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Subject: Re: [PATCH 13/15] devlink: support directly reading from region
 memory
To:     Jakub Kicinski <kuba@kernel.org>
Cc:     netdev@vger.kernel.org, jiri@resnulli.us, valex@mellanox.com,
        linyunsheng@huawei.com, lihong.yang@intel.com
References: <20200130225913.1671982-1-jacob.e.keller@intel.com>
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From:   Jacob Keller <jacob.e.keller@intel.com>
Organization: Intel Corporation
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Date:   Fri, 31 Jan 2020 11:15:39 -0800
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On 1/31/2020 10:07 AM, Jakub Kicinski wrote:
> On Thu, 30 Jan 2020 14:59:08 -0800, Jacob Keller wrote:
>> +static int devlink_nl_region_read_direct_fill(struct sk_buff *skb,
>> +					      struct devlink *devlink,
>> +					      struct devlink_region *region,
>> +					      struct nlattr **attrs,
>> +					      u64 start_offset,
>> +					      u64 end_offset,
>> +					      bool dump,
>> +					      u64 *new_offset)
>> +{
>> +	u64 curr_offset = start_offset;
>> +	int err = 0;
>> +	u8 *data;
>> +
>> +	/* Allocate and re-use a single buffer */
>> +	data = kzalloc(DEVLINK_REGION_READ_CHUNK_SIZE, GFP_KERNEL);
>> +	if (!data)
>> +		return -ENOMEM;
>> +
>> +	*new_offset = start_offset;
>> +
>> +	if (end_offset > region->size || dump)
>> +		end_offset = region->size;
>> +
>> +	while (curr_offset < end_offset) {
>> +		u32 data_size;
>> +
>> +		if (end_offset - curr_offset < DEVLINK_REGION_READ_CHUNK_SIZE)
>> +			data_size = end_offset - curr_offset;
>> +		else
>> +			data_size = DEVLINK_REGION_READ_CHUNK_SIZE;
> 
> Also known as min() ?

This was more or less adapted from the read_snapshot_fill function. I
could probably make more of an effort to share this logic.

Thanks,
Jake