NFSD: pass range end to vfs_fsync_range() instead of count

_nfsd_copy_file_range() calls vfs_fsync_range() with an offset and
count (bytes written), but the former wants the start and end bytes
of the range to sync. Fix it up.

Fixes: eac0b17 ("NFSD add vfs_fsync after async copy is done")
Signed-off-by: Brian Foster <bfoster@redhat.com>
Tested-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4proc.c

@@ -1642,6 +1642,7 @@ static ssize_t _nfsd_copy_file_range(struct nfsd4_copy *copy,
 	u64 src_pos = copy->cp_src_pos;
 	u64 dst_pos = copy->cp_dst_pos;
 	int status;
+	loff_t end;
 
 	/* See RFC 7862 p.67: */
 	if (bytes_total == 0)
@@ -1661,8 +1662,8 @@ static ssize_t _nfsd_copy_file_range(struct nfsd4_copy *copy,
 	/* for a non-zero asynchronous copy do a commit of data */
 	if (nfsd4_copy_is_async(copy) && copy->cp_res.wr_bytes_written > 0) {
 		since = READ_ONCE(dst->f_wb_err);
-		status = vfs_fsync_range(dst, copy->cp_dst_pos,
-					 copy->cp_res.wr_bytes_written, 0);
+		end = copy->cp_dst_pos + copy->cp_res.wr_bytes_written - 1;
+		status = vfs_fsync_range(dst, copy->cp_dst_pos, end, 0);
 		if (!status)
 			status = filemap_check_wb_err(dst->f_mapping, since);
 		if (!status)