On Tue, Sep 28, 2021 at 01:30:17PM +0000, Trond Myklebust wrote: > On Tue, 2021-09-28 at 11:14 +0800, Wang Hai wrote: > > When use-gss-proxy is set to 1, write_gssp() creates a rpc client in > > gssp_rpc_create(), this increases the netns refcount by 2, these > > refcounts are supposed to be released in rpcsec_gss_exit_net(), but > > it > > will never happen because rpcsec_gss_exit_net() is triggered only > > when > > the netns refcount gets to 0, specifically: > > refcount=0 -> cleanup_net() -> ops_exit_list -> > > rpcsec_gss_exit_net > > It is a deadlock situation here, refcount will never get to 0 unless > > rpcsec_gss_exit_net() is called. So, in this case, the netns refcount > > should not be increased. > > > > In this case, xprt will take a netns refcount which is not supposed > > to be taken. Add a new flag to rpc_create_args called > > RPC_CLNT_CREATE_NO_NET_REF for not increasing the netns refcount. > > > > It is safe not to hold the netns refcount, because when > > cleanup_net(), it > > will hold the gssp_lock and then shut down the rpc client > > synchronously. > > > > > I don't like this solution at all. Adding this kind of flag is going to > lead to problems down the road. > > Is there any reason whatsoever why we need this RPC client to exist > when there is no active knfsd server? IOW: Is there any reason why we > shouldn't defer creating this RPC client for when knfsd starts up in > this net namespace, and why we can't shut it down when knfsd shuts > down? The rpc create is done in the context of the process that writes to /proc/net/rpc/use-gss-proxy to get the right namespaces. I don't know how hard it would be capture that information for a later create. --b.
