linux-kernel - [PATCH] net: dccp: Replace GFP_ATOMIC with GFP_KERNEL in dccp

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Message-Id: <1523283004-25581-1-git-send-email-baijiaju1990@gmail.com>
Date:   Mon,  9 Apr 2018 22:10:04 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     gerrit@....abdn.ac.uk, davem@...emloft.net
Cc:     dccp@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] net: dccp: Replace GFP_ATOMIC with GFP_KERNEL in dccp_init

dccp_init() is never called in atomic context.
This function is only set as a parameter of module_init().

Despite never getting called from atomic context,
dccp_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 <baijiaju1990@...il.com>
---
 net/dccp/proto.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index b68168f..f63ba93 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -1159,7 +1159,7 @@ static int __init dccp_init(void)
 			hash_size--;
 		dccp_hashinfo.ehash_mask = hash_size - 1;
 		dccp_hashinfo.ehash = (struct inet_ehash_bucket *)
-			__get_free_pages(GFP_ATOMIC|__GFP_NOWARN, ehash_order);
+			__get_free_pages(GFP_KERNEL|__GFP_NOWARN, ehash_order);
 	} while (!dccp_hashinfo.ehash && --ehash_order > 0);
 
 	if (!dccp_hashinfo.ehash) {
@@ -1182,7 +1182,7 @@ static int __init dccp_init(void)
 		    bhash_order > 0)
 			continue;
 		dccp_hashinfo.bhash = (struct inet_bind_hashbucket *)
-			__get_free_pages(GFP_ATOMIC|__GFP_NOWARN, bhash_order);
+			__get_free_pages(GFP_KERNEL|__GFP_NOWARN, bhash_order);
 	} while (!dccp_hashinfo.bhash && --bhash_order >= 0);
 
 	if (!dccp_hashinfo.bhash) {
-- 
1.9.1