Remove optimization on blk free operation

The optimization in blk free may cause the following issue, just remove it and wait for GC handling:
- T1: blob1 is written with LSN 1 — [blkid=10, chunk=1, cnt=5].
- T2: blob1 is deleted with LSN 10, causing the last_append_offset to revert to 10.
- T3: blob2 is written with LSN 11 — [blkid=10, chunk=1, cnt=5].
- T4: The SM is terminated and restarted.
- T5: LSN 1 is replayed, committing block [blkid=10, chunk=1, cnt=5].
- T6: LSN 11 is replayed, committing block [blkid=10, chunk=1, cnt=5].
- T7: LSN 10 is committed, freeing block [blkid=10, chunk=1, cnt=5].
- T8: LSN 11 is committed again, but since the blocks have already been freed, they are not available for LSN 11.

conanfile.py

@@ -9,7 +9,7 @@
 
 class HomestoreConan(ConanFile):
     name = "homestore"
-    version = "6.6.19"
+    version = "6.6.20"
 
     homepage = "https://github.com/eBay/Homestore"
     description = "HomeStore Storage Engine"

src/lib/blkalloc/append_blk_allocator.cpp

@@ -127,33 +127,9 @@ void AppendBlkAllocator::cp_flush(CP* cp) {
     }
 }
 
-//
-// free operation does:
-// 1. book keeping "total freeable" space
-// 2. if the blk being freed happens to be last block, move last_append_offset backwards accordingly;
-//
+// free operation books keeping "total freeable" space
 void AppendBlkAllocator::free(const BlkId& bid) {
-    // If we are freeing the last block, just move the offset back
-    blk_num_t cur_last_offset = m_last_append_offset.load();
-    auto const input_last_offset = bid.blk_num() + bid.blk_count();
-    blk_num_t new_last_offset;
-    bool freeing_in_middle{false};
-    do {
-        if (input_last_offset == cur_last_offset) {
-            new_last_offset = bid.blk_num();
-            freeing_in_middle = false;
-        } else {
-            new_last_offset = cur_last_offset;
-            freeing_in_middle = true;
-        }
-    } while (!m_last_append_offset.compare_exchange_weak(cur_last_offset, new_last_offset));
-
-    if (freeing_in_middle) {
-        // Freeing something in the middle, increment the count
-        m_freeable_nblks.fetch_add(bid.blk_count());
-    } else {
-        m_commit_offset.store(m_last_append_offset.load());
-    }
+    m_freeable_nblks.fetch_add(bid.blk_count());
     m_is_dirty.store(true);
 }