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Mon, 7 Nov 2022 16:26:22 +0000 Received: from LV2PR12MB5869.namprd12.prod.outlook.com ([fe80::7a81:a4e4:bb9c:d1de]) by LV2PR12MB5869.namprd12.prod.outlook.com ([fe80::7a81:a4e4:bb9c:d1de%6]) with mapi id 15.20.5791.026; Mon, 7 Nov 2022 16:26:22 +0000 Date: Mon, 7 Nov 2022 12:26:21 -0400 From: Jason Gunthorpe To: Qi Zheng Cc: dvyukov@google.com, willy@infradead.org, akinobu.mita@gmail.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] mm: fix unexpected changes to {failslab|fail_page_alloc}.attr Message-ID: References: <20221107033109.59709-1-zhengqi.arch@bytedance.com> <4736d199-7e70-6bc3-30e6-0f644c81a10c@bytedance.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4736d199-7e70-6bc3-30e6-0f644c81a10c@bytedance.com> X-ClientProxiedBy: BL1PR13CA0446.namprd13.prod.outlook.com (2603:10b6:208:2c3::31) To LV2PR12MB5869.namprd12.prod.outlook.com (2603:10b6:408:176::16) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV2PR12MB5869:EE_|MW4PR12MB5626:EE_ X-MS-Office365-Filtering-Correlation-Id: 7aa3efc5-5a27-4357-9579-08dac0dccec0 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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dkim=pass header.d=Nvidia.com header.s=selector2 header.b=n4trIcou; spf=pass (imf14.hostedemail.com: domain of jgg@nvidia.com designates 40.107.102.70 as permitted sender) smtp.mailfrom=jgg@nvidia.com; dmarc=pass (policy=reject) header.from=nvidia.com; arc=pass ("microsoft.com:s=arcselector9901:i=1") X-Stat-Signature: 8415bzykaygzncdkbz1fqog86rra1gz8 X-Rspam-User: X-HE-Tag: 1667838384-666262 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000033, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Nov 07, 2022 at 11:05:42PM +0800, Qi Zheng wrote: > > > On 2022/11/7 20:42, Jason Gunthorpe wrote: > > On Mon, Nov 07, 2022 at 11:31:09AM +0800, Qi Zheng wrote: > > > > > @@ -31,9 +33,9 @@ bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags) > > > return false; > > > if (gfpflags & __GFP_NOWARN) > > > - failslab.attr.no_warn = true; > > > + flags |= FAULT_NOWARN; > > > > You should add a comment here about why this is required, to avoid > > deadlocking printk > > I think this comment should be placed where __GFP_NOWARN is specified > instead of here. What do you think? :) NOWARN is clear what it does, it is this specifically that is very subtle about avoiding deadlock aginst allocations triggered by printk/etc code. Jason