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Mon, 07 Nov 2022 18:48:04 -0800 (PST) Message-ID: <0fd0c72d-badc-ad75-f0fe-91bc148820f2@bytedance.com> Date: Tue, 8 Nov 2022 10:47:58 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.3.3 Subject: Re: [PATCH] mm: fix unexpected changes to {failslab|fail_page_alloc}.attr Content-Language: en-US To: Jason Gunthorpe 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 References: <20221107033109.59709-1-zhengqi.arch@bytedance.com> <4736d199-7e70-6bc3-30e6-0f644c81a10c@bytedance.com> From: Qi Zheng In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1667875687; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; 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spf=pass (imf05.hostedemail.com: domain of zhengqi.arch@bytedance.com designates 209.85.214.181 as permitted sender) smtp.mailfrom=zhengqi.arch@bytedance.com; dmarc=pass (policy=none) header.from=bytedance.com X-Stat-Signature: pfnb49exfrct9513io9r3454hgjm1g4w X-HE-Tag: 1667875685-453316 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000086, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2022/11/8 00:26, Jason Gunthorpe wrote: > 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. Oh, maybe I understand your concern. Some people may think that this is just a print of fault injection information, not a warning. I'll add a comment explaining why in some cases there must be no printing. Thanks, Qi > > Jason -- Thanks, Qi