From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) (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 4B9F1A930 for ; Wed, 9 Apr 2025 01:08:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744160915; cv=none; b=GO6ku9Xjumy4+iVskDDUCXr7GsnKbxuk17XBFgcVALMsO3dntuT347fbFBxewZu15sYO2ktplaHGXArcTOFhCxerZvuK0oJuZd6f4ZMydrq0/IxEysuxK9xu3vCBKyQXdKbg55VZwhT8jguwBWy2d0iA3t5b7LXslwBQsDIIKM4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744160915; c=relaxed/simple; bh=icNU03rTODoQM9pR94rINEAEiXrJBiIPWvswZUL1J7Y=; h=Message-ID:Date:MIME-Version:CC:Subject:To:References:From: In-Reply-To:Content-Type; b=AU5dFlY94Annl0wZyexLOj+AYit/GZ7JCh7kUq9onbt/Dp03TtjgOXjRJZcMgdiyHoFAJ9pGeHPERb0kKql09brdGLBAMozygaeYmrC3Pw6qd490eFF+Q/nCzahxj9QtyrXGSOtAkRMuZVcsFv7purA/5NsUXiTLDroowvyQZSM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.174]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4ZXPqc1cGWz5vMX; Wed, 9 Apr 2025 09:04:44 +0800 (CST) Received: from kwepemg100017.china.huawei.com (unknown [7.202.181.58]) by mail.maildlp.com (Postfix) with ESMTPS id 2BCDE1402C4; Wed, 9 Apr 2025 09:08:29 +0800 (CST) Received: from [10.174.178.114] (10.174.178.114) by kwepemg100017.china.huawei.com (7.202.181.58) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 9 Apr 2025 09:08:27 +0800 Message-ID: Date: Wed, 9 Apr 2025 09:08:27 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird CC: , , , , , , , , , , , , , , Subject: Re: [PATCH] arm64: dax: add devmap check for pmd_trans_huge To: References: <20250408085914.1946183-1-mawupeng1@huawei.com> From: mawupeng In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemg100017.china.huawei.com (7.202.181.58) On 2025/4/9 7:05, Alistair Popple wrote: > On Tue, Apr 08, 2025 at 04:59:14PM +0800, Wupeng Ma wrote: >> During our test in ext4 dax linux-v5.10 on arm64. A BUG_ON is trigger in >> follow_invalidate_pte as follow since this pmd is seem as pmd_trans_huge. >> However this page is really a dax-pmds rather than a pmd trans huge. >> >> Call trace is shown as follow: >> >> ------------[ cut here ]------------ >> kernel BUG at mm/memory.c:5185! >> CPU: 0 PID: 150 Comm: kworker/u8:10 Not tainted 5.10.0-01678-g1e62aad66bbc-dirty #36 > > This is an old kernel, and I couldn't correlate the line number of the BUG_ON() > probably because you have patches applied. But I assume this is the VM_BUG_ON() > in follow_invalidate_pte()? Does this issue reproduce on more recent kernel Yes. > versions (eg. v6.13)? Or some other upstream kernel version? Since Commit 06083a0921fd ("dax: fix missing writeprotect the pte entry"), the same issue can not be trigger in the same call trace. However the same issue may still exist in current kernel. > >> pc : follow_invalidate_pte+0xdc/0x5e0 >> lr : follow_invalidate_pte+0xc4/0x5e0 >> sp : ffffa00012997110 >> Call trace: >> follow_invalidate_pte+0xdc/0x5e0 >> dax_entry_mkclean+0x250/0x870 >> dax_writeback_one+0xac/0x380 >> dax_writeback_mapping_range+0x22c/0x704 >> ext4_dax_writepages+0x234/0x6e4 >> do_writepages+0xc8/0x1c0 >> __writeback_single_inode+0xb8/0x560 >> writeback_sb_inodes+0x344/0x7a0 >> wb_writeback+0x1f8/0x6b0 >> wb_do_writeback+0x194/0x3cc >> wb_workfn+0x14c/0x590 >> process_one_work+0x470/0xa30 >> worker_thread+0xac/0x510 >> kthread+0x1e0/0x220 >> ret_from_fork+0x10/0x18 >> ---[ end trace 0f479050bd4b1818 ]--- >> Kernel panic - not syncing: Oops - BUG: Fatal exception >> ---[ end Kernel panic - not syncing: Oops - BUG: Fatal exception ]--- >> >> Commit 5c7fb56e5e3f ("mm, dax: dax-pmd vs thp-pmd vs hugetlbfs-pmd") and >> commit 36b78402d97a ("powerpc/hash64/devmap: Use H_PAGE_THP_HUGE when >> setting up huge devmap PTE entries") already check pmd_devmap during >> checking pmd_trans_huge. Since pmd_devmap() is used to distinguish dax-pmds, >> add the same check for arm64 to fix this problem. > > That seems correct to me. In practice most callers of pmd_trans_huge() that can > see a dax-pmd already check for it explicitly with vma_is_dax(), but there are a > few cases that don't. > >> Add PTE_DEVMAP in pte_modify as commit 4628a64591e6 ("mm: Preserve >> _PAGE_DEVMAP across mprotect() calls") does to avoid the same issue in >> mprotect. >> >> Fixes: 73b20c84d42d ("arm64: mm: implement pte_devmap support") >> Signed-off-by: Wupeng Ma >> --- >> arch/arm64/include/asm/pgtable.h | 5 +++-- >> 1 file changed, 3 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h >> index d3b538be1500b..b9a618127c01b 100644 >> --- a/arch/arm64/include/asm/pgtable.h >> +++ b/arch/arm64/include/asm/pgtable.h >> @@ -740,7 +740,7 @@ static inline int pmd_trans_huge(pmd_t pmd) >> * as a table, so force the valid bit for the comparison. >> */ >> return pmd_val(pmd) && pmd_present(pmd) && >> - !pmd_table(__pmd(pmd_val(pmd) | PTE_VALID)); >> + !pmd_table(__pmd(pmd_val(pmd) | PTE_VALID)) && !pmd_devmap(pmd); >> } >> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ >> >> @@ -1186,7 +1186,8 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot) >> */ >> const pteval_t mask = PTE_USER | PTE_PXN | PTE_UXN | PTE_RDONLY | >> PTE_PRESENT_INVALID | PTE_VALID | PTE_WRITE | >> - PTE_GP | PTE_ATTRINDX_MASK | PTE_PO_IDX_MASK; >> + PTE_GP | PTE_ATTRINDX_MASK | PTE_PO_IDX_MASK | >> + PTE_DEVMAP; >> >> /* preserve the hardware dirty information */ >> if (pte_hw_dirty(pte)) >> -- >> 2.43.0 >> >>