BACKPORT: FROMLIST: scsi: sd: Contribute to randomness when running rotational device

Currently a scsi device won't contribute to kernel randomness when it
uses blk-mq. Since we commonly use scsi on rotational device with
blk-mq, it make sense to keep contributing to kernel randomness in these
cases. This is especially important for virtual machines.

commit b5b6e8c8d3b4 ("scsi: virtio_scsi: fix IO hang caused by automatic
irq vector affinity") made all virtio-scsi device to use blk-mq, which
does not contribute to randomness today. So for a virtual machine only
having virtio-scsi disk (which is common), it will simple stop getting
randomness from its disks in today's implementation.

With this patch, if the above VM has rotational virtio-scsi device, then
it can still benefit from the entropy generated from the disk.

Reported-by: Xuewei Zhang <xueweiz@google.com>
Signed-off-by: Xuewei Zhang <xueweiz@google.com>

BUG=b:113183351
TEST=COS validation test

(am from https://patchwork.kernel.org/patch/10591031/)

Change-Id: Ia1822f1ec9f1887474e7c67edd695d6f1bfb823e
Reviewed-on: https://chromium-review.googlesource.com/1212546
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Commit-Queue: Xuewei Zhang <xueweiz@google.com>
Tested-by: Xuewei Zhang <xueweiz@google.com>
1 file changed