[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 776615180b93..0e9bc120707d 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;
 }