WL#3072 Maria checkpoint

Preparation: for the two-checkpoint rule we will flush all pages
which have block->rec_lsn <= last_checkpoint_lsn. Pages with
rec_lsn not yet set (i.e. ==0) were dirtied very recently and so should
not be flushed (otherwise it's not efficient: we should try to let
a page be modified several times in memory before we flush it to disk).
To make this easy, "block->rec_lsn not yet set" is now expressed
with block->rec_lsn==LSN_MAX, not block->rec_lsn==0 anymore.
It is easier this way because LSN_MAX>last_checkpoint_lsn whereas
0<=last_checkpoint_lsn.


storage/maria/ma_blockrec.c:
  typo
storage/maria/ma_loghandler.c:
  typo
storage/maria/ma_loghandler_lsn.h:
  LSN_MAX
storage/maria/ma_pagecache.c:
  "block->rec_lsn not yet set" is now expressed by block->rec_lsn==LSN_MAX,
  not block_rec_lsn==0.

storage/maria/ma_blockrec.c

@@ -565,7 +565,7 @@ static my_bool check_if_zero(uchar *pos, uint length)
     We unpin pages in the reverse order as they where pinned; This may not
     be strictly necessary but may simplify things in the future.
 
-    info->s->rec_lsn contains the lsn for the first REDO
+    info->trn->rec_lsn contains the lsn for the first REDO
 
   RETURN
     0   ok

storage/maria/ma_loghandler_lsn.h

@@ -81,4 +81,12 @@ typedef LSN LSN_WITH_FLAGS;
 #define FILENO_IMPOSSIBLE     0 /**< log file's numbering starts at 1 */
 #define LOG_OFFSET_IMPOSSIBLE 0 /**< log always has a header */
 #define LSN_IMPOSSIBLE        0
+
+/**
+   @brief the maximum valid LSN.
+   Unlike ULONGLONG_MAX, it can be safely used in comparison with valid LSNs
+   (ULONGLONG_MAX is too big for correctness of cmp_translog_address()).
+*/
+#define LSN_MAX (LSN)ULL(0x00FFFFFFFFFFFFFF)
+
 #endif

storage/maria/ma_pagecache.c

@@ -314,7 +314,8 @@ struct st_pagecache_block_link
   enum pagecache_page_type type; /* type of the block                        */
   uint hits_left;         /* number of hits left until promotion             */
   ulonglong last_hit_time; /* timestamp of the last hit                      */
-  LSN rec_lsn;            /**< LSN when first became dirty                   */
+  /** @brief LSN when first became dirty; LSN_MAX means "not yet set"        */
+  LSN rec_lsn;
   KEYCACHE_CONDVAR *condvar; /* condition variable for 'no readers' event    */
 };
 
@@ -1120,7 +1121,7 @@ static void link_to_file_list(PAGECACHE *pagecache,
   if (block->status & PCBLOCK_CHANGED)
   {
     block->status&= ~PCBLOCK_CHANGED;
-    block->rec_lsn= 0;
+    block->rec_lsn= LSN_MAX;
     pagecache->blocks_changed--;
     pagecache->global_blocks_changed--;
   }
@@ -1892,6 +1893,7 @@ restart:
         block->temperature= PCBLOCK_COLD;
         block->hits_left= init_hits_left;
         block->last_hit_time= 0;
+        block->rec_lsn= LSN_MAX;
         link_to_file_list(pagecache, block, file, 0);
         block->hash_link= hash_link;
         hash_link->block= block;
@@ -2537,8 +2539,12 @@ void pagecache_unlock(PAGECACHE *pagecache,
   {
     DBUG_ASSERT(lock == PAGECACHE_LOCK_WRITE_UNLOCK);
     DBUG_ASSERT(pin == PAGECACHE_UNPIN);
-    if (block->rec_lsn == 0)
+    if (block->rec_lsn == LSN_MAX)
       block->rec_lsn= first_REDO_LSN_for_page;
+    else
+      DBUG_ASSERT(cmp_translog_addr(block->rec_lsn,
+                                    first_REDO_LSN_for_page) <= 0);
+
   }
   if (lsn != LSN_IMPOSSIBLE)
     check_and_set_lsn(pagecache, lsn, block);
@@ -2695,8 +2701,11 @@ void pagecache_unlock_by_link(PAGECACHE *pagecache,
     DBUG_ASSERT(lock == PAGECACHE_LOCK_WRITE_UNLOCK || 
                 lock == PAGECACHE_LOCK_READ_UNLOCK);
     DBUG_ASSERT(pin == PAGECACHE_UNPIN);
-    if (block->rec_lsn == 0)
+    if (block->rec_lsn == LSN_MAX)
       block->rec_lsn= first_REDO_LSN_for_page;
+    else
+      DBUG_ASSERT(cmp_translog_addr(block->rec_lsn,
+                                    first_REDO_LSN_for_page) <= 0);
   }
   if (lsn != LSN_IMPOSSIBLE)
     check_and_set_lsn(pagecache, lsn, block);
@@ -3377,7 +3386,7 @@ static void free_block(PAGECACHE *pagecache, PAGECACHE_BLOCK_LINK *block)
 #ifndef DBUG_OFF
   block->type= PAGECACHE_EMPTY_PAGE;
 #endif
-  block->rec_lsn= 0;
+  block->rec_lsn= LSN_MAX;
   KEYCACHE_THREAD_TRACE("free block");
   KEYCACHE_DBUG_PRINT("free_block",
                       ("block is freed"));
@@ -3850,7 +3859,7 @@ my_bool pagecache_collect_changed_blocks_with_lsn(PAGECACHE *pagecache,
   ulong stored_list_size= 0;
   uint file_hash;
   char *ptr;
-  LSN minimum_rec_lsn= ULONGLONG_MAX, maximum_rec_lsn= 0;
+  LSN minimum_rec_lsn= LSN_MAX, maximum_rec_lsn= 0;
   DBUG_ENTER("pagecache_collect_changed_blocks_with_LSN");
 
   DBUG_ASSERT(NULL == str->str);
@@ -3919,13 +3928,14 @@ my_bool pagecache_collect_changed_blocks_with_lsn(PAGECACHE *pagecache,
       ptr+= 4;
       lsn_store(ptr, block->rec_lsn);
       ptr+= LSN_STORE_SIZE;
-      if (block->rec_lsn != LSN_IMPOSSIBLE)
+      if (block->rec_lsn != LSN_MAX)
       {
+        DBUG_ASSERT(LSN_VALID(block->rec_lsn));
         if (cmp_translog_addr(block->rec_lsn, minimum_rec_lsn) < 0)
           minimum_rec_lsn= block->rec_lsn;
         if (cmp_translog_addr(block->rec_lsn, maximum_rec_lsn) > 0)
           maximum_rec_lsn= block->rec_lsn;
-      } /* otherwise, some trn->rec_lsn should hold the info */
+      } /* otherwise, some trn->rec_lsn should hold the correct info */
     }
   }
 end: