From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 16 Sep 2015 23:19:54 +0000 (+0200)
Subject: copy: be more careful when trying to reflink
X-Git-Tag: v227~101^2~12
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=c622fbdb8d37796c35ab1e08240a18b4222e5c9f;p=thirdparty%2Fsystemd.git

copy: be more careful when trying to reflink
---

diff --git a/src/basic/copy.c b/src/basic/copy.c
index b8cbe644d44..019b2764b95 100644
--- a/src/basic/copy.c
+++ b/src/basic/copy.c
@@ -37,7 +37,11 @@ int copy_bytes(int fdf, int fdt, uint64_t max_bytes, bool try_reflink) {
         assert(fdt >= 0);
 
         /* Try btrfs reflinks first. */
-        if (try_reflink && max_bytes == (uint64_t) -1) {
+        if (try_reflink &&
+            max_bytes == (uint64_t) -1 &&
+            lseek(fdf, 0, SEEK_CUR) == 0 &&
+            lseek(fdt, 0, SEEK_CUR) == 0) {
+
                 r = btrfs_reflink(fdf, fdt);
                 if (r >= 0)
                         return r;