This hashtable implementation is using hlist buckets to provide a simple
hashtable to prevent it from getting reimplemented all over the kernel.
Signed-off-by: Sasha Levin <levinsasha...@gmail.com>
---
Changes from v4:
- Addressed comments by Mathieu Desnoyers.
include/linux/hashtable.h | 190 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 190 insertions(+)
create mode 100644 include/linux/hashtable.h
diff --git a/include/linux/hashtable.h b/include/linux/hashtable.h
new file mode 100644
index 0000000..6d0c6c2
--- /dev/null
+++ b/include/linux/hashtable.h
@@ -0,0 +1,190 @@
+/*
+ * Hash table implementation
+ * (C) 2012 Sasha Levin <levinsasha...@gmail.com>
+ */
+
+#ifndef _LINUX_HASHTABLE_H
+#define _LINUX_HASHTABLE_H
+
+#include <linux/list.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/hash.h>
+#include <linux/rculist.h>
+
+#define DEFINE_HASHTABLE(name, bits)
\
+ struct hlist_head name[HASH_SIZE(bits)] =
\
+ { [0 ... HASH_SIZE(bits) - 1] = HLIST_HEAD_INIT }
+
+#define DECLARE_HASHTABLE(name, bits)
\
+ struct hlist_head name[1 << (bits)]
+
+#define HASH_SIZE(name) (1 << HASH_BITS(name))
+#define HASH_BITS(name) ilog2(ARRAY_SIZE(name))
+
+/* Use hash_32 when possible to allow for fast 32bit hashing in 64bit kernels.
*/
+#define hash_min(val, bits)
\
+({
\
+ sizeof(val) <= 4 ?
\
+ hash_32(val, bits) :
\
+ hash_long(val, bits);
\
+})
+
+/**
+ * hash_init - initialize a hash table
+ * @hashtable: hashtable to be initialized
+ *
+ * Calculates the size of the hashtable from the given parameter, otherwise
+ * same as hash_init_size.
+ *
+ * This has to be a macro since HASH_BITS() will not work on pointers since
+ * it calculates the size during preprocessing.
+ */
+#define hash_init(hashtable)
\
+({
\
+ int __i;
\
+
\
+ for (__i = 0; __i < HASH_BITS(hashtable); __i++)
\
+ INIT_HLIST_HEAD(&hashtable[__i]);
\
+})
+
+/**
+ * hash_add - add an object to a hashtable
+ * @hashtable: hashtable to add to
+ * @node: the &struct hlist_node of the object to be added
+ * @key: the key of the object to be added
+ */
+#define hash_add(hashtable, node, key)
\
+ hlist_add_head(node, &hashtable[hash_min(key, HASH_BITS(hashtable))]);
+
+/**
+ * hash_add_rcu - add an object to a rcu enabled hashtable
+ * @hashtable: hashtable to add to
+ * @node: the &struct hlist_node of the object to be added
+ * @key: the key of the object to be added
+ */
+#define hash_add_rcu(hashtable, node, key)
\
+ hlist_add_head_rcu(node, &hashtable[hash_min(key,
HASH_BITS(hashtable))]);
+
+/**
+ * hash_hashed - check whether an object is in any hashtable
+ * @node: the &struct hlist_node of the object to be checked
+ */
+#define hash_hashed(node) (!hlist_unhashed(node))
+
+/**
+ * hash_empty - check whether a hashtable is empty
+ * @hashtable: hashtable to check
+ *
+ * This has to be a macro since HASH_BITS() will not work on pointers since
+ * it calculates the size during preprocessing.
+ */
+#define hash_empty(hashtable)
\
+({
\
+ int __i;
\
+ bool __ret = true;
\
+
\
+ for (__i = 0; __i < HASH_SIZE(hashtable); __i++)
\
+ if (!hlist_empty(&hashtable[__i]))
\
+ __ret = false;
\
+
\
+ __ret;
\
+})
+
+/**
+ * hash_del - remove an object from a hashtable
+ * @node: &struct hlist_node of the object to remove
+ */
+static inline void hash_del(struct hlist_node *node)
+{
+ hlist_del_init(node);
+}
+
+/**
+ * hash_del_rcu - remove an object from a rcu enabled hashtable
+ * @node: &struct hlist_node of the object to remove
+ */
+static inline void hash_del_rcu(struct hlist_node *node)
+{
+ hlist_del_init_rcu(node);
+}
+
+/**
+ * hash_for_each - iterate over a hashtable
+ * @name: hashtable to iterate
+ * @bkt: integer to use as bucket loop cursor
+ * @node: the &struct list_head to use as a loop cursor for each entry
+ * @obj: the type * to use as a loop cursor for each entry
+ * @member: the name of the hlist_node within the struct
+ */
+#define hash_for_each(name, bkt, node, obj, member)
\
+ for (bkt = 0, node = NULL; node == NULL && bkt < HASH_SIZE(name);
bkt++)\
+ hlist_for_each_entry(obj, node, &name[bkt], member)
+
+/**
+ * hash_for_each_rcu - iterate over a rcu enabled hashtable
+ * @name: hashtable to iterate
+ * @bkt: integer to use as bucket loop cursor
+ * @node: the &struct list_head to use as a loop cursor for each entry
+ * @obj: the type * to use as a loop cursor for each entry
+ * @member: the name of the hlist_node within the struct
+ */
+#define hash_for_each_rcu(name, bkt, node, obj, member)
\
+ for (bkt = 0, node = NULL; node == NULL && bkt < HASH_SIZE(name);
bkt++)\
+ hlist_for_each_entry_rcu(obj, node, &name[bkt], member)
+
+/**
+ * hash_for_each_safe - iterate over a hashtable safe against removal of
+ * hash entry
+ * @name: hashtable to iterate
+ * @bkt: integer to use as bucket loop cursor
+ * @node: the &struct list_head to use as a loop cursor for each entry
+ * @tmp: a &struct used for temporary storage
+ * @obj: the type * to use as a loop cursor for each entry
+ * @member: the name of the hlist_node within the struct
+ */
+#define hash_for_each_safe(name, bkt, node, tmp, obj, member)
\
+ for (bkt = 0, node = NULL; node == NULL && bkt < HASH_SIZE(name);
bkt++)\
+ hlist_for_each_entry_safe(obj, node, tmp, &name[bkt], member)
+
+/**
+ * hash_for_each_possible - iterate over all possible objects hashing to the
+ * same bucket
+ * @name: hashtable to iterate
+ * @obj: the type * to use as a loop cursor for each entry
+ * @node: the &struct list_head to use as a loop cursor for each entry
+ * @member: the name of the hlist_node within the struct
+ * @key: the key of the objects to iterate over
+ */
+#define hash_for_each_possible(name, obj, node, member, key)
\
+ hlist_for_each_entry(obj, node, &name[hash_min(key, HASH_BITS(name))],
member)
+
+/**
+ * hash_for_each_possible_rcu - iterate over all possible objects hashing to
the
+ * same bucket in an rcu enabled hashtable
+ * in a rcu enabled hashtable
+ * @name: hashtable to iterate
+ * @obj: the type * to use as a loop cursor for each entry
+ * @node: the &struct list_head to use as a loop cursor for each entry
+ * @member: the name of the hlist_node within the struct
+ * @key: the key of the objects to iterate over
+ */
+#define hash_for_each_possible_rcu(name, obj, node, member, key)
\
+ hlist_for_each_entry_rcu(obj, node, &name[hash_min(key,
HASH_BITS(name))], member)
+
+/**
+ * hash_for_each_possible_safe - iterate over all possible objects hashing to
the
+ * same bucket safe against removals
+ * @name: hashtable to iterate
+ * @obj: the type * to use as a loop cursor for each entry
+ * @node: the &struct list_head to use as a loop cursor for each entry
+ * @tmp: a &struct used for temporary storage
+ * @member: the name of the hlist_node within the struct
+ * @key: the key of the objects to iterate over
+ */
+#define hash_for_each_possible_safe(name, obj, node, tmp, member, key)
\
+ hlist_for_each_entry_safe(obj, node, tmp,
\
+ &name[hash_min(key, HASH_BITS(name))], member)
+
+
+#endif
--
1.7.12
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