On Tue, Jul 06, 2021 at 05:47:26AM +0800, brookxu wrote:

From: Chunguang Xu <redacted>

On the IO submission path, blk_account_io_start() may interrupt
the system interruption. When the interruption returns, the value
of part->stamp may have been updated by other cores, so the time
value collected before the interruption may be less than part->
stamp. So when this happens, we should do nothing to make io_ticks
more accurate? For kernels less than 5.0, this may cause io_ticks
to become smaller, which in turn may cause abnormal ioutil values.

Just be curious, is there any user visible difference with this change?

It can only be one issue if the stamp update crosses two jiffies, but
this event should be very unlikely, right?

Thanks, 
Ming