From cc19fc624b1ee4d7e3248d1dfc8f89f8879a46bf Mon Sep 17 00:00:00 2001
From: "Yan, Zheng" <zyan@redhat.com>
Date: Mon, 13 Jul 2020 10:50:27 +0800
Subject: [PATCH] mds/OpenFileTable: add option that disables dirfrags prefetch

Dirfrags prefetch may speedup rejoin stage of mds recovery. But it may
use lots of memory and cause mds out of memory.

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
---
 src/common/options.cc    | 5 +++++
 src/mds/OpenFileTable.cc | 9 +++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/common/options.cc b/src/common/options.cc
index d00414625f52..1975f779fb76 100644
--- a/src/common/options.cc
+++ b/src/common/options.cc
@@ -8144,6 +8144,11 @@ std::vector<Option> get_mds_options() {
     .set_default(10.0)
     .set_description("rate of decay for export targets communicated to clients"),
 
+    Option("mds_oft_prefetch_dirfrags", Option::TYPE_BOOL, Option::LEVEL_ADVANCED)
+    .set_default(true)
+    .set_description("prefetch dirfrags recorded in open file table on startup")
+    .set_flag(Option::FLAG_STARTUP),
+
     Option("mds_replay_interval", Option::TYPE_FLOAT, Option::LEVEL_ADVANCED)
     .set_default(1.0)
     .set_description("time in seconds between replay of updates to journal by standby replay MDS"),
diff --git a/src/mds/OpenFileTable.cc b/src/mds/OpenFileTable.cc
index 01b25dc9e8b2..930b4d88d6a5 100644
--- a/src/mds/OpenFileTable.cc
+++ b/src/mds/OpenFileTable.cc
@@ -1028,8 +1028,13 @@ void OpenFileTable::_open_ino_finish(inodeno_t ino, int r)
   num_opening_inodes--;
   if (num_opening_inodes == 0) {
     if (prefetch_state == DIR_INODES)  {
-      prefetch_state = DIRFRAGS;
-      _prefetch_dirfrags();
+      if (g_conf().get_val<bool>("mds_oft_prefetch_dirfrags")) {
+	prefetch_state = DIRFRAGS;
+	_prefetch_dirfrags();
+      } else {
+	prefetch_state = FILE_INODES;
+	_prefetch_inodes();
+      }
     } else if (prefetch_state == FILE_INODES) {
       prefetch_state = DONE;
       logseg_destroyed_inos.clear();
-- 
2.47.3