[NET]: Fix heavy stack usage in seq_file output routines.

Plan C: we can follow the Al Viro's proposal about %n like in this patch.
The same applies to udp, fib (the /proc/net/route file), rt_cache and 
sctp debug. This is minus ~150-200 bytes for each.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 19 insertions, 17 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 7766151..0e9bc12 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2255,13 +2255,13 @@ void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo)
 }
 
 static void get_openreq4(struct sock *sk, struct request_sock *req,
-			 char *tmpbuf, int i, int uid)
+			 struct seq_file *f, int i, int uid, int *len)
 {
 	const struct inet_request_sock *ireq = inet_rsk(req);
 	int ttd = req->expires - jiffies;
 
-	sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X"
-		" %02X %08X:%08X %02X:%08lX %08X %5d %8d %u %d %p",
+	seq_printf(f, "%4d: %08X:%04X %08X:%04X"
+		" %02X %08X:%08X %02X:%08lX %08X %5d %8d %u %d %p%n",
 		i,
 		ireq->loc_addr,
 		ntohs(inet_sk(sk)->sport),
@@ -2276,10 +2276,11 @@ static void get_openreq4(struct sock *sk, struct request_sock *req,
 		0,  /* non standard timer */
 		0, /* open_requests have no inode */
 		atomic_read(&sk->sk_refcnt),
-		req);
+		req,
+		len);
 }
 
-static void get_tcp4_sock(struct sock *sk, char *tmpbuf, int i)
+static void get_tcp4_sock(struct sock *sk, struct seq_file *f, int i, int *len)
 {
 	int timer_active;
 	unsigned long timer_expires;
@@ -2305,8 +2306,8 @@ static void get_tcp4_sock(struct sock *sk, char *tmpbuf, int i)
 		timer_expires = jiffies;
 	}
 
-	sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X %02X %08X:%08X %02X:%08lX "
-			"%08X %5d %8d %lu %d %p %u %u %u %u %d",
+	seq_printf(f, "%4d: %08X:%04X %08X:%04X %02X %08X:%08X %02X:%08lX "
+			"%08X %5d %8d %lu %d %p %u %u %u %u %d%n",
 		i, src, srcp, dest, destp, sk->sk_state,
 		tp->write_seq - tp->snd_una,
 		sk->sk_state == TCP_LISTEN ? sk->sk_ack_backlog :
@@ -2322,11 +2323,12 @@ static void get_tcp4_sock(struct sock *sk, char *tmpbuf, int i)
 		icsk->icsk_ack.ato,
 		(icsk->icsk_ack.quick << 1) | icsk->icsk_ack.pingpong,
 		tp->snd_cwnd,
-		tp->snd_ssthresh >= 0xFFFF ? -1 : tp->snd_ssthresh);
+		tp->snd_ssthresh >= 0xFFFF ? -1 : tp->snd_ssthresh,
+		len);
 }
 
 static void get_timewait4_sock(struct inet_timewait_sock *tw,
-			       char *tmpbuf, int i)
+			       struct seq_file *f, int i, int *len)
 {
 	__be32 dest, src;
 	__u16 destp, srcp;
@@ -2340,11 +2342,11 @@ static void get_timewait4_sock(struct inet_timewait_sock *tw,
 	destp = ntohs(tw->tw_dport);
 	srcp  = ntohs(tw->tw_sport);
 
-	sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X"
-		" %02X %08X:%08X %02X:%08lX %08X %5d %8d %d %d %p",
+	seq_printf(f, "%4d: %08X:%04X %08X:%04X"
+		" %02X %08X:%08X %02X:%08lX %08X %5d %8d %d %d %p%n",
 		i, src, srcp, dest, destp, tw->tw_substate, 0, 0,
 		3, jiffies_to_clock_t(ttd), 0, 0, 0, 0,
-		atomic_read(&tw->tw_refcnt), tw);
+		atomic_read(&tw->tw_refcnt), tw, len);
 }
 
 #define TMPSZ 150
@@ -2352,7 +2354,7 @@ static void get_timewait4_sock(struct inet_timewait_sock *tw,
 static int tcp4_seq_show(struct seq_file *seq, void *v)
 {
 	struct tcp_iter_state* st;
-	char tmpbuf[TMPSZ + 1];
+	int len;
 
 	if (v == SEQ_START_TOKEN) {
 		seq_printf(seq, "%-*s\n", TMPSZ - 1,
@@ -2366,16 +2368,16 @@ static int tcp4_seq_show(struct seq_file *seq, void *v)
 	switch (st->state) {
 	case TCP_SEQ_STATE_LISTENING:
 	case TCP_SEQ_STATE_ESTABLISHED:
-		get_tcp4_sock(v, tmpbuf, st->num);
+		get_tcp4_sock(v, seq, st->num, &len);
 		break;
 	case TCP_SEQ_STATE_OPENREQ:
-		get_openreq4(st->syn_wait_sk, v, tmpbuf, st->num, st->uid);
+		get_openreq4(st->syn_wait_sk, v, seq, st->num, st->uid, &len);
 		break;
 	case TCP_SEQ_STATE_TIME_WAIT:
-		get_timewait4_sock(v, tmpbuf, st->num);
+		get_timewait4_sock(v, seq, st->num, &len);
 		break;
 	}
-	seq_printf(seq, "%-*s\n", TMPSZ - 1, tmpbuf);
+	seq_printf(seq, "%*s\n", TMPSZ - 1 - len, "");
 out:
 	return 0;
 }