[v2,6/9] block: vhdx - update log guid in header, and first write tracker

diff --git a/block/vhdx.c b/block/vhdx.c
index 9802b74..0de4d6f 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -233,7 +233,8 @@  static int vhdx_probe(const uint8_t *buf, int buf_size, const char *filename)
  *
  *  - non-current header is updated with largest sequence number
  */
-static int vhdx_update_header(BlockDriverState *bs, BDRVVHDXState *s, bool rw)
+static int vhdx_update_header(BlockDriverState *bs, BDRVVHDXState *s, bool rw,
+                              MSGUID *log_guid)
 {
     int ret = 0;
     int hdr_idx = 0;
@@ -266,6 +267,11 @@  static int vhdx_update_header(BlockDriverState *bs, BDRVVHDXState *s, bool rw)
         vhdx_guid_generate(&inactive_header->data_write_guid);
     }
 
+    /* update the log guid if present */
+    if (log_guid) {
+        memcpy(&inactive_header->log_guid, log_guid, sizeof(MSGUID));
+    }
+
     /* the header checksum is not over just the packed size of VHDXHeader,
      * but rather over the entire 'reserved' range for the header, which is
      * 4KB (VHDX_HEADER_SIZE). */
@@ -293,15 +299,16 @@  exit:
  * The VHDX spec calls for header updates to be performed twice, so that both
  * the current and non-current header have valid info
  */
-static int vhdx_update_headers(BlockDriverState *bs, BDRVVHDXState *s, bool rw)
+int vhdx_update_headers(BlockDriverState *bs, BDRVVHDXState *s, bool rw,
+                        MSGUID *log_guid)
 {
     int ret;
 
-    ret = vhdx_update_header(bs, s, rw);
+    ret = vhdx_update_header(bs, s, rw, log_guid);
     if (ret < 0) {
         return ret;
     }
-    ret = vhdx_update_header(bs, s, rw);
+    ret = vhdx_update_header(bs, s, rw, log_guid);
     return ret;
 }
 
@@ -781,6 +788,7 @@  static int vhdx_open(BlockDriverState *bs, QDict *options, int flags)
 
 
     s->bat = NULL;
+    s->first_visible_write = true;
 
     qemu_co_mutex_init(&s->lock);
 
@@ -861,7 +869,7 @@  static int vhdx_open(BlockDriverState *bs, QDict *options, int flags)
     }
 
     if (flags & BDRV_O_RDWR) {
-        vhdx_update_headers(bs, s, false);
+        vhdx_update_headers(bs, s, false, NULL);
     }
 
     /* TODO: differencing files, write */
@@ -998,6 +1006,16 @@  exit:
 
 
 
+/* Per the spec, on the first write of guest-visible data to the file the
+ * data write guid must be updated in the header */
+void vhdx_user_visible_write(BlockDriverState *bs, BDRVVHDXState *s)
+{
+    if (s->first_visible_write) {
+        s->first_visible_write = false;
+        vhdx_update_headers(bs, s, true, NULL);
+    }
+}
+
 static coroutine_fn int vhdx_co_writev(BlockDriverState *bs, int64_t sector_num,
                                       int nb_sectors, QEMUIOVector *qiov)
 {
diff --git a/block/vhdx.h b/block/vhdx.h
index 5e0a1d3..cb3ce0e 100644
--- a/block/vhdx.h
+++ b/block/vhdx.h
@@ -366,6 +366,7 @@  typedef struct BDRVVHDXState {
     VHDXBatEntry *bat;
     uint64_t bat_offset;
 
+    bool first_visible_write;
     MSGUID session_guid;
 
     VHDXLogEntries log;
@@ -377,6 +378,9 @@  typedef struct BDRVVHDXState {
 
 void vhdx_guid_generate(MSGUID *guid);
 
+int vhdx_update_headers(BlockDriverState *bs, BDRVVHDXState *s, bool rw,
+                        MSGUID *log_guid);
+
 uint32_t vhdx_update_checksum(uint8_t *buf, size_t size, int crc_offset);
 uint32_t vhdx_checksum_calc(uint32_t crc, uint8_t *buf, size_t size,
                             int crc_offset);
@@ -406,8 +410,7 @@  void vhdx_log_data_le_export(VHDXLogDataSector *d);
 void vhdx_log_entry_hdr_le_import(VHDXLogEntryHeader *hdr);
 void vhdx_log_entry_hdr_le_export(VHDXLogEntryHeader *hdr);
 
-
-
+void vhdx_user_visible_write(BlockDriverState *bs, BDRVVHDXState *s);