mm: add a low limit to alloc_large_system_hash

UDP stack needs a minimum hash size value for proper operation and also
uses alloc_large_system_hash() for proper NUMA distribution of its hash
tables and automatic sizing depending on available system memory.

On some low memory situations, udp_table_init() must ignore the
alloc_large_system_hash() result and reallocs a bigger memory area.

As we cannot easily free old hash table, we leak it and kmemleak can
issue a warning.

This patch adds a low limit parameter to alloc_large_system_hash() to
solve this problem.

We then specify UDP_HTABLE_SIZE_MIN for UDP/UDPLite hash table
allocation.

Reported-by: Mark Asselstine <mark.asselstine@windriver.com>
Reported-by: Tim Bird <tim.bird@am.sony.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 13 insertions, 20 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index ffcb3b016843..98b30d08efe9 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -3452,6 +3452,7 @@ int __init ip_rt_init(void)
                                         0,
                                         &rt_hash_log,
                                         &rt_hash_mask,
+                                        0,
                                         rhash_entries ? 0 : 512 * 1024);
         memset(rt_hash_table, 0, (rt_hash_mask + 1) * sizeof(struct rt_hash_bucket));
         rt_hash_lock_init();
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index bb485fcb077e..3ba605f60e4e 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3514,6 +3514,7 @@ void __init tcp_init(void)
                                         0,
                                         NULL,
                                         &tcp_hashinfo.ehash_mask,
+                                        0,
                                         thash_entries ? 0 : 512 * 1024);
         for (i = 0; i <= tcp_hashinfo.ehash_mask; i++) {
                 INIT_HLIST_NULLS_HEAD(&tcp_hashinfo.ehash[i].chain, i);
@@ -3530,6 +3531,7 @@ void __init tcp_init(void)
                                         0,
                                         &tcp_hashinfo.bhash_size,
                                         NULL,
+                                        0,
                                         64 * 1024);
         tcp_hashinfo.bhash_size = 1U << tcp_hashinfo.bhash_size;
         for (i = 0; i < tcp_hashinfo.bhash_size; i++) {
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 609397ee78fb..eaca73644e79 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2192,26 +2192,16 @@ void __init udp_table_init(struct udp_table *table, const char *name)
 {
         unsigned int i;
 
-        if (!CONFIG_BASE_SMALL)
-                table->hash = alloc_large_system_hash(name,
-                        2 * sizeof(struct udp_hslot),
-                        uhash_entries,
-                        21, /* one slot per 2 MB */
-                        0,
-                        &table->log,
-                        &table->mask,
-                        64 * 1024);
-        /*
-         * Make sure hash table has the minimum size
-         */
-        if (CONFIG_BASE_SMALL || table->mask < UDP_HTABLE_SIZE_MIN - 1) {
-                table->hash = kmalloc(UDP_HTABLE_SIZE_MIN *
-                                      2 * sizeof(struct udp_hslot), GFP_KERNEL);
-                if (!table->hash)
-                        panic(name);
-                table->log = ilog2(UDP_HTABLE_SIZE_MIN);
-                table->mask = UDP_HTABLE_SIZE_MIN - 1;
-        }
+        table->hash = alloc_large_system_hash(name,
+                                              2 * sizeof(struct udp_hslot),
+                                              uhash_entries,
+                                              21, /* one slot per 2 MB */
+                                              0,
+                                              &table->log,
+                                              &table->mask,
+                                              UDP_HTABLE_SIZE_MIN,
+                                              64 * 1024);
+
         table->hash2 = table->hash + (table->mask + 1);
         for (i = 0; i <= table->mask; i++) {
                 INIT_HLIST_NULLS_HEAD(&table->hash[i].head, i);