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>
Fixes: 1d91df85f399 ("mm/page_alloc: handle a missing case for memalloc_nocma_{save/restore} APIs")
Suggested-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx # v5.9+
Link: https://lore.kernel.org/all/CAGis_TWzSu=P7QJmjD58WWiu3zjMTVKSzdOwWE8ORaGytzWJwQ@xxxxxxxxxxxxxx/
Signed-off-by: Matt Fleming <mfleming@xxxxxxxxxxxxxx>
---
mm/page_alloc.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
v2: Update comment and add Fixes, Reviewed-by, and Cc: stable tags.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8afab64814dc..94a2ffe28008 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2893,12 +2893,12 @@ struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone,
page = __rmqueue(zone, order, migratetype, alloc_flags);
/*
- * If the allocation fails, allow OOM handling access
- * to HIGHATOMIC reserves as failing now is worse than
- * failing a high-order atomic allocation in the
- * future.
+ * If the allocation fails, allow OOM handling and
+ * order-0 (atomic) allocs access to HIGHATOMIC
+ * reserves as failing now is worse than 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
