netdev - Re: [PATCH 08/10] devlink: implement DEVLINK_CMD_REGION

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Date:   Wed, 25 Mar 2020 18:30:35 -0700
From:   Jacob Keller <jacob.e.keller@...el.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH 08/10] devlink: implement DEVLINK_CMD_REGION_NEW



On 3/25/2020 9:46 AM, Jiri Pirko wrote:
> Tue, Mar 24, 2020 at 11:34:43PM CET, jacob.e.keller@...el.com wrote:
>> +
>> +	/* Check to make sure it's empty first */
>> +	if (xa_load(&devlink->snapshot_ids, id))
> 
> How this can happen? The entry was just allocated. WARN_ON.
> 

Sure, I'll add WARN_ON. I think the return should still be kept, since
it causes the caller to fail instead of accidentally overwriting the
snapshot count.

> 
>> +		return -EBUSY;
>> +
>> +	err = xa_err(xa_store(&devlink->snapshot_ids, id, xa_mk_value(0),
>> +			      GFP_KERNEL));
> 
> Just return and avoid err variable.
> 

Yep, done.


>> +
>> +	if (region->cur_snapshots == region->max_snapshots) {
>> +		NL_SET_ERR_MSG_MOD(info->extack, "The region has reached the maximum number of stored snapshots");
>> +		return -ENOMEM;
> 
> Maybe ENOBUFS or ENOSPC? ENOMEM seems odd as it is related to memory
> allocation fails which this is not.
> 

Hmmm. This actually appears to be duplicated from the snapshot_create
function which used ENOMEM. Will add a patch to clean that up first.

It seems like we end up duplicating checks from within the
__devlink_region_snapshot_create merely because we have the extack
pointer here...

> 
>> +	}
>> +
>> +	snapshot_id = nla_get_u32(info->attrs[DEVLINK_ATTR_REGION_SNAPSHOT_ID]);
>> +
>> +	if (devlink_region_snapshot_get_by_id(region, snapshot_id)) {
>> +		NL_SET_ERR_MSG_MOD(info->extack, "The requested snapshot id is already in use");
>> +		return -EEXIST;
>> +	}
>> +
>> +	err = __devlink_snapshot_id_insert(devlink, snapshot_id);
>> +	if (err) {
>> +		NL_SET_ERR_MSG_MOD(info->extack, "The requested snapshot id is already in used");
> 
> Different message would be appropriate.
> 

Right. This is the "this shouldn't happen" case from above I think.

> 
>> +		return err;
>> +	}
>> +
>> +	err = region->ops->snapshot(devlink, info->extack, &data);
>> +	if (err)
>> +		goto err_decrement_snapshot_count;
>> +
>> +	err = __devlink_region_snapshot_create(region, data, snapshot_id);
>> +	if (err)
>> +		goto err_free_snapshot_data;
>> +
>> +	return 0;
>> +
>> +err_decrement_snapshot_count:
>> +	__devlink_snapshot_id_decrement(devlink, snapshot_id);
>> +err_free_snapshot_data:
> 
> In devlink the error labers are named according to actions that failed.
> Please align.
> 

Sure.

Thanks,
Jake