5 files changed, 167 insertions, 7 deletions
diff --git a/block/qcow2.c b/block/qcow2.c
index 32bdf75..316a8db 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -140,6 +140,7 @@ static int qcow2_read_extensions(BlockDriverState *bs, uint64_t start_offset,
                 return 3;
             }
             bs->backing_format[ext.len] = '\0';
+            s->image_backing_format = g_strdup(bs->backing_format);
 #ifdef DEBUG_EXT
             printf("Qcow2: Got format extension %s\n", bs->backing_format);
 #endif
@@ -884,6 +885,7 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
             goto fail;
         }
         bs->backing_file[len] = '\0';
+        s->image_backing_file = g_strdup(bs->backing_file);
     }
 
     /* Internal snapshots */
@@ -1457,6 +1459,9 @@ static void qcow2_close(BlockDriverState *bs)
     g_free(s->unknown_header_fields);
     cleanup_unknown_header_ext(bs);
 
+    g_free(s->image_backing_file);
+    g_free(s->image_backing_format);
+
     g_free(s->cluster_cache);
     qemu_vfree(s->cluster_data);
     qcow2_refcount_close(bs);
@@ -1622,9 +1627,10 @@ int qcow2_update_header(BlockDriverState *bs)
     }
 
     /* Backing file format header extension */
-    if (*bs->backing_format) {
+    if (s->image_backing_format) {
         ret = header_ext_add(buf, QCOW2_EXT_MAGIC_BACKING_FORMAT,
-                             bs->backing_format, strlen(bs->backing_format),
+                             s->image_backing_format,
+                             strlen(s->image_backing_format),
                              buflen);
         if (ret < 0) {
             goto fail;
@@ -1682,8 +1688,8 @@ int qcow2_update_header(BlockDriverState *bs)
     buflen -= ret;
 
     /* Backing file name */
-    if (*bs->backing_file) {
-        size_t backing_file_len = strlen(bs->backing_file);
+    if (s->image_backing_file) {
+        size_t backing_file_len = strlen(s->image_backing_file);
 
         if (buflen < backing_file_len) {
             ret = -ENOSPC;
@@ -1691,7 +1697,7 @@ int qcow2_update_header(BlockDriverState *bs)
         }
 
         /* Using strncpy is ok here, since buf is not NUL-terminated. */
-        strncpy(buf, bs->backing_file, buflen);
+        strncpy(buf, s->image_backing_file, buflen);
 
         header->backing_file_offset = cpu_to_be64(buf - ((char*) header));
         header->backing_file_size   = cpu_to_be32(backing_file_len);
@@ -1712,9 +1718,17 @@ fail:
 static int qcow2_change_backing_file(BlockDriverState *bs,
     const char *backing_file, const char *backing_fmt)
 {
+    BDRVQcowState *s = bs->opaque;
+
     pstrcpy(bs->backing_file, sizeof(bs->backing_file), backing_file ?: "");
     pstrcpy(bs->backing_format, sizeof(bs->backing_format), backing_fmt ?: "");
 
+    g_free(s->image_backing_file);
+    g_free(s->image_backing_format);
+
+    s->image_backing_file = backing_file ? g_strdup(bs->backing_file) : NULL;
+    s->image_backing_format = backing_fmt ? g_strdup(bs->backing_format) : NULL;
+
     return qcow2_update_header(bs);
 }
 
@@ -2751,8 +2765,9 @@ static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts,
     }
 
     if (backing_file || backing_format) {
-        ret = qcow2_change_backing_file(bs, backing_file ?: bs->backing_file,
-                                        backing_format ?: bs->backing_format);
+        ret = qcow2_change_backing_file(bs,
+                    backing_file ?: s->image_backing_file,
+                    backing_format ?: s->image_backing_format);
         if (ret < 0) {
             return ret;
         }
diff --git a/block/qcow2.h b/block/qcow2.h
index aa6d367..422b825 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -283,6 +283,12 @@ typedef struct BDRVQcowState {
     QLIST_HEAD(, Qcow2UnknownHeaderExtension) unknown_header_ext;
     QTAILQ_HEAD (, Qcow2DiscardRegion) discards;
     bool cache_discards;
+
+    /* Backing file path and format as stored in the image (this is not the
+     * effective path/format, which may be the result of a runtime option
+     * override) */
+    char *image_backing_file;
+    char *image_backing_format;
 } BDRVQcowState;
 
 struct QCowAIOCB;
diff --git a/tests/qemu-iotests/130 b/tests/qemu-iotests/130
new file mode 100755
index 0000000..bc26247
--- /dev/null
+++ b/tests/qemu-iotests/130
@@ -0,0 +1,95 @@
+#!/bin/bash
+#
+# Test that temporary backing file overrides (on the command line or in
+# blockdev-add) don't replace the original path stored in the image during
+# header updates.
+#
+# Copyright (C) 2015 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# creator
+owner=kwolf@redhat.com
+
+seq="$(basename $0)"
+echo "QA output created by $seq"
+
+here="$PWD"
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+_cleanup()
+{
+    _cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+. ./common.qemu
+
+_supported_fmt qcow2
+_supported_proto generic
+_supported_os Linux
+
+qemu_comm_method="monitor"
+
+
+TEST_IMG="$TEST_IMG.orig" _make_test_img 64M
+TEST_IMG="$TEST_IMG.base" _make_test_img 64M
+_make_test_img 64M
+_img_info | _filter_img_info
+
+echo
+echo "=== HMP commit ==="
+echo
+# bdrv_make_empty() involves a header update for qcow2
+
+# Test that a backing file isn't written
+_launch_qemu -drive file="$TEST_IMG",backing.file.filename="$TEST_IMG.base"
+_send_qemu_cmd $QEMU_HANDLE "commit ide0-hd0" "(qemu)"
+_send_qemu_cmd $QEMU_HANDLE '' '(qemu)'
+_cleanup_qemu
+_img_info | _filter_img_info
+
+# Make sure that if there was a backing file that was just overridden on the
+# command line, that backing file is retained, with the right format
+_make_test_img -F raw -b "$TEST_IMG.orig" 64M
+_launch_qemu -drive file="$TEST_IMG",backing.file.filename="$TEST_IMG.base",backing.driver=$IMGFMT
+_send_qemu_cmd $QEMU_HANDLE "commit ide0-hd0" "(qemu)"
+_send_qemu_cmd $QEMU_HANDLE '' '(qemu)'
+_cleanup_qemu
+_img_info | _filter_img_info
+
+echo
+echo "=== Marking image dirty (lazy refcounts) ==="
+echo
+
+# Test that a backing file isn't written
+_make_test_img 64M
+$QEMU_IO -c "open -o backing.file.filename=$TEST_IMG.base,lazy-refcounts=on $TEST_IMG" -c "write 0 4k" | _filter_qemu_io
+_img_info | _filter_img_info
+
+# Make sure that if there was a backing file that was just overridden on the
+# command line, that backing file is retained, with the right format
+_make_test_img -F raw -b "$TEST_IMG.orig" 64M
+$QEMU_IO -c "open -o backing.file.filename=$TEST_IMG.base,backing.driver=$IMGFMT,lazy-refcounts=on $TEST_IMG" -c "write 0 4k" | _filter_qemu_io
+_img_info | _filter_img_info
+
+# success, all done
+echo '*** done'
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/130.out b/tests/qemu-iotests/130.out
new file mode 100644
index 0000000..ea68b5d
--- /dev/null
+++ b/tests/qemu-iotests/130.out
@@ -0,0 +1,43 @@
+QA output created by 130
+Formatting 'TEST_DIR/t.IMGFMT.orig', fmt=IMGFMT size=67108864
+Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+image: TEST_DIR/t.IMGFMT
+file format: IMGFMT
+virtual size: 64M (67108864 bytes)
+
+=== HMP commit ===
+
+QEMU X.Y.Z monitor - type 'help' for more information
+(qemu) c[K[Dco[K[D[Dcom[K[D[D[Dcomm[K[D[D[D[Dcommi[K[D[D[D[D[Dcommit[K[D[D[D[D[D[Dcommit [K[D[D[D[D[D[D[Dcommit i[K[D[D[D[D[D[D[D[Dcommit id[K[D[D[D[D[D[D[D[D[Dcommit ide[K[D[D[D[D[D[D[D[D[D[Dcommit ide0[K[D[D[D[D[D[D[D[D[D[D[Dcommit ide0-[K[D[D[D[D[D[D[D[D[D[D[D[Dcommit ide0-h[K[D[D[D[D[D[D[D[D[D[D[D[D[Dcommit ide0-hd[K[D[D[D[D[D[D[D[D[D[D[D[D[D[Dcommit ide0-hd0[K
+(qemu) 
+image: TEST_DIR/t.IMGFMT
+file format: IMGFMT
+virtual size: 64M (67108864 bytes)
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file='TEST_DIR/t.IMGFMT.orig' backing_fmt='raw'
+QEMU X.Y.Z monitor - type 'help' for more information
+(qemu) c[K[Dco[K[D[Dcom[K[D[D[Dcomm[K[D[D[D[Dcommi[K[D[D[D[D[Dcommit[K[D[D[D[D[D[Dcommit [K[D[D[D[D[D[D[Dcommit i[K[D[D[D[D[D[D[D[Dcommit id[K[D[D[D[D[D[D[D[D[Dcommit ide[K[D[D[D[D[D[D[D[D[D[Dcommit ide0[K[D[D[D[D[D[D[D[D[D[D[Dcommit ide0-[K[D[D[D[D[D[D[D[D[D[D[D[Dcommit ide0-h[K[D[D[D[D[D[D[D[D[D[D[D[D[Dcommit ide0-hd[K[D[D[D[D[D[D[D[D[D[D[D[D[D[Dcommit ide0-hd0[K
+(qemu) 
+image: TEST_DIR/t.IMGFMT
+file format: IMGFMT
+virtual size: 64M (67108864 bytes)
+backing file: TEST_DIR/t.IMGFMT.orig
+backing file format: raw
+
+=== Marking image dirty (lazy refcounts) ===
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+wrote 4096/4096 bytes at offset 0
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+image: TEST_DIR/t.IMGFMT
+file format: IMGFMT
+virtual size: 64M (67108864 bytes)
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file='TEST_DIR/t.IMGFMT.orig' backing_fmt='raw'
+wrote 4096/4096 bytes at offset 0
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+image: TEST_DIR/t.IMGFMT
+file format: IMGFMT
+virtual size: 64M (67108864 bytes)
+backing file: TEST_DIR/t.IMGFMT.orig
+backing file format: raw
+*** done
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 6262127..bcf2578 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -124,3 +124,4 @@
 121 rw auto
 123 rw auto quick
 128 rw auto quick
+130 rw auto quick