tcp: fix/cleanup inet_ehash_locks_alloc()

If tcp ehash table is constrained to a very small number of buckets
(eg boot parameter thash_entries=128), then we can crash if spinlock
array has more entries.

While we are at it, un-inline inet_ehash_locks_alloc() and make
following changes :

- Budget 2 cache lines per cpu worth of 'spinlocks'
- Try to kmalloc() the array to avoid extra TLB pressure.
  (Most servers at Google allocate 8192 bytes for this hash table)
- Get rid of various #ifdef

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 31 insertions, 0 deletions

diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 3766bddb3e8a..185efef0f125 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -18,6 +18,7 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/wait.h>
+#include <linux/vmalloc.h>
 
 #include <net/inet_connection_sock.h>
 #include <net/inet_hashtables.h>
@@ -609,3 +610,33 @@ void inet_hashinfo_init(struct inet_hashinfo *h)
                 }
 }
 EXPORT_SYMBOL_GPL(inet_hashinfo_init);
+
+int inet_ehash_locks_alloc(struct inet_hashinfo *hashinfo)
+{
+        unsigned int i, nblocks = 1;
+
+        if (sizeof(spinlock_t) != 0) {
+                /* allocate 2 cache lines or at least one spinlock per cpu */
+                nblocks = max_t(unsigned int,
+                                2 * L1_CACHE_BYTES / sizeof(spinlock_t),
+                                1);
+                nblocks = roundup_pow_of_two(nblocks * num_possible_cpus());
+
+                /* no more locks than number of hash buckets */
+                nblocks = min(nblocks, hashinfo->ehash_mask + 1);
+
+                hashinfo->ehash_locks = kmalloc_array(nblocks, sizeof(spinlock_t),
+                                                      GFP_KERNEL | __GFP_NOWARN);
+                if (!hashinfo->ehash_locks)
+                        hashinfo->ehash_locks = vmalloc(nblocks * sizeof(spinlock_t));
+
+                if (!hashinfo->ehash_locks)
+                        return -ENOMEM;
+
+                for (i = 0; i < nblocks; i++)
+                        spin_lock_init(&hashinfo->ehash_locks[i]);
+        }
+        hashinfo->ehash_locks_mask = nblocks - 1;
+        return 0;
+}
+EXPORT_SYMBOL_GPL(inet_ehash_locks_alloc);