feat: export SetBackgroundThreads(n, Env::BOTTOM); (#7191)

Summary:
- https://github.com/rust-rocksdb/rust-rocksdb/pull/448

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7191

Reviewed By: riversand963

Differential Revision: D22809066

Pulled By: ajkr

fbshipit-source-id: 036939f9a28cacc3f677c318d1aed97fe5f4f85e

db/c.cc

@@ -3831,10 +3831,20 @@ void rocksdb_env_set_background_threads(rocksdb_env_t* env, int n) {
   env->rep->SetBackgroundThreads(n);
 }
 
+void rocksdb_env_set_bottom_priority_background_threads(rocksdb_env_t* env,
+                                                        int n) {
+  env->rep->SetBackgroundThreads(n, Env::BOTTOM);
+}
+
 void rocksdb_env_set_high_priority_background_threads(rocksdb_env_t* env, int n) {
   env->rep->SetBackgroundThreads(n, Env::HIGH);
 }
 
+void rocksdb_env_set_low_priority_background_threads(rocksdb_env_t* env,
+                                                     int n) {
+  env->rep->SetBackgroundThreads(n, Env::LOW);
+}
+
 void rocksdb_env_join_all_threads(rocksdb_env_t* env) {
   env->rep->WaitForJoin();
 }

include/rocksdb/c.h

@@ -1555,6 +1555,10 @@ extern ROCKSDB_LIBRARY_API void rocksdb_env_set_background_threads(
     rocksdb_env_t* env, int n);
 extern ROCKSDB_LIBRARY_API void
 rocksdb_env_set_high_priority_background_threads(rocksdb_env_t* env, int n);
+extern ROCKSDB_LIBRARY_API void rocksdb_env_set_low_priority_background_threads(
+    rocksdb_env_t* env, int n);
+extern ROCKSDB_LIBRARY_API void
+rocksdb_env_set_bottom_priority_background_threads(rocksdb_env_t* env, int n);
 extern ROCKSDB_LIBRARY_API void rocksdb_env_join_all_threads(
     rocksdb_env_t* env);
 extern ROCKSDB_LIBRARY_API void rocksdb_env_lower_thread_pool_io_priority(rocksdb_env_t* env);