ksm: use find_mergeable_vma in try_to_merge_with_ksm_page

Doing the VM_MERGEABLE check after the page == kpage check won't provide
any meaningful benefit.  The !vma->anon_vma check of find_mergeable_vma is
the only superfluous bit in using find_mergeable_vma because the !PageAnon
check of try_to_merge_one_page() implicitly checks for that, but it still
looks cleaner to share the same find_mergeable_vma().

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Petr Holasek <pholasek@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/ksm.c

@@ -1021,8 +1021,6 @@ static int try_to_merge_one_page(struct vm_area_struct *vma,
 	if (page == kpage)			/* ksm page forked */
 		return 0;
 
-	if (!(vma->vm_flags & VM_MERGEABLE))
-		goto out;
 	if (PageTransCompound(page) && page_trans_compound_anon_split(page))
 		goto out;
 	BUG_ON(PageTransCompound(page));
@@ -1087,10 +1085,8 @@ static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item,
 	int err = -EFAULT;
 
 	down_read(&mm->mmap_sem);
-	if (ksm_test_exit(mm))
-		goto out;
-	vma = find_vma(mm, rmap_item->address);
-	if (!vma || vma->vm_start > rmap_item->address)
+	vma = find_mergeable_vma(mm, rmap_item->address);
+	if (!vma)
 		goto out;
 
 	err = try_to_merge_one_page(vma, page, kpage);