On Thu, Jun 26, 2025 at 09:19:49AM +0000, Parav Pandit wrote: > > > From: Michael S. Tsirkin <mst@xxxxxxxxxx> > > Sent: 26 June 2025 12:04 PM > > To: Parav Pandit <parav@xxxxxxxxxx> > > Cc: Stefan Hajnoczi <stefanha@xxxxxxxxxx>; axboe@xxxxxxxxx; > > virtualization@xxxxxxxxxxxxxxx; linux-block@xxxxxxxxxxxxxxx; > > stable@xxxxxxxxxxxxxxx; NBU-Contact-Li Rongqing (EXTERNAL) > > <lirongqing@xxxxxxxxx>; Chaitanya Kulkarni <chaitanyak@xxxxxxxxxx>; > > xuanzhuo@xxxxxxxxxxxxxxxxx; pbonzini@xxxxxxxxxx; > > jasowang@xxxxxxxxxx; alok.a.tiwari@xxxxxxxxxx; Max Gurtovoy > > <mgurtovoy@xxxxxxxxxx>; Israel Rukshin <israelr@xxxxxxxxxx> > > Subject: Re: [PATCH v5] virtio_blk: Fix disk deletion hang on device surprise > > removal > > > > On Thu, Jun 26, 2025 at 06:29:09AM +0000, Parav Pandit wrote: > > > > > > yes however this is not at all different that hotunplug right after reset. > > > > > > > > > > > For hotunplug after reset, we likely need a timeout handler. > > > > > Because block driver running inside the remove() callback waiting > > > > > for the IO, > > > > may not get notified from driver core to synchronize ongoing remove(). > > > > > > > > > > > > Notified of what? > > > Notification that surprise-removal occurred. > > > > > > > So is the scenario that graceful remove starts, and meanwhile a > > > > surprise removal happens? > > > > > > > Right. > > > > > > where is it stuck then? can you explain? > > I am not sure I understood the question. > > Let me try: > Following scenario will hang even with the current fix: > > Say, > 1. the graceful removal is ongoing in the remove() callback, where disk deletion del_gendisk() is ongoing, which waits for the requests to complete, > > 2. Now few requests are yet to complete, and surprise removal started. > > At this point, virtio block driver will not get notified by the driver core layer, because it is likely serializing remove() happening by user/driver unload and PCI hotplug driver-initiated device removal. > So vblk driver doesn't know that device is removed, block layer is waiting for requests completions to arrive which it never gets. > So del_gendisk() gets stuck. > > This needs some kind of timeout handling to improve the situation to make removal more robust. > > Did I answer or I didn't understand the question? You did, thanks! How do other drivers handle this? The issue seems generic. -- MST
