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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 0392AC04AA8 for ; Wed, 1 May 2019 11:56:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D0FAB21670 for ; Wed, 1 May 2019 11:56:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726390AbfEAL4b (ORCPT ); Wed, 1 May 2019 07:56:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45674 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726040AbfEAL4b (ORCPT ); Wed, 1 May 2019 07:56:31 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 05281308AA11; Wed, 1 May 2019 11:56:31 +0000 (UTC) Received: from segfault.boston.devel.redhat.com (segfault.boston.devel.redhat.com [10.19.60.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2D4DD53; Wed, 1 May 2019 11:56:30 +0000 (UTC) From: Jeff Moyer To: axboe@kernel.dk, Shenghui Wang Cc: viro@zeniv.linux.org.uk, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH] io_uring: use cpu_online() to check p->sq_thread_cpu instead of cpu_possible() References: <20190501072430.6674-1-shhuiw@foxmail.com> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 Date: Wed, 01 May 2019 07:56:29 -0400 In-Reply-To: <20190501072430.6674-1-shhuiw@foxmail.com> (Shenghui Wang's message of "Wed, 1 May 2019 15:24:30 +0800") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Wed, 01 May 2019 11:56:31 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Shenghui Wang writes: > This issue is found by running liburing/test/io_uring_setup test. > > When test run, the testcase "attempt to bind to invalid cpu" would not > pass with messages like: > io_uring_setup(1, 0xbfc2f7c8), \ > flags: IORING_SETUP_SQPOLL|IORING_SETUP_SQ_AFF, \ > resv: 0x00000000 0x00000000 0x00000000 0x00000000 0x00000000, \ > sq_thread_cpu: 2 > expected -1, got 3 > FAIL > > On my system, there is: > CPU(s) possible : 0-3 > CPU(s) online : 0-1 > CPU(s) offline : 2-3 > CPU(s) present : 0-1 > > The sq_thread_cpu 2 is offline on my system, so the bind should fail. > But cpu_possible() will pass the check. We shouldn't be able to bind > to an offline cpu. Use cpu_online() to do the check. > > After the change, the testcase run as expected: EINVAL will be returned > for cpu offlined. > > Signed-off-by: Shenghui Wang > --- > fs/io_uring.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/io_uring.c b/fs/io_uring.c > index 0e9fb2cb1984..aa3d39860a1c 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -2241,7 +2241,7 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx, > ctx->sqo_mm = current->mm; > > ret = -EINVAL; > - if (!cpu_possible(p->sq_thread_cpu)) > + if (!cpu_online(p->sq_thread_cpu)) > goto err; > > if (ctx->flags & IORING_SETUP_SQPOLL) { > @@ -2258,7 +2258,7 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx, > > cpu = array_index_nospec(p->sq_thread_cpu, NR_CPUS); > ret = -EINVAL; > - if (!cpu_possible(p->sq_thread_cpu)) > + if (!cpu_online(p->sq_thread_cpu)) > goto err; > > ctx->sqo_thread = kthread_create_on_cpu(io_sq_thread, Hmm. Why are we doing this check twice? Oh... Jens, I think you braino'd commit 917257daa0fea. Have a look. You probably wanted to get rid of the first check for cpu_possible. -Jeff