Fix underflow in FIFOCompactionPicker (#10386)

Summary:
Fix https://github.com/facebook/rocksdb/issues/10133

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10386

Reviewed By: riversand963

Differential Revision: D38067265

Pulled By: ajkr

fbshipit-source-id: 3a99a98ac5d7ac37581b5b636fbfa7901563d834

HISTORY.md

@@ -10,6 +10,7 @@
 ### Bug Fixes
 * Fix a bug where `GenericRateLimiter` could revert the bandwidth set dynamically using `SetBytesPerSecond()` when a user configures a structure enclosing it, e.g., using `GetOptionsFromString()` to configure an `Options` that references an existing `RateLimiter` object.
 * Fix race conditions in `GenericRateLimiter`.
+* Fix a bug in `FIFOCompactionPicker::PickTTLCompaction` where total_size calculating might cause underflow
 
 ## 7.5.0 (07/15/2022)
 ### New Features

db/compaction/compaction_picker_fifo.cc

@@ -83,7 +83,7 @@ Compaction* FIFOCompactionPicker::PickTTLCompaction(
           break;
         }
       }
-      total_size -= f->compensated_file_size;
+      total_size -= f->fd.file_size;
       inputs[0].files.push_back(f);
     }
   }
@@ -191,7 +191,7 @@ Compaction* FIFOCompactionPicker::PickSizeCompaction(
 
   for (auto ritr = level_files.rbegin(); ritr != level_files.rend(); ++ritr) {
     auto f = *ritr;
-    total_size -= f->compensated_file_size;
+    total_size -= f->fd.file_size;
     inputs[0].files.push_back(f);
     char tmp_fsize[16];
     AppendHumanBytes(f->fd.GetFileSize(), tmp_fsize, sizeof(tmp_fsize));