On Thu, Sep 06, 2018 at 06:29:32PM +0200, Roger Pau Monné wrote:
On Wed, Sep 05, 2018 at 06:28:01PM +0200, Valentin Vidic wrote:
On Wed, Sep 05, 2018 at 01:35:15PM +0200, Valentin Vidic wrote:
AFAICT, this will cause the backend to never switch to 'Closed' state until the toolstack sets online to 0, which is not good IMO.
If for example a frontend decides to close a device, the backend will stay in state 'Closing' until the toolstack actually removes the disk by setting online to 0.
This will prevent resetting blk connections, as blkback will refuse to switch to state XenbusStateInitWait unless it's at XenbusStateClosed (see the XenbusStateInitialising case in frontend_changed), which will never be reached with your patch.
Would it be possible to call xen_vbd_free before the state change?
case XenbusStateClosed: xen_blkif_disconnect(be->blkif); xen_vbd_free(&be->blkif->vbd); xenbus_switch_state(dev, XenbusStateClosed);I think that will break reconnection, since xen_vbd_create is only called after hotplug script execution is performed (which happens only once at device attachment), but not when DomU changes frontend state.
If you want to perform this xen_vbd_free you will also have to move the xen_vbd_create call AFAICT, to a place that's also called when reconnecting a device. Note that I could be wrong, so it might be worth a shot to try different approaches since the blkback code is quite tangled and I might miss something.
It seems like the Closed state is not a good point to call the remove script since the device could go back from Closed to Connected.
Maybe it would help to introduce a new final state (7 = XenbusStateFree or XenbusStateRemove) that would be set after xen_vbd_free to let the userspace know it is safe to run the remove script?
static void xen_blkif_free(struct xen_blkif *blkif) {
WARN_ON(xen_blkif_disconnect(blkif)); xen_vbd_free(&blkif->vbd); xenbus_switch_state(blkif->be->dev, XenbusStateFree); kfree(blkif->be->mode); kfree(blkif->be);
/* Make sure everything is drained before shutting down */ kmem_cache_free(xen_blkif_cachep, blkif); }