From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id AD4A88615A for ; Tue, 17 Dec 2024 17:22:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734456169; cv=none; b=m/dex1wGRVHxbfHOYKreKkgFvT/CiBB1jOONB2b/mm0FepGPKhW7LMWPSeIbP58U26ioJ/qlnUwSihO9fMb6EDgfBTqIRS6SN9ftPopGRXiYIr2ShzX3Y3CH7iVl9QIQF5zdFHtfWaYLBu4TgXX4SKZsiHkSyb+gdtJghNYVPZw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734456169; c=relaxed/simple; bh=1BVthTLTbPqK7bDL3gnfMZHv94YuQQJpQrUM1OGCX78=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Wq9V2XPA0Cc2eJjcv9ZhxHBmvvI+GiUXvfJmXiWBBucGIHdrcsJqv+Z8bXhmOd/liuuvmXuJQ9cPrdStt+szKlkI/nFCMrGRx3tBRuHDOif3T4lDaKDGmb1ewqWuaLpDEqT9Pt+2D5ENKcl7XQg6I8cWbb9QyEaV9s8g1M8GbKM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1A7E2FEC; Tue, 17 Dec 2024 09:23:14 -0800 (PST) Received: from [10.57.91.184] (unknown [10.57.91.184]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 00D4A3F7B4; Tue, 17 Dec 2024 09:22:40 -0800 (PST) Message-ID: <4a2554ad-c204-4350-8898-545c1da124bb@arm.com> Date: Tue, 17 Dec 2024 17:22:39 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 06/12] khugepaged: Generalize __collapse_huge_page_copy_failed() Content-Language: en-GB To: Dev Jain , akpm@linux-foundation.org, david@redhat.com, willy@infradead.org, kirill.shutemov@linux.intel.com Cc: anshuman.khandual@arm.com, catalin.marinas@arm.com, cl@gentwo.org, vbabka@suse.cz, mhocko@suse.com, apopple@nvidia.com, dave.hansen@linux.intel.com, will@kernel.org, baohua@kernel.org, jack@suse.cz, srivatsa@csail.mit.edu, haowenchao22@gmail.com, hughd@google.com, aneesh.kumar@kernel.org, yang@os.amperecomputing.com, peterx@redhat.com, ioworker0@gmail.com, wangkefeng.wang@huawei.com, ziy@nvidia.com, jglisse@google.com, surenb@google.com, vishal.moola@gmail.com, zokeefe@google.com, zhengqi.arch@bytedance.com, jhubbard@nvidia.com, 21cnbao@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20241216165105.56185-1-dev.jain@arm.com> <20241216165105.56185-7-dev.jain@arm.com> From: Ryan Roberts In-Reply-To: <20241216165105.56185-7-dev.jain@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 16/12/2024 16:50, Dev Jain wrote: > Upon failure, we repopulate the PMD in case of PMD-THP collapse. Hence, make > this logic specific for PMD case. > > Signed-off-by: Dev Jain > --- > mm/khugepaged.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index de044b1f83d4..886c76816963 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -766,7 +766,7 @@ static void __collapse_huge_page_copy_failed(pte_t *pte, > pmd_t *pmd, > pmd_t orig_pmd, > struct vm_area_struct *vma, > - struct list_head *compound_pagelist) > + struct list_head *compound_pagelist, int order) nit: suggest putting order on its own line. > { > spinlock_t *pmd_ptl; > > @@ -776,14 +776,16 @@ static void __collapse_huge_page_copy_failed(pte_t *pte, > * pages. Since pages are still isolated and locked here, > * acquiring anon_vma_lock_write is unnecessary. > */ > - pmd_ptl = pmd_lock(vma->vm_mm, pmd); > - pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd)); > - spin_unlock(pmd_ptl); > + if (order == HPAGE_PMD_ORDER) { > + pmd_ptl = pmd_lock(vma->vm_mm, pmd); > + pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd)); > + spin_unlock(pmd_ptl); > + } > /* > * Release both raw and compound pages isolated > * in __collapse_huge_page_isolate. > */ > - release_pte_pages(pte, pte + HPAGE_PMD_NR, compound_pagelist); > + release_pte_pages(pte, pte + (1UL << order), compound_pagelist); > } Given this function is clearly so geared towards re-establishing the pmd, given that it takes the *pmd and orig_pmd as params, and given that in the non-pmd-order case, we only call through to release_pte_pages(), I wonder if it's better to make the decision at a higher level and either call this function or release_pte_pages() directly? No strong opinion, just looks a bit weird at the moment. > > /* > @@ -834,7 +836,7 @@ static int __collapse_huge_page_copy(pte_t *pte, struct folio *folio, > compound_pagelist); > else > __collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma, > - compound_pagelist); > + compound_pagelist, order); > > return result; > }