Remove atomics from zh_refcount

It is protected by z_hold_locks, so we do not need more serialization,
simple integer math should be fine.

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Ryan Moeller <[email protected]>
Reviewed-by: Richard Yao <[email protected]>
Signed-off-by:  Alexander Motin <[email protected]>
Closes openzfs#14196

Author: amotin

include/sys/zfs_znode.h

@@ -242,9 +242,9 @@ zfs_enter_verify_zp(zfsvfs_t *zfsvfs, znode_t *zp, const char *tag)
 
 typedef struct znode_hold {
 	uint64_t	zh_obj;		/* object id */
-	kmutex_t	zh_lock;	/* lock serializing object access */
 	avl_node_t	zh_node;	/* avl tree linkage */
-	zfs_refcount_t	zh_refcount;	/* active consumer reference count */
+	kmutex_t	zh_lock;	/* lock serializing object access */
+	int		zh_refcount;	/* active consumer reference count */
 } znode_hold_t;
 
 static inline uint64_t

module/os/linux/zfs/zfs_znode.c

@@ -169,8 +169,7 @@ zfs_znode_hold_cache_constructor(void *buf, void *arg, int kmflags)
 	znode_hold_t *zh = buf;
 
 	mutex_init(&zh->zh_lock, NULL, MUTEX_DEFAULT, NULL);
-	zfs_refcount_create(&zh->zh_refcount);
-	zh->zh_obj = ZFS_NO_OBJECT;
+	zh->zh_refcount = 0;
 
 	return (0);
 }
@@ -182,7 +181,6 @@ zfs_znode_hold_cache_destructor(void *buf, void *arg)
 	znode_hold_t *zh = buf;
 
 	mutex_destroy(&zh->zh_lock);
-	zfs_refcount_destroy(&zh->zh_refcount);
 }
 
 void
@@ -281,26 +279,26 @@ zfs_znode_hold_enter(zfsvfs_t *zfsvfs, uint64_t obj)
 	boolean_t found = B_FALSE;
 
 	zh_new = kmem_cache_alloc(znode_hold_cache, KM_SLEEP);
-	zh_new->zh_obj = obj;
 	search.zh_obj = obj;
 
 	mutex_enter(&zfsvfs->z_hold_locks[i]);
 	zh = avl_find(&zfsvfs->z_hold_trees[i], &search, NULL);
 	if (likely(zh == NULL)) {
 		zh = zh_new;
+		zh->zh_obj = obj;
 		avl_add(&zfsvfs->z_hold_trees[i], zh);
 	} else {
 		ASSERT3U(zh->zh_obj, ==, obj);
 		found = B_TRUE;
 	}
-	zfs_refcount_add(&zh->zh_refcount, NULL);
+	zh->zh_refcount++;
+	ASSERT3S(zh->zh_refcount, >, 0);
 	mutex_exit(&zfsvfs->z_hold_locks[i]);
 
 	if (found == B_TRUE)
 		kmem_cache_free(znode_hold_cache, zh_new);
 
 	ASSERT(MUTEX_NOT_HELD(&zh->zh_lock));
-	ASSERT3S(zfs_refcount_count(&zh->zh_refcount), >, 0);
 	mutex_enter(&zh->zh_lock);
 
 	return (zh);
@@ -313,11 +311,11 @@ zfs_znode_hold_exit(zfsvfs_t *zfsvfs, znode_hold_t *zh)
 	boolean_t remove = B_FALSE;
 
 	ASSERT(zfs_znode_held(zfsvfs, zh->zh_obj));
-	ASSERT3S(zfs_refcount_count(&zh->zh_refcount), >, 0);
 	mutex_exit(&zh->zh_lock);
 
 	mutex_enter(&zfsvfs->z_hold_locks[i]);
-	if (zfs_refcount_remove(&zh->zh_refcount, NULL) == 0) {
+	ASSERT3S(zh->zh_refcount, >, 0);
+	if (--zh->zh_refcount == 0) {
 		avl_remove(&zfsvfs->z_hold_trees[i], zh);
 		remove = B_TRUE;
 	}