netdev - [PATCH] netfilter: avoid stalls in nf_ct_alloc

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Date:   Tue, 24 Jul 2018 15:19:05 +0800
From:   Li RongQing <lirongqing@...du.com>
To:     netdev@...r.kernel.org, pablo@...filter.org,
        kadlec@...ckhole.kfki.hu, fw@...len.de
Subject: [PATCH] netfilter: avoid stalls in nf_ct_alloc_hashtable

when system forks a process with CLONE_NEWNET flag under the
high memory pressure, it will trigger memory reclaim and stall
for a long time because nf_ct_alloc_hashtable need to allocate
high-order memory at that time. The calltrace as below:

	delay_tsc
	__delay
	_raw_spin_lock
	_spin_lock
	mmu_shrink
	shrink_slab
	zone_reclaim
	get_page_from_freelist
	__alloc_pages_nodemask
	alloc_pages_current
	__get_free_pages
	nf_ct_alloc_hashtable
	nf_conntrack_init_net
	setup_net
	copy_net_ns
	create_new_namespaces
	copy_namespaces
	copy_process
	do_fork
	sys_clone
	stub_clone
	__clone

not use the directly memory reclaim flag to avoid stall

Signed-off-by: Ni Xun <nixun@...du.com>
Signed-off-by: Zhang Yu <zhangyu31@...du.com>
Signed-off-by: Wang Li <wangli39@...du.com>
Signed-off-by: Li RongQing <lirongqing@...du.com>
---
 net/netfilter/nf_conntrack_core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 8a113ca1eea2..672c5960530d 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -2120,8 +2120,8 @@ void *nf_ct_alloc_hashtable(unsigned int *sizep, int nulls)
 		return NULL;
 
 	sz = nr_slots * sizeof(struct hlist_nulls_head);
-	hash = (void *)__get_free_pages(GFP_KERNEL | __GFP_NOWARN | __GFP_ZERO,
-					get_order(sz));
+	hash = (void *)__get_free_pages((GFP_KERNEL & ~__GFP_DIRECT_RECLAIM) |
+				    __GFP_NOWARN | __GFP_ZERO, get_order(sz));
 	if (!hash)
 		hash = vzalloc(sz);
 
-- 
2.16.2