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Fixed broken discard handling in cache_start_sub_transaction().

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* This actually resolves a TODO.
This commit is contained in:
Axel Dörfler 2012-08-27 12:38:35 +02:00
parent 8f9dac699d
commit 153d895337
1 changed files with 20 additions and 21 deletions
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41
src/system/kernel/cache/block_cache.cpp vendored
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@ -1,5 +1,5 @@
/*
* Copyright 2004-2010, Axel Dörfler, axeld@pinc-software.de.
* Copyright 2004-2012, Axel Dörfler, axeld@pinc-software.de.
* Distributed under the terms of the MIT License.
*/
@ -1539,6 +1539,7 @@ void
block_cache::DiscardBlock(cached_block* block)
{
ASSERT(block->discard);
ASSERT(block->previous_transaction == NULL);
if (block->parent_data != NULL)
FreeBlockParentData(block);
@ -2830,8 +2831,10 @@ cache_end_transaction(void* _cache, int32 id,
cache->Free(block->original_data);
block->original_data = NULL;
}
if (transaction->has_sub_transaction && block->parent_data != NULL)
if (block->parent_data != NULL) {
ASSERT(transaction->has_sub_transaction);
cache->FreeBlockParentData(block);
}
// move the block to the previous transaction list
transaction->blocks.Add(block);
@ -3089,36 +3092,32 @@ cache_start_sub_transaction(void* _cache, int32 id)
// move all changed blocks up to the parent
cached_block* block = transaction->first_block;
cached_block* last = NULL;
cached_block* next;
for (; block != NULL; block = next) {
next = block->transaction_next;
if (block->discard) {
// This block has been discarded in the parent transaction
// TODO: this is wrong: since the parent transaction is not
// finished here (just extended), this block cannot be reverted
// anymore in case the parent transaction is aborted!!!
if (last != NULL)
last->transaction_next = next;
else
transaction->first_block = next;
cache->DiscardBlock(block);
transaction->num_blocks--;
continue;
}
if (transaction->has_sub_transaction && block->parent_data != NULL) {
// there already is an older sub transaction - we acknowledge
if (block->parent_data != NULL) {
// There already is an older sub transaction - we acknowledge
// its changes and move its blocks up to the parent
ASSERT(transaction->has_sub_transaction);
cache->FreeBlockParentData(block);
}
if (block->discard) {
// This block has been discarded in the parent transaction.
// Just throw away any changes made in this transaction, so that
// it can still be reverted to its original contents if needed
ASSERT(block->previous_transaction == NULL);
if (block->original_data != NULL) {
memcpy(block->current_data, block->original_data,
cache->block_size);
block->original_data = NULL;
}
continue;
}
// we "allocate" the parent data lazily, that means, we don't copy
// the data (and allocate memory for it) until we need to
block->parent_data = block->current_data;
last = block;
}
// all subsequent changes will go into the sub transaction