block: Add op blocker permission constants

This patch defines the permission categories that will be used by the
new op blocker system.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Acked-by: Fam Zheng <famz@redhat.com>

include/block/block.h

@@ -187,6 +187,42 @@ typedef enum BlockOpType {
     BLOCK_OP_TYPE_MAX,
 } BlockOpType;
 
+/* Block node permission constants */
+enum {
+    /**
+     * A user that has the "permission" of consistent reads is guaranteed that
+     * their view of the contents of the block device is complete and
+     * self-consistent, representing the contents of a disk at a specific
+     * point.
+     *
+     * For most block devices (including their backing files) this is true, but
+     * the property cannot be maintained in a few situations like for
+     * intermediate nodes of a commit block job.
+     */
+    BLK_PERM_CONSISTENT_READ    = 0x01,
+
+    /** This permission is required to change the visible disk contents. */
+    BLK_PERM_WRITE              = 0x02,
+
+    /**
+     * This permission (which is weaker than BLK_PERM_WRITE) is both enough and
+     * required for writes to the block node when the caller promises that
+     * the visible disk content doesn't change.
+     */
+    BLK_PERM_WRITE_UNCHANGED    = 0x04,
+
+    /** This permission is required to change the size of a block node. */
+    BLK_PERM_RESIZE             = 0x08,
+
+    /**
+     * This permission is required to change the node that this BdrvChild
+     * points to.
+     */
+    BLK_PERM_GRAPH_MOD          = 0x10,
+
+    BLK_PERM_ALL                = 0x1f,
+};
+
 /* disk I/O throttling */
 void bdrv_init(void);
 void bdrv_init_with_whitelist(void);