From 0254b455e9730691e9f90d53afe860a0f3229f6d Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 12 Dec 2014 03:20:53 +0100
Subject: [PATCH] copy: teach copy_bytes() btrfs reflink magic

---
 src/shared/copy.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/shared/copy.c b/src/shared/copy.c
index f22a94099..4c41f2fdd 100644
--- a/src/shared/copy.c
+++ b/src/shared/copy.c
@@ -27,10 +27,18 @@
 
 int copy_bytes(int fdf, int fdt, off_t max_bytes) {
         bool try_sendfile = true;
+        int r;
 
         assert(fdf >= 0);
         assert(fdt >= 0);
 
+        /* Try btrfs reflinks first. */
+        if (max_bytes == (off_t) -1) {
+                r = btrfs_reflink(fdf, fdt);
+                if (r >= 0)
+                        return 0;
+        }
+
         for (;;) {
                 size_t m = PIPE_BUF;
                 ssize_t n;
@@ -64,7 +72,6 @@ int copy_bytes(int fdf, int fdt, off_t max_bytes) {
                 /* As a fallback just copy bits by hand */
                 {
                         char buf[m];
-                        int r;
 
                         n = read(fdf, buf, m);
                         if (n < 0)
@@ -72,7 +79,7 @@ int copy_bytes(int fdf, int fdt, off_t max_bytes) {
                         if (n == 0) /* EOF */
                                 break;
 
-                        r = loop_write(fdt, buf, n, false);
+                        r = loop_write(fdt, buf, (size_t) n, false);
                         if (r < 0)
                                 return r;
 
-- 
2.30.2