netdev - [RFC net-next v3 07/29] net: don't track pfmemalloc for managed frags

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Date:   Tue, 28 Jun 2022 19:56:29 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     io-uring@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Jens Axboe <axboe@...nel.dk>, kernel-team@...com,
        Pavel Begunkov <asml.silence@...il.com>
Subject: [RFC net-next v3 07/29] net: don't track pfmemalloc for managed frags

Managed pages contain pinned userspace pages and controlled by upper
layers, there is no need in tracking skb->pfmemalloc for them.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 include/linux/skbuff.h | 28 +++++++++++++++++-----------
 net/core/datagram.c    |  7 +++++--
 2 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 5407cfd9cb89..6cca146be1f4 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2549,6 +2549,22 @@ static inline unsigned int skb_pagelen(const struct sk_buff *skb)
 	return skb_headlen(skb) + __skb_pagelen(skb);
 }
 
+static inline void __skb_fill_page_desc_noacc(struct skb_shared_info *shinfo,
+					      int i, struct page *page,
+					      int off, int size)
+{
+	skb_frag_t *frag = &shinfo->frags[i];
+
+	/*
+	 * Propagate page pfmemalloc to the skb if we can. The problem is
+	 * that not all callers have unique ownership of the page but rely
+	 * on page_is_pfmemalloc doing the right thing(tm).
+	 */
+	frag->bv_page		  = page;
+	frag->bv_offset		  = off;
+	skb_frag_size_set(frag, size);
+}
+
 /**
  * __skb_fill_page_desc - initialise a paged fragment in an skb
  * @skb: buffer containing fragment to be initialised
@@ -2565,17 +2581,7 @@ static inline unsigned int skb_pagelen(const struct sk_buff *skb)
 static inline void __skb_fill_page_desc(struct sk_buff *skb, int i,
 					struct page *page, int off, int size)
 {
-	skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
-
-	/*
-	 * Propagate page pfmemalloc to the skb if we can. The problem is
-	 * that not all callers have unique ownership of the page but rely
-	 * on page_is_pfmemalloc doing the right thing(tm).
-	 */
-	frag->bv_page		  = page;
-	frag->bv_offset		  = off;
-	skb_frag_size_set(frag, size);
-
+	__skb_fill_page_desc_noacc(skb_shinfo(skb), i, page, off, size);
 	page = compound_head(page);
 	if (page_is_pfmemalloc(page))
 		skb->pfmemalloc	= true;
diff --git a/net/core/datagram.c b/net/core/datagram.c
index a93c05156f56..3c913a6342ad 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -616,7 +616,8 @@ EXPORT_SYMBOL(skb_copy_datagram_from_iter);
 static int __zerocopy_sg_from_bvec(struct sock *sk, struct sk_buff *skb,
 				   struct iov_iter *from, size_t length)
 {
-	int frag = skb_shinfo(skb)->nr_frags;
+	struct skb_shared_info *shinfo = skb_shinfo(skb);
+	int frag = shinfo->nr_frags;
 	int ret = 0;
 	struct bvec_iter bi;
 	ssize_t copied = 0;
@@ -631,12 +632,14 @@ static int __zerocopy_sg_from_bvec(struct sock *sk, struct sk_buff *skb,
 
 		copied += v.bv_len;
 		truesize += PAGE_ALIGN(v.bv_len + v.bv_offset);
-		skb_fill_page_desc(skb, frag++, v.bv_page, v.bv_offset, v.bv_len);
+		__skb_fill_page_desc_noacc(shinfo, frag++, v.bv_page,
+					   v.bv_offset, v.bv_len);
 		bvec_iter_advance_single(from->bvec, &bi, v.bv_len);
 	}
 	if (bi.bi_size)
 		ret = -EMSGSIZE;
 
+	shinfo->nr_frags = frag;
 	from->bvec += bi.bi_idx;
 	from->nr_segs -= bi.bi_idx;
 	from->count = bi.bi_size;
-- 
2.36.1