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 D4B85C433EF for ; Mon, 20 Jun 2022 16:11:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243106AbiFTQL5 (ORCPT ); Mon, 20 Jun 2022 12:11:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37702 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242145AbiFTQL5 (ORCPT ); Mon, 20 Jun 2022 12:11:57 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6E9DC20BC7 for ; Mon, 20 Jun 2022 09:11:55 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 2FE8621B85; Mon, 20 Jun 2022 16:11:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1655741514; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=y2ws/QxBRb/M2rDqfKbqG9c7pW0RmRLlad4HiaJaQ2o=; b=MM8vOpUq6kNzxr402Z3QvaclRyMEtm5YEiVn6oW1cEHEVthIioNOAMAckKOzqpXygpquTo mzYY3JaMh3dPNH19RR/DiN0WoeigkSQRHHddVLjYY7qlSh7OlKTSF9qAHtHpgPob5K/ry7 CTR+r/aSB6mIXO+as8CCl9I9O2neRgE= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1655741514; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=y2ws/QxBRb/M2rDqfKbqG9c7pW0RmRLlad4HiaJaQ2o=; b=KMgmpFONVktmrWp2pFvMgTH1Vuo6rCSX8cJ7Bdn4kSvIZZWjfdPv/CJqqdYl+vdtJ9+PY4 O9wixsKzeERXHYAA== Received: from quack3.suse.cz (unknown [10.100.224.230]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id A50432C142; Mon, 20 Jun 2022 16:11:53 +0000 (UTC) Received: by quack3.suse.cz (Postfix, from userid 1000) id 39BFAA0637; Mon, 20 Jun 2022 18:11:53 +0200 (CEST) From: Jan Kara To: Jens Axboe Cc: , Damien Le Moal , Bart Van Assche , Niklas Cassel , Jan Kara Subject: [PATCH 1/8] block: fix default IO priority handling again Date: Mon, 20 Jun 2022 18:11:42 +0200 Message-Id: <20220620161153.11741-1-jack@suse.cz> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20220620160726.19798-1-jack@suse.cz> References: <20220620160726.19798-1-jack@suse.cz> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3263; h=from:subject; bh=PJc+JSJchvfeOzZSCrbFJ2fBI9++bCpTYDxnDWkhbBI=; b=owEBbQGS/pANAwAIAZydqgc/ZEDZAcsmYgBisJw/ZmWK9FC6GkB36zwOPYVbpI8w1LLy0yy3ms1c L4WtZ7aJATMEAAEIAB0WIQSrWdEr1p4yirVVKBycnaoHP2RA2QUCYrCcPwAKCRCcnaoHP2RA2c8sCA DRWzUveYUtr5xuIa3RDYS9zfHlHg2q3Ji1FgaW9fEq6IrzFGwEV7EDb6C/KGgBmbToivmjN+eG0gx7 XVIFkr4375nlrNblLUUmCQeNj0FUF4I2eK8LjjbeWMsJTF2zJ4LjICewAZXG/pCVD7UiqA683yRQND 9M4cZeXnjVkFqmX2KdsbJsp9VeuKOLX3D8uFnzLhEgUqysVja3krQRhAd54jemCqjokMFhy0y6SA5a sUXHwL0G/7M7SDTDKyXQufuw+2kPcRGGxzO4seLP+8lOMHKoucw7YTpkl7ZJY4xsd1JnnGymNaWuRh N8F2rZGqHc2yxCBQrWROKVhQPpuP8Z X-Developer-Key: i=jack@suse.cz; a=openpgp; fpr=93C6099A142276A28BBE35D815BC833443038D8C Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 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. Fixes: e70344c05995 ("block: fix default IO priority handling") Signed-off-by: Jan Kara --- block/blk-ioc.c | 2 ++ block/ioprio.c | 4 ++-- include/linux/ioprio.h | 2 +- 3 files changed, 5 insertions(+), 3 deletions(-) diff --git a/block/blk-ioc.c b/block/blk-ioc.c index df9cfe4ca532..63fc02042408 100644 --- a/block/blk-ioc.c +++ b/block/blk-ioc.c @@ -247,6 +247,8 @@ static struct io_context *alloc_io_context(gfp_t gfp_flags, int node) INIT_HLIST_HEAD(&ioc->icq_list); INIT_WORK(&ioc->release_work, ioc_release_fn); #endif + ioc->ioprio = IOPRIO_DEFAULT; + return ioc; } diff --git a/block/ioprio.c b/block/ioprio.c index 2fe068fcaad5..2a34cbca18ae 100644 --- a/block/ioprio.c +++ b/block/ioprio.c @@ -157,9 +157,9 @@ static int get_task_ioprio(struct task_struct *p) 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); } diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h index 3f53bc27a19b..3d088a88f832 100644 --- 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. -- 2.35.3