diff --git a/include/linux/mm.h b/include/linux/mm.h index 8bd74558c0e4..192c1bbe5fcd 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -330,6 +330,13 @@ struct fault_env { * Protects pte page table if 'pte' * is not NULL, otherwise pmd. */ + pgtable_t prealloc_pte; /* Pre-allocated pte page table. + * vm_ops->map_pages() calls + * alloc_set_pte() from atomic context. + * do_fault_around() pre-allocates + * page table to avoid allocation from + * atomic context. + */ }; /* @@ -618,7 +625,8 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma) return pte; } -void do_set_pte(struct fault_env *fe, struct page *page); +int alloc_set_pte(struct fault_env *fe, struct mem_cgroup *memcg, + struct page *page); #endif /* diff --git a/mm/filemap.c b/mm/filemap.c index 54d5318f8d3f..1efd2994dccf 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2144,11 +2144,6 @@ void filemap_map_pages(struct fault_env *fe, start_pgoff) { if (iter.index > end_pgoff) break; - fe->pte += iter.index - last_pgoff; - fe->address += (iter.index - last_pgoff) << PAGE_SHIFT; - last_pgoff = iter.index; - if (!pte_none(*fe->pte)) - goto next; repeat: page = radix_tree_deref_slot(slot); if (unlikely(!page)) @@ -2186,7 +2181,13 @@ void filemap_map_pages(struct fault_env *fe, if (file->f_ra.mmap_miss > 0) file->f_ra.mmap_miss--; - do_set_pte(fe, page); + + fe->address += (iter.index - last_pgoff) << PAGE_SHIFT; + if (fe->pte) + fe->pte += iter.index - last_pgoff; + last_pgoff = iter.index; + if (alloc_set_pte(fe, NULL, page)) + goto unlock; unlock_page(page); goto next; unlock: @@ -2194,6 +2195,9 @@ void filemap_map_pages(struct fault_env *fe, skip: put_page(page); next: + /* Huge page is mapped? No need to proceed. */ + if (pmd_trans_huge(*fe->pmd)) + break; if (iter.index == end_pgoff) break; } diff --git a/mm/memory.c b/mm/memory.c index 72b520897339..1991105bf67c 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2739,8 +2739,6 @@ static int do_anonymous_page(struct fault_env *fe) struct page *page; pte_t entry; - pte_unmap(fe->pte); - /* File mapping without ->vm_ops ? */ if (vma->vm_flags & VM_SHARED) return VM_FAULT_SIGBUS; @@ -2749,6 +2747,23 @@ static int do_anonymous_page(struct fault_env *fe) if (check_stack_guard_page(vma, fe->address) < 0) return VM_FAULT_SIGSEGV; + /* + * Use pte_alloc() instead of pte_alloc_map(). We can't run + * pte_offset_map() on pmds where a huge pmd might be created + * from a different thread. + * + * pte_alloc_map() is safe to use under down_write(mmap_sem) or when + * parallel threads are excluded by other means. + * + * Here we only have down_read(mmap_sem). + */ + if (pte_alloc(vma->vm_mm, fe->pmd, fe->address)) + return VM_FAULT_OOM; + + /* See the comment in pte_alloc_one_map() */ + if (unlikely(pmd_trans_unstable(fe->pmd))) + return 0; + /* Use the zero-page for reads */ if (!(fe->flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(vma->vm_mm)) { @@ -2865,23 +2880,76 @@ static int __do_fault(struct fault_env *fe, pgoff_t pgoff, return ret; } +static int pte_alloc_one_map(struct fault_env *fe) +{ + struct vm_area_struct *vma = fe->vma; + + if (!pmd_none(*fe->pmd)) + goto map_pte; + if (fe->prealloc_pte) { + fe->ptl = pmd_lock(vma->vm_mm, fe->pmd); + if (unlikely(!pmd_none(*fe->pmd))) { + spin_unlock(fe->ptl); + goto map_pte; + } + + atomic_long_inc(&vma->vm_mm->nr_ptes); + pmd_populate(vma->vm_mm, fe->pmd, fe->prealloc_pte); + spin_unlock(fe->ptl); + fe->prealloc_pte = 0; + } else if (unlikely(pte_alloc(vma->vm_mm, fe->pmd, fe->address))) { + return VM_FAULT_OOM; + } +map_pte: + /* + * If a huge pmd materialized under us just retry later. Use + * pmd_trans_unstable() instead of pmd_trans_huge() to ensure the pmd + * didn't become pmd_trans_huge under us and then back to pmd_none, as + * a result of MADV_DONTNEED running immediately after a huge pmd fault + * in a different thread of this mm, in turn leading to a misleading + * pmd_trans_huge() retval. All we have to ensure is that it is a + * regular pmd that we can walk with pte_offset_map() and we can do that + * through an atomic read in C, which is what pmd_trans_unstable() + * provides. + */ + if (pmd_trans_unstable(fe->pmd) || pmd_devmap(*fe->pmd)) + return VM_FAULT_NOPAGE; + + fe->pte = pte_offset_map_lock(vma->vm_mm, fe->pmd, fe->address, + &fe->ptl); + return 0; +} + /** - * do_set_pte - setup new PTE entry for given page and add reverse page mapping. + * alloc_set_pte - setup new PTE entry for given page and add reverse page + * mapping. If needed, the fucntion allocates page table or use pre-allocated. * * @fe: fault environment + * @memcg: memcg to charge page (only for private mappings) * @page: page to map * - * Caller must hold page table lock relevant for @fe->pte. + * Caller must take care of unlocking fe->ptl, if fe->pte is non-NULL on return. * * Target users are page handler itself and implementations of * vm_ops->map_pages. */ -void do_set_pte(struct fault_env *fe, struct page *page) +int alloc_set_pte(struct fault_env *fe, struct mem_cgroup *memcg, + struct page *page) { struct vm_area_struct *vma = fe->vma; bool write = fe->flags & FAULT_FLAG_WRITE; pte_t entry; + if (!fe->pte) { + int ret = pte_alloc_one_map(fe); + if (ret) + return ret; + } + + /* Re-check under ptl */ + if (unlikely(!pte_none(*fe->pte))) + return VM_FAULT_NOPAGE; + flush_icache_page(vma, page); entry = mk_pte(page, vma->vm_page_prot); if (write) @@ -2890,6 +2958,8 @@ void do_set_pte(struct fault_env *fe, struct page *page) if (write && !(vma->vm_flags & VM_SHARED)) { inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES); page_add_new_anon_rmap(page, vma, fe->address, false); + mem_cgroup_commit_charge(page, memcg, false, false); + lru_cache_add_active_or_unevictable(page, vma); } else { inc_mm_counter_fast(vma->vm_mm, mm_counter_file(page)); page_add_file_rmap(page); @@ -2898,6 +2968,8 @@ void do_set_pte(struct fault_env *fe, struct page *page) /* no need to invalidate: a not-present page won't be cached */ update_mmu_cache(vma, fe->address, fe->pte); + + return 0; } static unsigned long fault_around_bytes __read_mostly = @@ -2964,19 +3036,17 @@ late_initcall(fault_around_debugfs); * fault_around_pages() value (and therefore to page order). This way it's * easier to guarantee that we don't cross page table boundaries. */ -static void do_fault_around(struct fault_env *fe, pgoff_t start_pgoff) +static int do_fault_around(struct fault_env *fe, pgoff_t start_pgoff) { - unsigned long address = fe->address, start_addr, nr_pages, mask; - pte_t *pte = fe->pte; + unsigned long address = fe->address, nr_pages, mask; pgoff_t end_pgoff; - int off; + int off, ret = 0; nr_pages = READ_ONCE(fault_around_bytes) >> PAGE_SHIFT; mask = ~(nr_pages * PAGE_SIZE - 1) & PAGE_MASK; - start_addr = max(fe->address & mask, fe->vma->vm_start); - off = ((fe->address - start_addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1); - fe->pte -= off; + fe->address = max(address & mask, fe->vma->vm_start); + off = ((address - fe->address) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1); start_pgoff -= off; /* @@ -2984,30 +3054,45 @@ static void do_fault_around(struct fault_env *fe, pgoff_t start_pgoff) * or fault_around_pages() from start_pgoff, depending what is nearest. */ end_pgoff = start_pgoff - - ((start_addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)) + + ((fe->address >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)) + PTRS_PER_PTE - 1; end_pgoff = min3(end_pgoff, vma_pages(fe->vma) + fe->vma->vm_pgoff - 1, start_pgoff + nr_pages - 1); - /* Check if it makes any sense to call ->map_pages */ - fe->address = start_addr; - while (!pte_none(*fe->pte)) { - if (++start_pgoff > end_pgoff) - goto out; - fe->address += PAGE_SIZE; - if (fe->address >= fe->vma->vm_end) - goto out; - fe->pte++; + if (pmd_none(*fe->pmd)) { + fe->prealloc_pte = pte_alloc_one(fe->vma->vm_mm, fe->address); + smp_wmb(); /* See comment in __pte_alloc() */ } fe->vma->vm_ops->map_pages(fe, start_pgoff, end_pgoff); + + /* preallocated pagetable is unused: free it */ + if (fe->prealloc_pte) { + pte_free(fe->vma->vm_mm, fe->prealloc_pte); + fe->prealloc_pte = 0; + } + /* Huge page is mapped? Page fault is solved */ + if (pmd_trans_huge(*fe->pmd)) { + ret = VM_FAULT_NOPAGE; + goto out; + } + + /* ->map_pages() haven't done anything useful. Cold page cache? */ + if (!fe->pte) + goto out; + + /* check if the page fault is solved */ + fe->pte -= (fe->address >> PAGE_SHIFT) - (address >> PAGE_SHIFT); + if (!pte_none(*fe->pte)) + ret = VM_FAULT_NOPAGE; + pte_unmap_unlock(fe->pte, fe->ptl); out: - /* restore fault_env */ - fe->pte = pte; fe->address = address; + fe->pte = NULL; + return ret; } -static int do_read_fault(struct fault_env *fe, pgoff_t pgoff, pte_t orig_pte) +static int do_read_fault(struct fault_env *fe, pgoff_t pgoff) { struct vm_area_struct *vma = fe->vma; struct page *fault_page; @@ -3019,36 +3104,25 @@ static int do_read_fault(struct fault_env *fe, pgoff_t pgoff, pte_t orig_pte) * something). */ if (vma->vm_ops->map_pages && fault_around_bytes >> PAGE_SHIFT > 1) { - fe->pte = pte_offset_map_lock(vma->vm_mm, fe->pmd, fe->address, - &fe->ptl); - if (!pte_same(*fe->pte, orig_pte)) - goto unlock_out; - do_fault_around(fe, pgoff); - /* Check if the fault is handled by faultaround */ - if (!pte_same(*fe->pte, orig_pte)) - goto unlock_out; - pte_unmap_unlock(fe->pte, fe->ptl); + ret = do_fault_around(fe, pgoff); + if (ret) + return ret; } ret = __do_fault(fe, pgoff, NULL, &fault_page, NULL); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) return ret; - fe->pte = pte_offset_map_lock(vma->vm_mm, fe->pmd, fe->address, &fe->ptl); - if (unlikely(!pte_same(*fe->pte, orig_pte))) { + ret |= alloc_set_pte(fe, NULL, fault_page); + if (fe->pte) pte_unmap_unlock(fe->pte, fe->ptl); - unlock_page(fault_page); - put_page(fault_page); - return ret; - } - do_set_pte(fe, fault_page); unlock_page(fault_page); -unlock_out: - pte_unmap_unlock(fe->pte, fe->ptl); + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) + put_page(fault_page); return ret; } -static int do_cow_fault(struct fault_env *fe, pgoff_t pgoff, pte_t orig_pte) +static int do_cow_fault(struct fault_env *fe, pgoff_t pgoff) { struct vm_area_struct *vma = fe->vma; struct page *fault_page, *new_page; @@ -3077,29 +3151,17 @@ static int do_cow_fault(struct fault_env *fe, pgoff_t pgoff, pte_t orig_pte) copy_user_highpage(new_page, fault_page, fe->address, vma); __SetPageUptodate(new_page); - fe->pte = pte_offset_map_lock(vma->vm_mm, fe->pmd, fe->address, - &fe->ptl); - if (unlikely(!pte_same(*fe->pte, orig_pte))) { + ret |= alloc_set_pte(fe, memcg, new_page); + if (fe->pte) pte_unmap_unlock(fe->pte, fe->ptl); - if (!(ret & VM_FAULT_DAX_LOCKED)) { - unlock_page(fault_page); - put_page(fault_page); - } else { - dax_unlock_mapping_entry(vma->vm_file->f_mapping, - pgoff); - } - goto uncharge_out; - } - do_set_pte(fe, new_page); - mem_cgroup_commit_charge(new_page, memcg, false, false); - lru_cache_add_active_or_unevictable(new_page, vma); - pte_unmap_unlock(fe->pte, fe->ptl); if (!(ret & VM_FAULT_DAX_LOCKED)) { unlock_page(fault_page); put_page(fault_page); } else { dax_unlock_mapping_entry(vma->vm_file->f_mapping, pgoff); } + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) + goto uncharge_out; return ret; uncharge_out: mem_cgroup_cancel_charge(new_page, memcg, false); @@ -3107,7 +3169,7 @@ static int do_cow_fault(struct fault_env *fe, pgoff_t pgoff, pte_t orig_pte) return ret; } -static int do_shared_fault(struct fault_env *fe, pgoff_t pgoff, pte_t orig_pte) +static int do_shared_fault(struct fault_env *fe, pgoff_t pgoff) { struct vm_area_struct *vma = fe->vma; struct page *fault_page; @@ -3133,16 +3195,15 @@ static int do_shared_fault(struct fault_env *fe, pgoff_t pgoff, pte_t orig_pte) } } - fe->pte = pte_offset_map_lock(vma->vm_mm, fe->pmd, fe->address, - &fe->ptl); - if (unlikely(!pte_same(*fe->pte, orig_pte))) { + ret |= alloc_set_pte(fe, NULL, fault_page); + if (fe->pte) pte_unmap_unlock(fe->pte, fe->ptl); + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | + VM_FAULT_RETRY))) { unlock_page(fault_page); put_page(fault_page); return ret; } - do_set_pte(fe, fault_page); - pte_unmap_unlock(fe->pte, fe->ptl); if (set_page_dirty(fault_page)) dirtied = 1; @@ -3174,20 +3235,19 @@ static int do_shared_fault(struct fault_env *fe, pgoff_t pgoff, pte_t orig_pte) * The mmap_sem may have been released depending on flags and our * return value. See filemap_fault() and __lock_page_or_retry(). */ -static int do_fault(struct fault_env *fe, pte_t orig_pte) +static int do_fault(struct fault_env *fe) { struct vm_area_struct *vma = fe->vma; pgoff_t pgoff = linear_page_index(vma, fe->address); - pte_unmap(fe->pte); /* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND */ if (!vma->vm_ops->fault) return VM_FAULT_SIGBUS; if (!(fe->flags & FAULT_FLAG_WRITE)) - return do_read_fault(fe, pgoff, orig_pte); + return do_read_fault(fe, pgoff); if (!(vma->vm_flags & VM_SHARED)) - return do_cow_fault(fe, pgoff, orig_pte); - return do_shared_fault(fe, pgoff, orig_pte); + return do_cow_fault(fe, pgoff); + return do_shared_fault(fe, pgoff); } static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma, @@ -3327,37 +3387,63 @@ static int wp_huge_pmd(struct fault_env *fe, pmd_t orig_pmd) * with external mmu caches can use to update those (ie the Sparc or * PowerPC hashed page tables that act as extended TLBs). * - * We enter with non-exclusive mmap_sem (to exclude vma changes, - * but allow concurrent faults), and pte mapped but not yet locked. - * We return with pte unmapped and unlocked. + * We enter with non-exclusive mmap_sem (to exclude vma changes, but allow + * concurrent faults). * - * The mmap_sem may have been released depending on flags and our - * return value. See filemap_fault() and __lock_page_or_retry(). + * The mmap_sem may have been released depending on flags and our return value. + * See filemap_fault() and __lock_page_or_retry(). */ static int handle_pte_fault(struct fault_env *fe) { pte_t entry; - /* - * some architectures can have larger ptes than wordsize, - * e.g.ppc44x-defconfig has CONFIG_PTE_64BIT=y and CONFIG_32BIT=y, - * so READ_ONCE or ACCESS_ONCE cannot guarantee atomic accesses. - * The code below just needs a consistent view for the ifs and - * we later double check anyway with the ptl lock held. So here - * a barrier will do. - */ - entry = *fe->pte; - barrier(); - if (!pte_present(entry)) { + if (unlikely(pmd_none(*fe->pmd))) { + /* + * Leave __pte_alloc() until later: because vm_ops->fault may + * want to allocate huge page, and if we expose page table + * for an instant, it will be difficult to retract from + * concurrent faults and from rmap lookups. + */ + fe->pte = NULL; + } else { + /* See comment in pte_alloc_one_map() */ + if (pmd_trans_unstable(fe->pmd) || pmd_devmap(*fe->pmd)) + return 0; + /* + * A regular pmd is established and it can't morph into a huge + * pmd from under us anymore at this point because we hold the + * mmap_sem read mode and khugepaged takes it in write mode. + * So now it's safe to run pte_offset_map(). + */ + fe->pte = pte_offset_map(fe->pmd, fe->address); + + entry = *fe->pte; + + /* + * some architectures can have larger ptes than wordsize, + * e.g.ppc44x-defconfig has CONFIG_PTE_64BIT=y and + * CONFIG_32BIT=y, so READ_ONCE or ACCESS_ONCE cannot guarantee + * atomic accesses. The code below just needs a consistent + * view for the ifs and we later double check anyway with the + * ptl lock held. So here a barrier will do. + */ + barrier(); if (pte_none(entry)) { - if (vma_is_anonymous(fe->vma)) - return do_anonymous_page(fe); - else - return do_fault(fe, entry); + pte_unmap(fe->pte); + fe->pte = NULL; } - return do_swap_page(fe, entry); } + if (!fe->pte) { + if (vma_is_anonymous(fe->vma)) + return do_anonymous_page(fe); + else + return do_fault(fe); + } + + if (!pte_present(entry)) + return do_swap_page(fe, entry); + if (pte_protnone(entry)) return do_numa_page(fe, entry); @@ -3439,34 +3525,6 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address, } } - /* - * Use pte_alloc() instead of pte_alloc_map, because we can't - * run pte_offset_map on the pmd, if an huge pmd could - * materialize from under us from a different thread. - */ - if (unlikely(pte_alloc(fe.vma->vm_mm, fe.pmd, fe.address))) - return VM_FAULT_OOM; - /* - * If a huge pmd materialized under us just retry later. Use - * pmd_trans_unstable() instead of pmd_trans_huge() to ensure the pmd - * didn't become pmd_trans_huge under us and then back to pmd_none, as - * a result of MADV_DONTNEED running immediately after a huge pmd fault - * in a different thread of this mm, in turn leading to a misleading - * pmd_trans_huge() retval. All we have to ensure is that it is a - * regular pmd that we can walk with pte_offset_map() and we can do that - * through an atomic read in C, which is what pmd_trans_unstable() - * provides. - */ - if (unlikely(pmd_trans_unstable(fe.pmd) || pmd_devmap(*fe.pmd))) - return 0; - /* - * A regular pmd is established and it can't morph into a huge pmd - * from under us anymore at this point because we hold the mmap_sem - * read mode and khugepaged takes it in write mode. So now it's - * safe to run pte_offset_map(). - */ - fe.pte = pte_offset_map(fe.pmd, fe.address); - return handle_pte_fault(&fe); }