| Re: [PATCH v2 2/4] NFS: release per-net clients lock before calling PipeFS dentries creation [message #45346 is a reply to message #45345] |
Mon, 27 February 2012 16:20   |
Stanislav Kinsbursky
Messages: 683
Registered: October 2011
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Senior Member |
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27.02.2012 19:59, David Laight пишет:
>
>> spin_lock(&nn->nfs_client_lock);
>> - list_for_each_entry(clp,&nn->nfs_client_list, cl_share_link) {
>> + list_for_each_entry_safe(clp, tmp,&nn->nfs_client_list,
> cl_share_link) {
>> if (clp->rpc_ops !=&nfs_v4_clientops)
>> continue;
>> + atomic_inc(&clp->cl_count);
>> + spin_unlock(&nn->nfs_client_lock);
>> error = __rpc_pipefs_event(clp, event, sb);
>> + nfs_put_client(clp);
>> if (error)
>> break;
>> + spin_lock(&nn->nfs_client_lock);
>> }
>> spin_unlock(&nn->nfs_client_lock);
>> return error;
>
> The locking doesn't look right if the loop breaks on error.
> (Same applied to patch v2 1/4)
>
Thanks for the catch. I'll fix this.
> Although list_fo_each_entry_safe() allows the current entry
> to be freed, I don't believe it allows the 'next' to be freed.
> I doubt there is protection against that happening.
>
We need to use safe macro, because client can be destroyed on nfs_put_client() call.
About "protection against ... the 'next' to be freed" - I dont' think, that we
need any protection against it. This will be done under nfs_client_lock, and
current entry list pointers will be updated properly.
> Do you need to use an atomic_inc() for cl_count.
> I'd guess the nfs_client_lock is usually held?
>
Sorry, I don't understand this question.
--
Best regards,
Stanislav Kinsbursky
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