rhashtable: Add cap on number of elements in hash table

[mirror_ubuntu-artful-kernel.git] / include / linux / rhashtable.h

diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index dbcbcc59aa92e77de6c1c6065b403c0fa7d0dd15..843ceca9a21e5f1327fa5c82fa5f3089c5ebab23 100644 (file)
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -17,6 +17,7 @@
 #ifndef _LINUX_RHASHTABLE_H
 #define _LINUX_RHASHTABLE_H
 
+#include <linux/atomic.h>
 #include <linux/compiler.h>
 #include <linux/errno.h>
 #include <linux/jhash.h>
@@ -100,6 +101,7 @@ struct rhashtable;
  * @key_len: Length of key
  * @key_offset: Offset of key in struct to be hashed
  * @head_offset: Offset of rhash_head in struct to be hashed
+ * @insecure_max_entries: Maximum number of entries (may be exceeded)
  * @max_size: Maximum size while expanding
  * @min_size: Minimum size while shrinking
  * @nulls_base: Base value to generate nulls marker
@@ -115,6 +117,7 @@ struct rhashtable_params {
        size_t                  key_len;
        size_t                  key_offset;
        size_t                  head_offset;
+       unsigned int            insecure_max_entries;
        unsigned int            max_size;
        unsigned int            min_size;
        u32                     nulls_base;
@@ -286,6 +289,18 @@ static inline bool rht_grow_above_100(const struct rhashtable *ht,
                (!ht->p.max_size || tbl->size < ht->p.max_size);
 }
 
+/**
+ * rht_grow_above_max - returns true if table is above maximum
+ * @ht:                hash table
+ * @tbl:       current table
+ */
+static inline bool rht_grow_above_max(const struct rhashtable *ht,
+                                     const struct bucket_table *tbl)
+{
+       return ht->p.insecure_max_entries &&
+              atomic_read(&ht->nelems) >= ht->p.insecure_max_entries;
+}
+
 /* The bucket lock is selected based on the hash and protects mutations
  * on a group of hash buckets.
  *
@@ -589,6 +604,10 @@ restart:
                goto out;
        }
 
+       err = -E2BIG;
+       if (unlikely(rht_grow_above_max(ht, tbl)))
+               goto out;
+
        if (unlikely(rht_grow_above_100(ht, tbl))) {
 slow_path:
                spin_unlock_bh(lock);