diff options
Diffstat (limited to 'mm/rmap.c')
| -rw-r--r-- | mm/rmap.c | 134 |
1 files changed, 64 insertions, 70 deletions
@@ -67,11 +67,24 @@ static struct kmem_cache *anon_vma_chain_cachep; static inline struct anon_vma *anon_vma_alloc(void) { - return kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); + struct anon_vma *anon_vma; + + anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); + if (anon_vma) { + atomic_set(&anon_vma->refcount, 1); + /* + * Initialise the anon_vma root to point to itself. If called + * from fork, the root will be reset to the parents anon_vma. + */ + anon_vma->root = anon_vma; + } + + return anon_vma; } -void anon_vma_free(struct anon_vma *anon_vma) +static inline void anon_vma_free(struct anon_vma *anon_vma) { + VM_BUG_ON(atomic_read(&anon_vma->refcount)); kmem_cache_free(anon_vma_cachep, anon_vma); } @@ -133,11 +146,6 @@ int anon_vma_prepare(struct vm_area_struct *vma) if (unlikely(!anon_vma)) goto out_enomem_free_avc; allocated = anon_vma; - /* - * This VMA had no anon_vma yet. This anon_vma is - * the root of any anon_vma tree that might form. - */ - anon_vma->root = anon_vma; } anon_vma_lock(anon_vma); @@ -156,7 +164,7 @@ int anon_vma_prepare(struct vm_area_struct *vma) anon_vma_unlock(anon_vma); if (unlikely(allocated)) - anon_vma_free(allocated); + put_anon_vma(allocated); if (unlikely(avc)) anon_vma_chain_free(avc); } @@ -241,9 +249,9 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) */ anon_vma->root = pvma->anon_vma->root; /* - * With KSM refcounts, an anon_vma can stay around longer than the - * process it belongs to. The root anon_vma needs to be pinned - * until this anon_vma is freed, because the lock lives in the root. + * With refcounts, an anon_vma can stay around longer than the + * process it belongs to. The root anon_vma needs to be pinned until + * this anon_vma is freed, because the lock lives in the root. */ get_anon_vma(anon_vma->root); /* Mark this anon_vma as the one where our new (COWed) pages go. */ @@ -253,7 +261,7 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) return 0; out_error_free_anon_vma: - anon_vma_free(anon_vma); + put_anon_vma(anon_vma); out_error: unlink_anon_vmas(vma); return -ENOMEM; @@ -272,15 +280,11 @@ static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain) list_del(&anon_vma_chain->same_anon_vma); /* We must garbage collect the anon_vma if it's empty */ - empty = list_empty(&anon_vma->head) && !anonvma_external_refcount(anon_vma); + empty = list_empty(&anon_vma->head); anon_vma_unlock(anon_vma); - if (empty) { - /* We no longer need the root anon_vma */ - if (anon_vma->root != anon_vma) - drop_anon_vma(anon_vma->root); - anon_vma_free(anon_vma); - } + if (empty) + put_anon_vma(anon_vma); } void unlink_anon_vmas(struct vm_area_struct *vma) @@ -303,7 +307,7 @@ static void anon_vma_ctor(void *data) struct anon_vma *anon_vma = data; spin_lock_init(&anon_vma->lock); - anonvma_external_refcount_init(anon_vma); + atomic_set(&anon_vma->refcount, 0); INIT_LIST_HEAD(&anon_vma->head); } @@ -497,41 +501,51 @@ int page_referenced_one(struct page *page, struct vm_area_struct *vma, struct mm_struct *mm = vma->vm_mm; int referenced = 0; - /* - * Don't want to elevate referenced for mlocked page that gets this far, - * in order that it progresses to try_to_unmap and is moved to the - * unevictable list. - */ - if (vma->vm_flags & VM_LOCKED) { - *mapcount = 0; /* break early from loop */ - *vm_flags |= VM_LOCKED; - goto out; - } - - /* Pretend the page is referenced if the task has the - swap token and is in the middle of a page fault. */ - if (mm != current->mm && has_swap_token(mm) && - rwsem_is_locked(&mm->mmap_sem)) - referenced++; - if (unlikely(PageTransHuge(page))) { pmd_t *pmd; spin_lock(&mm->page_table_lock); + /* + * rmap might return false positives; we must filter + * these out using page_check_address_pmd(). + */ pmd = page_check_address_pmd(page, mm, address, PAGE_CHECK_ADDRESS_PMD_FLAG); - if (pmd && !pmd_trans_splitting(*pmd) && - pmdp_clear_flush_young_notify(vma, address, pmd)) + if (!pmd) { + spin_unlock(&mm->page_table_lock); + goto out; + } + + if (vma->vm_flags & VM_LOCKED) { + spin_unlock(&mm->page_table_lock); + *mapcount = 0; /* break early from loop */ + *vm_flags |= VM_LOCKED; + goto out; + } + + /* go ahead even if the pmd is pmd_trans_splitting() */ + if (pmdp_clear_flush_young_notify(vma, address, pmd)) referenced++; spin_unlock(&mm->page_table_lock); } else { pte_t *pte; spinlock_t *ptl; + /* + * rmap might return false positives; we must filter + * these out using page_check_address(). + */ pte = page_check_address(page, mm, address, &ptl, 0); if (!pte) goto out; + if (vma->vm_flags & VM_LOCKED) { + pte_unmap_unlock(pte, ptl); + *mapcount = 0; /* break early from loop */ + *vm_flags |= VM_LOCKED; + goto out; + } + if (ptep_clear_flush_young_notify(vma, address, pte)) { /* * Don't treat a reference through a sequentially read @@ -546,6 +560,12 @@ int page_referenced_one(struct page *page, struct vm_area_struct *vma, pte_unmap_unlock(pte, ptl); } + /* Pretend the page is referenced if the task has the + swap token and is in the middle of a page fault. */ + if (mm != current->mm && has_swap_token(mm) && + rwsem_is_locked(&mm->mmap_sem)) + referenced++; + (*mapcount)--; if (referenced) @@ -1470,41 +1490,15 @@ int try_to_munlock(struct page *page) return try_to_unmap_file(page, TTU_MUNLOCK); } -#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION) -/* - * Drop an anon_vma refcount, freeing the anon_vma and anon_vma->root - * if necessary. Be careful to do all the tests under the lock. Once - * we know we are the last user, nobody else can get a reference and we - * can do the freeing without the lock. - */ -void drop_anon_vma(struct anon_vma *anon_vma) +void __put_anon_vma(struct anon_vma *anon_vma) { - BUG_ON(atomic_read(&anon_vma->external_refcount) <= 0); - if (atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->root->lock)) { - struct anon_vma *root = anon_vma->root; - int empty = list_empty(&anon_vma->head); - int last_root_user = 0; - int root_empty = 0; + struct anon_vma *root = anon_vma->root; - /* - * The refcount on a non-root anon_vma got dropped. Drop - * the refcount on the root and check if we need to free it. - */ - if (empty && anon_vma != root) { - BUG_ON(atomic_read(&root->external_refcount) <= 0); - last_root_user = atomic_dec_and_test(&root->external_refcount); - root_empty = list_empty(&root->head); - } - anon_vma_unlock(anon_vma); + if (root != anon_vma && atomic_dec_and_test(&root->refcount)) + anon_vma_free(root); - if (empty) { - anon_vma_free(anon_vma); - if (root_empty && last_root_user) - anon_vma_free(root); - } - } + anon_vma_free(anon_vma); } -#endif #ifdef CONFIG_MIGRATION /* |