diff options
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/ksm.c | 32 |
1 files changed, 27 insertions, 5 deletions
@@ -1177,8 +1177,18 @@ again: cond_resched(); stable_node = rb_entry(*new, struct stable_node, node); tree_page = get_ksm_page(stable_node, false); - if (!tree_page) - return NULL; + if (!tree_page) { + /* + * If we walked over a stale stable_node, + * get_ksm_page() will call rb_erase() and it + * may rebalance the tree from under us. So + * restart the search from scratch. Returning + * NULL would be safe too, but we'd generate + * false negative insertions just because some + * stable_node was stale. + */ + goto again; + } ret = memcmp_pages(page, tree_page); put_page(tree_page); @@ -1254,12 +1264,14 @@ static struct stable_node *stable_tree_insert(struct page *kpage) unsigned long kpfn; struct rb_root *root; struct rb_node **new; - struct rb_node *parent = NULL; + struct rb_node *parent; struct stable_node *stable_node; kpfn = page_to_pfn(kpage); nid = get_kpfn_nid(kpfn); root = root_stable_tree + nid; +again: + parent = NULL; new = &root->rb_node; while (*new) { @@ -1269,8 +1281,18 @@ static struct stable_node *stable_tree_insert(struct page *kpage) cond_resched(); stable_node = rb_entry(*new, struct stable_node, node); tree_page = get_ksm_page(stable_node, false); - if (!tree_page) - return NULL; + if (!tree_page) { + /* + * If we walked over a stale stable_node, + * get_ksm_page() will call rb_erase() and it + * may rebalance the tree from under us. So + * restart the search from scratch. Returning + * NULL would be safe too, but we'd generate + * false negative insertions just because some + * stable_node was stale. + */ + goto again; + } ret = memcmp_pages(kpage, tree_page); put_page(tree_page); |