mm/rmap: use rmap_walk() in page_referenced()

Now, we have an infrastructure in rmap_walk() to handle difference from
variants of rmap traversing functions.

So, just use it in page_referenced().

In this patch, I change following things.

1. remove some variants of rmap traversing functions.
	cf> page_referenced_ksm, page_referenced_anon,
	page_referenced_file

2. introduce new struct page_referenced_arg and pass it to
   page_referenced_one(), main function of rmap_walk, in order to count
   reference, to store vm_flags and to check finish condition.

3. mechanical change to use rmap_walk() in page_referenced().

[liwanp@linux.vnet.ibm.com: fix BUG at rmap_walk]
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Hillf Danton <dhillf@gmail.com>
Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 55 deletions

diff --git a/mm/ksm.c b/mm/ksm.c
index 646d45a..3df141e 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1891,61 +1891,6 @@ struct page *ksm_might_need_to_copy(struct page *page,
 	return new_page;
 }
 
-int page_referenced_ksm(struct page *page, struct mem_cgroup *memcg,
-			unsigned long *vm_flags)
-{
-	struct stable_node *stable_node;
-	struct rmap_item *rmap_item;
-	unsigned int mapcount = page_mapcount(page);
-	int referenced = 0;
-	int search_new_forks = 0;
-
-	VM_BUG_ON(!PageKsm(page));
-	VM_BUG_ON(!PageLocked(page));
-
-	stable_node = page_stable_node(page);
-	if (!stable_node)
-		return 0;
-again:
-	hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) {
-		struct anon_vma *anon_vma = rmap_item->anon_vma;
-		struct anon_vma_chain *vmac;
-		struct vm_area_struct *vma;
-
-		anon_vma_lock_read(anon_vma);
-		anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root,
-					       0, ULONG_MAX) {
-			vma = vmac->vma;
-			if (rmap_item->address < vma->vm_start ||
-			    rmap_item->address >= vma->vm_end)
-				continue;
-			/*
-			 * Initially we examine only the vma which covers this
-			 * rmap_item; but later, if there is still work to do,
-			 * we examine covering vmas in other mms: in case they
-			 * were forked from the original since ksmd passed.
-			 */
-			if ((rmap_item->mm == vma->vm_mm) == search_new_forks)
-				continue;
-
-			if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
-				continue;
-
-			referenced += page_referenced_one(page, vma,
-				rmap_item->address, &mapcount, vm_flags);
-			if (!search_new_forks || !mapcount)
-				break;
-		}
-		anon_vma_unlock_read(anon_vma);
-		if (!mapcount)
-			goto out;
-	}
-	if (!search_new_forks++)
-		goto again;
-out:
-	return referenced;
-}
-
 int rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc)
 {
 	struct stable_node *stable_node;
@@ -1954,6 +1899,11 @@ int rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc)
 	int search_new_forks = 0;
 
 	VM_BUG_ON(!PageKsm(page));
+
+	/*
+	 * Rely on the page lock to protect against concurrent modifications
+	 * to that page's node of the stable tree.
+	 */
 	VM_BUG_ON(!PageLocked(page));
 
 	stable_node = page_stable_node(page);