[PATCH] Fix rmap comment

From: Hugh Dickins <hugh@veritas.com>

rmap's try_to_unmap_one comments on find_vma failure, that a page may
temporarily be absent from a vma during mremap: no longer, though it is still
possible for this find_vma to fail, while unmap_vmas drops page_table_lock
(but that is no problem for file truncation).

mm/rmap.c

@@ -315,8 +315,7 @@ static int fastcall try_to_unmap_one(struct page * page, pte_addr_t paddr)
 		return SWAP_AGAIN;
 	}
 
-
-	/* During mremap, it's possible pages are not in a VMA. */
+	/* unmap_vmas drops page_table_lock with vma unlinked */
 	vma = find_vma(mm, address);
 	if (!vma) {
 		ret = SWAP_FAIL;