Implementation of block cloning for ZFS

Block Cloning allows to manually clone a file (or a subset of its
blocks) into another (or the same) file by just creating additional
references to the data blocks without copying the data itself.
Those references are kept in the Block Reference Tables (BRTs).

The whole design of block cloning is documented in module/zfs/brt.c.

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Christian Schwarz <christian.schwarz@nutanix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Rich Ercolani <rincebrain@gmail.com>
Signed-off-by: Pawel Jakub Dawidek <pawel@dawidek.net>
Closes #13392

include/os/linux/kernel/linux/mod_compat.h

@@ -47,6 +47,7 @@ typedef const struct kernel_param zfs_kernel_param_t;
 enum scope_prefix_types {
 	zfs,
 	zfs_arc,
+	zfs_brt,
 	zfs_condense,
 	zfs_dbuf,
 	zfs_dbuf_cache,

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

@@ -86,7 +86,8 @@ extern "C" {
 #endif
 
 #define	zn_flush_cached_data(zp, sync)	write_inode_now(ZTOI(zp), sync)
-#define	zn_rlimit_fsize(zp, uio)	(0)
+#define	zn_rlimit_fsize(size)		(0)
+#define	zn_rlimit_fsize_uio(zp, uio)	(0)
 
 /*
  * zhold() wraps igrab() on Linux, and igrab() may fail when the