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Commit 5f74f82e authored by Hans Westgaard Ry's avatar Hans Westgaard Ry Committed by David S. Miller
Browse files

net:Add sysctl_max_skb_frags 



Devices may have limits on the number of fragments in an skb they support.
Current codebase uses a constant as maximum for number of fragments one
skb can hold and use.
When enabling scatter/gather and running traffic with many small messages
the codebase uses the maximum number of fragments and may thereby violate
the max for certain devices.
The patch introduces a global variable as max number of fragments.

Signed-off-by: default avatarHans Westgaard Ry <hans.westgaard.ry@oracle.com>
Reviewed-by: default avatarHåkon Bugge <haakon.bugge@oracle.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9cf74903

include/linux/skbuff.h

+1 −0
Original line number Diff line number Diff line
@@ -299,6 +299,7 @@ struct sk_buff; 
#else

#define MAX_SKB_FRAGS (65536/PAGE_SIZE + 1)

#endif

extern int sysctl_max_skb_frags;



typedef struct skb_frag_struct skb_frag_t;

net/core/skbuff.c

+2 −0
Original line number Diff line number Diff line
@@ -79,6 +79,8 @@ 


struct kmem_cache *skbuff_head_cache __read_mostly;

static struct kmem_cache *skbuff_fclone_cache __read_mostly;

int sysctl_max_skb_frags __read_mostly = MAX_SKB_FRAGS;

EXPORT_SYMBOL(sysctl_max_skb_frags);



/**

 *	skb_panic - private function for out-of-line support

net/core/sysctl_net_core.c

+10 −0
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ static int zero = 0; 
static int one = 1;

static int min_sndbuf = SOCK_MIN_SNDBUF;

static int min_rcvbuf = SOCK_MIN_RCVBUF;

static int max_skb_frags = MAX_SKB_FRAGS;



static int net_msg_warn;	/* Unused, but still a sysctl */
@@ -392,6 +393,15 @@ static struct ctl_table net_core_table[] = { 
		.mode		= 0644,

		.proc_handler	= proc_dointvec

	},

	{

		.procname	= "max_skb_frags",

		.data		= &sysctl_max_skb_frags,

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= proc_dointvec_minmax,

		.extra1		= &one,

		.extra2		= &max_skb_frags,

	},

	{ }

};

net/ipv4/tcp.c

+2 −2
Original line number Diff line number Diff line
@@ -940,7 +940,7 @@ static ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset, 


		i = skb_shinfo(skb)->nr_frags;

		can_coalesce = skb_can_coalesce(skb, i, page, offset);

		if (!can_coalesce && i >= MAX_SKB_FRAGS) {

		if (!can_coalesce && i >= sysctl_max_skb_frags) {

			tcp_mark_push(tp, skb);

			goto new_segment;

		}
@@ -1213,7 +1213,7 @@ int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size) 


			if (!skb_can_coalesce(skb, i, pfrag->page,

					      pfrag->offset)) {

				if (i == MAX_SKB_FRAGS || !sg) {

				if (i == sysctl_max_skb_frags || !sg) {

					tcp_mark_push(tp, skb);

					goto new_segment;

				}