net: Pass max frags into skb_append_pagefrags()

Pass the maximum number of fragments into skb_append_pagefrags() rather
than using MAX_SKB_FRAGS so that it can be used from code that wants to
specify sysctl_max_skb_frags.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: David Ahern <dsahern@kernel.org>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/skbuff.h

@@ -1383,7 +1383,7 @@ static inline int skb_pad(struct sk_buff *skb, int pad)
 #define dev_kfree_skb(a)	consume_skb(a)
 
 int skb_append_pagefrags(struct sk_buff *skb, struct page *page,
-			 int offset, size_t size);
+			 int offset, size_t size, size_t max_frags);
 
 struct skb_seq_state {
 	__u32		lower_offset;

net/core/skbuff.c

@@ -4188,13 +4188,13 @@ unsigned int skb_find_text(struct sk_buff *skb, unsigned int from,
 EXPORT_SYMBOL(skb_find_text);
 
 int skb_append_pagefrags(struct sk_buff *skb, struct page *page,
-			 int offset, size_t size)
+			 int offset, size_t size, size_t max_frags)
 {
 	int i = skb_shinfo(skb)->nr_frags;
 
 	if (skb_can_coalesce(skb, i, page, offset)) {
 		skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], size);
-	} else if (i < MAX_SKB_FRAGS) {
+	} else if (i < max_frags) {
 		skb_zcopy_downgrade_managed(skb);
 		get_page(page);
 		skb_fill_page_desc_noacc(skb, i, page, offset, size);

net/ipv4/ip_output.c

@@ -1450,7 +1450,8 @@ ssize_t	ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
 		if (len > size)
 			len = size;
 
-		if (skb_append_pagefrags(skb, page, offset, len)) {
+		if (skb_append_pagefrags(skb, page, offset, len,
+					 MAX_SKB_FRAGS)) {
 			err = -EMSGSIZE;
 			goto error;
 		}

net/unix/af_unix.c

@@ -2349,7 +2349,7 @@ static ssize_t unix_stream_sendpage(struct socket *socket, struct page *page,
 		newskb = NULL;
 	}
 
-	if (skb_append_pagefrags(skb, page, offset, size)) {
+	if (skb_append_pagefrags(skb, page, offset, size, MAX_SKB_FRAGS)) {
 		tail = skb;
 		goto alloc_skb;
 	}