From patchwork Mon Aug 31 02:53:52 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bart Van Assche X-Patchwork-Id: 257819 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=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, 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 80E8DC433E2 for ; Mon, 31 Aug 2020 02:54:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 65BDA2076D for ; Mon, 31 Aug 2020 02:54:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726775AbgHaCyK (ORCPT ); Sun, 30 Aug 2020 22:54:10 -0400 Received: from mail-pl1-f194.google.com ([209.85.214.194]:33545 "EHLO mail-pl1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726573AbgHaCyJ (ORCPT ); Sun, 30 Aug 2020 22:54:09 -0400 Received: by mail-pl1-f194.google.com with SMTP id h2so2361511plr.0 for ; Sun, 30 Aug 2020 19:54:08 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=S8GnYufv9MZP7N22DryU0jHU7x5XYfvZ5ydievKhN2I=; b=nj7YUQBlTcKnv8ItHN6MJwKS9XUgAAJy/VEsfl0kXy2tc6RsZptIkThHpu/pnrYKx3 zygP5sCFgmtwlD5PsKOTDKvgHw40/8lAfFhCcuhFqmQ5OyuvXzhE1VGLQLe8apavqmTM ezJksUbGty3GVa8v+KKOKee8XvOowqOEvpshMHneS+Mu9gu4ctuI5jeWOltBpfxK0332 SUynII4OK+qQfKOnW2xjMxP5n8zl3hMquQ5xg4W2uvzvIh1MG9I+EyAww9tv3A9vFDEO UEIwzdkbTf5G9dWjFP2lQ91UBk1uLDLPdM5CsFe8AqgjVyly8L2hX0im4G9TDf6cncmc C3sQ== X-Gm-Message-State: AOAM531utQesqxYQdgRmxVE8kmwbPtRfqcQnOcghP/evKhj5IIr2pPT2 omEELCZX1aQGf/H7Vnq1QN8= X-Google-Smtp-Source: ABdhPJxiV2BNFdqYaNOGPLBxH1mY8UlWyz3nQaUUXvxkxoPgH80f0ydipEcvLbdRkQVqvfEQwQCOdg== X-Received: by 2002:a17:90a:af84:: with SMTP id w4mr8678964pjq.94.1598842448395; Sun, 30 Aug 2020 19:54:08 -0700 (PDT) Received: from asus.hsd1.ca.comcast.net (c-73-241-217-19.hsd1.ca.comcast.net. [73.241.217.19]) by smtp.gmail.com with ESMTPSA id l123sm583569pgl.24.2020.08.30.19.54.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 30 Aug 2020 19:54:07 -0700 (PDT) From: Bart Van Assche To: Alan Stern Cc: linux-scsi@vger.kernel.org, Martin Kepplinger , Can Guo , Bart Van Assche , "David S . Miller" Subject: [PATCH RFC 1/6] ide: Do not set the RQF_PREEMPT flag for sense requests Date: Sun, 30 Aug 2020 19:53:52 -0700 Message-Id: <20200831025357.32700-2-bvanassche@acm.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200831025357.32700-1-bvanassche@acm.org> References: <20200831025357.32700-1-bvanassche@acm.org> MIME-Version: 1.0 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org 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. This patch is a first step towards removing the PREEMPT flag from the block layer. Cc: David S. Miller Signed-off-by: Bart Van Assche --- drivers/ide/ide-atapi.c | 1 - 1 file changed, 1 deletion(-) diff --git a/drivers/ide/ide-atapi.c b/drivers/ide/ide-atapi.c index 2162bc80f09e..013ad33fbbc8 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;