Re: [PATCH 1/4] block/part_stat: remove rcu_read_lock() from part_stat_lock()

[Christoph Hellwig]

On Mon, May 04, 2020 at 04:29:29PM +0300, Konstantin Khlebnikov wrote:
> RCU lock is required only in blk_account_io_start() to lookup partition.
> After that request holds reference to related hd_struct.
> 
> Replace get_cpu() with preempt_disable() - returned cpu index is unused.
> 
> Non-SMP case also needs preempt_disable, otherwise statistics update could
> be non-atomic. Previously that was provided by rcu_read_lock().
> 
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>

Looks good,

Signed-off-by: Christoph Hellwig <hch@xxxxxx>

although I wonder if we should just kill off part_stat_lock and
part_stat_unlock.