Re: [PATCH v7 05/10] NFSD introduce asynch copy feature

[Olga Kornievskaia <aglo@umich.edu>]

On Wed, Mar 7, 2018 at 4:05 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
> It looks like "struct nfsd_copy" is being used in at least three
> different ways: to hold the xdr arguments and reply, to hold the state
> needed while doing a copy, and to hold the callback arguments.  I wonder
> if the code would be clearer if those were three different data
> structures.

I'll take a look and see what I could do.

>> +static void dup_copy_fields(struct nfsd4_copy *src, struct nfsd4_copy *dst)
>> +{
>> +     memcpy(&dst->cp_src_stateid, &src->cp_src_stateid, sizeof(stateid_t));
>> +     memcpy(&dst->cp_dst_stateid, &src->cp_dst_stateid, sizeof(stateid_t));
>> +     dst->cp_src_pos = src->cp_src_pos;
>> +     dst->cp_dst_pos = src->cp_dst_pos;
>> +     dst->cp_count = src->cp_count;
>> +     dst->cp_consecutive = src->cp_consecutive;
>> +     dst->cp_synchronous = src->cp_synchronous;
>> +     memcpy(&dst->cp_res, &src->cp_res, sizeof(src->cp_res));
>> +     /* skipping nfsd4_callback */
>> +     memcpy(&dst->fh, &src->fh, sizeof(src->fh));
>> +     dst->net = src->net;
>> +     dst->cp_clp = src->cp_clp;
>> +     atomic_inc(&dst->cp_clp->cl_refcount);
>> +     dst->fh_dst = get_file(src->fh_dst);
>> +     dst->fh_src = get_file(src->fh_src);
>
> Just another minor gripe, but: could we name those fd_* or file_* or
> something instead of fh?  I tend to assume "fh" means "nfs filehandle".

Ok. "file_dst" and "file_src" it will be.


>
>> +}
>> +
>> +static void cleanup_async_copy(struct nfsd4_copy *copy, bool remove)
>> +{
>> +     fput(copy->fh_dst);
>> +     fput(copy->fh_src);
>> +     if (remove) {
>> +             spin_lock(&copy->cp_clp->async_lock);
>> +             list_del(&copy->copies);
>> +             spin_unlock(&copy->cp_clp->async_lock);
>> +     }
>
> I don't understand yet why you need these two cases.  Anyway, I'd rather
> you did this in the caller.  So the caller can do either:
>
>         spin_lock()
>         list_del()
>         spin_unlock()
>         cleanup_async_copy()
>
> or just
>
>         cleanup_async_copy()
>
> Or define another helper for the first case if you're really doing it a
> lot.  Just don't make me have to remember what that second argument
> means each time I see it used.

Ok I'll fix it. It was added after I changed where copy was added to
the list. In one case, now I needed to do all of the cleanup but the
copy wasn't added to the list yet.

>> +     atomic_dec(&copy->cp_clp->cl_refcount);
>> +     kfree(copy);
>> +}
> ...
>> +     copy->cp_clp = cstate->clp;
>> +     memcpy(&copy->fh, &cstate->current_fh.fh_handle,
>> +             sizeof(struct knfsd_fh));
>> +     copy->net = SVC_NET(rqstp);
>> +     /* for now disable asynchronous copy feature */
>> +     copy->cp_synchronous = 1;
>> +     if (!copy->cp_synchronous) {
>> +             status = nfsd4_init_copy_res(copy, 0);
>> +             async_copy = kzalloc(sizeof(struct nfsd4_copy), GFP_KERNEL);
>> +             if (!async_copy) {
>> +                     status = nfserrno(-ENOMEM);
>> +                     goto out;
>> +             }
>> +             dup_copy_fields(copy, async_copy);
>> +             memcpy(&copy->cp_res.cb_stateid, &copy->cp_dst_stateid,
>> +                     sizeof(copy->cp_dst_stateid));
>> +             async_copy->copy_task = kthread_create(nfsd4_do_async_copy,
>> +                             async_copy, "%s", "copy thread");
>> +             if (IS_ERR(async_copy->copy_task)) {
>> +                     status = PTR_ERR(async_copy->copy_task);
>
> status should be an nfs error.

Will fix that.

>
> --b.
>
>> +                     goto out_err;
>> +             }
>> +             spin_lock(&async_copy->cp_clp->async_lock);
>> +             list_add(&async_copy->copies,
>> +                             &async_copy->cp_clp->async_copies);
>> +             spin_unlock(&async_copy->cp_clp->async_lock);
>> +             wake_up_process(async_copy->copy_task);
>> +     } else {
>> +             status = nfsd4_do_copy(copy, 1);
>>       }
>> -
>> -     fput(src);
>> -     fput(dst);
>>  out:
>>       return status;
>> +out_err:
>> +     cleanup_async_copy(async_copy, false);
>> +     goto out;
>>  }
>>
>>  static __be32
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