| Re: [PATCH] NFS: init client before declaration [message #46475 is a reply to message #46469] |
Tue, 22 May 2012 15:03  |
Stanislav Kinsbursky
Messages: 683
Registered: October 2011
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Senior Member |
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On 22.05.2012 18:29, Myklebust, Trond wrote:
> On Tue, 2012-05-22 at 16:40 +0400, Stanislav Kinsbursky wrote:
>> Client have to be initialized prior to adding it to per-net clients list,
>> because otherwise there are races, shown below:
>>
>> CPU#0 CPU#1
>> _____ _____
>>
>> nfs_get_client
>> nfs_alloc_client
>> list_add(..., nfs_client_list)
>> rpc_fill_super
>> rpc_pipefs_event
>> nfs_get_client_for_event
>> __rpc_pipefs_event
>> (clp->cl_rpcclient is uninitialized)
>> BUG()
>> init_client
>> clp->cl_rpcclient = ...
>>
>
> Why not simply change nfs_get_client_for_event() so that it doesn't
> touch nfs_clients that have clp->cl_cons_state!=NFS_CS_READY?
>
> That should ensure that it doesn't touch nfs_clients that failed to
> initialise and/or are still in the process of being initialised.
>
It looks like in this case we will have another races:
CPU#0 CPU#1
_____ _____
nfs4_init_client
nfs_idmap_new
nfs_idmap_register
rpc_get_sb_net (fail - no pipefs)
rpc_fill_super
rpc_pipefs_event
nfs_get_client_for_event
(skip client - NFS_CS_READY is not set)
nfs_mark_client_ready(NFS_CS_READY)
And we are having client without idmap pipe...
> Cheers
> Trond
>
--
Best regards,
Stanislav Kinsbursky
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