block: Add a 'mutable_opts' field to BlockDriver

If we reopen a BlockDriverState and there is an option that is present
in bs->options but missing from the new set of options then we have to
return an error unless the driver is able to reset it to its default
value.

This patch adds a new 'mutable_opts' field to BlockDriver. This is
a list of runtime options that can be modified during reopen. If an
option in this list is unspecified on reopen then it must be reset (or
return an error).

Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/file-posix.c

@@ -442,6 +442,8 @@ static QemuOptsList raw_runtime_opts = {
     },
 };
 
+static const char *const mutable_opts[] = { "x-check-cache-dropped", NULL };
+
 static int raw_open_common(BlockDriverState *bs, QDict *options,
                            int bdrv_flags, int open_flags,
                            bool device, Error **errp)
@@ -2870,6 +2872,7 @@ BlockDriver bdrv_file = {
     .bdrv_set_perm   = raw_set_perm,
     .bdrv_abort_perm_update = raw_abort_perm_update,
     .create_opts = &raw_create_opts,
+    .mutable_opts = mutable_opts,
 };
 
 /***********************************************/
@@ -3321,6 +3324,7 @@ static BlockDriver bdrv_host_device = {
     .bdrv_reopen_abort   = raw_reopen_abort,
     .bdrv_co_create_opts = hdev_co_create_opts,
     .create_opts         = &raw_create_opts,
+    .mutable_opts        = mutable_opts,
     .bdrv_co_invalidate_cache = raw_co_invalidate_cache,
     .bdrv_co_pwrite_zeroes = hdev_co_pwrite_zeroes,
 
@@ -3447,6 +3451,7 @@ static BlockDriver bdrv_host_cdrom = {
     .bdrv_reopen_abort   = raw_reopen_abort,
     .bdrv_co_create_opts = hdev_co_create_opts,
     .create_opts         = &raw_create_opts,
+    .mutable_opts        = mutable_opts,
     .bdrv_co_invalidate_cache = raw_co_invalidate_cache,
 
 
@@ -3580,6 +3585,7 @@ static BlockDriver bdrv_host_cdrom = {
     .bdrv_reopen_abort   = raw_reopen_abort,
     .bdrv_co_create_opts = hdev_co_create_opts,
     .create_opts        = &raw_create_opts,
+    .mutable_opts       = mutable_opts,
 
     .bdrv_co_preadv         = raw_co_preadv,
     .bdrv_co_pwritev        = raw_co_pwritev,

block/qcow2.c

@@ -627,6 +627,30 @@ int qcow2_validate_table(BlockDriverState *bs, uint64_t offset,
     return 0;
 }
 
+static const char *const mutable_opts[] = {
+    QCOW2_OPT_LAZY_REFCOUNTS,
+    QCOW2_OPT_DISCARD_REQUEST,
+    QCOW2_OPT_DISCARD_SNAPSHOT,
+    QCOW2_OPT_DISCARD_OTHER,
+    QCOW2_OPT_OVERLAP,
+    QCOW2_OPT_OVERLAP_TEMPLATE,
+    QCOW2_OPT_OVERLAP_MAIN_HEADER,
+    QCOW2_OPT_OVERLAP_ACTIVE_L1,
+    QCOW2_OPT_OVERLAP_ACTIVE_L2,
+    QCOW2_OPT_OVERLAP_REFCOUNT_TABLE,
+    QCOW2_OPT_OVERLAP_REFCOUNT_BLOCK,
+    QCOW2_OPT_OVERLAP_SNAPSHOT_TABLE,
+    QCOW2_OPT_OVERLAP_INACTIVE_L1,
+    QCOW2_OPT_OVERLAP_INACTIVE_L2,
+    QCOW2_OPT_OVERLAP_BITMAP_DIRECTORY,
+    QCOW2_OPT_CACHE_SIZE,
+    QCOW2_OPT_L2_CACHE_SIZE,
+    QCOW2_OPT_L2_CACHE_ENTRY_SIZE,
+    QCOW2_OPT_REFCOUNT_CACHE_SIZE,
+    QCOW2_OPT_CACHE_CLEAN_INTERVAL,
+    NULL
+};
+
 static QemuOptsList qcow2_runtime_opts = {
     .name = "qcow2",
     .head = QTAILQ_HEAD_INITIALIZER(qcow2_runtime_opts.head),
@@ -5275,6 +5299,7 @@ BlockDriver bdrv_qcow2 = {
 
     .create_opts         = &qcow2_create_opts,
     .strong_runtime_opts = qcow2_strong_runtime_opts,
+    .mutable_opts        = mutable_opts,
     .bdrv_co_check       = qcow2_co_check,
     .bdrv_amend_options  = qcow2_amend_options,
 

block/raw-format.c

@@ -37,6 +37,8 @@ typedef struct BDRVRawState {
     bool has_size;
 } BDRVRawState;
 
+static const char *const mutable_opts[] = { "offset", "size", NULL };
+
 static QemuOptsList raw_runtime_opts = {
     .name = "raw",
     .head = QTAILQ_HEAD_INITIALIZER(raw_runtime_opts.head),
@@ -570,6 +572,7 @@ BlockDriver bdrv_raw = {
     .create_opts          = &raw_create_opts,
     .bdrv_has_zero_init   = &raw_has_zero_init,
     .strong_runtime_opts  = raw_strong_runtime_opts,
+    .mutable_opts         = mutable_opts,
 };
 
 static void bdrv_raw_init(void)

include/block/block_int.h

@@ -383,6 +383,14 @@ struct BlockDriver {
 
     /* List of options for creating images, terminated by name == NULL */
     QemuOptsList *create_opts;
+    /*
+     * If this driver supports reopening images this contains a
+     * NULL-terminated list of the runtime options that can be
+     * modified. If an option in this list is unspecified during
+     * reopen then it _must_ be reset to its default value or return
+     * an error.
+     */
+    const char *const *mutable_opts;
 
     /*
      * Returns 0 for completed check, -errno for internal errors.