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 286A819258A for ; Thu, 5 Sep 2024 08:52:32 +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=1725526355; cv=none; b=hopRSb8qhkUAdx5cBEyB8NtiuLEGwYFWIiDzRiuRzeJ5kVW6Ye6ifcKb6jUaZwiGiapKjNgSpEllwz7QAaomk2aZFi1OU9kMUL98pgknBWkLG7X8CJspj0tP+2OWfesH4dvOQMOuhkZ351Buo8CimlRP+xpgOUKWWyyALJRFV0o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725526355; c=relaxed/simple; bh=WY4CXGCsSNOlMxIL1QlPMP4MRWh/Ri31/+abr6S31AY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Y4T9zNtsUTvbAevUB54b5HN694T48V9QLRlzWSdzYhh29CWGiyR12FK5k1WPMLoxI5pP4ZdfQfBKSNgPsnNebRs5CSB4K1F82mAvj6GFYuKkozCB91Y2R/WuLv9zzFOGIom7gR7xeTVlar0//TNbV6Yk7Y3axRi7xFoIPPxJvCI= 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 D890FFEC; Thu, 5 Sep 2024 01:52:58 -0700 (PDT) Received: from [10.162.43.13] (e116581.arm.com [10.162.43.13]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 582FC3F73F; Thu, 5 Sep 2024 01:52:24 -0700 (PDT) Message-ID: <9411b518-2505-40ca-bd81-7127dc638521@arm.com> Date: Thu, 5 Sep 2024 14:22:21 +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 v2 2/2] mm: Allocate THP on hugezeropage wp-fault To: "Kirill A. Shutemov" Cc: akpm@linux-foundation.org, david@redhat.com, willy@infradead.org, 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, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20240904100923.290042-1-dev.jain@arm.com> <20240904100923.290042-3-dev.jain@arm.com> Content-Language: en-US From: Dev Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/5/24 13:56, 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. >> >> 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. Ah sorry! When I started out on this I may have planned to use it in mm/memory.c, but then completely forgot to drop this. > >> 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()? I was taking inspiration from split_huge_pud_locked() and the like. Although I guess I should open code it, since do_huge_zero_wp_pmd_locked() is small anyways. > >> +{ >> + 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); >> +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 >>