Re: [PATCH] cgroup/misc: Fix an overflow

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Hi
On Mon, 17 Jul 2023 15:37:08 -0500, Tejun Heo <tj@xxxxxxxxxx> wrote:

Hello,

On Mon, Jul 17, 2023 at 03:19:38PM -0500, Haitao Huang wrote:
Actually, we are using atomic_long_t for 'current' which is the same width
as long defined by arch/compiler. So new_usage should be long to be
consistent?

We can use atomic64_t, right? It's slower on 32bit machines but I think it'd be better to guarantee resource counter range than micro-optimizing charge operations. None of the current users are hot enough for this to matter and if somebody becomes that hot, the difference between atomic_t and atomic64_t isn't gonna matter that much. We'd need to batch allocations per-cpu and so
on.

ditto for event counter. Only max is plain unsigned long but I think it is
also OK as it only compared with 'current' without any arithmetic ops
involved.
Did I miss something here?

I'm saying that it'd be better to make everything explicitly 64bit.


Thanks for the explanation. I think I got it and sent it as a separate patch now just to be sure.
BR
Haitao



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