Re: [PATCH] mm/page_counter: use WRITE_ONCE() for emin/elow when parent is the root

[Gregory Price]

On Wed, Oct 21, 2026 at 01:48:18PM -0700, Shakeel Butt wrote:
> page_counter_calculate_protection() runs without locks. Several
> reclaimers can update the same counter's emin and elow at the same
> time, and readers such as mem_cgroup_below_min(), mem_cgroup_protection()
> and the dmem eviction code load them with READ_ONCE().
> 
...
> 
> Use WRITE_ONCE() for these two stores as well.
> 
> There is no functional change. Readers already accept stale values, and
> compilers emit a single word-sized store either way: with GCC 14 the
> x86-64 object code is the same before and after this change.
> 
> Fixes: b3a7822e5e75 ("mm, memcg: prevent mem_cgroup_protected store tearing")
> Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
> Signed-off-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>

Reviewed-by: Gregory Price (Meta) <gourry@xxxxxxxxxx>