Add "read-only" to the options QDict

index 553e18d..3ab5e0c 100644
@@ -243,14 +243,14 @@ void commit_start(const char *job_id, BlockDriverState *bs,
     orig_overlay_flags = bdrv_get_flags(overlay_bs);
 
     /* convert base & overlay_bs to r/w, if necessary */
-    if (!(orig_overlay_flags & BDRV_O_RDWR)) {
-        reopen_queue = bdrv_reopen_queue(reopen_queue, overlay_bs, NULL,
-                                         orig_overlay_flags | BDRV_O_RDWR);
-    }
     if (!(orig_base_flags & BDRV_O_RDWR)) {
         reopen_queue = bdrv_reopen_queue(reopen_queue, base, NULL,
                                          orig_base_flags | BDRV_O_RDWR);
     }
+    if (!(orig_overlay_flags & BDRV_O_RDWR)) {
+        reopen_queue = bdrv_reopen_queue(reopen_queue, overlay_bs, NULL,
+                                         orig_overlay_flags | BDRV_O_RDWR);
+    }
     if (reopen_queue) {
         bdrv_reopen_multiple(reopen_queue, &local_err);
         if (local_err != NULL) {

index 66ed1c0..1c75a6f 100644
@@ -2965,11 +2965,6 @@ bool bdrv_debug_is_suspended(BlockDriverState *bs, const char *tag)
     return false;
 }
 
-int bdrv_is_snapshot(BlockDriverState *bs)
-{
-    return !!(bs->open_flags & BDRV_O_SNAPSHOT);
-}
-
 /* backing_file can either be relative, or absolute, or a protocol.  If it is
  * relative, it must be relative to the chain.  So, passing in bs->filename
  * from a BDS as backing_file should not be done, as that may be relative to

index 7edce5c..9f0399f 100644
@@ -420,7 +420,6 @@ void bdrv_get_full_backing_filename_from_filename(const char *backed,
                                                   const char *backing,
                                                   char *dest, size_t sz,
                                                   Error **errp);
-int bdrv_is_snapshot(BlockDriverState *bs);
 
 int path_has_protocol(const char *path);
 int path_is_absolute(const char *path);

index 7cae841..f56d703 100644
@@ -913,6 +913,8 @@ static int bdrv_open_common(BlockDriverState *bs, BdrvChild *file,
         goto fail_opts;
     }
 
+    update_flags_from_options(&bs->open_flags, opts);
+
     driver_name = qemu_opt_get(opts, "driver");
     drv = bdrv_find_format(driver_name);
     assert(drv != NULL);

@@ -974,9 +976,6 @@ static int bdrv_open_common(BlockDriverState *bs, BdrvChild *file,
     bs->drv = drv;
     bs->opaque = g_malloc0(drv->instance_size);
 
-    /* Apply cache mode options */
-    update_flags_from_options(&bs->open_flags, opts);
-
     /* Open the image, either directly or using a protocol */
     open_flags = bdrv_open_flags(bs, bs->open_flags);
     if (drv->bdrv_file_open) {

index 3036af4..6db2c53 100644
@@ -811,7 +811,7 @@ QemuOptsList qemu_legacy_drive_opts = {
 
         /* Options that are passed on, but have special semantics with -drive */
         {
-            .name = "read-only",
+            .name = BDRV_OPT_READ_ONLY,
             .type = QEMU_OPT_BOOL,
             .help = "open drive file as read-only",
         },{

@@ -877,7 +877,7 @@ DriveInfo *drive_new(QemuOpts *all_opts, BlockInterfaceType block_default_type)
 
         { "group",          "throttling.group" },
 
-        { "readonly",       "read-only" },
+        { "readonly",       BDRV_OPT_READ_ONLY },
     };
 
     for (i = 0; i < ARRAY_SIZE(opt_renames); i++) {

@@ -949,7 +949,7 @@ DriveInfo *drive_new(QemuOpts *all_opts, BlockInterfaceType block_default_type)
     }
 
     /* copy-on-read is disabled with a warning for read-only devices */
-    read_only |= qemu_opt_get_bool(legacy_opts, "read-only", false);
+    read_only |= qemu_opt_get_bool(legacy_opts, BDRV_OPT_READ_ONLY, false);
     copy_on_read = qemu_opt_get_bool(legacy_opts, "copy-on-read", false);
 
     if (read_only && copy_on_read) {

@@ -957,7 +957,7 @@ DriveInfo *drive_new(QemuOpts *all_opts, BlockInterfaceType block_default_type)
         copy_on_read = false;
     }
 
-    qdict_put(bs_opts, "read-only",
+    qdict_put(bs_opts, BDRV_OPT_READ_ONLY,
               qstring_from_str(read_only ? "on" : "off"));
     qdict_put(bs_opts, "copy-on-read",
               qstring_from_str(copy_on_read ? "on" :"off"));

@@ -4046,7 +4046,7 @@ QemuOptsList qemu_common_drive_opts = {
             .type = QEMU_OPT_STRING,
             .help = "write error action",
         },{
-            .name = "read-only",
+            .name = BDRV_OPT_READ_ONLY,
             .type = QEMU_OPT_BOOL,
             .help = "open drive file as read-only",
         },{

@@ -4165,7 +4165,7 @@ static QemuOptsList qemu_root_bds_opts = {
             .type = QEMU_OPT_STRING,
             .help = "host AIO implementation (threads, native)",
         },{
-            .name = "read-only",
+            .name = BDRV_OPT_READ_ONLY,
             .type = QEMU_OPT_BOOL,
             .help = "open drive file as read-only",
         },{

index f56d703..cf9c513 100644
@@ -707,6 +707,9 @@ static void bdrv_inherited_options(int *child_flags, QDict *child_options,
     qdict_copy_default(child_options, parent_options, BDRV_OPT_CACHE_DIRECT);
     qdict_copy_default(child_options, parent_options, BDRV_OPT_CACHE_NO_FLUSH);
 
+    /* Inherit the read-only option from the parent if it's not set */
+    qdict_copy_default(child_options, parent_options, BDRV_OPT_READ_ONLY);
+
     /* Our block drivers take care to send flushes and respect unmap policy,
      * so we can default to enable both on lower layers regardless of the
      * corresponding parent options. */

@@ -760,7 +763,8 @@ static void bdrv_backing_options(int *child_flags, QDict *child_options,
     qdict_copy_default(child_options, parent_options, BDRV_OPT_CACHE_NO_FLUSH);
 
     /* backing files always opened read-only */
-    flags &= ~(BDRV_O_RDWR | BDRV_O_COPY_ON_READ);
+    qdict_set_default_str(child_options, BDRV_OPT_READ_ONLY, "on");
+    flags &= ~BDRV_O_COPY_ON_READ;
 
     /* snapshot=on is handled on the top layer */
     flags &= ~(BDRV_O_SNAPSHOT | BDRV_O_TEMPORARY);

@@ -807,6 +811,14 @@ static void update_flags_from_options(int *flags, QemuOpts *opts)
     if (qemu_opt_get_bool(opts, BDRV_OPT_CACHE_DIRECT, false)) {
         *flags |= BDRV_O_NOCACHE;
     }
+
+    *flags &= ~BDRV_O_RDWR;
+
+    assert(qemu_opt_find(opts, BDRV_OPT_READ_ONLY));
+    if (!qemu_opt_get_bool(opts, BDRV_OPT_READ_ONLY, false)) {
+        *flags |= BDRV_O_RDWR;
+    }
+
 }
 
 static void update_options_from_flags(QDict *options, int flags)

@@ -819,6 +831,10 @@ static void update_options_from_flags(QDict *options, int flags)
         qdict_put(options, BDRV_OPT_CACHE_NO_FLUSH,
                   qbool_from_bool(flags & BDRV_O_NO_FLUSH));
     }
+    if (!qdict_haskey(options, BDRV_OPT_READ_ONLY)) {
+        qdict_put(options, BDRV_OPT_READ_ONLY,
+                  qbool_from_bool(!(flags & BDRV_O_RDWR)));
+    }
 }
 
 static void bdrv_assign_node_name(BlockDriverState *bs,

@@ -882,6 +898,11 @@ static QemuOptsList bdrv_runtime_opts = {
             .type = QEMU_OPT_BOOL,
             .help = "Ignore flush requests",
         },
+        {
+            .name = BDRV_OPT_READ_ONLY,
+            .type = QEMU_OPT_BOOL,
+            .help = "Node is opened in read-only mode",
+        },
         { /* end of list */ }
     },
 };

@@ -1626,14 +1647,22 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
         goto fail;
     }
 
-    if (flags & BDRV_O_RDWR) {
-        flags |= BDRV_O_ALLOW_RDWR;
+    /* Set the BDRV_O_RDWR and BDRV_O_ALLOW_RDWR flags.
+     * FIXME: we're parsing the QDict to avoid having to create a
+     * QemuOpts just for this, but neither option is optimal. */
+    if (g_strcmp0(qdict_get_try_str(options, BDRV_OPT_READ_ONLY), "on") &&
+        !qdict_get_try_bool(options, BDRV_OPT_READ_ONLY, false)) {
+        flags |= (BDRV_O_RDWR | BDRV_O_ALLOW_RDWR);
+    } else {
+        flags &= ~BDRV_O_RDWR;
     }
 
     if (flags & BDRV_O_SNAPSHOT) {
         snapshot_options = qdict_new();
         bdrv_temp_snapshot_options(&snapshot_flags, snapshot_options,
                                    flags, options);
+        /* Let bdrv_backing_options() override "read-only" */
+        qdict_del(options, BDRV_OPT_READ_ONLY);
         bdrv_backing_options(&flags, options, flags, options);
     }
 

index ba2620f..ded2109 100644
@@ -2971,7 +2971,8 @@ static BlockDriver vvfat_write_target = {
 static void vvfat_qcow_options(int *child_flags, QDict *child_options,
                                int parent_flags, QDict *parent_options)
 {
-    *child_flags = BDRV_O_RDWR | BDRV_O_NO_FLUSH;
+    qdict_set_default_str(child_options, BDRV_OPT_READ_ONLY, "off");
+    *child_flags = BDRV_O_NO_FLUSH;
 }
 
 static const BdrvChildRole child_vvfat_qcow = {

index 1399fbd..3036af4 100644
@@ -360,9 +360,6 @@ static void extract_common_blockdev_options(QemuOpts *opts, int *bdrv_flags,
     const char *aio;
 
     if (bdrv_flags) {
-        if (!qemu_opt_get_bool(opts, "read-only", false)) {
-            *bdrv_flags |= BDRV_O_RDWR;
-        }
         if (qemu_opt_get_bool(opts, "copy-on-read", false)) {
             *bdrv_flags |= BDRV_O_COPY_ON_READ;
         }

@@ -471,7 +468,7 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
     int bdrv_flags = 0;
     int on_read_error, on_write_error;
     bool account_invalid, account_failed;
-    bool writethrough;
+    bool writethrough, read_only;
     BlockBackend *blk;
     BlockDriverState *bs;
     ThrottleConfig cfg;

@@ -567,6 +564,8 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
         bdrv_flags |= BDRV_O_SNAPSHOT;
     }
 
+    read_only = qemu_opt_get_bool(opts, BDRV_OPT_READ_ONLY, false);
+
     /* init */
     if ((!file || !*file) && !qdict_size(bs_opts)) {
         BlockBackendRootState *blk_rs;

@@ -574,7 +573,7 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
         blk = blk_new();
         blk_rs = blk_get_root_state(blk);
         blk_rs->open_flags    = bdrv_flags;
-        blk_rs->read_only     = !(bdrv_flags & BDRV_O_RDWR);
+        blk_rs->read_only     = read_only;
         blk_rs->detect_zeroes = detect_zeroes;
 
         QDECREF(bs_opts);

@@ -588,6 +587,8 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
          * Apply the defaults here instead. */
         qdict_set_default_str(bs_opts, BDRV_OPT_CACHE_DIRECT, "off");
         qdict_set_default_str(bs_opts, BDRV_OPT_CACHE_NO_FLUSH, "off");
+        qdict_set_default_str(bs_opts, BDRV_OPT_READ_ONLY,
+                              read_only ? "on" : "off");
         assert((bdrv_flags & BDRV_O_CACHE_MASK) == 0);
 
         if (runstate_check(RUN_STATE_INMIGRATE)) {

@@ -657,6 +658,7 @@ static BlockDriverState *bds_tree_init(QDict *bs_opts, Error **errp)
     QemuOpts *opts;
     Error *local_error = NULL;
     BlockdevDetectZeroesOptions detect_zeroes;
+    bool read_only;
     int bdrv_flags = 0;
 
     opts = qemu_opts_create(&qemu_root_bds_opts, NULL, 1, errp);

@@ -677,11 +679,15 @@ static BlockDriverState *bds_tree_init(QDict *bs_opts, Error **errp)
         goto fail;
     }
 
+    read_only = qemu_opt_get_bool(opts, BDRV_OPT_READ_ONLY, false);
+
     /* bdrv_open() defaults to the values in bdrv_flags (for compatibility
      * with other callers) rather than what we want as the real defaults.
      * Apply the defaults here instead. */
     qdict_set_default_str(bs_opts, BDRV_OPT_CACHE_DIRECT, "off");
     qdict_set_default_str(bs_opts, BDRV_OPT_CACHE_NO_FLUSH, "off");
+    qdict_set_default_str(bs_opts, BDRV_OPT_READ_ONLY,
+                          read_only ? "on" : "off");
 
     if (runstate_check(RUN_STATE_INMIGRATE)) {
         bdrv_flags |= BDRV_O_INACTIVE;

index 9f0399f..57ae122 100644
@@ -107,6 +107,7 @@ typedef struct HDGeometry {
 #define BDRV_OPT_CACHE_WB       "cache.writeback"
 #define BDRV_OPT_CACHE_DIRECT   "cache.direct"
 #define BDRV_OPT_CACHE_NO_FLUSH "cache.no-flush"
+#define BDRV_OPT_READ_ONLY      "read-only"
 
 
 #define BDRV_SECTOR_BITS   9

index 1c75a6f..7cae841 100644
@@ -1627,6 +1627,17 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
         goto fail;
     }
 
+    if (flags & BDRV_O_RDWR) {
+        flags |= BDRV_O_ALLOW_RDWR;
+    }
+
+    if (flags & BDRV_O_SNAPSHOT) {
+        snapshot_options = qdict_new();
+        bdrv_temp_snapshot_options(&snapshot_flags, snapshot_options,
+                                   flags, options);
+        bdrv_backing_options(&flags, options, flags, options);
+    }
+
     bs->open_flags = flags;
     bs->options = options;
     options = qdict_clone_shallow(options);

@@ -1651,18 +1662,6 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
 
     /* Open image file without format layer */
     if ((flags & BDRV_O_PROTOCOL) == 0) {
-        if (flags & BDRV_O_RDWR) {
-            flags |= BDRV_O_ALLOW_RDWR;
-        }
-        if (flags & BDRV_O_SNAPSHOT) {
-            snapshot_options = qdict_new();
-            bdrv_temp_snapshot_options(&snapshot_flags, snapshot_options,
-                                       flags, options);
-            bdrv_backing_options(&flags, options, flags, options);
-        }
-
-        bs->open_flags = flags;
-
         file = bdrv_open_child(filename, options, "file", bs,
                                &child_file, true, &local_err);
         if (local_err) {

index cf9c513..57f4b2c 100644
@@ -1874,6 +1874,13 @@ static BlockReopenQueue *bdrv_reopen_queue_child(BlockReopenQueue *bs_queue,
         options = qdict_new();
     }
 
+    /* Check if this BlockDriverState is already in the queue */
+    QSIMPLEQ_FOREACH(bs_entry, bs_queue, entry) {
+        if (bs == bs_entry->state.bs) {
+            break;
+        }
+    }
+
     /*
      * Precedence of options:
      * 1. Explicitly passed in options (highest)

@@ -1894,7 +1901,11 @@ static BlockReopenQueue *bdrv_reopen_queue_child(BlockReopenQueue *bs_queue,
     }
 
     /* Old explicitly set values (don't overwrite by inherited value) */
-    old_options = qdict_clone_shallow(bs->explicit_options);
+    if (bs_entry) {
+        old_options = qdict_clone_shallow(bs_entry->state.explicit_options);
+    } else {
+        old_options = qdict_clone_shallow(bs->explicit_options);
+    }
     bdrv_join_options(bs, options, old_options);
     QDECREF(old_options);
 

@@ -1933,8 +1944,13 @@ static BlockReopenQueue *bdrv_reopen_queue_child(BlockReopenQueue *bs_queue,
                                 child->role, options, flags);
     }
 
-    bs_entry = g_new0(BlockReopenQueueEntry, 1);
-    QSIMPLEQ_INSERT_TAIL(bs_queue, bs_entry, entry);
+    if (!bs_entry) {
+        bs_entry = g_new0(BlockReopenQueueEntry, 1);
+        QSIMPLEQ_INSERT_TAIL(bs_queue, bs_entry, entry);
+    } else {
+        QDECREF(bs_entry->state.options);
+        QDECREF(bs_entry->state.explicit_options);
+    }
 
     bs_entry->state.bs = bs;
     bs_entry->state.options = options;