branches/zip: Fix two bugs in the relocation of block descriptors.

Improve diagnostics.

buf_buddy_relocate(): Do not assume all small blocks to contain only one
buf_page_t object.  Require an exact size match, as in the case of
compressed pages.

buf_relocate(): Relocate buf_pool->LRU_old if needed.
Validate the LRU list in debug builds.

buf_LRU_block_remove_hashed_page(): Do not overwrite FIL_PAGE_OFFSET
or FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID.  The memory will be invalidated
in debug builds of buf_buddy_free().

buf0buddy.c: Add assertions for not holding buf_pool->zip_mutex.
The calling thread should not be holding any block->mutex, but it might
be too time-consuming to assert against that, even #ifdef UNIV_SYNC_DEBUG.

buf/buf0buddy.c

@@ -102,6 +102,7 @@ buf_buddy_block_free(
 
 #ifdef UNIV_SYNC_DEBUG
 	ut_a(mutex_own(&buf_pool->mutex));
+	ut_a(!mutex_own(&buf_pool->zip_mutex));
 #endif /* UNIV_SYNC_DEBUG */
 	ut_a(buf == ut_align_down(buf, UNIV_PAGE_SIZE));
 
@@ -130,6 +131,7 @@ buf_buddy_block_register(
 	ulint		fold;
 #ifdef UNIV_SYNC_DEBUG
 	ut_a(mutex_own(&buf_pool->mutex));
+	ut_a(!mutex_own(&buf_pool->zip_mutex));
 #endif /* UNIV_SYNC_DEBUG */
 	buf_block_set_state(block, BUF_BLOCK_MEMORY);
 
@@ -187,6 +189,7 @@ buf_buddy_alloc_clean(
 
 #ifdef UNIV_SYNC_DEBUG
 	ut_a(mutex_own(&buf_pool->mutex));
+	ut_a(!mutex_own(&buf_pool->zip_mutex));
 #endif /* UNIV_SYNC_DEBUG */
 
 	if (BUF_BUDDY_LOW << i >= PAGE_ZIP_MIN_SIZE
@@ -294,6 +297,7 @@ buf_buddy_alloc_low(
 
 #ifdef UNIV_SYNC_DEBUG
 	ut_a(mutex_own(&buf_pool->mutex));
+	ut_a(!mutex_own(&buf_pool->zip_mutex));
 #endif /* UNIV_SYNC_DEBUG */
 
 	if (i < BUF_BUDDY_SIZES) {
@@ -355,6 +359,7 @@ buf_buddy_relocate(
 
 #ifdef UNIV_SYNC_DEBUG
 	ut_a(mutex_own(&buf_pool->mutex));
+	ut_a(!mutex_own(&buf_pool->zip_mutex));
 #endif /* UNIV_SYNC_DEBUG */
 	ut_ad(!ut_align_offset(src, size));
 	ut_ad(!ut_align_offset(dst, size));
@@ -418,7 +423,7 @@ buf_buddy_relocate(
 		}
 
 		mutex_exit(mutex);
-	} else {
+	} else if (i == buf_buddy_get_slot(sizeof(buf_page_t))) {
 		/* This must be a buf_page_t object. */
 		bpage = (buf_page_t*) src;
 
@@ -484,6 +489,7 @@ buf_buddy_free_low(
 	buf_page_t*	buddy;
 #ifdef UNIV_SYNC_DEBUG
 	ut_a(mutex_own(&buf_pool->mutex));
+	ut_a(!mutex_own(&buf_pool->zip_mutex));
 #endif /* UNIV_SYNC_DEBUG */
 recombine:
 	if (i == BUF_BUDDY_SIZES) {

buf/buf0buf.c

@@ -990,6 +990,12 @@ buf_relocate(
 		UT_LIST_ADD_FIRST(LRU, buf_pool->LRU, dpage);
 	}
 
+	if (UNIV_UNLIKELY(buf_pool->LRU_old == bpage)) {
+		buf_pool->LRU_old = dpage;
+	}
+
+	ut_d(UT_LIST_VALIDATE(LRU, buf_page_t, buf_pool->LRU));
+
 	/* relocate buf_pool->page_hash */
 	fold = buf_page_address_fold(bpage->space, bpage->offset);
 

buf/buf0lru.c

@@ -1094,9 +1094,6 @@ buf_LRU_block_remove_hashed_page(
 		ut_ad(!bpage->in_LRU_list);
 		ut_a(bpage->zip.data);
 		ut_a(buf_page_get_zip_size(bpage));
-		memset(bpage->zip.data + FIL_PAGE_OFFSET, 0xff, 4);
-		memset(bpage->zip.data + FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID,
-		       0xff, 4);
 
 		UT_LIST_REMOVE(list, buf_pool->zip_clean, bpage);