diff options
| -rw-r--r-- | mm/ksm.c | 23 |
1 files changed, 13 insertions, 10 deletions
@@ -514,15 +514,14 @@ static void remove_node_from_stable_tree(struct stable_node *stable_node) * but this is different - made simpler by ksm_thread_mutex being held, but * interesting for assuming that no other use of the struct page could ever * put our expected_mapping into page->mapping (or a field of the union which - * coincides with page->mapping). The RCU calls are not for KSM at all, but - * to keep the page_count protocol described with page_cache_get_speculative. + * coincides with page->mapping). * * Note: it is possible that get_ksm_page() will return NULL one moment, * then page the next, if the page is in between page_freeze_refs() and * page_unfreeze_refs(): this shouldn't be a problem anywhere, the page * is on its way to being freed; but it is an anomaly to bear in mind. */ -static struct page *get_ksm_page(struct stable_node *stable_node) +static struct page *get_ksm_page(struct stable_node *stable_node, bool locked) { struct page *page; void *expected_mapping; @@ -530,7 +529,6 @@ static struct page *get_ksm_page(struct stable_node *stable_node) page = pfn_to_page(stable_node->kpfn); expected_mapping = (void *)stable_node + (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM); - rcu_read_lock(); if (page->mapping != expected_mapping) goto stale; if (!get_page_unless_zero(page)) @@ -539,10 +537,16 @@ static struct page *get_ksm_page(struct stable_node *stable_node) put_page(page); goto stale; } - rcu_read_unlock(); + if (locked) { + lock_page(page); + if (page->mapping != expected_mapping) { + unlock_page(page); + put_page(page); + goto stale; + } + } return page; stale: - rcu_read_unlock(); remove_node_from_stable_tree(stable_node); return NULL; } @@ -558,11 +562,10 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) struct page *page; stable_node = rmap_item->head; - page = get_ksm_page(stable_node); + page = get_ksm_page(stable_node, true); if (!page) goto out; - lock_page(page); hlist_del(&rmap_item->hlist); unlock_page(page); put_page(page); @@ -1042,7 +1045,7 @@ static struct page *stable_tree_search(struct page *page) cond_resched(); stable_node = rb_entry(node, struct stable_node, node); - tree_page = get_ksm_page(stable_node); + tree_page = get_ksm_page(stable_node, false); if (!tree_page) return NULL; @@ -1086,7 +1089,7 @@ 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); + tree_page = get_ksm_page(stable_node, false); if (!tree_page) return NULL; |