linux-kernel - [PATCH net-next v6 2/5] page_frag: unify gfp bits for order 3 page allocation

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Date: Wed, 28 Feb 2024 17:30:09 +0800
From: Yunsheng Lin <linyunsheng@...wei.com>
To: <davem@...emloft.net>, <kuba@...nel.org>, <pabeni@...hat.com>
CC: <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Yunsheng Lin
	<linyunsheng@...wei.com>, Alexander Duyck <alexanderduyck@...com>, Alexander
 Duyck <alexander.duyck@...il.com>, "Michael S. Tsirkin" <mst@...hat.com>,
	Jason Wang <jasowang@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>,
	<kvm@...r.kernel.org>, <virtualization@...ts.linux.dev>, <linux-mm@...ck.org>
Subject: [PATCH net-next v6 2/5] page_frag: unify gfp bits for order 3 page allocation

Currently there seems to be three page frag implementations
which all try to allocate order 3 page, if that fails, it
then fail back to allocate order 0 page, and each of them
all allow order 3 page allocation to fail under certain
condition by using specific gfp bits.

The gfp bits for order 3 page allocation are different
between different implementation, __GFP_NOMEMALLOC is
or'd to forbid access to emergency reserves memory for
__page_frag_cache_refill(), but it is not or'd in other
implementions, __GFP_DIRECT_RECLAIM is masked off to avoid
direct reclaim in vhost_net_page_frag_refill(), but it is
not masked off in __page_frag_cache_refill().

This patch unifies the gfp bits used between different
implementions by or'ing __GFP_NOMEMALLOC and masking off
__GFP_DIRECT_RECLAIM for order 3 page allocation to avoid
possible pressure for mm.

Leave the gfp unifying for page frag implementation in sock.c
for now as suggested by Paolo Abeni.

Signed-off-by: Yunsheng Lin <linyunsheng@...wei.com>
Reviewed-by: Alexander Duyck <alexanderduyck@...com>
CC: Alexander Duyck <alexander.duyck@...il.com>
---
 drivers/vhost/net.c | 2 +-
 mm/page_alloc.c     | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index f2ed7167c848..e574e21cc0ca 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -670,7 +670,7 @@ static bool vhost_net_page_frag_refill(struct vhost_net *net, unsigned int sz,
 		/* Avoid direct reclaim but allow kswapd to wake */
 		pfrag->page = alloc_pages((gfp & ~__GFP_DIRECT_RECLAIM) |
 					  __GFP_COMP | __GFP_NOWARN |
-					  __GFP_NORETRY,
+					  __GFP_NORETRY | __GFP_NOMEMALLOC,
 					  SKB_FRAG_PAGE_ORDER);
 		if (likely(pfrag->page)) {
 			pfrag->size = PAGE_SIZE << SKB_FRAG_PAGE_ORDER;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c0f7e67c4250..636145c29f70 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4685,8 +4685,8 @@ static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
 	gfp_t gfp = gfp_mask;

 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
-	gfp_mask |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY |
-		    __GFP_NOMEMALLOC;
+	gfp_mask = (gfp_mask & ~__GFP_DIRECT_RECLAIM) |  __GFP_COMP |
+		   __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC;
 	page = alloc_pages_node(NUMA_NO_NODE, gfp_mask,
 				PAGE_FRAG_CACHE_MAX_ORDER);
 	nc->size = page ? PAGE_FRAG_CACHE_MAX_SIZE : PAGE_SIZE;
-- 
2.33.0