block: Create authorizations mechanism for external snapshot and resize.

Signed-off-by: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

2 files changed, 19 insertions, 13 deletions

diff --git a/include/block/block.h b/include/block/block.h
index b4a77e6cff..59d9f12ce4 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -287,16 +287,16 @@ int bdrv_amend_options(BlockDriverState *bs_new, QEMUOptionParameter *options);
 /* external snapshots */
 
 typedef enum {
-    EXT_SNAPSHOT_ALLOWED,
-    EXT_SNAPSHOT_FORBIDDEN,
-} ExtSnapshotPerm;
-
-/* return EXT_SNAPSHOT_ALLOWED if external snapshot is allowed
- * return EXT_SNAPSHOT_FORBIDDEN if external snapshot is forbidden
- */
-ExtSnapshotPerm bdrv_check_ext_snapshot(BlockDriverState *bs);
-/* helper used to forbid external snapshots like in blkverify */
-ExtSnapshotPerm bdrv_check_ext_snapshot_forbidden(BlockDriverState *bs);
+    BS_IS_A_FILTER,
+    BS_FILTER_PASS_DOWN,
+    BS_AUTHORIZATION_COUNT,
+} BsAuthorization;
+
+bool bdrv_generic_is_first_non_filter(BlockDriverState *bs,
+                                      BlockDriverState *candidate);
+bool bdrv_recurse_is_first_non_filter(BlockDriverState *bs,
+                                      BlockDriverState *candidate);
+bool bdrv_is_first_non_filter(BlockDriverState *candidate);
 
 /* async block I/O */
 typedef void BlockDriverDirtyHandler(BlockDriverState *bs, int64_t sector,
diff --git a/include/block/block_int.h b/include/block/block_int.h
index f3f518c4d2..611a955712 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -69,10 +69,16 @@ struct BlockDriver {
     const char *format_name;
     int instance_size;
 
-    /* if not defined external snapshots are allowed
-     * future block filters will query their children to build the response
+    /* this table of boolean contains authorizations for the block operations */
+    bool authorizations[BS_AUTHORIZATION_COUNT];
+    /* for snapshots complex block filter like Quorum can implement the
+     * following recursive callback instead of BS_IS_A_FILTER.
+     * It's purpose is to recurse on the filter children while calling
+     * bdrv_recurse_is_first_non_filter on them.
+     * For a sample implementation look in the future Quorum block filter.
      */
-    ExtSnapshotPerm (*bdrv_check_ext_snapshot)(BlockDriverState *bs);
+    bool (*bdrv_recurse_is_first_non_filter)(BlockDriverState *bs,
+                                             BlockDriverState *candidate);
 
     int (*bdrv_probe)(const uint8_t *buf, int buf_size, const char *filename);
     int (*bdrv_probe_device)(const char *filename);