Thread (3 messages) flat view 3 messages, 2 authors, 2018-04-09

Re: [PATCH] net: decnet: Replace GFP_ATOMIC with GFP_KERNEL in dn_route_init

From: Eric Dumazet <hidden>
Date: 2018-04-09 14:44:55
Also in: lkml


On 04/09/2018 07:10 AM, Jia-Ju Bai wrote:
quoted hunk ↗ jump to hunk
dn_route_init() is never called in atomic context.

The call chain ending up at dn_route_init() is:
[1] dn_route_init() <- decnet_init()
decnet_init() is only set as a parameter of module_init().

Despite never getting called from atomic context,
dn_route_init() calls __get_free_pages() with GFP_ATOMIC,
which waits busily for allocation.
GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
to avoid busy waiting and improve the possibility of sucessful allocation.

This is found by a static analysis tool named DCNS written by myself.
And I also manually check it.

Signed-off-by: Jia-Ju Bai <redacted>
---
 net/decnet/dn_route.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index 0bd3afd..59ed12a 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -1898,7 +1898,7 @@ void __init dn_route_init(void)
 		while(dn_rt_hash_mask & (dn_rt_hash_mask - 1))
 			dn_rt_hash_mask--;
 		dn_rt_hash_table = (struct dn_rt_hash_bucket *)
-			__get_free_pages(GFP_ATOMIC, order);
+			__get_free_pages(GFP_KERNEL, order);
 	} while (dn_rt_hash_table == NULL && --order > 0);
 
 	if (!dn_rt_hash_table)
This might OOM under pressure.

This would need __GFP_NOWARN | __GFP_NORETRY  I guess, and would target net-next
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