On Wed, Nov 20, 2013 at 04:22:00PM +0100, Heinz Graalfs wrote: > Hi, > > when an active virtio block device is hot-unplugged from a KVM guest, running > affected guest user applications are not aware of any errors that occur due > to the lost device. This patch-set adds code to avoid further request queueing > when a lost block device is detected, resulting in appropriate error info. > > On System z there exists no handshake mechanism between host and guest > when a device is hot-unplugged. The device is removed and no further I/O > is possible. > > When an online channel device disappears on System z the kernel's CIO layer > informs the driver (virtio_ccw) about the lost device. > > It's just the block device drivers that care to provide a notify > callback. > > Here are some more error details: > > For a particular block device virtio's request function virtblk_request() > is called by the block layer to queue requests to be handled by the host. > In case of a lost device requests can still be queued, but an appropriate > subsequent host kick usually fails. This leads to situations where no error > feedback is shown. > > In order to prevent request queueing for lost devices appropriate settings > in the block layer should be made. Exploiting System z's CIO notify handler > callback, and adding a corresponding new virtio_driver notify() handler to > 'inform' the block layer, solve this task. > > Patch 1 adds an optional notify() callback to virtio_driver. > > Patch 2 adds a new notify() callback for the virtio_blk driver. When called > for a lost device settings are made to prevent future request queueing. > > Patch 3 modifies the CIO notify handler in virtio_ccw's transport layer to pass > on the lost device info to virtio's backend driver virtio_blk. Question: I guess remove callback is invoked eventually? Could you please clarify why isn't this sufficient? > Heinz Graalfs (3): > virtio: add notify() callback to virtio_driver > virtio_blk: add virtblk_notify() as virtio_driver's notify() callback > virtio_ccw: invoke virtio_driver's notify() on CIO_GONE notification > > drivers/block/virtio_blk.c | 14 ++++++++++++++ > drivers/s390/kvm/virtio_ccw.c | 14 ++++++++++++-- > drivers/virtio/virtio.c | 8 ++++++++ > include/linux/virtio.h | 10 ++++++++++ > 4 files changed, 44 insertions(+), 2 deletions(-) > > -- > 1.8.3.1 _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
