[PATCH] dlm: fix variable key length lookup

[Alexander Aring <aahringo@redhat.com>]

Before commit 6c648035cbe7 ("dlm: switch to use rhashtable for rsbs")
the rsb hashtable was dynamic key length. Accidentally it was changed to
switch to static key length which can end in different results. We
fixing this back to the original behaviour by adding the necessary
functionality to rhashtable to handle the objects and lookups as dynamic
key lengths.

Fixes: 6c648035cbe7 ("dlm: switch to use rhashtable for rsbs")
Signed-off-by: Alexander Aring <aahringo@redhat.com>
---
 fs/dlm/config.c       | 30 ++++++++++++++++++++++++++++--
 fs/dlm/dlm_internal.h |  5 +++++
 fs/dlm/lock.c         |  6 ++++--
 3 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/fs/dlm/config.c b/fs/dlm/config.c
index 53cd332930423..6c5c3f049b33a 100644
--- a/fs/dlm/config.c
+++ b/fs/dlm/config.c
@@ -64,11 +64,37 @@ static void release_node(struct config_item *);
 static struct configfs_attribute *comm_attrs[];
 static struct configfs_attribute *node_attrs[];
 
+static u32 rsb_hashfn(const void *data, u32 len, u32 seed)
+{
+	const struct dlm_rsb_key *key = data;
+
+	return jhash(key->name, key->len, 0);
+}
+
+static u32 rsb_obj_hashfn(const void *data, u32 len, u32 seed)
+{
+	const struct dlm_rsb *r = data;
+
+	return r->res_hash;
+}
+
+static int rsb_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
+{
+	const struct dlm_rsb_key *key = arg->key;
+	const struct dlm_rsb *r = obj;
+
+	if (key->len != r->res_length)
+		return -1;
+
+	return memcmp(&r->res_name, key->name, key->len);
+}
+
 const struct rhashtable_params dlm_rhash_rsb_params = {
 	.nelem_hint = 3, /* start small */
-	.key_len = DLM_RESNAME_MAXLEN,
-	.key_offset = offsetof(struct dlm_rsb, res_name),
 	.head_offset = offsetof(struct dlm_rsb, res_node),
+	.hashfn = rsb_hashfn,
+	.obj_hashfn = rsb_obj_hashfn,
+	.obj_cmpfn = rsb_obj_cmpfn,
 	.automatic_shrinking = true,
 };
 
diff --git a/fs/dlm/dlm_internal.h b/fs/dlm/dlm_internal.h
index 9df842421ae06..74c2e77d1b553 100644
--- a/fs/dlm/dlm_internal.h
+++ b/fs/dlm/dlm_internal.h
@@ -340,6 +340,11 @@ struct dlm_rsb {
 	char			res_name[DLM_RESNAME_MAXLEN+1];
 };
 
+struct dlm_rsb_key {
+	char name[DLM_RESNAME_MAXLEN];
+	size_t len;
+};
+
 /* dlm_master_lookup() flags */
 
 #define DLM_LU_RECOVER_DIR	1
diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c
index d73c4aed1f8ac..2609e4fdeba84 100644
--- a/fs/dlm/lock.c
+++ b/fs/dlm/lock.c
@@ -625,12 +625,14 @@ static int get_rsb_struct(struct dlm_ls *ls, const void *name, int len,
 int dlm_search_rsb_tree(struct rhashtable *rhash, const void *name,
 			unsigned int len, struct dlm_rsb **r_ret)
 {
-	char key[DLM_RESNAME_MAXLEN] = {};
+	struct dlm_rsb_key key = {
+		.len = len,
+	};
 
 	if (len > DLM_RESNAME_MAXLEN)
 		return -EINVAL;
 
-	memcpy(key, name, len);
+	memcpy(key.name, name, len);
 	*r_ret = rhashtable_lookup_fast(rhash, &key, dlm_rhash_rsb_params);
 	if (*r_ret)
 		return 0;
-- 
2.43.0