Re: [PATCH v2 7/7] virtio-scsi: use scsi_device_get

[Stefan Hajnoczi]

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 <address@hidden>
> Signed-off-by: Maxim Levitsky <address@hidden>
> ---
>  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.

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