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Re: [Qemu-devel] [PATCH] migration, xen: Fix block image lock issue on l
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH] migration, xen: Fix block image lock issue on live migration |
Date: |
Mon, 2 Oct 2017 20:18:22 +0100 |
User-agent: |
Mutt/1.9.0 (2017-09-02) |
Adding in kwolf; it looks sane to me; Kevin?
If I'm reading this right, this is just after the device state save.
Dave
* Anthony PERARD (address@hidden) wrote:
> When doing a live migration of a Xen guest with libxl, the images for
> block devices are locked by the original QEMU process, and this prevent
> the QEMU at the destination to take the lock and the migration fail.
>
> From QEMU point of view, once the RAM of a domain is migrated, there is
> two QMP commands, "stop" then "xen-save-devices-state", at which point a
> new QEMU is spawned at the destination.
>
> Release locks in "xen-save-devices-state" so the destination can takes
> them.
>
> Signed-off-by: Anthony PERARD <address@hidden>
> ---
> CCing libxl maintainers:
> CC: Ian Jackson <address@hidden>
> CC: Wei Liu <address@hidden>
> ---
> migration/savevm.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 4a88228614..69d904c179 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2263,6 +2263,20 @@ void qmp_xen_save_devices_state(const char *filename,
> Error **errp)
> qemu_fclose(f);
> if (ret < 0) {
> error_setg(errp, QERR_IO_ERROR);
> + } else {
> + /* libxl calls the QMP command "stop" before calling
> + * "xen-save-devices-state" and in case of migration failure, libxl
> + * would call "cont".
> + * So call bdrv_inactivate_all (release locks) here to let the other
> + * side of the migration take controle of the images.
> + */
> + if (!saved_vm_running) {
> + ret = bdrv_inactivate_all();
> + if (ret) {
> + error_setg(errp, "%s: bdrv_inactivate_all() failed (%d)",
> + __func__, ret);
> + }
> + }
> }
>
> the_end:
> --
> Anthony PERARD
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK