Re: [PATCH v2 0/3] cgroup/dmem: allow atomic irrestrictive writes to dmem.max

[Thadeu Lima de Souza Cascardo]

On Mon, Mar 23, 2026 at 05:46:28PM +0100, Maarten Lankhorst wrote:
> Hey,
> 
> 
> Den 2026-03-21 kl. 20:27, skrev Tejun Heo:
> > Hello,
> > 
> > Generally looks okay to me. One comment on 3/3 — the naked xchg() in
> > set_resource_max() needs a comment explaining why it's used instead of
> > page_counter_set_max() and what the semantics are (unconditionally sets max
> > regardless of current usage to prevent further allocations, since there's no
> > eviction mechanism yet).
> > 
> > Applied 1/3. Maarten, Michal, what do you think?
> 
> Yeah probably drop 2/3 too since there is no longer a case where setting a limit may fail.
> 
> Kind regards,
> ~Maarten Lankhorst

Actually, this can still happen if an invalid region name is given.

So, one could write:

echo -e 'region1 max\ninvalidregion2 max\n' > dmem.max

And even though setting the value for region1 would be applied, the write
would return -EINVAL.

Cascardo.