vvfat: Add migration blocker

vvfat caches more or less everything when in writable mode. For migration
to work, it would have to be invalidated. Block migration for now when
in writable mode (default is readonly).
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/vvfat.c

@@ -27,6 +27,7 @@
 #include "qemu-common.h"
 #include "block_int.h"
 #include "module.h"
+#include "migration.h"
 
 #ifndef S_IWGRP
 #define S_IWGRP 0
@@ -350,6 +351,8 @@ typedef struct BDRVVVFATState {
     array_t commits;
     const char* path;
     int downcase_short_names;
+
+    Error *migration_blocker;
 } BDRVVVFATState;
 
 /* take the sector position spos and convert it to Cylinder/Head/Sector position
@@ -1073,6 +1076,15 @@ DLOG(if (stderr == NULL) {
 
     //    assert(is_consistent(s));
     qemu_co_mutex_init(&s->lock);
+
+    /* Disable migration when vvfat is used rw */
+    if (s->qcow) {
+        error_set(&s->migration_blocker,
+                  QERR_BLOCK_FORMAT_FEATURE_NOT_SUPPORTED,
+                  "vvfat (rw)", bs->device_name, "live migration");
+        migrate_add_blocker(s->migration_blocker);
+    }
+
     return 0;
 }
 
@@ -2829,6 +2841,11 @@ static void vvfat_close(BlockDriverState *bs)
     array_free(&(s->directory));
     array_free(&(s->mapping));
     g_free(s->cluster_buffer);
+
+    if (s->qcow) {
+        migrate_del_blocker(s->migration_blocker);
+        error_free(s->migration_blocker);
+    }
 }
 
 static BlockDriver bdrv_vvfat = {