[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v5 05/21] virtio-scsi: stop using aio_disable_external() during unplug
Am 04.05.2023 um 21:53 hat Stefan Hajnoczi geschrieben: > This patch is part of an effort to remove the aio_disable_external() > API because it does not fit in a multi-queue block layer world where > many AioContexts may be submitting requests to the same disk. > > The SCSI emulation code is already in good shape to stop using > aio_disable_external(). It was only used by commit 9c5aad84da1c > ("virtio-scsi: fixed virtio_scsi_ctx_check failed when detaching scsi > disk") to ensure that virtio_scsi_hotunplug() works while the guest > driver is submitting I/O. > > Ensure virtio_scsi_hotunplug() is safe as follows: > > 1. qdev_simple_device_unplug_cb() -> qdev_unrealize() -> > device_set_realized() calls qatomic_set(&dev->realized, false) so > that future scsi_device_get() calls return NULL because they exclude > SCSIDevices with realized=false. > > That means virtio-scsi will reject new I/O requests to this > SCSIDevice with VIRTIO_SCSI_S_BAD_TARGET even while > virtio_scsi_hotunplug() is still executing. We are protected against > new requests! > > 2. scsi_device_unrealize() already contains a call to I think you mean scsi_qdev_unrealize(). Can be fixed while applying. > scsi_device_purge_requests() so that in-flight requests are cancelled > synchronously. This ensures that no in-flight requests remain once > qdev_simple_device_unplug_cb() returns. > > Thanks to these two conditions we don't need aio_disable_external() > anymore. > > Cc: Zhengui Li <lizhengui@xxxxxxxxxx> > Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> > Reviewed-by: Daniil Tatianin <d-tatianin@xxxxxxxxxxxxxx> > Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx> Kevin
|
![]() |
Lists.xenproject.org is hosted with RackSpace, monitoring our |