During page flush it may be enqueued for flush again when innodb_flush_neighbours=0

I've got the following crash: Assertion failure in thread 1274956096 in file buf/buf0buf.c line 3428

Ther reason is that block_mutex temporary released after checking buf_flush_ready_for_flush in buf_flush_batch and if
--innodb_flush_neighbor_pages is set to 0 it doesn't checked after mutex acquired again. So can be queued for flush again when the page already being flushed.

I think the safer solution is as follows:

diff -r 101cd9bcb1fa storage/innobase/buf/buf0flu.c
--- a/storage/innobase/buf/buf0flu.c Thu Jul 23 23:25:41 2009 +0700
+++ b/storage/innobase/buf/buf0flu.c Tue Jul 28 15:56:59 2009 +0700
@@ -863,8 +863,9 @@
      /* out: number of pages flushed */
  ulint space, /* in: space id */
  ulint offset, /* in: page offset */
- enum buf_flush flush_type) /* in: BUF_FLUSH_LRU or
+ enum buf_flush flush_type, /* in: BUF_FLUSH_LRU or
      BUF_FLUSH_LIST */
+ ibool flush_neighbors)
 {
  buf_page_t* bpage;
  ulint low, high;
@@ -873,7 +874,7 @@

  ut_ad(flush_type == BUF_FLUSH_LRU || flush_type == BUF_FLUSH_LIST);

- if (UT_LIST_GET_LEN(buf_pool->LRU) < BUF_LRU_OLD_MIN_LEN) {
+ if (UT_LIST_GET_LEN(buf_pool->LRU) < BUF_LRU_OLD_MIN_LEN || !flush_neighbors) {
   /* If there is little space, it is better not to flush any
   block except from the end of the LRU list */

@@ -1048,23 +1049,10 @@

     old_page_count = page_count;

- if (srv_flush_neighbor_pages) {
- /* Try to flush also all the neighbors */
     page_count += buf_flush_try_neighbors(
- space, offset, flush_type);
- } else {
- /* Try to flush the page only */
- buf_pool_mutex_enter();
+ space, offset, flush_type,
+ srv_flush_neighbor_pages);

- mutex_t* block_mutex = buf_page_get_mutex(bpage);
- mutex_enter(block_mutex);
-
- buf_page_t* bpage_tmp = buf_page_hash_get(space, offset);
- if (bpage_tmp) {
- buf_flush_page(bpage_tmp, flush_type);
- page_count++;
- }
- }
     /* fprintf(stderr,
     "Flush type %lu, page no %lu, neighb %lu\n",
     flush_type, offset,