From e30297b0969895ba6859aaa281ca8b88323cad6a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=A1n=20Tomko?= <jtomko@redhat.com>
Date: Fri, 3 Jul 2015 12:47:02 +0200
Subject: [PATCH] Rewrite allocation tracking when cloning volumes

Instead of storing the remaining bytes, store the position of the first
unallocated byte. This will allow changing the amount of bytes copied
by virStorageBackendCopyToFD without changing the safezero call.

No functional impact.
---
 src/storage/storage_backend.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/storage/storage_backend.c b/src/storage/storage_backend.c
index ce59f63acf..c71545cf63 100644
--- a/src/storage/storage_backend.c
+++ b/src/storage/storage_backend.c
@@ -399,7 +399,7 @@ createRawFile(int fd, virStorageVolDefPtr vol,
 {
     bool need_alloc = true;
     int ret = 0;
-    unsigned long long remain;
+    unsigned long long pos = 0;
 
     /* Seek to the final size, so the capacity is available upfront
      * for progress reporting */
@@ -433,9 +433,9 @@ createRawFile(int fd, virStorageVolDefPtr vol,
     }
 #endif
 
-    remain = vol->target.allocation;
 
     if (inputvol) {
+        unsigned long long remain = vol->target.allocation;
         /* allow zero blocks to be skipped if we've requested sparse
          * allocation (allocation < capacity) or we have already
          * been able to allocate the required space. */
@@ -446,10 +446,12 @@ createRawFile(int fd, virStorageVolDefPtr vol,
                                         want_sparse, reflink_copy);
         if (ret < 0)
             goto cleanup;
+
+        pos = vol->target.allocation - remain;
     }
 
-    if (remain && need_alloc) {
-        if (safezero(fd, vol->target.allocation - remain, remain) < 0) {
+    if (need_alloc) {
+        if (safezero(fd, pos, vol->target.allocation - pos) < 0) {
             ret = -errno;
             virReportSystemError(errno, _("cannot fill file '%s'"),
                                  vol->target.path);