From: Timo Sirainen <timo.sirainen@open-xchange.com>
Date: Fri, 13 Mar 2026 11:36:47 +0000 (+0200)
Subject: lib: ostream-file - Shrink buffer to optimal size after it is flushed
X-Git-Tag: 2.4.3~75
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=116ca47dc83bc8a23014ba3bfae41f187cb7b010;p=thirdparty%2Fdovecot%2Fcore.git

lib: ostream-file - Shrink buffer to optimal size after it is flushed

If the ostream buffer was temporarily grown large, it was never shrunk back
to a small value, causing memory to be wasted for long-lived streams.
---

diff --git a/src/lib/ostream-file.c b/src/lib/ostream-file.c
index df1ea27364..2bc66098fa 100644
--- a/src/lib/ostream-file.c
+++ b/src/lib/ostream-file.c
@@ -360,7 +360,16 @@ static int buffer_flush(struct file_ostream *fstream)
 		update_buffer(fstream, ret);
 	}
 
-	return IS_STREAM_EMPTY(fstream) ? 1 : 0;
+	if (!IS_STREAM_EMPTY(fstream))
+		return 0;
+
+	if (fstream->buffer_size > fstream->optimal_block_size) {
+		fstream->buffer = i_realloc(fstream->buffer,
+					    fstream->buffer_size,
+					    fstream->optimal_block_size);
+		fstream->buffer_size = fstream->optimal_block_size;
+	}
+	return 1;
 }
 
 static void o_stream_tcp_flush_via_nodelay(struct file_ostream *fstream)