[PATCH 3/9] tests/qtest/migration: Fix file migration offset check

[Fabiano Rosas]

When doing file migration, QEMU accepts an offset that should be
skipped when writing the migration stream to the file. The purpose of
the offset is to allow the management layer to put its own metadata at
the start of the file.

We have tests for this in migration-test, but only testing that the
migration stream starts at the correct offset and not that it actually
leaves the data intact. Unsurprisingly, there's been a bug in that
area that the tests didn't catch.

Fix the tests to write some data to the offset region and check that
it's actually there after the migration.

Fixes: 3dc35470c8 ("tests/qtest: migration-test: Add tests for file-based 
migration")
Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
 tests/qtest/migration-test.c | 70 +++++++++++++++++++++++++++++++++---
 1 file changed, 65 insertions(+), 5 deletions(-)

diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
index 5d6d8cd634..7b177686b4 100644
--- a/tests/qtest/migration-test.c
+++ b/tests/qtest/migration-test.c
@@ -2081,6 +2081,63 @@ static void test_precopy_file(void)
     test_file_common(&args, true);
 }
 
+#ifndef _WIN32
+static void file_dirty_offset_region(void)
+{
+#if defined(__linux__)
+    g_autofree char *path = g_strdup_printf("%s/%s", tmpfs, 
FILE_TEST_FILENAME);
+    size_t size = FILE_TEST_OFFSET;
+    uintptr_t *addr, *p;
+    int fd;
+
+    fd = open(path, O_CREAT | O_RDWR, 0660);
+    g_assert(fd != -1);
+
+    g_assert(!ftruncate(fd, size));
+
+    addr = mmap(NULL, size, PROT_WRITE, MAP_SHARED, fd, 0);
+    g_assert(addr != MAP_FAILED);
+
+    /* ensure the skipped offset contains some data */
+    p = addr;
+    while (p < addr + FILE_TEST_OFFSET / sizeof(uintptr_t)) {
+        *p = (unsigned long) FILE_TEST_FILENAME;
+        p++;
+    }
+
+    munmap(addr, size);
+    fsync(fd);
+    close(fd);
+#endif
+}
+
+static void *file_offset_start_hook(QTestState *from, QTestState *to)
+{
+    g_autofree char *file = g_strdup_printf("%s/%s", tmpfs, 
FILE_TEST_FILENAME);
+    int src_flags = O_WRONLY;
+    int dst_flags = O_RDONLY;
+    int fds[2];
+
+    file_dirty_offset_region();
+
+    fds[0] = open(file, src_flags, 0660);
+    assert(fds[0] != -1);
+
+    fds[1] = open(file, dst_flags, 0660);
+    assert(fds[1] != -1);
+
+    qtest_qmp_fds_assert_success(from, &fds[0], 1, "{'execute': 'add-fd', "
+                                 "'arguments': {'fdset-id': 1}}");
+
+    qtest_qmp_fds_assert_success(to, &fds[1], 1, "{'execute': 'add-fd', "
+                                 "'arguments': {'fdset-id': 1}}");
+
+    close(fds[0]);
+    close(fds[1]);
+
+    return NULL;
+}
+
 static void file_offset_finish_hook(QTestState *from, QTestState *to,
                                     void *opaque)
 {
@@ -2096,12 +2153,12 @@ static void file_offset_finish_hook(QTestState *from, 
QTestState *to,
     g_assert(addr != MAP_FAILED);
 
     /*
-     * Ensure the skipped offset contains zeros and the migration
-     * stream starts at the right place.
+     * Ensure the skipped offset region's data has not been touched
+     * and the migration stream starts at the right place.
      */
     p = addr;
     while (p < addr + FILE_TEST_OFFSET / sizeof(uintptr_t)) {
-        g_assert(*p == 0);
+        g_assert_cmpstr((char *) *p, ==, FILE_TEST_FILENAME);
         p++;
     }
     g_assert_cmpint(cpu_to_be64(*p) >> 32, ==, QEMU_VM_FILE_MAGIC);
@@ -2113,17 +2170,18 @@ static void file_offset_finish_hook(QTestState *from, 
QTestState *to,
 
 static void test_precopy_file_offset(void)
 {
-    g_autofree char *uri = g_strdup_printf("file:%s/%s,offset=%d", tmpfs,
-                                           FILE_TEST_FILENAME,
+    g_autofree char *uri = g_strdup_printf("file:/dev/fdset/1,offset=%d",
                                            FILE_TEST_OFFSET);
     MigrateCommon args = {
         .connect_uri = uri,
         .listen_uri = "defer",
+        .start_hook = file_offset_start_hook,
         .finish_hook = file_offset_finish_hook,
     };
 
     test_file_common(&args, false);
 }
+#endif
 
 static void test_precopy_file_offset_bad(void)
 {
@@ -3636,8 +3694,10 @@ int main(int argc, char **argv)
 
     migration_test_add("/migration/precopy/file",
                        test_precopy_file);
+#ifndef _WIN32
     migration_test_add("/migration/precopy/file/offset",
                        test_precopy_file_offset);
+#endif
     migration_test_add("/migration/precopy/file/offset/bad",
                        test_precopy_file_offset_bad);
 
-- 
2.35.3