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charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/19/26 20:48, Gregory Price (Meta) wrote: > free_frozen_page_commit() clears a hopeless node's kswapd failures once > its zone recovers above the high watermark, but only if another memory > node exists for allocations to fall back to. > > The test `next_memory_node(nid) < MAX_NUMNODES` finds only memory nodes > with a higher id. The highest-numbered memory node therefore never > recovers on this path, and its kswapd stays disabled until reclaim on > that node makes progress and balances it, or demotion is re-enabled. > > In many cases, direct reclaim many never fully run against a lower > node (CXL/kmem), and that means its kswapd can end up full disabled > in rare situations. > > To reproduce, fill the highest memory node with bound, non-THP anonymous > memory and no swap until kswapd gives up, then free it: /proc/zoneinfo > keeps showing node_unreclaimable 1 for that node. A lower node recovers. > > Count the memory nodes instead. Adding first_memory_node != nid to the > existing test would also work, but a count says directly what the check > means: some other memory node exists. > > Fixes: e7a5f249e6db ("mm: re-enable kswapd when memory pressure subsides or demotion is toggled") > Cc: stable@vger.kernel.org > Signed-off-by: Gregory Price (Meta) LGTM enough for a stable hotfix Acked-by: Vlastimil Babka (SUSE) > --- > mm/page_alloc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 417c427b196d9..6d4f03faf96ee 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2929,7 +2929,7 @@ static bool free_frozen_page_commit(struct zone *zone, > * kswapd work again by resetting kswapd_failures. > */ > if (kswapd_test_hopeless(pgdat) && > - next_memory_node(pgdat->node_id) < MAX_NUMNODES) > + num_node_state(N_MEMORY) > 1) > kswapd_clear_hopeless(pgdat, KSWAPD_CLEAR_HOPELESS_PCP); > } > return ret;