From 7d69d4553403178478d7e97294ad745718f30960 Mon Sep 17 00:00:00 2001
From: marko <>
Date: Fri, 8 Aug 2008 13:01:02 +0000
Subject: [PATCH] branches/zip: buf_LRU_free_block(): When buf_page_is_old(b),
 we incremented buf_pool->LRU_old_len.  However, we forgot to check if
 buf_pool->LRU_old happens to point to b's successor in the LRU list.  If it
 does, we must assign buf_pool->LRU_old = b.  The following invariants hold:

In the LRU list, the "old" flag should grow monotonically, i.e., it is 0
for the first few items and 1 from thereafter.

If buf_pool->LRU_old != NULL, it must point to the first item with old=1
in the LRU list, and there must be buf_pool->LRU_old_len old items in the list.

This should fix Mantis issue#50 and issue#68.
---
 buf/buf0lru.c     | 6 ++++++
 include/buf0buf.h | 8 ++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/buf/buf0lru.c b/buf/buf0lru.c
index 7922e885671..576a6c9f319 100644
--- a/buf/buf0lru.c
+++ b/buf/buf0lru.c
@@ -1246,6 +1246,12 @@ alloc:
 
 				if (buf_page_is_old(b)) {
 					buf_pool->LRU_old_len++;
+					if (UNIV_UNLIKELY
+					    (buf_pool->LRU_old
+					     == UT_LIST_GET_NEXT(LRU, b))) {
+
+						buf_pool->LRU_old = b;
+					}
 				}
 
 				lru_len = UT_LIST_GET_LEN(buf_pool->LRU);
diff --git a/include/buf0buf.h b/include/buf0buf.h
index afdf6c353f8..84337fef54a 100644
--- a/include/buf0buf.h
+++ b/include/buf0buf.h
@@ -1277,13 +1277,17 @@ struct buf_pool_struct{
 					/* base node of the LRU list */
 	buf_page_t*	LRU_old;	/* pointer to the about 3/8 oldest
 					blocks in the LRU list; NULL if LRU
-					length less than BUF_LRU_OLD_MIN_LEN */
+					length less than BUF_LRU_OLD_MIN_LEN;
+					NOTE: when LRU_old != NULL, its length
+					should always equal LRU_old_len */
 	ulint		LRU_old_len;	/* length of the LRU list from
 					the block to which LRU_old points
 					onward, including that block;
 					see buf0lru.c for the restrictions
 					on this value; not defined if
-					LRU_old == NULL */
+					LRU_old == NULL;
+					NOTE: LRU_old_len must be adjusted
+					whenever LRU_old shrinks or grows! */
 
 	UT_LIST_BASE_NODE_T(buf_block_t) unzip_LRU;
 					/* base node of the unzip_LRU list */