raw-format: Fix open with 'file' in iothread

When opening the 'file' child moves bs to an iothread, we need to hold
the AioContext lock of it before we can call raw_apply_options() (and
more specifically, bdrv_getlength() inside of it).

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230525124713.401149-8-kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/raw-format.c

@@ -468,6 +468,7 @@ static int raw_open(BlockDriverState *bs, QDict *options, int flags,
                     Error **errp)
 {
     BDRVRawState *s = bs->opaque;
+    AioContext *ctx;
     bool has_size;
     uint64_t offset, size;
     BdrvChildRole file_role;
@@ -515,7 +516,11 @@ static int raw_open(BlockDriverState *bs, QDict *options, int flags,
                 bs->file->bs->filename);
     }
 
+    ctx = bdrv_get_aio_context(bs);
+    aio_context_acquire(ctx);
     ret = raw_apply_options(bs, s, offset, has_size, size, errp);
+    aio_context_release(ctx);
+
     if (ret < 0) {
         return ret;
     }

tests/unit/test-block-iothread.c

@@ -833,12 +833,9 @@ static void test_attach_second_node(void)
     qdict_put_str(options, "driver", "raw");
     qdict_put_str(options, "file", "base");
 
-    /* FIXME raw_open() should take ctx's lock internally */
-    aio_context_acquire(ctx);
     aio_context_acquire(main_ctx);
     filter = bdrv_open(NULL, NULL, options, BDRV_O_RDWR, &error_abort);
     aio_context_release(main_ctx);
-    aio_context_release(ctx);
 
     g_assert(blk_get_aio_context(blk) == ctx);
     g_assert(bdrv_get_aio_context(bs) == ctx);