Avoid passing existing BG error to WriteStatusCheck (#8511)

Summary:
In ```DBImpl::WriteImpl()```, we call ```PreprocessWrite()``` which, among other things, checks the BG error and returns it set. This return status is later on passed to ```WriteStatusCheck()```, which calls ```SetBGError()```. This results in a spurious call, and info logs, on every user write request. We should avoid passing the ```PreprocessWrite()``` return status to ```WriteStatusCheck()```, as the former would have called ```SetBGError()``` already if it encountered any new errors, such as error when creating a new WAL file.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8511

Test Plan: Run existing tests

Reviewed By: zhichao-cao

Differential Revision: D29639917

Pulled By: anand1976

fbshipit-source-id: 19234163969e1645dbeb273712aaf5cd9ea2b182

HISTORY.md

@@ -7,6 +7,7 @@
 * Blob file checksums are now printed in hexadecimal format when using the `manifest_dump` `ldb` command.
 * `GetLiveFilesMetaData()` now populates the `temperature`, `oldest_ancester_time`, and `file_creation_time` fields of its `LiveFileMetaData` results when the information is available. Previously these fields always contained zero indicating unknown.
 * Fix mismatches of OnCompaction{Begin,Completed} in case of DisableManualCompaction().
+* Fix continuous logging of an existing background error on every user write
 
 ### New Features
 * ldb has a new feature, `list_live_files_metadata`, that shows the live SST files, as well as their LSM storage level and the column family they belong to.

db/db_impl/db_impl_write.cc

@@ -251,6 +251,7 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
       write_thread_.EnterAsBatchGroupLeader(&w, &write_group);
 
   IOStatus io_s;
+  Status pre_release_cb_status;
   if (status.ok()) {
     // Rules for when we can update the memtable concurrently
     // 1. supported by memtable
@@ -361,7 +362,7 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
               writer->sequence, disable_memtable, writer->log_used, index++,
               pre_release_callback_cnt);
           if (!ws.ok()) {
-            status = ws;
+            status = pre_release_cb_status = ws;
             break;
           }
         }
@@ -414,10 +415,13 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
 
   if (!w.CallbackFailed()) {
     if (!io_s.ok()) {
+      assert(pre_release_cb_status.ok());
       IOStatusCheck(io_s);
     } else {
-      WriteStatusCheck(status);
+      WriteStatusCheck(pre_release_cb_status);
     }
+  } else {
+    assert(io_s.ok() && pre_release_cb_status.ok());
   }
 
   if (need_log_sync) {