Merge branch 'akpm' (patches from Andrew)

Merge updates from Andrew Morton:

 - a few misc things

 - ocfs2 updates

 - the v9fs maintainers have been missing for a long time. I've taken
   over v9fs patch slinging.

 - most of MM

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (116 commits)
  mm,oom_reaper: check for MMF_OOM_SKIP before complaining
  mm/ksm: fix interaction with THP
  mm/memblock.c: cast constant ULLONG_MAX to phys_addr_t
  headers: untangle kmemleak.h from mm.h
  include/linux/mmdebug.h: make VM_WARN* non-rvals
  mm/page_isolation.c: make start_isolate_page_range() fail if already isolated
  mm: change return type to vm_fault_t
  mm, oom: remove 3% bonus for CAP_SYS_ADMIN processes
  mm, page_alloc: wakeup kcompactd even if kswapd cannot free more memory
  kernel/fork.c: detect early free of a live mm
  mm: make counting of list_lru_one::nr_items lockless
  mm/swap_state.c: make bool enable_vma_readahead and swap_vma_readahead() static
  block_invalidatepage(): only release page if the full page was invalidated
  mm: kernel-doc: add missing parameter descriptions
  mm/swap.c: remove @cold parameter description for release_pages()
  mm/nommu: remove description of alloc_vm_area
  zram: drop max_zpage_size and use zs_huge_class_size()
  zsmalloc: introduce zs_huge_class_size()
  mm: fix races between swapoff and flush dcache
  fs/direct-io.c: minor cleanups in do_blockdev_direct_IO
  ...

1 files changed, 32 insertions, 4 deletions

diff --git a/mm/ksm.c b/mm/ksm.c
index adb5f991da8e..e8d6c6210b80 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1318,10 +1318,10 @@ 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 +2082,22 @@ 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 +2124,20 @@ 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);
 		}
 	}
 }