Re: [Libguestfs] [PATCH] lib: direct: Disable qemu locking when opening drives readonly.

On Tue, Sep 05, 2017 at 03:55:08PM +0100, Richard W.M. Jones wrote: > Since qemu 2.10, qemu locks all drives even when they are opened > readonly. This disables this locking in this safe case. > > Incomplete fix for > https://bugzilla.redhat.com/show_bug.cgi?id=1417306 > --- > lib/launch-direct.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/lib/launch-direct.c b/lib/launch-direct.c > index 3b848165c..e5465539d 100644 > --- a/lib/launch-direct.c > +++ b/lib/launch-direct.c > @@ -221,8 +221,11 @@ add_drive_standard_params (guestfs_h *g, struct backend_direct_data *data, > file = guestfs_int_drive_source_qemu_param (g, &drv->src); > append_list_format ("file=%s", file); > > - if (drv->readonly) > + if (drv->readonly) { > append_list ("snapshot=on"); > + if (guestfs_int_version_ge (&data->qemu_version, 2, 10, 0)) > + append_list ("locking=off"); Don't we have a way to enumerate supported options?

Depending on QEMU version is not going to play nice with vendor-shipped QEMU where features are often backported. > + } > append_list_format ("cache=%s", > drv->cachemode ? drv->cachemode : "writeback"); > if (drv->src.format) Roman.