From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-170.mta0.migadu.com (out-170.mta0.migadu.com [91.218.175.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 570CD7E0FF for ; Thu, 30 Apr 2026 04:29:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777523345; cv=none; b=IGyppcAisQHXIO1FpSNGr6/Ona0RRTLj6D7NHE5a1preTrpikHr2Nixr5K+j6klCHnsYapa6u/i5oNX8ldK9cHHB0NN0lBG8vCpnZZgWs5b4DHv6ccvbgeiIh2C/b8xnWI/eLYxIoYU3GorgGmPuCLYzYPrBuT/Y+QRqeCRk4Rk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777523345; c=relaxed/simple; bh=OLltAXUT+BfKUeduiDY0AHczMo4cqC90l6kfLAB2Ftc=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=KXZYDtFAZxnmBOk4H9KF3IHcHRVzv51HMw1/aX9lanRkcNHCAMCesRu85wXcSCkXVv+Rp4kfuqaw4RC70+lQmqI7xmubEmVXPoRuqO+cEv6QuS1bOua9+bMpJoFyjttQAVyJr0/oBSv8pMeEf8QeGbAS48YDbg5Y0CAzAZU6ulM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=iOFjQWsq; arc=none smtp.client-ip=91.218.175.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="iOFjQWsq" 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=1777523341; 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=+VundzSntS2gV5ZiUeYZYQvjRIQ1VA1EGbZoM05E5Ls=; b=iOFjQWsq7xQKQLdPc8DwBEEwfmCSpU2T+2vJ8IOEDcvQxO7GHlLeSQoDo7KCDHvXZRvrEA GR9SpBeC9M4ZAlym2lJ9yvN6AGGrbhXVUSsfEqXO50DMhLmnxv0WkuHD1xFg6cHiOkFAA3 Ny7OvBnv4CdurRMIfwp7FjlKtY7Rpfo= From: Lance Yang To: maobibo@loongson.cn 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, lance.yang@linux.dev, 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 12:28:34 +0800 Message-Id: <20260430042834.80895-1-lance.yang@linux.dev> In-Reply-To: <20260430041121.2839350-1-maobibo@loongson.cn> References: <20260430041121.2839350-1-maobibo@loongson.cn> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 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/ Thanks, Lance