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=-11.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 7FA96C43214 for ; Fri, 13 Aug 2021 20:17:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 662C2610FF for ; Fri, 13 Aug 2021 20:17:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234510AbhHMURw (ORCPT ); Fri, 13 Aug 2021 16:17:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:42158 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234198AbhHMURv (ORCPT ); Fri, 13 Aug 2021 16:17:51 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5B5F4610CC; Fri, 13 Aug 2021 20:17:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628885844; bh=BSAHNaF2hq41VI5supF0uF+3EBwFFPHhfcd9ufAOMmM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=MAwG61mOYN7IhRo4JZHLdA0ZCaTjY7dxtcDwP4gVtPQ2m4eO3ZeJF1xPFzBJBacIA /8sRDlI5ULE+UyJGNPtkT+wBX6J1uadgg9dVzNAJB+k4cjrNzFI/xnRO4Kz5vdQxR5 cUMGI9U+IbZNcGifM12lQMuirGg+TkM0jH07xUTFh3GzpUhSdqsrTZmt5yQG76ydGr FTTmXs6+TufDl7NxLyzIoAqwmkfYRqfwcuXheWiskKLDao/Rlj9XAJrDDvsL3LWgnQ +gELDoXB+RhTBZLYLaBzEZsiJi8tg4tVh5IOEiFBiCUKkNwhkbpBQCj/+HCX3njaGS 71fH6tWIgxZug== Date: Fri, 13 Aug 2021 13:17:22 -0700 From: Keith Busch To: Jens Axboe Cc: io-uring@vger.kernel.org, linux-block@vger.kernel.org, hch@infradead.org Subject: Re: [PATCH 4/6] block: clear BIO_PERCPU_CACHE flag if polling isn't supported Message-ID: <20210813201722.GB2661@dhcp-10-100-145-180.wdc.com> References: <20210812154149.1061502-1-axboe@kernel.dk> <20210812154149.1061502-5-axboe@kernel.dk> <20210812173143.GA3138953@dhcp-10-100-145-180.wdc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu, Aug 12, 2021 at 11:41:58AM -0600, Jens Axboe wrote: > Indeed. Wonder if we should make that a small helper, as any clear of > REQ_HIPRI should clear BIO_PERCPU_CACHE as well. > > > diff --git a/block/blk-core.c b/block/blk-core.c > index 7e852242f4cc..d2722ecd4d9b 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -821,11 +821,8 @@ static noinline_for_stack bool submit_bio_checks(struct bio *bio) > } > } > > - if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) { > - /* can't support alloc cache if we turn off polling */ > - bio_clear_flag(bio, BIO_PERCPU_CACHE); > - bio->bi_opf &= ~REQ_HIPRI; > - } > + if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) > + bio_clear_hipri(bio); Since BIO_PERCPU_CACHE doesn't work without REQ_HIRPI, should this check look more like this? if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) bio->bi_opf &= ~REQ_HIPRI; if (!(bio->bi_opf & REQ_HIPRI)) bio_clear_flag(bio, BIO_PERCPU_CACHE); I realise the only BIO_PERCPU_CACHE user in this series never sets it without REQ_HIPRI, but it looks like a problem waiting to happen if nothing enforces this pairing: someone could set the CACHE flag on a QUEUE_FLAG_POLL enabled queue without setting HIPRI and get the wrong bio_put() action.