vmdk: Make VMDK3Header and VmdkGrainMarker QEMU_PACKED

[qemu.git] / block / vmdk.c

diff --git a/block/vmdk.c b/block/vmdk.c
index 3756333c60585229e2d5b48ffd2b1cc459cc01bf..5c3c24086fd3e7863d2273c844fb1397defec335 100644 (file)
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -62,7 +62,7 @@ typedef struct {
     uint32_t cylinders;
     uint32_t heads;
     uint32_t sectors_per_track;
-} VMDK3Header;
+} QEMU_PACKED VMDK3Header;
 
 typedef struct {
     uint32_t version;
@@ -131,7 +131,7 @@ typedef struct VmdkGrainMarker {
     uint64_t lba;
     uint32_t size;
     uint8_t  data[0];
-} VmdkGrainMarker;
+} QEMU_PACKED VmdkGrainMarker;
 
 enum {
     MARKER_END_OF_STREAM    = 0,
@@ -1200,8 +1200,10 @@ static coroutine_fn int vmdk_co_read(BlockDriverState *bs, int64_t sector_num,
 /**
  * vmdk_write:
  * @zeroed:       buf is ignored (data is zero), use zeroed_grain GTE feature
- * if possible, otherwise return -ENOTSUP.
- * @zero_dry_run: used for zeroed == true only, don't update L2 table, just
+ *                if possible, otherwise return -ENOTSUP.
+ * @zero_dry_run: used for zeroed == true only, don't update L2 table, just try
+ *                with each cluster. By dry run we can find if the zero write
+ *                is possible without modifying image data.
  *
  * Returns: error code with 0 for success.
  */
@@ -1328,6 +1330,8 @@ static int coroutine_fn vmdk_co_write_zeroes(BlockDriverState *bs,
     int ret;
     BDRVVmdkState *s = bs->opaque;
     qemu_co_mutex_lock(&s->lock);
+    /* write zeroes could fail if sectors not aligned to cluster, test it with
+     * dry_run == true before really updating image */
     ret = vmdk_write(bs, sector_num, NULL, nb_sectors, true, true);
     if (!ret) {
         ret = vmdk_write(bs, sector_num, NULL, nb_sectors, true, false);