NFS Share was mounted with NFSv3 but showing NFSv4 statistics

Issue

• A remote server is mounted using NFS vers=3:

nfsserver:/vol/foo/bar on /foo/bar type nfs (rw,nosuid,bg,hard,nointr,rsize=32768,wsize=32768,tcp,vers=3,timeo=600,actimeo=120,addr=w.x.y.z)

But we see NFSv4 reads and writes:

# nfsstat
Client rpc stats:
calls      retrans    authrefrsh
13468181   0          13468574

Client nfs v3:
null         getattr      setattr      lookup       access       readlink
0         0% 48434    18% 0         0% 0         0% 0         0% 0         0%
read         write        create       mkdir        symlink      mknod
0         0% 0         0% 0         0% 0         0% 0         0% 0         0%
remove       rmdir        rename       link         readdir      readdirplus
0         0% 0         0% 0         0% 0         0% 0         0% 0         0%
fsstat       fsinfo       pathconf     commit
219500   81% 2         0% 1         0% 0         0%

Client nfs v4:
null         read         write        commit       open         open_conf
0         0% 112       0% 13187629 99% 0         0% 1080      0% 0         0%
open_noat    open_dgrd    close        setattr      fsinfo       renew
0         0% 0         0% 1080      0% 2048      0% 168       0% 340       0%
setclntid    confirm      lock         lockt        locku        access
56        0% 56        0% 0         0% 0         0% 0         0% 2359      0%
getattr      lookup       lookup_root  remove       rename       link
537       0% 2736      0% 56        0% 856       0% 0         0% 0         0%
symlink      create       pathconf     statfs       readlink     readdir
0         0% 56        0% 112       0% 352       0% 0         0% 168       0%
server_caps  delegreturn  getacl       setacl       fs_locations rel_lkowner
280       0% 0         0% 0         0% 0         0% 0         0% 0         0%
exchange_id  create_ses   destroy_ses  sequence     get_lease_t  reclaim_comp
0         0% 0         0% 0         0% 0         0% 0         0% 0         0%
layoutget    layoutcommit layoutreturn getdevlist   getdevinfo   ds_write
0         0% 0         0% 0         0% 0         0% 0         0% 0         0%
ds_commit
0         0%