Optimize flush tables with read lock (FTWRL) to not wait for select's

Part of MDEV-5336 Implement LOCK FOR BACKUP

The idea is that instead of waiting in close_cached_tables() for all
tables to be closed, we instead call flush_tables() that does:
- Flush not used objects in table cache to free memory
- Collect all tables that are open
- Call HA_EXTRA_FLUSH on the objects, to get them into "closed state"
- Added HA_EXTRA_FLUSH support to archive and CSV
- Added multi-user protection to HA_EXTRA_FLUSH in MyISAM and Aria

The benefit compared to old code is:
- FTWRL doesn't have to wait for long running read operations or
  open HANDLER's

3 files changed, 19 insertions, 1 deletions

diff --git a/storage/archive/azio.c b/storage/archive/azio.c
index 0f66b999c94..3529d875f72 100644
--- a/storage/archive/azio.c
+++ b/storage/archive/azio.c
@@ -866,7 +866,10 @@ int azclose (azio_stream *s)
   if (s->mode == 'w') 
   {
     if (do_flush(s, Z_FINISH) != Z_OK)
-      return destroy(s);
+    {
+      destroy(s);
+      return Z_ERRNO;
+    }
 
     putLong(s->file, s->crc);
     putLong(s->file, (uLong)(s->in & 0xffffffff));
diff --git a/storage/archive/ha_archive.cc b/storage/archive/ha_archive.cc
index bb15aa9297d..f97bc52b6a9 100644
--- a/storage/archive/ha_archive.cc
+++ b/storage/archive/ha_archive.cc
@@ -1737,6 +1737,20 @@ int ha_archive::info(uint flag)
 }
 
 
+int ha_archive::extra(enum ha_extra_function operation)
+{
+  switch (operation) {
+  case HA_EXTRA_FLUSH:
+    mysql_mutex_lock(&share->mutex);
+    share->close_archive_writer();
+    mysql_mutex_unlock(&share->mutex);
+    break;
+  default:
+    break;
+  }
+  return 0;
+}
+
 /*
   This method tells us that a bulk insert operation is about to occur. We set
   a flag which will keep write_row from saying that its data is dirty. This in
diff --git a/storage/archive/ha_archive.h b/storage/archive/ha_archive.h
index 1f25fba4eed..17649c9c110 100644
--- a/storage/archive/ha_archive.h
+++ b/storage/archive/ha_archive.h
@@ -148,6 +148,7 @@ public:
   int read_data_header(azio_stream *file_to_read);
   void position(const uchar *record);
   int info(uint);
+  int extra(enum ha_extra_function operation);
   void update_create_info(HA_CREATE_INFO *create_info);
   int create(const char *name, TABLE *form, HA_CREATE_INFO *create_info);
   int optimize(THD* thd, HA_CHECK_OPT* check_opt);