From 294a754c9ef4970d5f3283bdf172f4b9a1671602 Mon Sep 17 00:00:00 2001
From: Vitaliy Filippov <vitalif@yourcmc.ru>
Date: Fri, 27 Oct 2023 00:35:06 +0300
Subject: [PATCH] Allow write-back by default in NBD & NFS

---
 src/nbd_proxy.cpp |  8 ++++++++
 src/nfs_proxy.cpp | 13 +++++++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/nbd_proxy.cpp b/src/nbd_proxy.cpp
index c87592ca..c2d45c97 100644
--- a/src/nbd_proxy.cpp
+++ b/src/nbd_proxy.cpp
@@ -216,6 +216,14 @@ public:
         {
             nbd_timeout = cfg["nbd_timeout"].uint64_value();
         }
+        if (cfg["client_writeback_allowed"].is_null())
+        {
+            // NBD is always aware of fsync, so we allow write-back cache
+            // by default if it's enabled
+            auto obj = cfg.object_items();
+            obj["client_writeback_allowed"] = true;
+            cfg = obj;
+        }
         // Create client
         ringloop = new ring_loop_t(512);
         epmgr = new epoll_manager_t(ringloop);
diff --git a/src/nfs_proxy.cpp b/src/nfs_proxy.cpp
index 04a64291..b0167844 100644
--- a/src/nfs_proxy.cpp
+++ b/src/nfs_proxy.cpp
@@ -65,8 +65,9 @@ json11::Json::object nfs_proxy_t::parse_args(int narg, const char *args[])
                 "  --pool <POOL>     use <POOL> as default pool for new files (images)\n"
                 "  --foreground 1    stay in foreground, do not daemonize\n"
                 "\n"
-                "NFS proxy is stateless if you use immediate_commit=all in your cluster, so\n"
-                "you can freely use multiple NFS proxies with L3 load balancing in this case.\n"
+                "NFS proxy is stateless if you use immediate_commit=all in your cluster and if\n"
+                "you do not use client_enable_writeback=true, so you can freely use multiple\n"
+                "NFS proxies with L3 load balancing in this case.\n"
                 "\n"
                 "Example start and mount commands for a custom NFS port:\n"
                 "  %s --etcd_address 192.168.5.10:2379 --portmap 0 --port 2050 --pool testpool\n"
@@ -114,6 +115,14 @@ void nfs_proxy_t::run(json11::Json cfg)
         if (name_prefix.size())
             name_prefix += "/";
     }
+    if (cfg["client_writeback_allowed"].is_null())
+    {
+        // NFS is always aware of fsync, so we allow write-back cache
+        // by default if it's enabled
+        auto obj = cfg.object_items();
+        obj["client_writeback_allowed"] = true;
+        cfg = obj;
+    }
     // Create client
     ringloop = new ring_loop_t(512);
     epmgr = new epoll_manager_t(ringloop);