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Shutemov" To: Dev Jain 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 Subject: Re: [PATCH v2 2/2] mm: Allocate THP on hugezeropage wp-fault Message-ID: References: <20240904100923.290042-1-dev.jain@arm.com> <20240904100923.290042-3-dev.jain@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240904100923.290042-3-dev.jain@arm.com> X-Rspamd-Queue-Id: 1EC19C0007 X-Stat-Signature: d196jccxer9pawotmidr5qrfxepodjno X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1725524824-860891 X-HE-Meta: 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 4ST45Hnb O++j5VbkUIdRucMlBZl0ouG8CzvIHcbuMj4nRXrezwe/5Ih6chok54hEviSrE62Gj/HTPThbm53GgEb9awEWsa2XyUae8PiHOGdAQf4eUsHVuBmqG8AeBnPqeCGY+ZBQUJ4G1X6Vch6MmIVxMq8miYohO3aNGcu1vTHE4pKX+b1kl1WG4RHo4v+pdmQ0tZHfq30rZFxdN1fzHcU9ogZZ/Jz1qFJgukHSeTL8gTSwfDrbZeef2zLdKrjEQFw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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. > 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); > +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 > -- Kiryl Shutsemau / Kirill A. Shutemov