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 77E03C19F2D for ; Tue, 9 Aug 2022 18:19:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345903AbiHISTb (ORCPT ); Tue, 9 Aug 2022 14:19:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42600 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346823AbiHISRt (ORCPT ); Tue, 9 Aug 2022 14:17:49 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E45A42ED42; Tue, 9 Aug 2022 11:06:57 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 645C5B818B7; Tue, 9 Aug 2022 18:06:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9C25C43141; Tue, 9 Aug 2022 18:06:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1660068390; bh=mOhX7/1JiVZXl/rUxysqLLJzKJJU34tJ44uNbeSOHMw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QTaspwzr1X6z07//rISv7i4ZvL83XQCozOcU2RuHLCEfv5qErOQX4bG9YotMZ5lNC CmdZnC/R41SBZKJR7mRXeYIRr5yKP+Y8HMySiD3fikJn2WOKbnAbbc67xy5wzfFqBw Y31vLyuJ6Uy9aqZU+AHE2wXyatA/UIvHLh+BgpcI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Damien Le Moal , Jan Kara , Christoph Hellwig , Jens Axboe Subject: [PATCH 5.18 02/35] block: fix default IO priority handling again Date: Tue, 9 Aug 2022 20:00:31 +0200 Message-Id: <20220809175515.135974385@linuxfoundation.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20220809175515.046484486@linuxfoundation.org> References: <20220809175515.046484486@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: stable@vger.kernel.org From: Jan Kara commit e589f46445960c274cc813a1cc8e2fc73b2a1849 upstream. Commit e70344c05995 ("block: fix default IO priority handling") introduced an inconsistency in get_current_ioprio() that tasks without IO context return IOPRIO_DEFAULT priority while tasks with freshly allocated IO context will return 0 (IOPRIO_CLASS_NONE/0) IO priority. Tasks without IO context used to be rare before 5a9d041ba2f6 ("block: move io_context creation into where it's needed") but after this commit they became common because now only BFQ IO scheduler setups task's IO context. Similar inconsistency is there for get_task_ioprio() so this inconsistency is now exposed to userspace and userspace will see different IO priority for tasks operating on devices with BFQ compared to devices without BFQ. Furthemore the changes done by commit e70344c05995 change the behavior when no IO priority is set for BFQ IO scheduler which is also documented in ioprio_set(2) manpage: "If no I/O scheduler has been set for a thread, then by default the I/O priority will follow the CPU nice value (setpriority(2)). In Linux kernels before version 2.6.24, once an I/O priority had been set using ioprio_set(), there was no way to reset the I/O scheduling behavior to the default. Since Linux 2.6.24, specifying ioprio as 0 can be used to reset to the default I/O scheduling behavior." So make sure we default to IOPRIO_CLASS_NONE as used to be the case before commit e70344c05995. Also cleanup alloc_io_context() to explicitely set this IO priority for the allocated IO context to avoid future surprises. Note that we tweak ioprio_best() to maintain ioprio_get(2) behavior and make this commit easily backportable. CC: stable@vger.kernel.org Fixes: e70344c05995 ("block: fix default IO priority handling") Reviewed-by: Damien Le Moal Tested-by: Damien Le Moal Signed-off-by: Jan Kara Reviewed-by: Christoph Hellwig Link: https://lore.kernel.org/r/20220623074840.5960-1-jack@suse.cz Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/blk-ioc.c | 2 ++ block/ioprio.c | 4 ++-- include/linux/ioprio.h | 2 +- 3 files changed, 5 insertions(+), 3 deletions(-) --- a/block/blk-ioc.c +++ b/block/blk-ioc.c @@ -247,6 +247,8 @@ static struct io_context *alloc_io_conte INIT_HLIST_HEAD(&ioc->icq_list); INIT_WORK(&ioc->release_work, ioc_release_fn); #endif + ioc->ioprio = IOPRIO_DEFAULT; + return ioc; } --- a/block/ioprio.c +++ b/block/ioprio.c @@ -157,9 +157,9 @@ out: int ioprio_best(unsigned short aprio, unsigned short bprio) { if (!ioprio_valid(aprio)) - aprio = IOPRIO_DEFAULT; + aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_BE_NORM); if (!ioprio_valid(bprio)) - bprio = IOPRIO_DEFAULT; + bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_BE_NORM); return min(aprio, bprio); } --- a/include/linux/ioprio.h +++ b/include/linux/ioprio.h @@ -11,7 +11,7 @@ /* * Default IO priority. */ -#define IOPRIO_DEFAULT IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_BE_NORM) +#define IOPRIO_DEFAULT IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0) /* * Check that a priority value has a valid class.