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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 612BAFF886F for ; Thu, 30 Apr 2026 07:08:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 789026B008A; Thu, 30 Apr 2026 03:08:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 712656B008C; Thu, 30 Apr 2026 03:08:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5D9F96B0092; Thu, 30 Apr 2026 03:08:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 481556B008A for ; Thu, 30 Apr 2026 03:08:57 -0400 (EDT) Received: from smtpin11.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay05.hostedemail.com (Postfix) with ESMTP id C8762404C3 for ; 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s=arc-20220608; d=hostedemail.com; t=1777532934; a=rsa-sha256; cv=none; b=ZXAI6WMsHkNJ00xY4cyT2JBQIsPzMBtFsBjFhBMvw8dj7rFfa0BCtJGxnBYkQhwiBUP4NJ lQsMpMScrSVCbMhycRRnBFGPvSUX0Pwd7adZubplKinJgRRU96XD5ILjuMpywjImpFMKmZ CV0W3oM+vAmxJRo/2Jcxs6fQCy51PAs= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf22.hostedemail.com: domain of maobibo@loongson.cn designates 114.242.206.163 as permitted sender) smtp.mailfrom=maobibo@loongson.cn Received: from loongson.cn (unknown [10.20.42.62]) by gateway (Coremail) with SMTP id _____8AxX+v6__Jpl2kFAA--.18221S3; Thu, 30 Apr 2026 15:08:43 +0800 (CST) Received: from [10.20.42.62] (unknown [10.20.42.62]) by front1 (Coremail) with SMTP id qMiowJDxzsLy__JpuPJ3AA--.31891S3; Thu, 30 Apr 2026 15:08:34 +0800 (CST) Subject: Re: [PATCH] mm/huge_memory: skip huge_zero_pmd in zap_huge_pmd_folio() To: Lance Yang Cc: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260430070217.39679-1-lance.yang@linux.dev> From: Bibo Mao Message-ID: <6cdeb3e7-c399-4ead-e809-44e3d4d84bc7@loongson.cn> Date: Thu, 30 Apr 2026 15:05:41 +0800 User-Agent: Mozilla/5.0 (X11; Linux loongarch64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20260430070217.39679-1-lance.yang@linux.dev> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-CM-TRANSID:qMiowJDxzsLy__JpuPJ3AA--.31891S3 X-CM-SenderInfo: xpdruxter6z05rqj20fqof0/ X-Coremail-Antispam: 1Uk129KBj93XoWxAF1rCr1UXryUJFy8Xw4UJrc_yoW5Cr45pF yUGFn0kr48tr9rJw1Ivw4Uta4FywnavFy5X343Kr4rZFn0yry2grsrGr4jkry0gr4rGF4S vF42vasavF9xt3gCm3ZEXasCq-sJn29KB7ZKAUJUUUU7529EdanIXcx71UUUUU7KY7ZEXa sCq-sGcSsGvfJ3Ic02F40EFcxC0VAKzVAqx4xG6I80ebIjqfuFe4nvWSU5nxnvy29KBjDU 0xBIdaVrnRJUUUPIb4IE77IF4wAFF20E14v26r1j6r4UM7CY07I20VC2zVCF04k26cxKx2 IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48v e4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_JFI_Gr1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI 0_Gr0_Cr1l84ACjcxK6I8E87Iv67AKxVWxJVW8Jr1l84ACjcxK6I8E87Iv6xkF7I0E14v2 6r4UJVWxJr1ln4kS14v26r1Y6r17M2AIxVAIcxkEcVAq07x20xvEncxIr21l57IF6xkI12 xvs2x26I8E6xACxx1l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r12 6r1DMcIj6I8E87Iv67AKxVW8JVWxJwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IY64vIr4 1lc7I2V7IY0VAS07AlzVAYIcxG8wCY1x0262kKe7AKxVWUAVWUtwCF04k20xvY0x0EwIxG rwCFx2IqxVCFs4IE7xkEbVWUJVW8JwCFI7km07C267AKxVWUtVW8ZwC20s026c02F40E14 v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkG c2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI 0_Jr0_Gr1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r4j6F4U MIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x07jOeOJUUU UU= X-Rspam-User: X-Rspamd-Queue-Id: 96510C0007 X-Rspamd-Server: rspam04 X-Stat-Signature: u99wdfqp5aepp7obhk6nw7xrah3nwxmz X-HE-Tag: 1777532932-178444 X-HE-Meta: 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 3fA7Mwao wNexNbNCYAok55YY571X7f5iqUWOgFK5ZnJayIHoJlQT8QI54nPSfL9iLW4ekpv4wWLXky4wowgBwdg2wk766O9gB4lLBj8ZQSsS25eNQ8lsaS2Ckhf/SzfE7+0w9Fjp95nwB Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026/4/30 下午3:02, Lance Yang wrote: > > On Thu, Apr 30, 2026 at 02:34:20PM +0800, Bibo Mao wrote: >> >> >> On 2026/4/30 下午12:28, Lance Yang wrote: >>> >>> On Thu, Apr 30, 2026 at 12:11:20PM +0800, Bibo Mao wrote: >>>> when executing command "make check" with qemu software, there is >>>> error report like this: >>>> BUG: Bad rss-counter state mm:00000000972846bc type:MM_FILEPAGES val:-4096 Comm:bios-tables-tes Pid:27802 >>>> BUG: Bad rss-counter state mm:00000000752180c5 type:MM_FILEPAGES val:-2048 Comm:worker Pid:27815 >>>> BUG: Bad rss-counter state mm:000000009c2f6a61 type:MM_FILEPAGES val:-2048 Comm:qom-test Pid:27825 >>> >>> Good catch! >>> >>>> The problem is that when application exits, rss counter is calculated >>>> with huge_zero_pmd huge page, instead it should be skipped. >>> >>> Looks like the same problem[1] we discussed recently. >>> >>> [1] https://lore.kernel.org/linux-mm/74a75b59-2e13-3985-ee99-d5521f39df2a@google.com/ >>> >>>> Signed-off-by: Bibo Mao >>>> --- >>>> mm/huge_memory.c | 3 +++ >>>> 1 file changed, 3 insertions(+) >>>> >>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>>> index 970e077019b7..3cbea344d4a2 100644 >>>> --- a/mm/huge_memory.c >>>> +++ b/mm/huge_memory.c >>>> @@ -2423,6 +2423,9 @@ static void zap_huge_pmd_folio(struct mm_struct *mm, struct vm_area_struct *vma, >>>> { >>>> const bool is_device_private = folio_is_device_private(folio); >>>> >>>> + if (is_huge_zero_pmd(pmdval)) >>>> + return; >>>> + >>> >>> The huge zero PMD should not be returned by vm_normal_page_pmd() or >>> vm_normal_folio_pmd() as a normal folio. If it reaches >>> zap_huge_pmd_folio(), we already made the wrong normal-vs-special >>> decision ... >>> >>> So I don't think we should special-case it in zap_huge_pmd_folio(). That >>> only avoids this RSS decrement :) >>> >>> Could you please check whether the fix[2] also fixes your QEMU test? >>> >>> [2] https://lore.kernel.org/linux-mm/ea1453a6-14c9-4334-ac7e-2758586393b2@kernel.org/ >> yes, I think it will solve this problem. >> >> Only that I think that there should be tlb flush operation after >> pmdp_huge_get_and_clear_full() even with huge_zero_pmd page, so >> tlb_remove_page_size() should be called. Is that right? > > Calling tlb_remove_page_size() is not necessary there :) > > zap_huge_pmd() already marks the PMD range for TLB invalidation right > after clearing the entry: > > orig_pmd = pmdp_huge_get_and_clear_full(...); > tlb_remove_pmd_tlb_entry(tlb, pmd, addr); Yes, it is. I forget the tlb_flush_pmd_range() calling in tlb_remove_pmd_tlb_entry(). So the fix solves this problem. And thanks for your explanation. Regards Bibo Mao > > The later tlb_remove_page_size() is guarded by "is_present && folio", > and is for the normal folio case after normal_or_softleaf_folio_pmd() > return one :) > > Please correct me if I missed something :D > > Cheers, Lance >