[Devel] [PATCH] nfs: abort delegation in dying VE

[Kirill Tkhai]

On 15.11.2017 19:50, Stanislav Kinsburskiy wrote:
> Don't queue delegation request, if ve init is exiting.
> 
> https://jira.sw.ru/browse/PSBM-77061
> 
> Inspired-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> Signed-off-by: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
> ---
>  fs/nfs/delegation.c |   16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
> index 66af497..2422754 100644
> --- a/fs/nfs/delegation.c
> +++ b/fs/nfs/delegation.c
> @@ -189,15 +189,29 @@ void nfs_inode_reclaim_delegation(struct inode *inode, struct rpc_cred *cred,
>  	nfs_inode_set_delegation(inode, cred, res);
>  }
>  
> +static bool ve_abort_delegation(struct inode *inode)
> +{
> +	struct nfs_client *clp = NFS_SERVER(inode)->nfs_client;
> +	struct rpc_xprt *xprt;
> +
> +	rcu_read_lock();
> +	xprt = rcu_dereference(clp->cl_rpcclient->cl_xprt);
> +	rcu_read_unlock();
> +
> +	return xprt->xprt_net->owner_ve->ve_netns == NULL;

Usually, memory pointed by a pointer, which was obtained via rcu, has to be used
in rcu_read_* brackets:

rcu_read_lock();
xprt = rcu_dereference(clp->cl_rpcclient->cl_xprt);
ret = (xprt->xprt_net->owner_ve->ve_netns == NULL);
rcu_read_unlock();

return ret;

If there is no an exception, we have to do something like above.

> +}
> +
>  static int nfs_do_return_delegation(struct inode *inode, struct nfs_delegation *delegation, int issync)
>  {
>  	int res = 0;
>  
> -	if (!test_bit(NFS_DELEGATION_REVOKED, &delegation->flags))
> +	if (!test_bit(NFS_DELEGATION_REVOKED, &delegation->flags) &&
> +	    !ve_abort_delegation(inode)) {
>  		res = nfs4_proc_delegreturn(inode,
>  				delegation->cred,
>  				&delegation->stateid,
>  				issync);
> +	}
>  	nfs_free_delegation(delegation);
>  	return res;
>  }
>