9p: Drop kref usage

An upcoming patch is going to require passing the client through
p9_req_put() -> p9_req_free(), but that's awkward with the kref
indirection - so this patch switches to using refcount_t directly.

Link: https://lkml.kernel.org/r/20220704014243.153050-1-kent.overstreet@gmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

include/net/9p/client.h

@@ -77,7 +77,7 @@ enum p9_req_status_t {
 struct p9_req_t {
 	int status;
 	int t_err;
-	struct kref refcount;
+	refcount_t refcount;
 	wait_queue_head_t wq;
 	struct p9_fcall tc;
 	struct p9_fcall rc;
@@ -228,12 +228,12 @@ struct p9_req_t *p9_tag_lookup(struct p9_client *c, u16 tag);
 
 static inline void p9_req_get(struct p9_req_t *r)
 {
-	kref_get(&r->refcount);
+	refcount_inc(&r->refcount);
 }
 
 static inline int p9_req_try_get(struct p9_req_t *r)
 {
-	return kref_get_unless_zero(&r->refcount);
+	return refcount_inc_not_zero(&r->refcount);
 }
 
 int p9_req_put(struct p9_req_t *r);

net/9p/client.c

@@ -305,7 +305,7 @@ p9_tag_alloc(struct p9_client *c, int8_t type, unsigned int max_size)
 	 * callback), so p9_client_cb eats the second ref there
 	 * as the pointer is duplicated directly by virtqueue_add_sgs()
 	 */
-	refcount_set(&req->refcount.refcount, 2);
+	refcount_set(&req->refcount, 2);
 
 	return req;
 
@@ -370,18 +370,15 @@ static int p9_tag_remove(struct p9_client *c, struct p9_req_t *r)
 	return p9_req_put(r);
 }
 
-static void p9_req_free(struct kref *ref)
-{
-	struct p9_req_t *r = container_of(ref, struct p9_req_t, refcount);
-
-	p9_fcall_fini(&r->tc);
-	p9_fcall_fini(&r->rc);
-	kmem_cache_free(p9_req_cache, r);
-}
-
 int p9_req_put(struct p9_req_t *r)
 {
-	return kref_put(&r->refcount, p9_req_free);
+	if (refcount_dec_and_test(&r->refcount)) {
+		p9_fcall_fini(&r->tc);
+		p9_fcall_fini(&r->rc);
+		kmem_cache_free(p9_req_cache, r);
+		return 1;
+	}
+	return 0;
 }
 EXPORT_SYMBOL(p9_req_put);