netdev - [PATCH bpf] bpf: use __GFP_COMP while allocating page

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Message-Id: <1536783329-784-1-git-send-email-tushar.n.dave@oracle.com>
Date:   Wed, 12 Sep 2018 22:15:29 +0200
From:   Tushar Dave <tushar.n.dave@...cle.com>
To:     ast@...nel.org, daniel@...earbox.net, davem@...emloft.net,
        netdev@...r.kernel.org, john.fastabend@...il.com
Subject: [PATCH bpf] bpf: use __GFP_COMP while allocating page

Helper bpg_msg_pull_data() can allocate multiple pages while
linearizing multiple scatterlist elements into one shared page.
However, if the shared page has size > PAGE_SIZE, using
copy_page_to_iter() causes below warning.

e.g.
[ 6367.019832] WARNING: CPU: 2 PID: 7410 at lib/iov_iter.c:825
page_copy_sane.part.8+0x0/0x8

To avoid above warning, use __GFP_COMP while allocating multiple
contiguous pages.

Signed-off-by: Tushar Dave <tushar.n.dave@...cle.com>
---
 net/core/filter.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index d301134..0b40f95 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2344,7 +2344,8 @@ struct sock *do_msg_redirect_map(struct sk_msg_buff *msg)
 	if (unlikely(bytes_sg_total > copy))
 		return -EINVAL;
 
-	page = alloc_pages(__GFP_NOWARN | GFP_ATOMIC, get_order(copy));
+	page = alloc_pages(__GFP_NOWARN | GFP_ATOMIC | __GFP_COMP,
+			   get_order(copy));
 	if (unlikely(!page))
 		return -ENOMEM;
 	p = page_address(page);
-- 
1.8.3.1