From 71a173472b6e5365a1d35d16aed81f12de0e8a6d Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Thu, 30 Jul 2026 17:41:01 +0100
Subject: [PATCH] dropbox: use much less memory when uploading small files -
 fixes #9685

Since batch mode became the default all uploads go through
uploadChunked, which allocated a full chunk-size retry buffer (48 MiB
by default) regardless of the file size. With the `--transfers 32`
recommended for small file uploads that is ~1.5 GiB of buffer to
upload tiny files.

Size the buffer to the file size when it is known and smaller than a
chunk.
---
 backend/dropbox/dropbox.go | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/backend/dropbox/dropbox.go b/backend/dropbox/dropbox.go
index 556a3c520..bb2f62449 100644
--- a/backend/dropbox/dropbox.go
+++ b/backend/dropbox/dropbox.go
@@ -2042,7 +2042,11 @@ func (o *Object) uploadChunked(ctx context.Context, in0 io.Reader, commitInfo *f
 
 	// write chunks
 	in := readers.NewCountingReader(in0)
-	buf := make([]byte, int(chunkSize))
+	bufSize := chunkSize
+	if size >= 0 && size < bufSize {
+		bufSize = size
+	}
+	buf := make([]byte, int(bufSize))
 	cursor := files.UploadSessionCursor{
 		SessionId: res.SessionId,
 		Offset:    0,