block: Image file option amendment

This patch adds the "amend" option to qemu-img which allows changing
image options on existing image files. It also adds the generic bdrv
implementation which is basically just a wrapper for the image format
specific function.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -4579,3 +4579,11 @@ void bdrv_add_before_write_notifier(BlockDriverState *bs,
 {
     notifier_with_return_list_add(&bs->before_write_notifiers, notifier);
 }
+
+int bdrv_amend_options(BlockDriverState *bs, QEMUOptionParameter *options)
+{
+    if (bs->drv->bdrv_amend_options == NULL) {
+        return -ENOTSUP;
+    }
+    return bs->drv->bdrv_amend_options(bs, options);
+}

include/block/block.h

@@ -241,6 +241,8 @@ typedef enum {
 
 int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res, BdrvCheckMode fix);
 
+int bdrv_amend_options(BlockDriverState *bs_new, QEMUOptionParameter *options);
+
 /* async block I/O */
 typedef void BlockDriverDirtyHandler(BlockDriverState *bs, int64_t sector,
                                      int sector_num);

include/block/block_int.h

@@ -188,6 +188,9 @@ struct BlockDriver {
     int (*bdrv_check)(BlockDriverState* bs, BdrvCheckResult *result,
         BdrvCheckMode fix);
 
+    int (*bdrv_amend_options)(BlockDriverState *bs,
+        QEMUOptionParameter *options);
+
     void (*bdrv_debug_event)(BlockDriverState *bs, BlkDebugEvent event);
 
     /* TODO Better pass a option string/QDict/QemuOpts to add any rule? */

qemu-img-cmds.hx

@@ -67,5 +67,11 @@ DEF("resize", img_resize,
     "resize [-q] filename [+ | -]size")
 STEXI
 @item resize [-q] @var{filename} [+ | -]@var{size}
+ETEXI
+
+DEF("amend", img_amend,
+    "amend [-q] [-f fmt] -o options filename")
+STEXI
+@item amend [-q] [-f @var{fmt}] -o @var{options} @var{filename}
 @end table
 ETEXI

qemu-img.c

@@ -2525,6 +2525,90 @@ out:
     return 0;
 }
 
+static int img_amend(int argc, char **argv)
+{
+    int c, ret = 0;
+    char *options = NULL;
+    QEMUOptionParameter *create_options = NULL, *options_param = NULL;
+    const char *fmt = NULL, *filename;
+    bool quiet = false;
+    BlockDriverState *bs = NULL;
+
+    for (;;) {
+        c = getopt(argc, argv, "hqf:o:");
+        if (c == -1) {
+            break;
+        }
+
+        switch (c) {
+            case 'h':
+            case '?':
+                help();
+                break;
+            case 'o':
+                options = optarg;
+                break;
+            case 'f':
+                fmt = optarg;
+                break;
+            case 'q':
+                quiet = true;
+                break;
+        }
+    }
+
+    if (optind != argc - 1) {
+        help();
+    }
+
+    if (!options) {
+        help();
+    }
+
+    filename = argv[argc - 1];
+
+    bs = bdrv_new_open(filename, fmt, BDRV_O_FLAGS | BDRV_O_RDWR, true, quiet);
+    if (!bs) {
+        error_report("Could not open image '%s'", filename);
+        ret = -1;
+        goto out;
+    }
+
+    fmt = bs->drv->format_name;
+
+    if (is_help_option(options)) {
+        ret = print_block_option_help(filename, fmt);
+        goto out;
+    }
+
+    create_options = append_option_parameters(create_options,
+            bs->drv->create_options);
+    options_param = parse_option_parameters(options, create_options,
+            options_param);
+    if (options_param == NULL) {
+        error_report("Invalid options for file format '%s'", fmt);
+        ret = -1;
+        goto out;
+    }
+
+    ret = bdrv_amend_options(bs, options_param);
+    if (ret < 0) {
+        error_report("Error while amending options: %s", strerror(-ret));
+        goto out;
+    }
+
+out:
+    if (bs) {
+        bdrv_unref(bs);
+    }
+    free_option_parameters(create_options);
+    free_option_parameters(options_param);
+    if (ret) {
+        return 1;
+    }
+    return 0;
+}
+
 static const img_cmd_t img_cmds[] = {
 #define DEF(option, callback, arg_string)        \
     { option, callback },

qemu-img.texi

@@ -350,6 +350,11 @@ sizes accordingly.  Failure to do so will result in data loss!
 After using this command to grow a disk image, you must use file system and
 partitioning tools inside the VM to actually begin using the new space on the
 device.
+
+@item amend [-f @var{fmt}] -o @var{options} @var{filename}
+
+Amends the image format specific @var{options} for the image file
+@var{filename}. Not all file formats support this operation.
 @end table
 @c man end