From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) (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 1E683196446 for ; Thu, 5 Sep 2024 09:41:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.255 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725529281; cv=none; b=S90XwFJBrqFvLZJ9xoOTafFM49I9ArZbiQgqthat6rrWlwS0kzFhHf2Aqtc7mnZSVAgAjM7EbHaCKcC6oC57Q0BdlzKinNabUCy0ojCIMvxOec5n/hpCp/DxBVySIWHSpqZRoaRLOhekDxtdjy6R6lgW5IA0Gc12fiCP5Tcrk9w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725529281; c=relaxed/simple; bh=jgSF04qFHRMlTCn0metBHGuRm/9fbtLCWsgjg8pNTmY=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=OvMF5uCsCGGcRJl0HDU0mYr83oMWwXWRK3hQdcjcKgw9NMRpKLQ7tOWsn+ZJGWxAY6CHphPNZNJM4cw+KrKB5MdzbPGxTzZO/+8x6ZB5E7/W5V0svyd2Of7DCfVHIw9aumDHwvlXQWTlp1F18r4E9yXTpLdJU3U+iQA9KALLMMA= 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=45.249.212.255 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 [172.19.162.254]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4WzvV24Wwxz1BNDW; Thu, 5 Sep 2024 17:40:10 +0800 (CST) Received: from dggpemf100008.china.huawei.com (unknown [7.185.36.138]) by mail.maildlp.com (Postfix) with ESMTPS id 477E1180100; Thu, 5 Sep 2024 17:41:09 +0800 (CST) Received: from [10.174.177.243] (10.174.177.243) by dggpemf100008.china.huawei.com (7.185.36.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Thu, 5 Sep 2024 17:41:08 +0800 Message-ID: Date: Thu, 5 Sep 2024 17:41:07 +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 Subject: Re: [PATCH v2 2/2] mm: Allocate THP on hugezeropage wp-fault Content-Language: en-US To: "Kirill A. Shutemov" , Dev Jain CC: , , , , , , , , , , , , , , , , , , , , , , , References: <20240904100923.290042-1-dev.jain@arm.com> <20240904100923.290042-3-dev.jain@arm.com> From: Kefeng Wang In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpemf100008.china.huawei.com (7.185.36.138) On 2024/9/5 16:26, Kirill A. Shutemov wrote: > On Wed, Sep 04, 2024 at 03:39:23PM +0530, Dev Jain wrote: >> Introduce do_huge_zero_wp_pmd() to handle wp-fault on a hugezeropage and >> replace it with a PMD-mapped THP. Change the helpers introduced in the >> previous patch to flush TLB entry corresponding to the hugezeropage, >> and preserve PMD uffd-wp marker. In case of failure, fallback to >> splitting the PMD. We met same issue, and a very similar function in our kernel, >> >> Signed-off-by: Dev Jain >> --- >> include/linux/huge_mm.h | 6 ++++ >> mm/huge_memory.c | 79 +++++++++++++++++++++++++++++++++++------ >> mm/memory.c | 5 +-- >> 3 files changed, 78 insertions(+), 12 deletions(-) >> >> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h >> index e25d9ebfdf89..fdd2cf473a3c 100644 >> --- a/include/linux/huge_mm.h >> +++ b/include/linux/huge_mm.h >> @@ -9,6 +9,12 @@ >> #include >> >> vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf); >> +vm_fault_t thp_fault_alloc(gfp_t gfp, int order, struct vm_area_struct *vma, >> + unsigned long haddr, struct folio **foliop, >> + unsigned long addr); >> +void map_pmd_thp(struct folio *folio, struct vm_fault *vmf, >> + struct vm_area_struct *vma, unsigned long haddr, >> + pgtable_t pgtable); > > Why? I don't see users outside huge_memory.c. > >> int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, >> pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, >> struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma); >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 58125fbcc532..150163ad77d3 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -943,9 +943,9 @@ unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr, >> } >> EXPORT_SYMBOL_GPL(thp_get_unmapped_area); >> >> -static vm_fault_t thp_fault_alloc(gfp_t gfp, int order, struct vm_area_struct *vma, >> - unsigned long haddr, struct folio **foliop, >> - unsigned long addr) >> +vm_fault_t thp_fault_alloc(gfp_t gfp, int order, struct vm_area_struct *vma, >> + unsigned long haddr, struct folio **foliop, >> + unsigned long addr) >> { >> struct folio *folio = vma_alloc_folio(gfp, order, vma, haddr, true); >> >> @@ -984,21 +984,29 @@ static void __thp_fault_success_stats(struct vm_area_struct *vma, int order) >> count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC); >> } >> >> -static void map_pmd_thp(struct folio *folio, struct vm_fault *vmf, >> - struct vm_area_struct *vma, unsigned long haddr, >> - pgtable_t pgtable) >> +void map_pmd_thp(struct folio *folio, struct vm_fault *vmf, >> + struct vm_area_struct *vma, unsigned long haddr, >> + pgtable_t pgtable) >> { >> - pmd_t entry; >> + pmd_t entry, old_pmd; >> + bool is_pmd_none = pmd_none(*vmf->pmd); >> >> entry = mk_huge_pmd(&folio->page, vma->vm_page_prot); >> entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); >> folio_add_new_anon_rmap(folio, vma, haddr, RMAP_EXCLUSIVE); >> folio_add_lru_vma(folio, vma); >> - pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable); >> + if (!is_pmd_none) { >> + old_pmd = pmdp_huge_clear_flush(vma, haddr, vmf->pmd); >> + if (pmd_uffd_wp(old_pmd)) >> + entry = pmd_mkuffd_wp(entry); >> + } >> + if (pgtable) >> + pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable); >> set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); >> update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); >> add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); >> - mm_inc_nr_ptes(vma->vm_mm); >> + if (is_pmd_none) >> + mm_inc_nr_ptes(vma->vm_mm); >> } >> >> static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf) >> @@ -1576,6 +1584,50 @@ void huge_pmd_set_accessed(struct vm_fault *vmf) >> spin_unlock(vmf->ptl); >> } >> >> +static vm_fault_t do_huge_zero_wp_pmd_locked(struct vm_fault *vmf, >> + unsigned long haddr, >> + struct folio *folio) > > Why the helper is needed? Cannot it be just opencodded in > do_huge_zero_wp_pmd()? > >> +{ >> + struct vm_area_struct *vma = vmf->vma; >> + vm_fault_t ret = 0; >> + >> + ret = check_stable_address_space(vma->vm_mm); >> + if (ret) >> + goto out; >> + map_pmd_thp(folio, vmf, vma, haddr, NULL); >> +out: >> + return ret; >> +} >> + >> +static vm_fault_t do_huge_zero_wp_pmd(struct vm_fault *vmf, unsigned long haddr) >> +{ >> + struct vm_area_struct *vma = vmf->vma; >> + gfp_t gfp = vma_thp_gfp_mask(vma); >> + struct mmu_notifier_range range; >> + struct folio *folio = NULL; >> + vm_fault_t ret = 0; >> + >> + ret = thp_fault_alloc(gfp, HPAGE_PMD_ORDER, vma, haddr, &folio, >> + vmf->address); >> + if (ret) >> + 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 unlock; >> + ret = do_huge_zero_wp_pmd_locked(vmf, haddr, folio); >> + if (!ret) >> + __thp_fault_success_stats(vma, HPAGE_PMD_ORDER); >> +unlock: >> + spin_unlock(vmf->ptl); >> + mmu_notifier_invalidate_range_end(&range); the folio need to released when !pmd_same() and check_stable_address_space() return VM_FAULT_SIGBUS. >> +out: >> + return ret; >> +} >> + >> vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf) >> { >> const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE; >> @@ -1588,8 +1640,15 @@ 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, haddr); >> + >> + if (!(ret & VM_FAULT_FALLBACK)) >> + return ret; >> + >> + /* Fallback to splitting PMD if THP cannot be allocated */ >> goto fallback; >> + } >> >> spin_lock(vmf->ptl); >> >> diff --git a/mm/memory.c b/mm/memory.c >> index 3c01d68065be..c081a25f5173 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -5409,9 +5409,10 @@ static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf) >> if (vma_is_anonymous(vma)) { >> if (likely(!unshare) && >> userfaultfd_huge_pmd_wp(vma, vmf->orig_pmd)) { >> - if (userfaultfd_wp_async(vmf->vma)) >> + if (!userfaultfd_wp_async(vmf->vma)) >> + return handle_userfault(vmf, VM_UFFD_WP); >> + if (!is_huge_zero_pmd(vmf->orig_pmd)) >> goto split; >> - return handle_userfault(vmf, VM_UFFD_WP); >> } >> return do_huge_pmd_wp_page(vmf); >> } >> -- >> 2.30.2 >> >