rhashtable: Supports for nulls marker
In order to allow for wider usage of rhashtable, use a special nulls
marker to terminate each chain. The reason for not using the existing
nulls_list is that the prev pointer usage would not be valid as entries
can be linked in two different buckets at the same time.
The 4 nulls base bits can be set through the rhashtable_params structure
like this:
struct rhashtable_params params = {
[...]
.nulls_base = (1U << RHT_BASE_SHIFT),
};
This reduces the hash length from 32 bits to 27 bits.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/list_nulls.h b/include/linux/list_nulls.h
index 5d10ae3..e8c300e 100644
--- a/include/linux/list_nulls.h
+++ b/include/linux/list_nulls.h
@@ -21,8 +21,9 @@
struct hlist_nulls_node {
struct hlist_nulls_node *next, **pprev;
};
+#define NULLS_MARKER(value) (1UL | (((long)value) << 1))
#define INIT_HLIST_NULLS_HEAD(ptr, nulls) \
- ((ptr)->first = (struct hlist_nulls_node *) (1UL | (((long)nulls) << 1)))
+ ((ptr)->first = (struct hlist_nulls_node *) NULLS_MARKER(nulls))
#define hlist_nulls_entry(ptr, type, member) container_of(ptr,type,member)
/**