Re: [PATCH v2 7/7] virtio-scsi: use scsi_device_get
On Wed, 2020-05-27 at 16:50 +0100, Stefan Hajnoczi wrote: > On Mon, May 11, 2020 at 07:09:51PM +0300, Maxim Levitsky wrote: > > This will help us to avoid the scsi device disappearing > > after we took a reference to it. > > > > It doesn't by itself forbid case when we try to access > > an unrealized device > > > > Suggested-by: Stefan Hajnoczi > > Signed-off-by: Maxim Levitsky > > --- > > hw/scsi/virtio-scsi.c | 23 +++ > > 1 file changed, 15 insertions(+), 8 deletions(-) > > I'm not very familiar with the SCSI emulation code, but this looks > correct. My understanding of what this patch does: > > This patch keeps SCSIDevice alive between scsi_device_find() and > scsi_req_new(). Previously no SCSIDevice ref was taken so the device > could have been freed before scsi_req_new() had a chance to take a ref. Yep, I also verified now that this is what happens. > > The TMF case is similar: the SCSIDevice ref must be held during > virtio_scsi_do_tmf(). We don't need to worry about the async cancel > notifiers because the request being canceled already holds a ref. This code I understand less to be honest, but in the worst case, the patch shoudn't make it worse. Best regards, Maxim Levitsky
Re: [PATCH v2 7/7] virtio-scsi: use scsi_device_get
On Mon, May 11, 2020 at 07:09:51PM +0300, Maxim Levitsky wrote: > This will help us to avoid the scsi device disappearing > after we took a reference to it. > > It doesn't by itself forbid case when we try to access > an unrealized device > > Suggested-by: Stefan Hajnoczi > Signed-off-by: Maxim Levitsky > --- > hw/scsi/virtio-scsi.c | 23 +++ > 1 file changed, 15 insertions(+), 8 deletions(-) I'm not very familiar with the SCSI emulation code, but this looks correct. My understanding of what this patch does: This patch keeps SCSIDevice alive between scsi_device_find() and scsi_req_new(). Previously no SCSIDevice ref was taken so the device could have been freed before scsi_req_new() had a chance to take a ref. The TMF case is similar: the SCSIDevice ref must be held during virtio_scsi_do_tmf(). We don't need to worry about the async cancel notifiers because the request being canceled already holds a ref. signature.asc Description: PGP signature
Re: [PATCH v2 7/7] virtio-scsi: use scsi_device_get
On Mon, May 11, 2020 at 07:09:51PM +0300, Maxim Levitsky wrote: > This will help us to avoid the scsi device disappearing > after we took a reference to it. > > It doesn't by itself forbid case when we try to access > an unrealized device > > Suggested-by: Stefan Hajnoczi > Signed-off-by: Maxim Levitsky > --- > hw/scsi/virtio-scsi.c | 23 +++ > 1 file changed, 15 insertions(+), 8 deletions(-) Reviewed-by: Stefan Hajnoczi signature.asc Description: PGP signature
