[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>

5 files changed, 52 insertions, 45 deletions

diff --git a/net/ipv4/fib_hash.c b/net/ipv4/fib_hash.c
index 02088deb046..2e2fc3376ac 100644
--- a/net/ipv4/fib_hash.c
+++ b/net/ipv4/fib_hash.c
@@ -1003,7 +1003,7 @@ static unsigned fib_flag_trans(int type, __be32 mask, struct fib_info *fi)
 static int fib_seq_show(struct seq_file *seq, void *v)
 {
         struct fib_iter_state *iter;
-        char bf[128];
+        int len;
         __be32 prefix, mask;
         unsigned flags;
         struct fib_node *f;
@@ -1025,18 +1025,19 @@ static int fib_seq_show(struct seq_file *seq, void *v)
         mask    = FZ_MASK(iter->zone);
         flags   = fib_flag_trans(fa->fa_type, mask, fi);
         if (fi)
-                snprintf(bf, sizeof(bf),
-                         "%s\t%08X\t%08X\t%04X\t%d\t%u\t%d\t%08X\t%d\t%u\t%u",
+                seq_printf(seq,
+                         "%s\t%08X\t%08X\t%04X\t%d\t%u\t%d\t%08X\t%d\t%u\t%u%n",
                          fi->fib_dev ? fi->fib_dev->name : "*", prefix,
                          fi->fib_nh->nh_gw, flags, 0, 0, fi->fib_priority,
                          mask, (fi->fib_advmss ? fi->fib_advmss + 40 : 0),
                          fi->fib_window,
-                         fi->fib_rtt >> 3);
+                         fi->fib_rtt >> 3, &len);
         else
-                snprintf(bf, sizeof(bf),
-                         "*\t%08X\t%08X\t%04X\t%d\t%u\t%d\t%08X\t%d\t%u\t%u",
-                         prefix, 0, flags, 0, 0, 0, mask, 0, 0, 0);
-        seq_printf(seq, "%-127s\n", bf);
+                seq_printf(seq,
+                         "*\t%08X\t%08X\t%04X\t%d\t%u\t%d\t%08X\t%d\t%u\t%u%n",
+                         prefix, 0, flags, 0, 0, 0, mask, 0, 0, 0, &len);
+
+        seq_printf(seq, "%*s\n", 127 - len, "");
 out:
         return 0;
 }
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index ea294fffb9c..4b02d14e7ab 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -2602,15 +2602,16 @@ static int fib_route_seq_show(struct seq_file *seq, void *v)
                 list_for_each_entry_rcu(fa, &li->falh, fa_list) {
                         const struct fib_info *fi = fa->fa_info;
                         unsigned flags = fib_flag_trans(fa->fa_type, mask, fi);
-                        char bf[128];
+                        int len;
 
                         if (fa->fa_type == RTN_BROADCAST
                             || fa->fa_type == RTN_MULTICAST)
                                 continue;
 
                         if (fi)
-                                snprintf(bf, sizeof(bf),
-                                         "%s\t%08X\t%08X\t%04X\t%d\t%u\t%d\t%08X\t%d\t%u\t%u",
+                                seq_printf(seq,
+                                         "%s\t%08X\t%08X\t%04X\t%d\t%u\t"
+                                         "%d\t%08X\t%d\t%u\t%u%n",
                                          fi->fib_dev ? fi->fib_dev->name : "*",
                                          prefix,
                                          fi->fib_nh->nh_gw, flags, 0, 0,
@@ -2619,14 +2620,15 @@ static int fib_route_seq_show(struct seq_file *seq, void *v)
                                          (fi->fib_advmss ?
                                           fi->fib_advmss + 40 : 0),
                                          fi->fib_window,
-                                         fi->fib_rtt >> 3);
+                                         fi->fib_rtt >> 3, &len);
                         else
-                                snprintf(bf, sizeof(bf),
-                                         "*\t%08X\t%08X\t%04X\t%d\t%u\t%d\t%08X\t%d\t%u\t%u",
+                                seq_printf(seq,
+                                         "*\t%08X\t%08X\t%04X\t%d\t%u\t"
+                                         "%d\t%08X\t%d\t%u\t%u%n",
                                          prefix, 0, flags, 0, 0, 0,
-                                         mask, 0, 0, 0);
+                                         mask, 0, 0, 0, &len);
 
-                        seq_printf(seq, "%-127s\n", bf);
+                        seq_printf(seq, "%*s\n", 127 - len, "");
                 }
         }
 
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 780e9484c82..ce25a13f343 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -367,10 +367,10 @@ static int rt_cache_seq_show(struct seq_file *seq, void *v)
                            "HHUptod\tSpecDst");
         else {
                 struct rtable *r = v;
-                char temp[256];
+                int len;
 
-                sprintf(temp, "%s\t%08lX\t%08lX\t%8X\t%d\t%u\t%d\t"
-                              "%08lX\t%d\t%u\t%u\t%02X\t%d\t%1d\t%08X",
+                seq_printf(seq, "%s\t%08lX\t%08lX\t%8X\t%d\t%u\t%d\t"
+                              "%08lX\t%d\t%u\t%u\t%02X\t%d\t%1d\t%08X%n",
                         r->u.dst.dev ? r->u.dst.dev->name : "*",
                         (unsigned long)r->rt_dst, (unsigned long)r->rt_gateway,
                         r->rt_flags, atomic_read(&r->u.dst.__refcnt),
@@ -384,8 +384,9 @@ static int rt_cache_seq_show(struct seq_file *seq, void *v)
                         r->u.dst.hh ? atomic_read(&r->u.dst.hh->hh_refcnt) : -1,
                         r->u.dst.hh ? (r->u.dst.hh->hh_output ==
                                        dev_queue_xmit) : 0,
-                        r->rt_spec_dst);
-                seq_printf(seq, "%-127s\n", temp);
+                        r->rt_spec_dst, &len);
+
+                seq_printf(seq, "%*s\n", 127 - len, "");
         }
         return 0;
 }
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 776615180b9..0e9bc120707 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;
 }
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index b053ac79527..1f535e31518 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1619,7 +1619,8 @@ void udp_proc_unregister(struct net *net, struct udp_seq_afinfo *afinfo)
 }
 
 /* ------------------------------------------------------------------------ */
-static void udp4_format_sock(struct sock *sp, char *tmpbuf, int bucket)
+static void udp4_format_sock(struct sock *sp, struct seq_file *f,
+                int bucket, int *len)
 {
         struct inet_sock *inet = inet_sk(sp);
         __be32 dest = inet->daddr;
@@ -1627,13 +1628,13 @@ static void udp4_format_sock(struct sock *sp, char *tmpbuf, int bucket)
         __u16 destp       = ntohs(inet->dport);
         __u16 srcp        = ntohs(inet->sport);
 
-        sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X"
-                " %02X %08X:%08X %02X:%08lX %08X %5d %8d %lu %d %p",
+        seq_printf(f, "%4d: %08X:%04X %08X:%04X"
+                " %02X %08X:%08X %02X:%08lX %08X %5d %8d %lu %d %p%n",
                 bucket, src, srcp, dest, destp, sp->sk_state,
                 atomic_read(&sp->sk_wmem_alloc),
                 atomic_read(&sp->sk_rmem_alloc),
                 0, 0L, 0, sock_i_uid(sp), 0, sock_i_ino(sp),
-                atomic_read(&sp->sk_refcnt), sp);
+                atomic_read(&sp->sk_refcnt), sp, len);
 }
 
 int udp4_seq_show(struct seq_file *seq, void *v)
@@ -1644,11 +1645,11 @@ int udp4_seq_show(struct seq_file *seq, void *v)
                            "rx_queue tr tm->when retrnsmt   uid  timeout "
                            "inode");
         else {
-                char tmpbuf[129];
                 struct udp_iter_state *state = seq->private;
+                int len;
 
-                udp4_format_sock(v, tmpbuf, state->bucket);
-                seq_printf(seq, "%-127s\n", tmpbuf);
+                udp4_format_sock(v, seq, state->bucket, &len);
+                seq_printf(seq, "%*s\n", 127 - len ,"");
         }
         return 0;
 }