nfscl: Make vfs.nfs.maxcopyrange larger by default

As of commit 103b207536, the NFSv4.2 server will limit the size
of a Copy operation based upon a 1 second timeout.  The Linux 5.2
kernel server also limits Copy operation size to 4Mbytes.
As such, the NFSv4.2 client can attempt a large Copy without
resulting in a long RPC RTT for these servers.

This patch changes vfs.nfs.maxcopyrange to 64bits and sets
the default to the maximum possible size of SSIZE_MAX, since
a larger size makes the Copy operation more efficient and
allows for copying to complete with fewer RPCs.
The sysctl may be need to be made smaller for other non-FreeBSD
NFSv4.2 servers.

MFC after:	2 weeks

sys/fs/nfs/nfs_commonsubs.c

@@ -95,10 +95,6 @@ int nfsrv_maxpnfsmirror = 1;
 SYSCTL_INT(_vfs_nfs, OID_AUTO, pnfsmirror, CTLFLAG_RD,
     &nfsrv_maxpnfsmirror, 0, "Mirror level for pNFS service");
 
-int nfs_maxcopyrange = 10 * 1024 * 1024;
-SYSCTL_INT(_vfs_nfs, OID_AUTO, maxcopyrange, CTLFLAG_RW,
-    &nfs_maxcopyrange, 0, "Max size of a Copy so RPC times reasonable");
-
 /*
  * This array of structures indicates, for V4:
  * retfh - which of 3 types of calling args are used

sys/fs/nfsclient/nfs_clrpcops.c

@@ -62,6 +62,10 @@ static int	nfscl_dssameconn = 0;
 SYSCTL_INT(_vfs_nfs, OID_AUTO, dssameconn, CTLFLAG_RW,
     &nfscl_dssameconn, 0, "Use same TCP connection to multiple DSs");
 
+static uint64_t nfs_maxcopyrange = SSIZE_MAX;
+SYSCTL_U64(_vfs_nfs, OID_AUTO, maxcopyrange, CTLFLAG_RW,
+    &nfs_maxcopyrange, 0, "Max size of a Copy so RPC times reasonable");
+
 /*
  * Global variables
  */
@@ -75,7 +79,6 @@ extern char nfsv4_callbackaddr[INET6_ADDRSTRLEN];
 extern int nfscl_debuglevel;
 extern int nfs_pnfsiothreads;
 extern u_long sb_max_adj;
-extern int nfs_maxcopyrange;
 NFSCLSTATEMUTEX;
 int nfstest_outofseq = 0;
 int nfscl_assumeposixlocks = 1;