From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-186.mta1.migadu.com (out-186.mta1.migadu.com [95.215.58.186]) (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 EBE61F9C0 for ; Sat, 4 Oct 2025 03:06:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.186 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759547179; cv=none; b=QvIBM8OSIr/az4kcMhg4yBOFjyzTmuUHSQT3iTFyAdPS3GvcA7NcEqyvEzbgyCfAPNWGYw3IYhyFK6eIrDgFIA99sNwTRVPv8Rnrbh3uNKa9GdPuJ00upLCZMOEn8exyLKO6iUyMyJtQrG/cLZzuHZz8dFCSS8sYnOut92VpPc8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759547179; c=relaxed/simple; bh=HD6yOrpFaMTM4o+sS+vXSeulxyFFdSnPq8JKD25RFCE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=O6NRJoMph0tOGDlvXwIMlKwzygh355KDMiYuW83NozUXzKKe0BXzdR8W/zfukXMhs3SvNmn2DpvRNTXY0UpkCIK1c8LH95wZ/XzHrO6k2hWCb0K4/rME/Bl74DtxwfVs0ptZ19Czwimsci/0JTa69lEldgGdo4Pq0KpDY3ttxvI= 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=QFiiD5fQ; arc=none smtp.client-ip=95.215.58.186 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="QFiiD5fQ" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1759547176; 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=PXNNFB9m2tpLPVfzBH/OyS3UoK141cw9zK+ucGD3NqE=; b=QFiiD5fQfK8Dx7oW/mtMnx22p7DIXuSnRzi9FM6gwKqugyl7A35FGw56L/dJgRpG2TgTXT aGtDUze/msQHXXHOCfRz7nNPrM49gbEwx16cXMq+1VT1oWJUyDDPcR3g0uw3T3VHVA2Td9 3osGwZBkPG/d+s1POuCdUAQvCZEcSyU= Date: Sat, 4 Oct 2025 11:06:02 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH mm-new 2/2] mm/khugepaged: merge PTE scanning logic into a new helper Content-Language: en-US To: Zi Yan Cc: akpm@linux-foundation.org, david@redhat.com, lorenzo.stoakes@oracle.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, ioworker0@gmail.com, richard.weiyang@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20251002073255.14867-1-lance.yang@linux.dev> <20251002073255.14867-3-lance.yang@linux.dev> <9DF437D8-E98B-4061-A8C7-521D89070C97@nvidia.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <9DF437D8-E98B-4061-A8C7-521D89070C97@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 2025/10/4 01:11, Zi Yan wrote: > On 2 Oct 2025, at 3:32, Lance Yang wrote: > >> From: Lance Yang >> >> As David suggested, the PTE scanning logic in hpage_collapse_scan_pmd() >> and __collapse_huge_page_isolate() was almost duplicated. >> >> This patch cleans things up by moving all the common PTE checking logic >> into a new shared helper, thp_collapse_check_pte(). >> >> Suggested-by: David Hildenbrand >> Signed-off-by: Lance Yang >> --- >> mm/khugepaged.c | 167 ++++++++++++++++++++++++++++++------------------ >> 1 file changed, 104 insertions(+), 63 deletions(-) >> >> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >> index 808523f92c7b..2a897cfb1d03 100644 >> --- a/mm/khugepaged.c >> +++ b/mm/khugepaged.c >> @@ -61,6 +61,12 @@ enum scan_result { >> SCAN_PAGE_FILLED, >> }; >> >> +enum pte_check_result { >> + PTE_CHECK_SUCCEED, >> + PTE_CHECK_CONTINUE, >> + PTE_CHECK_FAIL, >> +}; >> + >> #define CREATE_TRACE_POINTS >> #include >> >> @@ -533,6 +539,87 @@ static void release_pte_pages(pte_t *pte, pte_t *_pte, >> } >> } >> >> +/* >> + * thp_collapse_check_pte - Check if a PTE is suitable for THP collapse >> + * @pte: PTE to check >> + * @vma: VMA the PTE belongs to >> + * @cc: Collapse control settings >> + * @scan_swap_pte: Allow scanning of swap PTEs if true >> + * @none_or_zero: Counter for none/zero PTEs (must be non-NULL) >> + * @unmapped: Counter for swap PTEs (must be non-NULL if scan_swap_pte >> + * is true) >> + * @scan_result: Used to return the failure reason (SCAN_*) on a >> + * PTE_CHECK_FAIL return. Must be non-NULL >> + * >> + * Returns: >> + * PTE_CHECK_SUCCEED - Valid PTE, proceed with collapse >> + * PTE_CHECK_CONTINUE - Skip this none/zero PTE but continue scanning >> + * PTE_CHECK_FAIL - Abort collapse scan >> + */ >> +static inline int thp_collapse_check_pte(pte_t pte, struct vm_area_struct *vma, >> + struct collapse_control *cc, bool scan_swap_pte, >> + int *none_or_zero, int *unmapped, int *scan_result) >> +{ >> + VM_BUG_ON(!none_or_zero || !scan_result); >> + VM_BUG_ON(scan_swap_pte && !unmapped); > > Please use VM_WARN_ONCE_ON and just return. Or put all stats in a struct, > pass and check the struct pointer instead. Yes, will use VM_WARN_ONCE_ON instead of VM_BUG_ON, and just return PTE_CHECK_FAIL. Thanks, Lance > > > Best Regards, > Yan, Zi