innodb_flush_neighbors=2 is treated like innodb_flush_neighbors=0

diff --git a/storage/innobase/buf/buf0flu.cc b/storage/innobase/buf/buf0flu.cc

--- a/storage/innobase/buf/buf0flu.cc

+++ b/storage/innobase/buf/buf0flu.cc

@@ -966,10 +966,12 @@ static bool buf_flush_check_neighbor(const page_id_t id, ulint fold, bool lru)

 /** Check which neighbors of a page can be flushed from the buf_pool.

 @param space       tablespace

 @param id          page identifier of a dirty page

+@param contiguous  whether to consider contiguous areas of pages

 @param lru         true=buf_pool.LRU; false=buf_pool.flush_list

 @return last page number that can be flushed */

 static page_id_t buf_flush_check_neighbors(const fil_space_t &space,

-                                           page_id_t &id, bool lru)

+                                           page_id_t &id, bool contiguous,

+                                           bool lru)

 {

   ut_ad(id.page_no() < space.size);

   /* When flushed, dirty blocks are searched in neighborhoods of this

@@ -983,6 +985,13 @@ static page_id_t buf_flush_check_neighbors(const fil_space_t &space,

   high.set_page_no(std::min(high.page_no(),

                             static_cast<uint32_t>(space.committed_size - 1)));

+  if (!contiguous)

+  {

+    high= std::max(id + 1, high);

+    id= low;

+    return high;

+  }

+

   /* Determine the contiguous dirty area around id. */

   const ulint id_fold= id.fold();

@@ -1090,13 +1099,15 @@ static ulint buf_flush_try_neighbors(const page_id_t page_id, bool lru,

         /* Flush the freed ranges while flushing the neighbors */

         buf_flush_freed_pages(space);

+	const auto neighbors = srv_flush_neighbors;

+

 	page_id_t id = page_id;

-	page_id_t high = (srv_flush_neighbors != 1

+	page_id_t high = (!neighbors

 			  || UT_LIST_GET_LEN(buf_pool.LRU)

 			  < BUF_LRU_OLD_MIN_LEN

 			  || !space->is_rotational())

 		? id + 1 /* Flush the minimum. */

-		: buf_flush_check_neighbors(*space, id, lru);

+		: buf_flush_check_neighbors(*space, id, neighbors == 1, lru);

 	ut_ad(page_id >= id);

 	ut_ad(page_id < high);