diff options
| -rw-r--r-- | include/linux/ksm.h | 18 | ||||
| -rw-r--r-- | mm/ksm.c | 83 | ||||
| -rw-r--r-- | mm/memory.c | 19 |
3 files changed, 92 insertions, 28 deletions
diff --git a/include/linux/ksm.h b/include/linux/ksm.h index 3319a6967626..45c9b6a17bcb 100644 --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -16,9 +16,6 @@ struct stable_node; struct mem_cgroup; -struct page *ksm_does_need_to_copy(struct page *page, - struct vm_area_struct *vma, unsigned long address); - #ifdef CONFIG_KSM int ksm_madvise(struct vm_area_struct *vma, unsigned long start, unsigned long end, int advice, unsigned long *vm_flags); @@ -73,15 +70,8 @@ static inline void set_page_stable_node(struct page *page, * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE, * but what if the vma was unmerged while the page was swapped out? */ -static inline int ksm_might_need_to_copy(struct page *page, - struct vm_area_struct *vma, unsigned long address) -{ - struct anon_vma *anon_vma = page_anon_vma(page); - - return anon_vma && - (anon_vma->root != vma->anon_vma->root || - page->index != linear_page_index(vma, address)); -} +struct page *ksm_might_need_to_copy(struct page *page, + struct vm_area_struct *vma, unsigned long address); int page_referenced_ksm(struct page *page, struct mem_cgroup *memcg, unsigned long *vm_flags); @@ -113,10 +103,10 @@ static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start, return 0; } -static inline int ksm_might_need_to_copy(struct page *page, +static inline struct page *ksm_might_need_to_copy(struct page *page, struct vm_area_struct *vma, unsigned long address) { - return 0; + return page; } static inline int page_referenced_ksm(struct page *page, @@ -644,6 +644,57 @@ static int unmerge_ksm_pages(struct vm_area_struct *vma, /* * Only called through the sysfs control interface: */ +static int remove_stable_node(struct stable_node *stable_node) +{ + struct page *page; + int err; + + page = get_ksm_page(stable_node, true); + if (!page) { + /* + * get_ksm_page did remove_node_from_stable_tree itself. + */ + return 0; + } + + if (WARN_ON_ONCE(page_mapped(page))) + err = -EBUSY; + else { + /* + * This page might be in a pagevec waiting to be freed, + * or it might be PageSwapCache (perhaps under writeback), + * or it might have been removed from swapcache a moment ago. + */ + set_page_stable_node(page, NULL); + remove_node_from_stable_tree(stable_node); + err = 0; + } + + unlock_page(page); + put_page(page); + return err; +} + +static int remove_all_stable_nodes(void) +{ + struct stable_node *stable_node; + int nid; + int err = 0; + + for (nid = 0; nid < nr_node_ids; nid++) { + while (root_stable_tree[nid].rb_node) { + stable_node = rb_entry(root_stable_tree[nid].rb_node, + struct stable_node, node); + if (remove_stable_node(stable_node)) { + err = -EBUSY; + break; /* proceed to next nid */ + } + cond_resched(); + } + } + return err; +} + static int unmerge_and_remove_all_rmap_items(void) { struct mm_slot *mm_slot; @@ -691,6 +742,8 @@ static int unmerge_and_remove_all_rmap_items(void) } } + /* Clean up stable nodes, but don't worry if some are still busy */ + remove_all_stable_nodes(); ksm_scan.seqnr = 0; return 0; @@ -1586,11 +1639,19 @@ int __ksm_enter(struct mm_struct *mm) spin_lock(&ksm_mmlist_lock); insert_to_mm_slots_hash(mm, mm_slot); /* - * Insert just behind the scanning cursor, to let the area settle + * When KSM_RUN_MERGE (or KSM_RUN_STOP), + * insert just behind the scanning cursor, to let the area settle * down a little; when fork is followed by immediate exec, we don't * want ksmd to waste time setting up and tearing down an rmap_list. + * + * But when KSM_RUN_UNMERGE, it's important to insert ahead of its + * scanning cursor, otherwise KSM pages in newly forked mms will be + * missed: then we might as well insert at the end of the list. */ - list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); + if (ksm_run & KSM_RUN_UNMERGE) + list_add_tail(&mm_slot->mm_list, &ksm_mm_head.mm_list); + else + list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); spin_unlock(&ksm_mmlist_lock); set_bit(MMF_VM_MERGEABLE, &mm->flags); @@ -1640,11 +1701,25 @@ void __ksm_exit(struct mm_struct *mm) } } -struct page *ksm_does_need_to_copy(struct page *page, +struct page *ksm_might_need_to_copy(struct page *page, struct vm_area_struct *vma, unsigned long address) { + struct anon_vma *anon_vma = page_anon_vma(page); struct page *new_page; + if (PageKsm(page)) { + if (page_stable_node(page) && + !(ksm_run & KSM_RUN_UNMERGE)) + return page; /* no need to copy it */ + } else if (!anon_vma) { + return page; /* no need to copy it */ + } else if (anon_vma->root == vma->anon_vma->root && + page->index == linear_page_index(vma, address)) { + return page; /* still no need to copy it */ + } + if (!PageUptodate(page)) + return page; /* let do_swap_page report the error */ + new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); if (new_page) { copy_user_highpage(new_page, page, address, vma); @@ -2024,7 +2099,7 @@ static ssize_t merge_across_nodes_store(struct kobject *kobj, mutex_lock(&ksm_thread_mutex); if (ksm_merge_across_nodes != knob) { - if (ksm_pages_shared) + if (ksm_pages_shared || remove_all_stable_nodes()) err = -EBUSY; else ksm_merge_across_nodes = knob; diff --git a/mm/memory.c b/mm/memory.c index 054250ee4a68..7bd22a621817 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2994,17 +2994,16 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma, if (unlikely(!PageSwapCache(page) || page_private(page) != entry.val)) goto out_page; - if (ksm_might_need_to_copy(page, vma, address)) { - swapcache = page; - page = ksm_does_need_to_copy(page, vma, address); - - if (unlikely(!page)) { - ret = VM_FAULT_OOM; - page = swapcache; - swapcache = NULL; - goto out_page; - } + swapcache = page; + page = ksm_might_need_to_copy(page, vma, address); + if (unlikely(!page)) { + ret = VM_FAULT_OOM; + page = swapcache; + swapcache = NULL; + goto out_page; } + if (page == swapcache) + swapcache = NULL; if (mem_cgroup_try_charge_swapin(mm, page, GFP_KERNEL, &ptr)) { ret = VM_FAULT_OOM; |