[Qemu-devel] [PATCH 12/22] qcow2-bitmap: add IN_USE flag

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

This flag means that the bitmap is now in use by the software or was not
successfully saved. In any way, with this flag set the bitmap data must
be considered inconsistent and should not be loaded.

With current implementation this flag is never set, as we just remove
bitmaps from the image after loading. But it defined in qcow2 spec and
must be handled. Also, it can be used in future, if async schemes of
bitmap loading/saving are implemented.

We also remove in-use bitmaps from the image on open.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/qcow2-bitmap.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
index a5be25a..8cf40f0 100644
--- a/block/qcow2-bitmap.c
+++ b/block/qcow2-bitmap.c
@@ -28,6 +28,7 @@
 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "qemu/cutils.h"
+#include "exec/log.h"
 
 #include "block/block_int.h"
 #include "block/qcow2.h"
@@ -44,7 +45,8 @@
 #define BME_MAX_NAME_SIZE 1023
 
 /* Bitmap directory entry flags */
-#define BME_RESERVED_FLAGS 0xfffffffd
+#define BME_RESERVED_FLAGS 0xfffffffc
+#define BME_FLAG_IN_USE 1
 #define BME_FLAG_AUTO   (1U << 1)
 
 /* bits [1, 8] U [56, 63] are reserved */
@@ -287,6 +289,11 @@ static BdrvDirtyBitmap *load_bitmap(BlockDriverState *bs,
     BdrvDirtyBitmap *bitmap = NULL;
     char *name = g_strndup(dir_entry_name_notcstr(entry), entry->name_size);
 
+    if (entry->flags & BME_FLAG_IN_USE) {
+        error_setg(errp, "Bitmap '%s' is in use", name);
+        goto fail;
+    }
+
     ret = bitmap_table_load(bs, entry, &bitmap_table);
     if (ret < 0) {
         error_setg_errno(errp, -ret,
@@ -533,6 +540,14 @@ int qcow2_read_bitmaps(BlockDriverState *bs, Error **errp)
     for_each_bitmap_dir_entry(e, dir, dir_size) {
         uint32_t fl = e->flags;
 
+        if (fl & BME_FLAG_IN_USE) {
+            qemu_log("qcow2 warning: "
+                     "removing in_use bitmap '%.*s' for image %s.\n",
+                     e->name_size, (char *)(e + 1), bdrv_get_device_or_node_name(bs));
+
+            continue;
+        }
+
         if (fl & BME_FLAG_AUTO) {
             BdrvDirtyBitmap *bitmap = load_bitmap(bs, e, errp);
             if (bitmap == NULL) {
-- 
1.8.3.1