Re: [PATCH 06/21] nfs client: exit_net cleanup check added

[Trond Myklebust]

On Sun, 2017-11-05 at 19:48 +0300, Vasily Averin wrote:
> On 2017-11-05 19:02, Trond Myklebust wrote:
> > On Sun, 2017-11-05 at 13:00 +0300, Vasily Averin wrote:
> > > Be sure that nfs_client_list and nfs_volume_list lists
> > > initialized
> > > in net_init hook were return to initial state in net_exit hook.
> > > 
> > > Signed-off-by: Vasily Averin 
> > > ---
> > >  fs/nfs/client.c | 4 
> > >  1 file changed, 4 insertions(+)
> > > 
> > > diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> > > index 22880ef..7c0691c 100644
> > > --- a/fs/nfs/client.c
> > > +++ b/fs/nfs/client.c
> > > @@ -204,6 +204,10 @@ void nfs_cleanup_cb_ident_idr(struct net
> > > *net)
> > >   struct nfs_net *nn = net_generic(net, nfs_net_id);
> > >  
> > >   idr_destroy(>cb_ident_idr);
> > > + WARN(!list_empty(>nfs_client_list),
> > > +  "net %p exit: nfs_client_list is not empty\n",
> > > net);
> > > + WARN(!list_empty(>nfs_volume_list),
> > > +  "net %p exit: nfs_volume_list is not empty\n",
> > > net);
> > >  }
> > >  
> > 
> > Why do we need these? Is there a specific bug that you are trying
> > to
> > track down?
> 
> I hope such checks allows to detect leaked per-netns objects.
> Also I hope that all new pernet_operations will inherit such checks
> too.
> 
> I assume that elements added into per-net lists should not live
> longer than net namespace,
> and should be deleted from the list. I think exit_net hook is good
> place for such check.
> 
> Recently I've found lost list_entry and enabled timer on stop of net
> namespace.
> Then I've reviewed all existing pernet_operations and found that many
> drivers
> have such checks already. So I decided to complete this task and add
> such checks
> into all affected subsystems.
> 

Unless there is a known problem that has specific debugging needs, this
kind of assert should take the form of a WARN_ONCE() so that it doesn't
fill user syslogs with redundant warnings if triggered.

-- 
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.mykleb...@primarydata.com

Re: [PATCH 06/21] nfs client: exit_net cleanup check added

[Vasily Averin]

On 2017-11-05 19:02, Trond Myklebust wrote:
> On Sun, 2017-11-05 at 13:00 +0300, Vasily Averin wrote:
>> Be sure that nfs_client_list and nfs_volume_list lists initialized
>> in net_init hook were return to initial state in net_exit hook.
>>
>> Signed-off-by: Vasily Averin 
>> ---
>>  fs/nfs/client.c | 4 
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
>> index 22880ef..7c0691c 100644
>> --- a/fs/nfs/client.c
>> +++ b/fs/nfs/client.c
>> @@ -204,6 +204,10 @@ void nfs_cleanup_cb_ident_idr(struct net *net)
>>  struct nfs_net *nn = net_generic(net, nfs_net_id);
>>  
>>  idr_destroy(>cb_ident_idr);
>> +WARN(!list_empty(>nfs_client_list),
>> + "net %p exit: nfs_client_list is not empty\n", net);
>> +WARN(!list_empty(>nfs_volume_list),
>> + "net %p exit: nfs_volume_list is not empty\n", net);
>>  }
>>  
> 
> Why do we need these? Is there a specific bug that you are trying to
> track down?

I hope such checks allows to detect leaked per-netns objects.
Also I hope that all new pernet_operations will inherit such checks too.

I assume that elements added into per-net lists should not live longer than net 
namespace,
and should be deleted from the list. I think exit_net hook is good place for 
such check.

Recently I've found lost list_entry and enabled timer on stop of net namespace.
Then I've reviewed all existing pernet_operations and found that many drivers
have such checks already. So I decided to complete this task and add such checks
into all affected subsystems.

Re: [PATCH 06/21] nfs client: exit_net cleanup check added

[Trond Myklebust]

On Sun, 2017-11-05 at 13:00 +0300, Vasily Averin wrote:
> Be sure that nfs_client_list and nfs_volume_list lists initialized
> in net_init hook were return to initial state in net_exit hook.
> 
> Signed-off-by: Vasily Averin 
> ---
>  fs/nfs/client.c | 4 
>  1 file changed, 4 insertions(+)
> 
> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> index 22880ef..7c0691c 100644
> --- a/fs/nfs/client.c
> +++ b/fs/nfs/client.c
> @@ -204,6 +204,10 @@ void nfs_cleanup_cb_ident_idr(struct net *net)
>   struct nfs_net *nn = net_generic(net, nfs_net_id);
>  
>   idr_destroy(>cb_ident_idr);
> + WARN(!list_empty(>nfs_client_list),
> +  "net %p exit: nfs_client_list is not empty\n", net);
> + WARN(!list_empty(>nfs_volume_list),
> +  "net %p exit: nfs_volume_list is not empty\n", net);
>  }
>  

Why do we need these? Is there a specific bug that you are trying to
track down?

-- 
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.mykleb...@primarydata.com