From: Matt Fleming <mfleming@xxxxxxxxxxxxxx> Under memory pressure it's possible for GFP_ATOMIC order-0 allocations to fail even though free pages are available in the highatomic reserves. GFP_ATOMIC allocations cannot trigger unreserve_highatomic_pageblock() since it's only run from reclaim. Given that such allocations will pass the watermarks in __zone_watermark_unusable_free(), it makes sense to fallback to highatomic reserves the same way that ALLOC_OOM can. This fixes order-0 page allocation failures observed on Cloudflare's fleet when handling network packets: kswapd1: page allocation failure: order:0, mode:0x820(GFP_ATOMIC), nodemask=(null),cpuset=/,mems_allowed=0-7 CPU: 10 PID: 696 Comm: kswapd1 Kdump: loaded Tainted: G O 6.6.43-CUSTOM #1 Hardware name: MACHINE Call Trace: <IRQ> dump_stack_lvl+0x3c/0x50 warn_alloc+0x13a/0x1c0 __alloc_pages_slowpath.constprop.0+0xc9d/0xd10 __alloc_pages+0x327/0x340 __napi_alloc_skb+0x16d/0x1f0 bnxt_rx_page_skb+0x96/0x1b0 [bnxt_en] bnxt_rx_pkt+0x201/0x15e0 [bnxt_en] __bnxt_poll_work+0x156/0x2b0 [bnxt_en] bnxt_poll+0xd9/0x1c0 [bnxt_en] __napi_poll+0x2b/0x1b0 bpf_trampoline_6442524138+0x7d/0x1000 __napi_poll+0x5/0x1b0 net_rx_action+0x342/0x740 handle_softirqs+0xcf/0x2b0 irq_exit_rcu+0x6c/0x90 sysvec_apic_timer_interrupt+0x72/0x90 </IRQ> Suggested-by: Vlastimil Babka <vbabka@xxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: linux-mm@xxxxxxxxx Link: https://lore.kernel.org/all/CAGis_TWzSu=P7QJmjD58WWiu3zjMTVKSzdOwWE8ORaGytzWJwQ@xxxxxxxxxxxxxx/ Signed-off-by: Matt Fleming <mfleming@xxxxxxxxxxxxxx> --- 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 8afab64814dc..0c4c359f5ba7 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2898,7 +2898,7 @@ struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone, * failing a high-order atomic allocation in the * future. */ - if (!page && (alloc_flags & ALLOC_OOM)) + if (!page && (alloc_flags & (ALLOC_OOM|ALLOC_NON_BLOCK))) page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC); if (!page) { -- 2.34.1
