[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, 10 insertions, 8 deletions

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index ea294fffb9ce..4b02d14e7ab9 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, "");
                 }
         }