Linux: i_op: use .free_inode

as per Documentation/filesystems/porting.rst:

quote:

**strongly recommended**

take the RCU-delayed parts of ->destroy_inode() into a new method -
->free_inode().  If ->destroy_inode() becomes empty - all the better,
just get rid of it.

endquote.

Signed-off-by: Pavel Snajdr <[email protected]>

Author: snajpa

include/os/linux/zfs/sys/zfs_znode_impl.h

@@ -158,6 +158,7 @@ struct znode;
 extern int	zfs_sync(struct super_block *, int, cred_t *);
 extern int	zfs_inode_alloc(struct super_block *, struct inode **ip);
 extern void	zfs_inode_destroy(struct inode *);
+extern void	zfs_inode_free(struct inode *);
 extern void	zfs_mark_inode_dirty(struct inode *);
 extern boolean_t zfs_relatime_need_update(const struct inode *);
 extern zil_replay_func_t *const zfs_replay_vector[TX_MAX_TYPE];

module/os/linux/zfs/zfs_znode_os.c

@@ -370,9 +370,14 @@ zfs_inode_alloc(struct super_block *sb, struct inode **ip)
 	return (0);
 }
 
-/*
- * Called in multiple places when an inode should be destroyed.
- */
+void
+zfs_inode_free(struct inode *ip)
+{
+	znode_t *zp = ITOZ(ip);
+
+	kmem_cache_free(znode_cache, zp);
+}
+
 void
 zfs_inode_destroy(struct inode *ip)
 {
@@ -395,7 +400,9 @@ zfs_inode_destroy(struct inode *ip)
 		zp->z_xattr_cached = NULL;
 	}
 
-	kmem_cache_free(znode_cache, zp);
+#if 0
+	zfs_inode_free(ip);
+#endif
 }
 
 static void

module/os/linux/zfs/zpl_super.c

@@ -44,9 +44,14 @@ zpl_inode_alloc(struct super_block *sb)
 }
 
 static void
+zpl_inode_free(struct inode *ip)
+{
+	zfs_inode_free(ip);
+}
+
+static void __maybe_unused
 zpl_inode_destroy(struct inode *ip)
 {
-	ASSERT(atomic_read(&ip->i_count) == 0);
 	zfs_inode_destroy(ip);
 }
 
@@ -89,6 +94,9 @@ zpl_evict_inode(struct inode *ip)
 	truncate_inode_pages_final(&ip->i_data);
 	clear_inode(ip);
 	zfs_inactive(ip);
+#if 1
+	zfs_inode_destroy(ip);
+#endif
 	spl_fstrans_unmark(cookie);
 }
 
@@ -384,7 +392,11 @@ zpl_prune_sb(uint64_t nr_to_scan, void *arg)
 
 const struct super_operations zpl_super_operations = {
 	.alloc_inode		= zpl_inode_alloc,
+#if 1
+	.free_inode		= zpl_inode_free,
+#else
 	.destroy_inode		= zpl_inode_destroy,
+#endif
 	.dirty_inode		= zpl_dirty_inode,
 	.write_inode		= NULL,
 	.evict_inode		= zpl_evict_inode,