NFS: remove revoked delegation from server's delegation list

JIRA: https://issues.redhat.com/browse/RHEL-123617

commit 7ef6010
Author: Dai Ngo <dai.ngo@oracle.com>
Date:   Tue Oct 8 15:58:07 2024 -0700

    NFS: remove revoked delegation from server's delegation list

    After the delegation is returned to the NFS server remove it
    from the server's delegations list to reduce the time it takes
    to scan this list.

    Network trace captured while running the below script shows the
    time taken to service the CB_RECALL increases gradually due to
    the overhead of traversing the delegation list in
    nfs_delegation_find_inode_server.

    The NFS server in this test is a Solaris server which issues
    CB_RECALL when receiving the all-zero stateid in the SETATTR.

    mount=/mnt/data
    for i in $(seq 1 20)
    do
       echo $i
       mkdir $mount/testtarfile$i
       time  tar -C $mount/testtarfile$i -xf 5000_files.tar
    done

    Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
    Reviewed-by: Trond Myklebust <trond.myklebust@hammerspace.com>
    Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>

Author: bcodding-rh

fs/nfs/delegation.c

@@ -1045,6 +1045,11 @@ void nfs_delegation_mark_returned(struct inode *inode,
 	}
 
 	nfs_mark_delegation_revoked(delegation);
+	clear_bit(NFS_DELEGATION_RETURNING, &delegation->flags);
+	spin_unlock(&delegation->lock);
+	if (nfs_detach_delegation(NFS_I(inode), delegation, NFS_SERVER(inode)))
+		nfs_put_delegation(delegation);
+	goto out_rcu_unlock;
 
 out_clear_returning:
 	clear_bit(NFS_DELEGATION_RETURNING, &delegation->flags);