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 6E0051B85D1 for ; Wed, 25 Sep 2024 05:31:24 +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=1727242286; cv=none; b=p29Md91a+J5Y3bG2owj0dbQB8ZynkLLu0SxqR1gZiWFcbEcyql0Xhk7dT/8sxLG93FAgFaHv70HrFIiN0RSwoveD6FOARUWwYPC3+AWUhx9BUgyuimZtY3xBaNddN31tX0VPgs4c+XU1D7EEU4NUlykBZpVg2U1Aoqq+M0GCJJQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727242286; c=relaxed/simple; bh=pvGwlwzxPWNgtYxefMYr8drFNbR3hfLG8+2Io21SEds=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=JXlqh0cAXbU5FB7pOJk0uy+jV+36Qqp2I5d0E07tpULCam87jJVyggbwwMlPFmQhcrJDe+bARbUMZnS4vp/JMtYNMD1g/GiHJKqCJ4sXdFmts5wYxZQrIaTKT0/+tbr1J5UJIWfvscCB5zN6Ujm2ftpRyXpWdLaJnOf1QloW79Y= 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 2B0F0DA7; Tue, 24 Sep 2024 22:31:53 -0700 (PDT) Received: from [10.162.43.26] (e116581.arm.com [10.162.43.26]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 22D523F528; Tue, 24 Sep 2024 22:31:14 -0700 (PDT) Message-ID: <903de160-e2cf-42cc-93ee-6b356cdca6de@arm.com> Date: Wed, 25 Sep 2024 11:01:11 +0530 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: [PATCH v5 2/2] mm: Allocate THP on hugezeropage wp-fault To: Kefeng Wang , akpm@linux-foundation.org, david@redhat.com, willy@infradead.org, kirill.shutemov@linux.intel.com Cc: ryan.roberts@arm.com, 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, mark.rutland@arm.com, hughd@google.com, aneesh.kumar@kernel.org, yang@os.amperecomputing.com, peterx@redhat.com, ioworker0@gmail.com, jglisse@google.com, ziy@nvidia.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20240924101654.1777697-1-dev.jain@arm.com> <20240924101654.1777697-3-dev.jain@arm.com> <7d21314c-9c53-4aa0-9a27-b07d21da429e@huawei.com> Content-Language: en-US From: Dev Jain In-Reply-To: <7d21314c-9c53-4aa0-9a27-b07d21da429e@huawei.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 9/24/24 18:43, Kefeng Wang wrote: > > > On 2024/9/24 18:16, Dev Jain wrote: >> Introduce do_huge_zero_wp_pmd() to handle wp-fault on a hugezeropage and >> replace it with a PMD-mapped THP. Remember to flush TLB entry >> corresponding to the hugezeropage. In case of failure, fallback >> to splitting the PMD. >> >> Signed-off-by: Dev Jain >> --- >>   mm/huge_memory.c | 44 +++++++++++++++++++++++++++++++++++++++++++- >>   1 file changed, 43 insertions(+), 1 deletion(-) >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index bdbf67c18f6c..fbb195bc2038 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -1790,6 +1790,41 @@ void huge_pmd_set_accessed(struct vm_fault *vmf) >>       spin_unlock(vmf->ptl); >>   } >>   +static vm_fault_t do_huge_zero_wp_pmd(struct vm_fault *vmf) >> +{ >> +    unsigned long haddr = vmf->address & HPAGE_PMD_MASK; >> +    struct vm_area_struct *vma = vmf->vma; >> +    struct mmu_notifier_range range; >> +    struct folio *folio; >> +    vm_fault_t ret = 0; >> + >> +    folio = vma_alloc_anon_folio_pmd(vma, vmf->address); >> +    if (unlikely(!folio)) { >> +        ret = VM_FAULT_FALLBACK; > > I'd like to return VM_FAULT_FALLBACK if you re-post. That's cleaner. I need to keep my "goto" obsession in control... > > Reviewed-by: Kefeng Wang Thanks! > >> +        goto out; >> +    } >> + >> +    mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm, >> haddr, >> +                haddr + HPAGE_PMD_SIZE); >> +    mmu_notifier_invalidate_range_start(&range); >> +    vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); >> +    if (unlikely(!pmd_same(pmdp_get(vmf->pmd), vmf->orig_pmd))) >> +        goto release; >> +    ret = check_stable_address_space(vma->vm_mm); >> +    if (ret) >> +        goto release; >> +    (void)pmdp_huge_clear_flush(vma, haddr, vmf->pmd); >> +    map_anon_folio_pmd(folio, vmf->pmd, vma, haddr); >> +    goto unlock; >> +release: >> +    folio_put(folio); >> +unlock: >> +    spin_unlock(vmf->ptl); >> +    mmu_notifier_invalidate_range_end(&range); >> +out: >> +    return ret; >> +} >> + >>   vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf) >>   { >>       const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE; >> @@ -1802,8 +1837,15 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault >> *vmf) >>       vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd); >>       VM_BUG_ON_VMA(!vma->anon_vma, vma); >>   -    if (is_huge_zero_pmd(orig_pmd)) >> +    if (is_huge_zero_pmd(orig_pmd)) { >> +        vm_fault_t ret = do_huge_zero_wp_pmd(vmf); >> + >> +        if (!(ret & VM_FAULT_FALLBACK)) >> +            return ret; >> + >> +        /* Fallback to splitting PMD if THP cannot be allocated */ >>           goto fallback; >> +    } >>         spin_lock(vmf->ptl); > >