How does the fuser command works ?

Issue

On a NFSv3 client, a mount point is configured and mounted without problems similar to this:

server:/vol/export  /mount/export nfs vers=3,rsize=32768,wsize=32768,rw,suid,soft  0 0

When the command fuser is run although it works, these errors are sometimes seen:

$ fuser *
Cannot stat file /proc/3660/fd/293: Stale NFS file handle
Cannot stat file /proc/3660/fd/297: Stale NFS file handle
Cannot stat file /proc/4230/fd/294: Stale NFS file handle
Cannot stat file /proc/4230/fd/561: Stale NFS file handle

When one of the reported processes is analysed there's always the same error about one deleted file:

$ lsof -d 293                
COMMAND    PID     USER   FD      TYPE     DEVICE SIZE NODE NAME
command   3660     user  293u    unknown    0,22            /path/to/log/file (deleted) (server:/vol/export)