linux-kernel - [PATCH] net/packet: simply allocations in alloc_one_pg_vec

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Date:   Fri, 15 May 2020 19:17:36 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Shakeel Butt <shakeelb@...gle.com>
Subject: [PATCH] net/packet: simply allocations in alloc_one_pg_vec_page

Currently the initial allocation for pg_vec buffers are done through
page allocator with __GFP_NORETRY, the first fallbacks is vzalloc and
the second fallback is page allocator without __GFP_NORETRY.

First, there is no need to do vzalloc if the order is 0 and second the
vzalloc internally use GFP_KERNEL for each individual page allocation
and thus there is no need to have any fallback after vzalloc.

Signed-off-by: Shakeel Butt <shakeelb@...gle.com>
---
 net/packet/af_packet.c | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 29bd405adbbd..d6f96b9f5b01 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -4243,19 +4243,12 @@ static char *alloc_one_pg_vec_page(unsigned long order)
 	if (buffer)
 		return buffer;
 
-	/* __get_free_pages failed, fall back to vmalloc */
-	buffer = vzalloc(array_size((1 << order), PAGE_SIZE));
-	if (buffer)
-		return buffer;
+	/* __get_free_pages failed, fall back to vmalloc for high order. */
+	if (order)
+		return vzalloc(array_size((1 << order), PAGE_SIZE));
 
-	/* vmalloc failed, lets dig into swap here */
 	gfp_flags &= ~__GFP_NORETRY;
-	buffer = (char *) __get_free_pages(gfp_flags, order);
-	if (buffer)
-		return buffer;
-
-	/* complete and utter failure */
-	return NULL;
+	return (char *)__get_free_pages(gfp_flags, order);
 }
 
 static struct pgv *alloc_pg_vec(struct tpacket_req *req, int order)
-- 
2.26.2.761.g0e0b3e54be-goog