[Qemu-devel] [PATCH 14/17] qcow2-dirty-bitmap: add IN_USE flag

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

This flag is set on bitmap load and unset on store. If it is already
set when loading the bitmap, the bitmap should not be load (it is in
use by other drive or it is inconsistent (was not successfully saved))

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/qcow2-dirty-bitmap.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/block/qcow2-dirty-bitmap.c b/block/qcow2-dirty-bitmap.c
index e96ee18..3d3c624 100644
--- a/block/qcow2-dirty-bitmap.c
+++ b/block/qcow2-dirty-bitmap.c
@@ -39,7 +39,8 @@
 #define DBM_MAX_NAME_SIZE 1023
 
 /* Dirty Bitmap Directory Enrty flags */
-#define DBM_RESERVED_FLAGS 0xffffffff
+#define DBM_RESERVED_FLAGS 0xfffffffe
+#define DBM_FLAG_IN_USE 1
 
 /* bits [0, 8] U [56, 63] are reserved */
 #define DBM_TABLE_ENTRY_RESERVED_MASK 0xff000000000001ff
@@ -127,6 +128,29 @@ static QCowDirtyBitmapHeader *bitmap_header(BDRVQcowState *s,
            (s->dirty_bitmap_directory + bitmap->offset);
 }
 
+static int update_bitmap_header_sync(BlockDriverState *bs, QCowDirtyBitmap *bitmap)
+{
+    int ret;
+    BDRVQcowState *s = bs->opaque;
+    QCowDirtyBitmapHeader *h = bitmap_header(s, bitmap);
+
+    bitmap_header_to_be(h);
+    ret = bdrv_pwrite(bs->file,
+                      s->dirty_bitmap_directory_offset + bitmap->offset,
+                      h, dir_entry_size(h));
+    bitmap_header_to_cpu(h);
+    if (ret < 0) {
+        return ret;
+    }
+
+    ret = bdrv_flush(bs);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return 0;
+}
+
 static int directory_read(BlockDriverState *bs)
 {
     int ret;
@@ -330,6 +354,11 @@ BdrvDirtyBitmap * qcow2_dirty_bitmap_load(BlockDriverState *bs_for,
     }
     bmh = bitmap_header(s, bm);
 
+    if (bmh->flags & DBM_FLAG_IN_USE) {
+        error_setg(errp, "Bitmap '%s' is in use", name);
+        return NULL;
+    }
+
     if (size != bmh->nb_virtual_bits) {
         error_setg(errp,
                    "Bitmap '%s' in the node '%s' has size = %" PRIu64
@@ -367,6 +396,13 @@ BdrvDirtyBitmap * qcow2_dirty_bitmap_load(BlockDriverState *bs_for,
         goto finish;
     }
 
+    bmh->flags |= DBM_FLAG_IN_USE;
+    ret = update_bitmap_header_sync(bs_file, bm);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Could not set in_use in bitmap header");
+        goto finish;
+    }
+
 finish:
     if (*errp != NULL) {
         bdrv_release_dirty_bitmap(bs_for, bitmap);
@@ -773,6 +809,12 @@ int qcow2_dirty_bitmap_store(BlockDriverState *bs, const BdrvDirtyBitmap *bitmap
         goto finish;
     }
 
+    bmh->flags &= ~DBM_FLAG_IN_USE;
+    ret = update_bitmap_header_sync(bs, bm);
+    if (ret < 0) {
+        goto finish;
+    }
+
 finish:
     g_free(dirty_bitmap_table);
     return ret;
-- 
2.1.4