Am 19.05.2017 um 12:32 hat Stefan Hajnoczi geschrieben:
> blk/bdrv_drain_all() only takes effect for a single instant and then
> resumes block jobs, guest devices, and other external clients like the
> NBD server. This can be handy when performing a synchronous drain
> before terminating the program, for example.
>
> Monitor commands usually need to quiesce I/O across an entire code
> region so blk/bdrv_drain_all() is not suitable. They must use
> bdrv_drain_all_begin/end() to mark the region. This prevents new I/O
> requests from slipping in or worse - block jobs completing and modifying
> the graph.
>
> I audited other blk/bdrv_drain_all() callers but did not find anything
> that needs a similar fix. This patch fixes the savevm/loadvm commands.
> Although I haven't encountered a read world issue this makes the code
> safer.
>
> Suggested-by: Kevin Wolf <kw...@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
> @@ -2279,7 +2284,7 @@ int load_vmstate(const char *name, Error **errp)
> }
>
> /* Flush all IO requests so they don't interfere with the new state. */
> - bdrv_drain_all();
> + bdrv_drain_all_begin();
>
> ret = bdrv_all_goto_snapshot(name, &bs);
> if (ret < 0) {
> @@ -2303,6 +2308,8 @@ int load_vmstate(const char *name, Error **errp)
> qemu_fclose(f);
> aio_context_release(aio_context);
>
> + bdrv_drain_all_end();
> +
> migration_incoming_state_destroy();
> if (ret < 0) {
> error_setg(errp, "Error %d while loading VM state", ret);
There are a few error returns between these two places where a
bdrv_drain_all_end() is missing.
Kevin
