MDEV-19055 Failures with temporary tables and Aria

There was two separate problems:
- Aria pagecache didn't properly handle re-reading of blocks
  that have given errors before (this triggered an assert)
- temporary tables that where opened several times where
  not properly closed in ALTER, REPAIR or OPTIMIZE table

Other things
- Added a couple of asserts that will make it easier to
  find problems like this in the future.

1 files changed, 1 insertions, 2 deletions

diff --git a/storage/maria/ma_pagecache.c b/storage/maria/ma_pagecache.c
index 7b0f395f926..f8c83e12a18 100644
--- a/storage/maria/ma_pagecache.c
+++ b/storage/maria/ma_pagecache.c
@@ -3464,8 +3464,6 @@ restart:
         pagecache_pthread_mutex_lock(&pagecache->cache_lock);
 #endif
       }
-      if (status & PCBLOCK_ERROR)
-        my_errno= block->error;
     }
 
     remove_reader(block);
@@ -3497,6 +3495,7 @@ restart:
 
     if (status & PCBLOCK_ERROR)
     {
+      my_errno= block->error;
       DBUG_ASSERT(my_errno != 0);
       DBUG_PRINT("error", ("Got error %d when doing page read", my_errno));
       DBUG_RETURN((uchar *) 0);