[PATCH v3] blk-cgroup: Replace u64 sync with spinlock for iostat update

[tj at kernel.org]

Hello,

On Thu, Jul 18, 2024 at 01:21:32AM +0000, Boy Wu (吳勃誼) wrote:
...
> I think this will work, but as I mentioned before, this issue is only
> on 32 bit SMP systems. Replacing u64 sync with spinlock will increase
> overhead on 64 bit systems, because u64 sync does nothing on 64 bit
> systems. However, if it is acceptable, we can proceed with this
> solution.

We can encapsulate the spinlock in some helpers and make them conditional on
32bit. However, the u64_sync -> spinlock conversions in the suggested patch
are all on cold paths, so I doubt it'd be all that noticeable especially
given that the hottest path of them all is already grabbing blkg_stat_lock,
but either way is fine by me.

Thanks.

-- 
tejun