370626; bh=44NJXjj/d4Ugm0c5usw7vv7MSf4YLcnYQL4+KEEKQcU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zoH9Z5V1fRzQwQExL1AyAGL/Lc4DNgp367T1SHs3cmbmsueNZCMokFfPcF0t6d4hE 9zoWiw+zjbp2Sm79R88K/nlVKk/eY6uQhB+RkEBZ1f9jFtEryt+TDtauqTkuTR/JhF 3R3844uP3MUr2uRSoLsUco8UZD6uR7ls40HelOO4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "David S. Miller" , Alan Stern , Can Guo , Stanley Chu , Ming Lei , "Rafael J. Wysocki" , Christoph Hellwig , Hannes Reinecke , Jens Axboe , Bart Van Assche , "Martin K. Petersen" , Sasha Levin Subject: [PATCH 5.4 04/92] scsi: ide: Do not set the RQF_PREEMPT flag for sense requests Date: Mon, 11 Jan 2021 14:01:08 +0100 Message-Id: <20210111130039.373290696@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210111130039.165470698@linuxfoundation.org> References: <20210111130039.165470698@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Bart Van Assche [ Upstream commit 96d86e6a80a3ab9aff81d12f9f1f2a0da2917d38 ] RQF_PREEMPT is used for two different purposes in the legacy IDE code: 1. To mark power management requests. 2. To mark requests that should preempt another request. An (old) explanation of that feature is as follows: "The IDE driver in the Linux kernel normally uses a series of busywait delays during its initialization. When the driver executes these busywaits, the kernel does nothing for the duration of the wait. The time spent in these waits could be used for other initialization activities, if they could be run concurrently with these waits. More specifically, busywait-style delays such as udelay() in module init functions inhibit kernel preemption because the Big Kernel Lock is held, while yielding APIs such as schedule_timeout() allow preemption. This is true because the kernel handles the BKL specially and releases and reacquires it across reschedules allowed by the current thread. This IDE-preempt specification requires that the driver eliminate these busywaits and replace them with a mechanism that allows other work to proceed while the IDE driver is initializing." Since I haven't found an implementation of (2), do not set the PREEMPT flag for sense requests. This patch causes sense requests to be postponed while a drive is suspended instead of being submitted to ide_queue_rq(). If it would ever be necessary to restore the IDE PREEMPT functionality, that can be done by introducing a new flag in struct ide_request. Link: https://lore.kernel.org/r/20201209052951.16136-4-bvanassche@acm.org Cc: David S. Miller Cc: Alan Stern Cc: Can Guo Cc: Stanley Chu Cc: Ming Lei Cc: Rafael J. Wysocki Reviewed-by: Christoph Hellwig Reviewed-by: Hannes Reinecke Reviewed-by: Jens Axboe Signed-off-by: Bart Van Assche Signed-off-by: Martin K. Petersen Signed-off-by: Sasha Levin --- drivers/ide/ide-atapi.c | 1 - drivers/ide/ide-io.c | 5 ----- 2 files changed, 6 deletions(-) diff --git a/drivers/ide/ide-atapi.c b/drivers/ide/ide-atapi.c index 80bc3bf82f4d7..775fd34132abb 100644 --- a/drivers/ide/ide-atapi.c +++ b/drivers/ide/ide-atapi.c @@ -223,7 +223,6 @@ void ide_prep_sense(ide_drive_t *drive, struct request *rq) sense_rq->rq_disk = rq->rq_disk; sense_rq->cmd_flags = REQ_OP_DRV_IN; ide_req(sense_rq)->type = ATA_PRIV_SENSE; - sense_rq->rq_flags |= RQF_PREEMPT; req->cmd[0] = GPCMD_REQUEST_SENSE; req->cmd[4] = cmd_len; diff --git a/drivers/ide/ide-io.c b/drivers/ide/ide-io.c index b137f27a34d58..b32a013d827a0 100644 --- a/drivers/ide/ide-io.c +++ b/drivers/ide/ide-io.c @@ -512,11 +512,6 @@ repeat: * above to return us whatever is in the queue. Since we call * ide_do_request() ourselves, we end up taking requests while * the queue is blocked... - * - * We let requests forced at head of queue with ide-preempt - * though. I hope that doesn't happen too much, hopefully not - * unless the subdriver triggers such a thing in its own PM - * state machine. */ if ((drive->dev_flags & IDE_DFLAG_BLOCKED) && ata_pm_request(rq) == 0 && -- 2.27.0