[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, 9 insertions, 8 deletions

diff --git a/net/ipv4/fib_hash.c b/net/ipv4/fib_hash.c
index 02088deb0461..2e2fc3376ac9 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;
 }