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 CD0DDFF886F for ; Thu, 30 Apr 2026 07:02:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3AF166B0088; Thu, 30 Apr 2026 03:02:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 35F766B008A; Thu, 30 Apr 2026 03:02:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 275526B008C; Thu, 30 Apr 2026 03:02:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 171626B0088 for ; Thu, 30 Apr 2026 03:02:32 -0400 (EDT) Received: from smtpin21.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id C32E01404E8 for ; Thu, 30 Apr 2026 07:02:31 +0000 (UTC) X-FDA: 84714328902.21.B88642B Received: from out-170.mta0.migadu.com (out-170.mta0.migadu.com [91.218.175.170]) by imf15.hostedemail.com (Postfix) with ESMTP id D4092A000E for ; Thu, 30 Apr 2026 07:02:29 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=tWkuXsrx; spf=pass (imf15.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.170 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1777532550; 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; bh=XnPzbyjR2RPMnocbYTJgY5ykVBYijb42BCSHLD8WL2M=; b=NqR90YCFnV3OfsB1dENh0AKxKhLEi/4G2vZrm/4ir4ghgKDWvES734lBADRjb0pyju7PK6 62KMtS9GyJJl1GlfgJUCSIAWCj0mxHpLHjSO2h4v8URTAdBWUVhHoteqx2lfoww7h1bTfm SWkyN5pmq+75a2DpZXKkdUqALvQLSPA= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1777532550; a=rsa-sha256; cv=none; b=KOFyuFzmaW+0w4/PcgFGCd3kmfqxOvT2/PFaMgBynOxkg1h+9zLoCioMbwCK403OvC4XQE CLQSss0uUL2v1j9tBZ+CZdnfHp8hCz0aX8XDrYZKMvh0FGdzETcpdUxBawUa2v3H/voG3s MTTG2pZuHLq914Dn3JYUX3qnqDh2vVk= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=tWkuXsrx; spf=pass (imf15.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.170 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1777532546; h=from:from: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; bh=XnPzbyjR2RPMnocbYTJgY5ykVBYijb42BCSHLD8WL2M=; b=tWkuXsrxh5SQivLKUD5ssncT32NSJKFFaVzBCoyNLPGomQrobwv7fdWUgoeRCujr65JgpM 0x8cfxLH8zeVfolyz3QQkTiYrkymYbDM6vL+7DpD0sLayloESPYZ0FIWe9ZT4u7UhCr1Br czHtnmha6ci4sX71feYkefSZbepLSC4= From: Lance Yang To: maobibo@loongson.cn Cc: lance.yang@linux.dev, 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 Subject: Re: [PATCH] mm/huge_memory: skip huge_zero_pmd in zap_huge_pmd_folio() Date: Thu, 30 Apr 2026 15:02:17 +0800 Message-Id: <20260430070217.39679-1-lance.yang@linux.dev> In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: D4092A000E X-Rspam-User: X-Stat-Signature: nm3y79xo3eyxbbicjsox89wprehfxjq9 X-HE-Tag: 1777532549-569501 X-HE-Meta: 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 ocyHNBJq jqnlp4R6oROnpz7tMLVtGlGuFd8Zlbr0ylf/luWAzmDDSsg5VHIazq3OTMlTz9NXwiE6g2+omRWxQyPP2XU/hVk739ntSCJdoVu3SPMzGymf+wJj5F8tb4hT26K9cDPhcdT8UmnK20zRfSHcHmQB8Y71Ohm5kqdo81k0I3iU8PhmjDUTQjxz9zxJbPMtQIUGxJZrTA9Z6tQVdNplFU3ogPpi/++WZ4bu693bVZEkDcwyoJ6F/3tjJfuPOgXQRZy3KgT1eT1R5CxyjR/LaQ5AoqegKhuYcbAJ5tQsFpYbChoiMNGu1cjjSqwFeHDpT2j6eMt+u/S5ZfwMBfM0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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); 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