1 files changed, 23 insertions, 7 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index 413af51f3b..6fca9853e1 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -298,6 +298,13 @@ static void blk_root_detach(BdrvChild *child)
     }
 }
 
+static AioContext *blk_root_get_parent_aio_context(BdrvChild *c)
+{
+    BlockBackend *blk = c->opaque;
+
+    return blk_get_aio_context(blk);
+}
+
 static const BdrvChildClass child_root = {
     .inherit_options    = blk_root_inherit_options,
 
@@ -318,6 +325,8 @@ static const BdrvChildClass child_root = {
 
     .can_set_aio_ctx    = blk_root_can_set_aio_ctx,
     .set_aio_ctx        = blk_root_set_aio_ctx,
+
+    .get_parent_aio_context = blk_root_get_parent_aio_context,
 };
 
 /*
@@ -398,15 +407,19 @@ BlockBackend *blk_new_open(const char *filename, const char *reference,
     BlockBackend *blk;
     BlockDriverState *bs;
     uint64_t perm = 0;
+    uint64_t shared = BLK_PERM_ALL;
 
-    /* blk_new_open() is mainly used in .bdrv_create implementations and the
-     * tools where sharing isn't a concern because the BDS stays private, so we
-     * just request permission according to the flags.
+    /*
+     * blk_new_open() is mainly used in .bdrv_create implementations and the
+     * tools where sharing isn't a major concern because the BDS stays private
+     * and the file is generally not supposed to be used by a second process,
+     * so we just request permission according to the flags.
      *
      * The exceptions are xen_disk and blockdev_init(); in these cases, the
      * caller of blk_new_open() doesn't make use of the permissions, but they
      * shouldn't hurt either. We can still share everything here because the
-     * guest devices will add their own blockers if they can't share. */
+     * guest devices will add their own blockers if they can't share.
+     */
     if ((flags & BDRV_O_NO_IO) == 0) {
         perm |= BLK_PERM_CONSISTENT_READ;
         if (flags & BDRV_O_RDWR) {
@@ -416,8 +429,11 @@ BlockBackend *blk_new_open(const char *filename, const char *reference,
     if (flags & BDRV_O_RESIZE) {
         perm |= BLK_PERM_RESIZE;
     }
+    if (flags & BDRV_O_NO_SHARE) {
+        shared = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED;
+    }
 
-    blk = blk_new(qemu_get_aio_context(), perm, BLK_PERM_ALL);
+    blk = blk_new(qemu_get_aio_context(), perm, shared);
     bs = bdrv_open(filename, reference, options, flags, errp);
     if (!bs) {
         blk_unref(blk);
@@ -426,7 +442,7 @@ BlockBackend *blk_new_open(const char *filename, const char *reference,
 
     blk->root = bdrv_root_attach_child(bs, "root", &child_root,
                                        BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
-                                       blk->ctx, perm, BLK_PERM_ALL, blk, errp);
+                                       perm, shared, blk, errp);
     if (!blk->root) {
         blk_unref(blk);
         return NULL;
@@ -840,7 +856,7 @@ int blk_insert_bs(BlockBackend *blk, BlockDriverState *bs, Error **errp)
     bdrv_ref(bs);
     blk->root = bdrv_root_attach_child(bs, "root", &child_root,
                                        BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
-                                       blk->ctx, blk->perm, blk->shared_perm,
+                                       blk->perm, blk->shared_perm,
                                        blk, errp);
     if (blk->root == NULL) {
         return -EPERM;