[Qemu-devel] [PATCH v3 6/9] block: vhdx - update log guid in header, and first write tracker

[Jeff Cody <jcody@redhat.com>]

Allow tracking of first file write in the VHDX image, as well as
the ability to update the GUID in the header.  This is in preparation
for log support.

Signed-off-by: Jeff Cody <jcody@redhat.com>
---
 block/vhdx.c | 30 ++++++++++++++++++++++++------
 block/vhdx.h |  6 ++++++
 2 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/block/vhdx.c b/block/vhdx.c
index 15a4d1d..4dc056b 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -229,7 +229,7 @@ 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 generate_data_write_guid)
+                              bool generate_data_write_guid, MSGUID *log_guid)
 {
     int ret = 0;
     int hdr_idx = 0;
@@ -261,6 +261,11 @@ static int vhdx_update_header(BlockDriverState *bs, BDRVVHDXState *s,
         vhdx_guid_generate(&inactive_header->data_write_guid);
     }
 
+    /* update the log guid if present */
+    if (log_guid) {
+        inactive_header->log_guid = *log_guid;
+    }
+
     /* 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). */
@@ -293,16 +298,16 @@ 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 generate_data_write_guid)
+int vhdx_update_headers(BlockDriverState *bs, BDRVVHDXState *s,
+                        bool generate_data_write_guid, MSGUID *log_guid)
 {
     int ret;
 
-    ret = vhdx_update_header(bs, s, generate_data_write_guid);
+    ret = vhdx_update_header(bs, s, generate_data_write_guid, log_guid);
     if (ret < 0) {
         return ret;
     }
-    ret = vhdx_update_header(bs, s, generate_data_write_guid);
+    ret = vhdx_update_header(bs, s, generate_data_write_guid, log_guid);
     return ret;
 }
 
@@ -782,6 +787,7 @@ static int vhdx_open(BlockDriverState *bs, QDict *options, int flags)
 
 
     s->bat = NULL;
+    s->first_visible_write = true;
 
     qemu_co_mutex_init(&s->lock);
 
@@ -862,7 +868,7 @@ static int vhdx_open(BlockDriverState *bs, QDict *options, int flags)
     }
 
     if (flags & BDRV_O_RDWR) {
-        ret = vhdx_update_headers(bs, s, false);
+        ret = vhdx_update_headers(bs, s, false, NULL);
         if (ret < 0) {
             goto fail;
         }
@@ -1002,6 +1008,18 @@ 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 */
+int vhdx_user_visible_write(BlockDriverState *bs, BDRVVHDXState *s)
+{
+    int ret = 0;
+    if (s->first_visible_write) {
+        s->first_visible_write = false;
+        ret = vhdx_update_headers(bs, s, true, NULL);
+    }
+    return ret;
+}
+
 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 89d9a78..8c61bfd 100644
--- a/block/vhdx.h
+++ b/block/vhdx.h
@@ -361,6 +361,7 @@ typedef struct BDRVVHDXState {
     VHDXBatEntry *bat;
     uint64_t bat_offset;
 
+    bool first_visible_write;
     MSGUID session_guid;
 
     VHDXLogEntries log;
@@ -372,6 +373,9 @@ 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);
@@ -401,4 +405,6 @@ 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);
 
+int vhdx_user_visible_write(BlockDriverState *bs, BDRVVHDXState *s);
+
 #endif
-- 
1.8.1.4