Re: [PATCH net-next nfs 0/6] Converting pernet_operations (part #7)

Kirill Tkhai
2018-03-15T14:46:45Z

On 15.03.2018 17:24, J. Bruce Fields wrote:
> On Thu, Mar 15, 2018 at 04:32:30PM +0300, Kirill Tkhai wrote:
>> Trond, Anna, Bruce, Jeff, David and other NFS and RXRPC people,
>> could you please provide your vision on this patches?
>
> Whoops, sorry, I haven't been paying attention. Do you have a pointer
> to documentation? I'm unclear what the actual concurrency change
> is--sounds like it becomes possible that e.g. multiple ->init methods
> (from the same pernet_operations but for different namespaces) could run
> in parallel?

There is a commentary near struct pernet_operations in fresh net-next.git:

struct pernet_operations {
struct list_head list;
/*
* Below methods are called without any exclusive locks.
* More than one net may be constructed and destructed
* in parallel on several cpus. Every pernet_operations
* have to keep in mind all other pernet_operations and
* to introduce a locking, if they share common resources.
*
* Exit methods using blocking RCU primitives, such as
* synchronize_rcu(), should be implemented via exit_batch.
* Then, destruction of a group of net requires single
* synchronize_rcu() related to these pernet_operations,
* instead of separate synchronize_rcu() for every net.
* Please, avoid synchronize_rcu() at all, where it's possible.
*/

I hope this is enough. Please tell me, if there is unclear thing, I'll
extend it.

> Sounds likely to be safe, and I don't actually care too much who merges
> them as they look very unlikely to conflict with anything pending. But
> unless anyone tells me otherwise I'll take the one nfsd_net_ops patch
> and leave the rest to Anna or Trond.

Sounds great. Thanks!

Kirill

>> Thanks,
>> Kirill
>>
>> On 13.03.2018 13:49, Kirill Tkhai wrote:
>>> Hi,
>>>
>>> this series continues to review and to convert pernet_operations
>>> to make them possible to be executed in parallel for several
>>> net namespaces in the same time. There are nfs pernet_operations
>>> in this series. All of them look similar each other, they mostly
>>> create and destroy caches with small exceptions.
>>>
>>> Also, there is rxrpc_net_ops, which is used in AFS.
>>>
>>> Thanks,
>>> Kirill
>>> ---
>>>
>>> Kirill Tkhai (6):
>>> net: Convert rpcsec_gss_net_ops
>>> net: Convert sunrpc_net_ops
>>> net: Convert nfsd_net_ops
>>> net: Convert nfs4_dns_resolver_ops
>>> net: Convert nfs4blocklayout_net_ops
>>> net: Convert rxrpc_net_ops
>>>
>>>
>>> fs/nfs/blocklayout/rpc_pipefs.c | 1 +
>>> fs/nfs/dns_resolve.c | 1 +
>>> fs/nfsd/nfsctl.c | 1 +
>>> net/rxrpc/net_ns.c | 1 +
>>> net/sunrpc/auth_gss/auth_gss.c | 1 +
>>> net/sunrpc/sunrpc_syms.c | 1 +
>>> 6 files changed, 6 insertions(+)
>>>
>>> --
>>> Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
>>>