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

Damien Le Moal
2022-06-03T08:18:25Z

On 6/3/22 16:42, Hannes Reinecke wrote:
> On 6/3/22 09:07, Damien Le Moal wrote:
>> 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.
>>
> Sigh. Can't we have a 'bytes_to_sectors' helper? All this shifting by 9
> is getting on my nerves ...

Haha ! Yes, we can do that. But not in this patch since that is a bug fix.

--
Damien Le Moal
Western Digital Research