backports: Add rhashtable_lookup_get_insert_fast()

rhashtable_lookup_get_insert_fast() was added in kernel 4.12 in Linux
upstream commit f9fe1c12d12 ("rhashtable: Add
rhashtable_lookup_get_insert_fast") It is now used by mac80211.

For kernel < 4.9 we already backport the complete rhashtable
implementation, so this is only needed for kernels more recent than 4.9.

This is copied from upstreamn Linux kernel.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

1 files changed, 31 insertions, 0 deletions

diff --git a/backport/backport-include/linux/rhashtable.h b/backport/backport-include/linux/rhashtable.h
new file mode 100644
index 00000000..8e493bc5
--- /dev/null
+++ b/backport/backport-include/linux/rhashtable.h
@@ -0,0 +1,31 @@
+#ifndef __BACKPORT_RHASHTABLE_H
+#define __BACKPORT_RHASHTABLE_H
+#include_next <linux/rhashtable.h>
+#include <linux/version.h>
+
+#if LINUX_VERSION_IS_LESS(4,12,0)
+/**
+ * rhashtable_lookup_get_insert_fast - lookup and insert object into hash table
+ * @ht:		hash table
+ * @obj:	pointer to hash head inside object
+ * @params:	hash table parameters
+ *
+ * Just like rhashtable_lookup_insert_fast(), but this function returns the
+ * object if it exists, NULL if it did not and the insertion was successful,
+ * and an ERR_PTR otherwise.
+ */
+#define rhashtable_lookup_get_insert_fast LINUX_BACKPORT(rhashtable_lookup_get_insert_fast)
+static inline void *rhashtable_lookup_get_insert_fast(
+	struct rhashtable *ht, struct rhash_head *obj,
+	const struct rhashtable_params params)
+{
+	const char *key = rht_obj(ht, obj);
+
+	BUG_ON(ht->p.obj_hashfn);
+
+	return __rhashtable_insert_fast(ht, key + ht->p.key_offset, obj, params,
+					false);
+}
+#endif
+
+#endif /* __BACKPORT_RHASHTABLE_H */