diff options
| -rw-r--r-- | mm/memory.c | 265 |
1 files changed, 147 insertions, 118 deletions
diff --git a/mm/memory.c b/mm/memory.c index 0e28fddafdaf..cfd3c78f00fe 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2042,6 +2042,146 @@ static inline int wp_page_reuse(struct mm_struct *mm, } /* + * Handle the case of a page which we actually need to copy to a new page. + * + * Called with mmap_sem locked and the old page referenced, but + * without the ptl held. + * + * High level logic flow: + * + * - Allocate a page, copy the content of the old page to the new one. + * - Handle book keeping and accounting - cgroups, mmu-notifiers, etc. + * - Take the PTL. If the pte changed, bail out and release the allocated page + * - If the pte is still the way we remember it, update the page table and all + * relevant references. This includes dropping the reference the page-table + * held to the old page, as well as updating the rmap. + * - In any case, unlock the PTL and drop the reference we took to the old page. + */ +static int wp_page_copy(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long address, pte_t *page_table, pmd_t *pmd, + pte_t orig_pte, struct page *old_page) +{ + struct page *new_page = NULL; + spinlock_t *ptl = NULL; + pte_t entry; + int page_copied = 0; + const unsigned long mmun_start = address & PAGE_MASK; /* For mmu_notifiers */ + const unsigned long mmun_end = mmun_start + PAGE_SIZE; /* For mmu_notifiers */ + struct mem_cgroup *memcg; + + if (unlikely(anon_vma_prepare(vma))) + goto oom; + + if (is_zero_pfn(pte_pfn(orig_pte))) { + new_page = alloc_zeroed_user_highpage_movable(vma, address); + if (!new_page) + goto oom; + } else { + new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); + if (!new_page) + goto oom; + cow_user_page(new_page, old_page, address, vma); + } + __SetPageUptodate(new_page); + + if (mem_cgroup_try_charge(new_page, mm, GFP_KERNEL, &memcg)) + goto oom_free_new; + + mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); + + /* + * Re-check the pte - we dropped the lock + */ + page_table = pte_offset_map_lock(mm, pmd, address, &ptl); + if (likely(pte_same(*page_table, orig_pte))) { + if (old_page) { + if (!PageAnon(old_page)) { + dec_mm_counter_fast(mm, MM_FILEPAGES); + inc_mm_counter_fast(mm, MM_ANONPAGES); + } + } else { + inc_mm_counter_fast(mm, MM_ANONPAGES); + } + flush_cache_page(vma, address, pte_pfn(orig_pte)); + entry = mk_pte(new_page, vma->vm_page_prot); + entry = maybe_mkwrite(pte_mkdirty(entry), vma); + /* + * Clear the pte entry and flush it first, before updating the + * pte with the new entry. This will avoid a race condition + * seen in the presence of one thread doing SMC and another + * thread doing COW. + */ + ptep_clear_flush_notify(vma, address, page_table); + page_add_new_anon_rmap(new_page, vma, address); + mem_cgroup_commit_charge(new_page, memcg, false); + lru_cache_add_active_or_unevictable(new_page, vma); + /* + * We call the notify macro here because, when using secondary + * mmu page tables (such as kvm shadow page tables), we want the + * new page to be mapped directly into the secondary page table. + */ + set_pte_at_notify(mm, address, page_table, entry); + update_mmu_cache(vma, address, page_table); + if (old_page) { + /* + * Only after switching the pte to the new page may + * we remove the mapcount here. Otherwise another + * process may come and find the rmap count decremented + * before the pte is switched to the new page, and + * "reuse" the old page writing into it while our pte + * here still points into it and can be read by other + * threads. + * + * The critical issue is to order this + * page_remove_rmap with the ptp_clear_flush above. + * Those stores are ordered by (if nothing else,) + * the barrier present in the atomic_add_negative + * in page_remove_rmap. + * + * Then the TLB flush in ptep_clear_flush ensures that + * no process can access the old page before the + * decremented mapcount is visible. And the old page + * cannot be reused until after the decremented + * mapcount is visible. So transitively, TLBs to + * old page will be flushed before it can be reused. + */ + page_remove_rmap(old_page); + } + + /* Free the old page.. */ + new_page = old_page; + page_copied = 1; + } else { + mem_cgroup_cancel_charge(new_page, memcg); + } + + if (new_page) + page_cache_release(new_page); + + pte_unmap_unlock(page_table, ptl); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + if (old_page) { + /* + * Don't let another task, with possibly unlocked vma, + * keep the mlocked page. + */ + if (page_copied && (vma->vm_flags & VM_LOCKED)) { + lock_page(old_page); /* LRU manipulation */ + munlock_vma_page(old_page); + unlock_page(old_page); + } + page_cache_release(old_page); + } + return page_copied ? VM_FAULT_WRITE : 0; +oom_free_new: + page_cache_release(new_page); +oom: + if (old_page) + page_cache_release(old_page); + return VM_FAULT_OOM; +} + +/* * This routine handles present pages, when users try to write * to a shared page. It is done by copying the page to a new address * and decrementing the shared-page counter for the old page. @@ -2064,12 +2204,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, spinlock_t *ptl, pte_t orig_pte) __releases(ptl) { - struct page *old_page, *new_page = NULL; - pte_t entry; - int page_copied = 0; - unsigned long mmun_start = 0; /* For mmu_notifiers */ - unsigned long mmun_end = 0; /* For mmu_notifiers */ - struct mem_cgroup *memcg; + struct page *old_page; old_page = vm_normal_page(vma, address, orig_pte); if (!old_page) { @@ -2085,7 +2220,10 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, (VM_WRITE|VM_SHARED)) return wp_page_reuse(mm, vma, address, page_table, ptl, orig_pte, old_page, 0, 0); - goto gotten; + + pte_unmap_unlock(page_table, ptl); + return wp_page_copy(mm, vma, address, page_table, pmd, + orig_pte, old_page); } /* @@ -2165,119 +2303,10 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, * Ok, we need to copy. Oh, well.. */ page_cache_get(old_page); -gotten: - pte_unmap_unlock(page_table, ptl); - - if (unlikely(anon_vma_prepare(vma))) - goto oom; - - if (is_zero_pfn(pte_pfn(orig_pte))) { - new_page = alloc_zeroed_user_highpage_movable(vma, address); - if (!new_page) - goto oom; - } else { - new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); - if (!new_page) - goto oom; - cow_user_page(new_page, old_page, address, vma); - } - __SetPageUptodate(new_page); - - if (mem_cgroup_try_charge(new_page, mm, GFP_KERNEL, &memcg)) - goto oom_free_new; - - mmun_start = address & PAGE_MASK; - mmun_end = mmun_start + PAGE_SIZE; - mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); - - /* - * Re-check the pte - we dropped the lock - */ - page_table = pte_offset_map_lock(mm, pmd, address, &ptl); - if (likely(pte_same(*page_table, orig_pte))) { - if (old_page) { - if (!PageAnon(old_page)) { - dec_mm_counter_fast(mm, MM_FILEPAGES); - inc_mm_counter_fast(mm, MM_ANONPAGES); - } - } else - inc_mm_counter_fast(mm, MM_ANONPAGES); - flush_cache_page(vma, address, pte_pfn(orig_pte)); - entry = mk_pte(new_page, vma->vm_page_prot); - entry = maybe_mkwrite(pte_mkdirty(entry), vma); - /* - * Clear the pte entry and flush it first, before updating the - * pte with the new entry. This will avoid a race condition - * seen in the presence of one thread doing SMC and another - * thread doing COW. - */ - ptep_clear_flush_notify(vma, address, page_table); - page_add_new_anon_rmap(new_page, vma, address); - mem_cgroup_commit_charge(new_page, memcg, false); - lru_cache_add_active_or_unevictable(new_page, vma); - /* - * We call the notify macro here because, when using secondary - * mmu page tables (such as kvm shadow page tables), we want the - * new page to be mapped directly into the secondary page table. - */ - set_pte_at_notify(mm, address, page_table, entry); - update_mmu_cache(vma, address, page_table); - if (old_page) { - /* - * Only after switching the pte to the new page may - * we remove the mapcount here. Otherwise another - * process may come and find the rmap count decremented - * before the pte is switched to the new page, and - * "reuse" the old page writing into it while our pte - * here still points into it and can be read by other - * threads. - * - * The critical issue is to order this - * page_remove_rmap with the ptp_clear_flush above. - * Those stores are ordered by (if nothing else,) - * the barrier present in the atomic_add_negative - * in page_remove_rmap. - * - * Then the TLB flush in ptep_clear_flush ensures that - * no process can access the old page before the - * decremented mapcount is visible. And the old page - * cannot be reused until after the decremented - * mapcount is visible. So transitively, TLBs to - * old page will be flushed before it can be reused. - */ - page_remove_rmap(old_page); - } - - /* Free the old page.. */ - new_page = old_page; - page_copied = 1; - } else - mem_cgroup_cancel_charge(new_page, memcg); - - if (new_page) - page_cache_release(new_page); pte_unmap_unlock(page_table, ptl); - mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); - if (old_page) { - /* - * Don't let another task, with possibly unlocked vma, - * keep the mlocked page. - */ - if (page_copied && (vma->vm_flags & VM_LOCKED)) { - lock_page(old_page); /* LRU manipulation */ - munlock_vma_page(old_page); - unlock_page(old_page); - } - page_cache_release(old_page); - } - return page_copied ? VM_FAULT_WRITE : 0; -oom_free_new: - page_cache_release(new_page); -oom: - if (old_page) - page_cache_release(old_page); - return VM_FAULT_OOM; + return wp_page_copy(mm, vma, address, page_table, pmd, + orig_pte, old_page); } static void unmap_mapping_range_vma(struct vm_area_struct *vma, |