Messages in this thread | | | Subject | Re: [PATCH] scsi: sd: Contribute to randomness when running rotational device | From | Bart Van Assche <> | Date | Thu, 06 Sep 2018 15:27:53 -0700 |
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On Thu, 2018-09-06 at 13:37 -0700, Xuewei Zhang wrote: > 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> > --- > drivers/scsi/sd.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c > index b79b366a94f7..5e4f10d28065 100644 > --- a/drivers/scsi/sd.c > +++ b/drivers/scsi/sd.c > @@ -2959,6 +2959,9 @@ static void sd_read_block_characteristics(struct > scsi_disk *sdkp) > if (rot == 1) { > blk_queue_flag_set(QUEUE_FLAG_NONROT, q); > blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, q); > + } else { > + blk_queue_flag_clear(QUEUE_FLAG_NONROT, q); > + blk_queue_flag_set(QUEUE_FLAG_ADD_RANDOM, q); > } > > if (sdkp->device->type == TYPE_ZBC) {
Although this patch looks fine to me, seeing this patch makes me wonder whether the default should be changed (QUEUE_FLAG_MQ_DEFAULT) instead of modifying the sd driver. Can anyone remind me why QUEUE_FLAG_MQ_DEFAULT does not include QUEUE_FLAG_ADD_RANDOM?
Thanks,
Bart.
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