diff options
| -rw-r--r-- | include/linux/ksm.h | 24 | ||||
| -rw-r--r-- | mm/ksm.c | 99 |
2 files changed, 51 insertions, 72 deletions
diff --git a/include/linux/ksm.h b/include/linux/ksm.h index 1401a313fa77..ef55ce14a2ce 100644 --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -12,6 +12,8 @@ #include <linux/sched.h> #include <linux/vmstat.h> +struct stable_node; + #ifdef CONFIG_KSM int ksm_madvise(struct vm_area_struct *vma, unsigned long start, unsigned long end, int advice, unsigned long *vm_flags); @@ -34,7 +36,8 @@ static inline void ksm_exit(struct mm_struct *mm) /* * A KSM page is one of those write-protected "shared pages" or "merged pages" * which KSM maps into multiple mms, wherever identical anonymous page content - * is found in VM_MERGEABLE vmas. It's a PageAnon page, with NULL anon_vma. + * is found in VM_MERGEABLE vmas. It's a PageAnon page, pointing not to any + * anon_vma, but to that page's node of the stable tree. */ static inline int PageKsm(struct page *page) { @@ -42,15 +45,22 @@ static inline int PageKsm(struct page *page) (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM); } -/* - * But we have to avoid the checking which page_add_anon_rmap() performs. - */ +static inline struct stable_node *page_stable_node(struct page *page) +{ + return PageKsm(page) ? page_rmapping(page) : NULL; +} + +static inline void set_page_stable_node(struct page *page, + struct stable_node *stable_node) +{ + page->mapping = (void *)stable_node + + (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM); +} + static inline void page_add_ksm_rmap(struct page *page) { - if (atomic_inc_and_test(&page->_mapcount)) { - page->mapping = (void *) (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM); + if (atomic_inc_and_test(&page->_mapcount)) __inc_zone_page_state(page, NR_ANON_PAGES); - } } #else /* !CONFIG_KSM */ @@ -107,10 +107,12 @@ struct ksm_scan { /** * struct stable_node - node of the stable rbtree + * @page: pointer to struct page of the ksm page * @node: rb node of this ksm page in the stable tree * @hlist: hlist head of rmap_items using this ksm page */ struct stable_node { + struct page *page; struct rb_node node; struct hlist_head hlist; }; @@ -435,23 +437,6 @@ out: page = NULL; } /* - * get_ksm_page: checks if the page at the virtual address in rmap_item - * is still PageKsm, in which case we can trust the content of the page, - * and it returns the gotten page; but NULL if the page has been zapped. - */ -static struct page *get_ksm_page(struct rmap_item *rmap_item) -{ - struct page *page; - - page = get_mergeable_page(rmap_item); - if (page && !PageKsm(page)) { - put_page(page); - page = NULL; - } - return page; -} - -/* * Removing rmap_item from stable or unstable tree. * This function will clean the information from the stable/unstable tree. */ @@ -465,6 +450,9 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) if (stable_node->hlist.first) ksm_pages_sharing--; else { + set_page_stable_node(stable_node->page, NULL); + put_page(stable_node->page); + rb_erase(&stable_node->node, &root_stable_tree); free_stable_node(stable_node); ksm_pages_shared--; @@ -740,8 +728,7 @@ out: * try_to_merge_one_page - take two pages and merge them into one * @vma: the vma that holds the pte pointing to page * @page: the PageAnon page that we want to replace with kpage - * @kpage: the PageKsm page (or newly allocated page which page_add_ksm_rmap - * will make PageKsm) that we want to map instead of page + * @kpage: the PageKsm page that we want to map instead of page * * This function returns 0 if the pages were merged, -EFAULT otherwise. */ @@ -793,6 +780,9 @@ static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item, struct vm_area_struct *vma; int err = -EFAULT; + if (page == kpage) /* ksm page forked */ + return 0; + down_read(&mm->mmap_sem); if (ksm_test_exit(mm)) goto out; @@ -846,6 +836,9 @@ static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, goto up; copy_user_highpage(kpage, page, rmap_item->address, vma); + + set_page_stable_node(kpage, NULL); /* mark it PageKsm */ + err = try_to_merge_one_page(vma, page, kpage); up: up_read(&mm->mmap_sem); @@ -876,41 +869,31 @@ up: * This function returns the stable tree node of identical content if found, * NULL otherwise. */ -static struct stable_node *stable_tree_search(struct page *page, - struct page **tree_pagep) +static struct stable_node *stable_tree_search(struct page *page) { struct rb_node *node = root_stable_tree.rb_node; struct stable_node *stable_node; + stable_node = page_stable_node(page); + if (stable_node) { /* ksm page forked */ + get_page(page); + return stable_node; + } + while (node) { - struct hlist_node *hlist, *hnext; - struct rmap_item *tree_rmap_item; - struct page *tree_page; int ret; + cond_resched(); stable_node = rb_entry(node, struct stable_node, node); - hlist_for_each_entry_safe(tree_rmap_item, hlist, hnext, - &stable_node->hlist, hlist) { - BUG_ON(!in_stable_tree(tree_rmap_item)); - cond_resched(); - tree_page = get_ksm_page(tree_rmap_item); - if (tree_page) - break; - remove_rmap_item_from_tree(tree_rmap_item); - } - if (!hlist) - return NULL; - ret = memcmp_pages(page, tree_page); + ret = memcmp_pages(page, stable_node->page); - if (ret < 0) { - put_page(tree_page); + if (ret < 0) node = node->rb_left; - } else if (ret > 0) { - put_page(tree_page); + else if (ret > 0) node = node->rb_right; - } else { - *tree_pagep = tree_page; + else { + get_page(stable_node->page); return stable_node; } } @@ -932,26 +915,12 @@ static struct stable_node *stable_tree_insert(struct page *kpage) struct stable_node *stable_node; while (*new) { - struct hlist_node *hlist, *hnext; - struct rmap_item *tree_rmap_item; - struct page *tree_page; int ret; + cond_resched(); stable_node = rb_entry(*new, struct stable_node, node); - hlist_for_each_entry_safe(tree_rmap_item, hlist, hnext, - &stable_node->hlist, hlist) { - BUG_ON(!in_stable_tree(tree_rmap_item)); - cond_resched(); - tree_page = get_ksm_page(tree_rmap_item); - if (tree_page) - break; - remove_rmap_item_from_tree(tree_rmap_item); - } - if (!hlist) - return NULL; - ret = memcmp_pages(kpage, tree_page); - put_page(tree_page); + ret = memcmp_pages(kpage, stable_node->page); parent = *new; if (ret < 0) @@ -977,6 +946,10 @@ static struct stable_node *stable_tree_insert(struct page *kpage) INIT_HLIST_HEAD(&stable_node->hlist); + get_page(kpage); + stable_node->page = kpage; + set_page_stable_node(kpage, stable_node); + return stable_node; } @@ -1085,14 +1058,10 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) remove_rmap_item_from_tree(rmap_item); /* We first start with searching the page inside the stable tree */ - stable_node = stable_tree_search(page, &tree_page); + stable_node = stable_tree_search(page); if (stable_node) { - kpage = tree_page; - if (page == kpage) /* forked */ - err = 0; - else - err = try_to_merge_with_ksm_page(rmap_item, - page, kpage); + kpage = stable_node->page; + err = try_to_merge_with_ksm_page(rmap_item, page, kpage); if (!err) { /* * The page was successfully merged: |