Re: [PATCH v2 1/3] libata: fix reading concurrent positioning ranges log

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

On 6/3/22 15:17, Hannes Reinecke wrote:
> On 6/3/22 00:51, Tyler Erickson wrote:
>> The concurrent positioning ranges log is not a fixed size and may depend
>> on how many ranges are supported by the device. This patch uses the size
>> reported in the GPL directory to determine the number of pages supported
>> by the device before attempting to read this log page.
>>
>> This resolves this error from the dmesg output:
>>      ata6.00: Read log 0x47 page 0x00 failed, Emask 0x1
>>
>> Cc: stable@vger.kernel.org
>> Fixes: fe22e1c2f705 ("libata: support concurrent positioning ranges log")
>> Signed-off-by: Tyler Erickson <tyler.erickson@seagate.com>
>> Reviewed-by: Muhammad Ahmad <muhammad.ahmad@seagate.com>
>> Tested-by: Michael English <michael.english@seagate.com>
>> ---
>>   drivers/ata/libata-core.c | 21 +++++++++++++--------
>>   1 file changed, 13 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
>> index 40e816419f48..3ea10f72cb70 100644
>> --- a/drivers/ata/libata-core.c
>> +++ b/drivers/ata/libata-core.c
>> @@ -2010,16 +2010,16 @@ unsigned int ata_read_log_page(struct ata_device *dev, u8 log,
>>   	return err_mask;
>>   }
>>   
>> -static bool ata_log_supported(struct ata_device *dev, u8 log)
>> +static int ata_log_supported(struct ata_device *dev, u8 log)
>>   {
>>   	struct ata_port *ap = dev->link->ap;
>>   
>>   	if (dev->horkage & ATA_HORKAGE_NO_LOG_DIR)
>> -		return false;
>> +		return 0;
>>   
>>   	if (ata_read_log_page(dev, ATA_LOG_DIRECTORY, 0, ap->sector_buf, 1))
>> -		return false;
>> -	return get_unaligned_le16(&ap->sector_buf[log * 2]) ? true : false;
>> +		return 0;
>> +	return get_unaligned_le16(&ap->sector_buf[log * 2]);
>>   }
>>   
> Maybe we should change to name of the function here; 
> 'ata_log_supported()' suggests a bool return.
> 
> ata_check_log_page() ?
> 
>>   static bool ata_identify_page_supported(struct ata_device *dev, u8 page)
>> @@ -2455,15 +2455,20 @@ static void ata_dev_config_cpr(struct ata_device *dev)
>>   	struct ata_cpr_log *cpr_log = NULL;
>>   	u8 *desc, *buf = NULL;
>>   
>> -	if (ata_id_major_version(dev->id) < 11 ||
>> -	    !ata_log_supported(dev, ATA_LOG_CONCURRENT_POSITIONING_RANGES))
>> +	if (ata_id_major_version(dev->id) < 11)
>> +		goto out;
>> +
>> +	buf_len = ata_log_supported(dev, ATA_LOG_CONCURRENT_POSITIONING_RANGES);
>> +	if (buf_len == 0)
>>   		goto out;
>>   
>>   	/*
>>   	 * Read the concurrent positioning ranges log (0x47). We can have at
>> -	 * most 255 32B range descriptors plus a 64B header.
>> +	 * most 255 32B range descriptors plus a 64B header. This log varies in
>> +	 * size, so use the size reported in the GPL directory. Reading beyond
>> +	 * the supported length will result in an error.
>>   	 */
>> -	buf_len = (64 + 255 * 32 + 511) & ~511;
>> +	buf_len <<= 9;
>>   	buf = kzalloc(buf_len, GFP_KERNEL);
>>   	if (!buf)
>>   		goto out;
> 
> I don't get it.
> You just returned the actual length of the log page from the previous 
> function. Why do you need to calculate the length here?

Calculate ? This is only converting from 512B sectors to bytes.
The calculation was mine, a gross error :) This is what this patch is fixing.

> 
> Cheers,
> 
> Hannes


-- 
Damien Le Moal
Western Digital Research