block: new bdrv_reopen_bitmaps_rw interface

Add format driver handler, which should mark loaded read-only
bitmaps as 'IN_USE' in the image and unset read_only field in
corresponding BdrvDirtyBitmap's.
Signed-off-by: NVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: NJohn Snow <jsnow@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Message-id: 20170628120530.31251-14-vsementsov@virtuozzo.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>

block.c

@@ -2983,12 +2983,16 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state)
 {
     BlockDriver *drv;
     BlockDriverState *bs;
+    bool old_can_write, new_can_write;
 
     assert(reopen_state != NULL);
     bs = reopen_state->bs;
     drv = bs->drv;
     assert(drv != NULL);
 
+    old_can_write =
+        !bdrv_is_read_only(bs) && !(bdrv_get_flags(bs) & BDRV_O_INACTIVE);
+
     /* If there are any driver level actions to take */
     if (drv->bdrv_reopen_commit) {
         drv->bdrv_reopen_commit(reopen_state);
@@ -3002,6 +3006,21 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state)
     bs->read_only = !(reopen_state->flags & BDRV_O_RDWR);
 
     bdrv_refresh_limits(bs, NULL);
+
+    new_can_write =
+        !bdrv_is_read_only(bs) && !(bdrv_get_flags(bs) & BDRV_O_INACTIVE);
+    if (!old_can_write && new_can_write && drv->bdrv_reopen_bitmaps_rw) {
+        Error *local_err = NULL;
+        if (drv->bdrv_reopen_bitmaps_rw(bs, &local_err) < 0) {
+            /* This is not fatal, bitmaps just left read-only, so all following
+             * writes will fail. User can remove read-only bitmaps to unblock
+             * writes.
+             */
+            error_reportf_err(local_err,
+                              "%s: Failed to make dirty bitmaps writable: ",
+                              bdrv_get_node_name(bs));
+        }
+    }
 }
 
 /*

include/block/block_int.h

@@ -381,6 +381,13 @@ struct BlockDriver {
                              uint64_t parent_perm, uint64_t parent_shared,
                              uint64_t *nperm, uint64_t *nshared);
 
+    /**
+     * Bitmaps should be marked as 'IN_USE' in the image on reopening image
+     * as rw. This handler should realize it. It also should unset readonly
+     * field of BlockDirtyBitmap's in case of success.
+     */
+    int (*bdrv_reopen_bitmaps_rw)(BlockDriverState *bs, Error **errp);
+
     QLIST_ENTRY(BlockDriver) list;
 };