diff options
Diffstat (limited to 'mm/ksm.c')
| -rw-r--r-- | mm/ksm.c | 43 |
1 files changed, 39 insertions, 4 deletions
@@ -1131,6 +1131,13 @@ static int replace_page(struct vm_area_struct *vma, struct page *page, } else { newpte = pte_mkspecial(pfn_pte(page_to_pfn(kpage), vma->vm_page_prot)); + /* + * We're replacing an anonymous page with a zero page, which is + * not anonymous. We need to do proper accounting otherwise we + * will get wrong values in /proc, and a BUG message in dmesg + * when tearing down the mm. + */ + dec_mm_counter(mm, MM_ANONPAGES); } flush_cache_page(vma, addr, pte_pfn(*ptep)); @@ -1318,10 +1325,10 @@ bool is_page_sharing_candidate(struct stable_node *stable_node) return __is_page_sharing_candidate(stable_node, 0); } -struct page *stable_node_dup(struct stable_node **_stable_node_dup, - struct stable_node **_stable_node, - struct rb_root *root, - bool prune_stale_stable_nodes) +static struct page *stable_node_dup(struct stable_node **_stable_node_dup, + struct stable_node **_stable_node, + struct rb_root *root, + bool prune_stale_stable_nodes) { struct stable_node *dup, *found = NULL, *stable_node = *_stable_node; struct hlist_node *hlist_safe; @@ -2082,8 +2089,22 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) tree_rmap_item = unstable_tree_search_insert(rmap_item, page, &tree_page); if (tree_rmap_item) { + bool split; + kpage = try_to_merge_two_pages(rmap_item, page, tree_rmap_item, tree_page); + /* + * If both pages we tried to merge belong to the same compound + * page, then we actually ended up increasing the reference + * count of the same compound page twice, and split_huge_page + * failed. + * Here we set a flag if that happened, and we use it later to + * try split_huge_page again. Since we call put_page right + * afterwards, the reference count will be correct and + * split_huge_page should succeed. + */ + split = PageTransCompound(page) + && compound_head(page) == compound_head(tree_page); put_page(tree_page); if (kpage) { /* @@ -2110,6 +2131,20 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) break_cow(tree_rmap_item); break_cow(rmap_item); } + } else if (split) { + /* + * We are here if we tried to merge two pages and + * failed because they both belonged to the same + * compound page. We will split the page now, but no + * merging will take place. + * We do not want to add the cost of a full lock; if + * the page is locked, it is better to skip it and + * perhaps try again later. + */ + if (!trylock_page(page)) + return; + split_huge_page(page); + unlock_page(page); } } } |