[09/19] block/amend: add 'force' option

diff --git a/docs/tools/qemu-img.rst b/docs/tools/qemu-img.rst
index 7f0737488a..e33f5575e3 100644
--- a/docs/tools/qemu-img.rst
+++ b/docs/tools/qemu-img.rst
@@ -253,11 +253,14 @@  Command description:
 
 .. program:: qemu-img-commands
 
-.. option:: amend [--object OBJECTDEF] [--image-opts] [-p] [-q] [-f FMT] [-t CACHE] -o OPTIONS FILENAME
+.. option:: amend [--object OBJECTDEF] [--image-opts] [-p] [-q] [-f FMT] [-t CACHE] [--force] -o OPTIONS FILENAME
 
   Amends the image format specific *OPTIONS* for the image file
   *FILENAME*. Not all file formats support this operation.
 
+  --force allows some unsafe operations. Currently for -f luks, it allows to
+  erase the last encryption key, and to overwrite an active encryption key.
+
 .. option:: bench [-c COUNT] [-d DEPTH] [-f FMT] [--flush-interval=FLUSH_INTERVAL] [-i AIO] [-n] [--no-drain] [-o OFFSET] [--pattern=PATTERN] [-q] [-s BUFFER_SIZE] [-S STEP_SIZE] [-t CACHE] [-w] [-U] FILENAME
 
   Run a simple sequential I/O benchmark on the specified image. If ``-w`` is
diff --git a/include/block/block.h b/include/block/block.h
index 25e299605e..86f9728f00 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -450,6 +450,7 @@  typedef void BlockDriverAmendStatusCB(BlockDriverState *bs, int64_t offset,
                                       int64_t total_work_size, void *opaque);
 int bdrv_amend_options(BlockDriverState *bs_new, QemuOpts *opts,
                        BlockDriverAmendStatusCB *status_cb, void *cb_opaque,
+                       bool force,
                        Error **errp);
 
 /* check if a named node can be replaced when doing drive-mirror */
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 791de6a59c..066b9eaa40 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -440,6 +440,7 @@  struct BlockDriver {
     int (*bdrv_amend_options)(BlockDriverState *bs, QemuOpts *opts,
                               BlockDriverAmendStatusCB *status_cb,
                               void *cb_opaque,
+                              bool force,
                               Error **errp);
 
     void (*bdrv_debug_event)(BlockDriverState *bs, BlkdebugEvent event);
diff --git a/block.c b/block.c
index 6dbcb7e083..144f52e413 100644
--- a/block.c
+++ b/block.c
@@ -6482,6 +6482,7 @@  void bdrv_remove_aio_context_notifier(BlockDriverState *bs,
 
 int bdrv_amend_options(BlockDriverState *bs, QemuOpts *opts,
                        BlockDriverAmendStatusCB *status_cb, void *cb_opaque,
+                       bool force,
                        Error **errp)
 {
     if (!bs->drv) {
@@ -6493,7 +6494,8 @@  int bdrv_amend_options(BlockDriverState *bs, QemuOpts *opts,
                    bs->drv->format_name);
         return -ENOTSUP;
     }
-    return bs->drv->bdrv_amend_options(bs, opts, status_cb, cb_opaque, errp);
+    return bs->drv->bdrv_amend_options(bs, opts, status_cb,
+                                       cb_opaque, force, errp);
 }
 
 /*
diff --git a/block/qcow2.c b/block/qcow2.c
index 0cd2e6757e..2ab0c382f7 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -5340,6 +5340,7 @@  static void qcow2_amend_helper_cb(BlockDriverState *bs,
 static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts,
                                BlockDriverAmendStatusCB *status_cb,
                                void *cb_opaque,
+                               bool force,
                                Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
diff --git a/qemu-img.c b/qemu-img.c
index d7e846e607..10d81f09db 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -79,6 +79,7 @@  enum {
     OPTION_DISABLE = 273,
     OPTION_MERGE = 274,
     OPTION_BITMAPS = 275,
+    OPTION_FORCE = 276,
 };
 
 typedef enum OutputFormat {
@@ -4099,6 +4100,7 @@  static int img_amend(int argc, char **argv)
     BlockBackend *blk = NULL;
     BlockDriverState *bs = NULL;
     bool image_opts = false;
+    bool force = false;
 
     cache = BDRV_DEFAULT_CACHE;
     for (;;) {
@@ -4106,6 +4108,7 @@  static int img_amend(int argc, char **argv)
             {"help", no_argument, 0, 'h'},
             {"object", required_argument, 0, OPTION_OBJECT},
             {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
+            {"force", no_argument, 0, OPTION_FORCE},
             {0, 0, 0, 0}
         };
         c = getopt_long(argc, argv, ":ho:f:t:pq",
@@ -4153,6 +4156,9 @@  static int img_amend(int argc, char **argv)
         case OPTION_IMAGE_OPTS:
             image_opts = true;
             break;
+        case OPTION_FORCE:
+            force = true;
+            break;
         }
     }
 
@@ -4230,7 +4236,7 @@  static int img_amend(int argc, char **argv)
 
     /* In case the driver does not call amend_status_cb() */
     qemu_progress_print(0.f, 0);
-    ret = bdrv_amend_options(bs, opts, &amend_status_cb, NULL, &err);
+    ret = bdrv_amend_options(bs, opts, &amend_status_cb, NULL, force, &err);
     qemu_progress_print(100.f, 0);
     if (ret < 0) {
         error_report_err(err);
diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
index 10b910b67c..b89c019b76 100644
--- a/qemu-img-cmds.hx
+++ b/qemu-img-cmds.hx
@@ -10,9 +10,9 @@  HXCOMM When amending the rST sections, please remember to copy the usage
 HXCOMM over to the per-command sections in docs/tools/qemu-img.rst.
 
 DEF("amend", img_amend,
-    "amend [--object objectdef] [--image-opts] [-p] [-q] [-f fmt] [-t cache] -o options filename")
+    "amend [--object objectdef] [--image-opts] [-p] [-q] [-f fmt] [-t cache] [--force] -o options filename")
 SRST
-.. option:: amend [--object OBJECTDEF] [--image-opts] [-p] [-q] [-f FMT] [-t CACHE] -o OPTIONS FILENAME
+.. option:: amend [--object OBJECTDEF] [--image-opts] [-p] [-q] [-f FMT] [-t CACHE] [--force] -o OPTIONS FILENAME
 ERST
 
 DEF("bench", img_bench,