On Fri, 2017-08-18 at 17:12 +1000, NeilBrown wrote:
> If you try an NFSv4 mount from an inaccessible server, it will hang
> as
> you would expect.
> If you then try an NFSv4 mount from a different accessible server,
> it will also hang. This is not expected.
>
> The second mount is blocked in
> nfs4_init_client()
> -> nfs4_discover_server_trunking()
> -> nfs40_discover_server_trunking()
> -> nfs40_walk_client_list()
> -> nfs4_match_client()
> -> nfs_wait_client_init_complete()
> It is waiting for the first mount to complete so that it can then
> see if the two servers are really one and the same.
>
> It is not necessary to wait here when an nfs_client cl_cons_state is
> NFS_CS_INITING. Such a client will, after changing cl_cons_state,
> call
> nfs4_discover_server_trunking() itself. So if the current client
> just
> skips those clients, trunking will still be discovered if necessary.
>
> I am unsure of situation with NFS_CS_SESSION_INITING, but I suspect
> that the comment "Wait for CREATE_SESSION to finish" implies that
> it is only clients in NFS_CS_SESSION_INITING that need to be waited
> for.
>
> Signed-off-by: NeilBrown <neilb@xxxxxxxx>
> ---
> fs/nfs/nfs4client.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
> index e9bea90dc017..d8b9b7ff19a9 100644
> --- a/fs/nfs/nfs4client.c
> +++ b/fs/nfs/nfs4client.c
> @@ -482,7 +482,7 @@ static int nfs4_match_client(struct
> nfs_client *pos, struct nfs_client *new,
> * remaining fields in "pos", especially the client
> * ID and serverowner fields. Wait for CREATE_SESSION
> * to finish. */
> - if (pos->cl_cons_state > NFS_CS_READY) {
> + if (pos->cl_cons_state == NFS_CS_SESSION_INITING) {
> atomic_inc(&pos->cl_count);
> spin_unlock(&nn->nfs_client_lock);
This could cause us to declare a false positive match with a client
that is uninitialised.
--
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@xxxxxxxxxxxxxxx
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