Log error message when LinkFile() is not supported when ingesting files (#10010)

Summary:
Right now, whether moving file is skipped due to LinkFile() is not supported is opaque to users. Add a log message to help users debug.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10010

Test Plan: Run existing test. Manual test verify the log message printed out.

Reviewed By: riversand963

Differential Revision: D36463237

fbshipit-source-id: b00bd5041bd5c11afa4e326819c8461ee2c98a91

db/external_sst_file_ingestion_job.cc

@@ -142,6 +142,9 @@ Status ExternalSstFileIngestionJob::Prepare(
                  ingestion_options_.failed_move_fall_back_to_copy) {
         // Original file is on a different FS, use copy instead of hard linking.
         f.copy_file = true;
+        ROCKS_LOG_INFO(db_options_.info_log,
+                       "Triy to link file %s but it's not supported : %s",
+                       path_outside_db.c_str(), status.ToString().c_str());
       }
     } else {
       f.copy_file = true;

db/import_column_family_job.cc

@@ -97,6 +97,9 @@ Status ImportColumnFamilyJob::Prepare(uint64_t next_file_number,
       if (status.IsNotSupported()) {
         // Original file is on a different FS, use copy instead of hard linking
         hardlink_files = false;
+        ROCKS_LOG_INFO(db_options_.info_log,
+                       "Try to link file %s but it's not supported : %s",
+                       f.internal_file_path.c_str(), status.ToString().c_str());
       }
     }
     if (!hardlink_files) {