From 47d08ac1f12fefe03dd9eb6fd9bdb236364d5587 Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Tue, 18 Aug 2020 17:31:39 +0100
Subject: [PATCH] vfs: recommend --vfs-cache-modes writes on backends which
 can't stream

---
 vfs/vfs.go | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/vfs/vfs.go b/vfs/vfs.go
index 58d725648..dd54bdb9a 100644
--- a/vfs/vfs.go
+++ b/vfs/vfs.go
@@ -216,7 +216,8 @@ func New(f fs.Fs, opt *vfscommon.Options) *VFS {
 	vfs.root = newDir(vfs, f, nil, fsDir)
 
 	// Start polling function
-	if do := vfs.f.Features().ChangeNotify; do != nil {
+	features := vfs.f.Features()
+	if do := features.ChangeNotify; do != nil {
 		vfs.pollChan = make(chan time.Duration)
 		do(context.TODO(), vfs.root.changeNotify, vfs.pollChan)
 		vfs.pollChan <- vfs.Opt.PollInterval
@@ -224,6 +225,11 @@ func New(f fs.Fs, opt *vfscommon.Options) *VFS {
 		fs.Infof(f, "poll-interval is not supported by this remote")
 	}
 
+	// Warn if can't stream
+	if !vfs.Opt.ReadOnly && vfs.Opt.CacheMode < vfscommon.CacheModeWrites && features.PutStream == nil {
+		fs.Logf(f, "--vfs-cache-mode writes or full is recommended for this remote as it can't stream")
+	}
+
 	vfs.SetCacheMode(vfs.Opt.CacheMode)
 
 	// Pin the Fs into the cache so that when we use cache.NewFs