Re: [PATCH] libata: Don't trust current capacity values in identify words 57-58

Robert Hancock
2009-02-16T23:54:26Z

Mark Lord wrote:
> Robert Hancock wrote:
>> Hanno Böck reported a problem where an old Conner CP30254 240MB hard
>> drive
>> was reported as 1.1TB in capacity by libata:
>>
>> http://lkml.org/lkml/2009/2/13/134
>>
>> This was caused by libata trusting the drive's reported current
>> capacity in sectors in identify words 57 and 58 if the drive does not
>> support LBA and the
>> current CHS translation values appear valid. Unfortunately it seems older
>> ATA specs were vague about what this field should contain and a number
>> of drives
>> used values with wrong byte order or that were totally bogus. There's no
>> unique information that it conveys and so we can just calculate the
>> number
>> of sectors from the reported current CHS values.
>>
>> Signed-off-by: Robert Hancock <hancockrwd@gmail.com>
> ..
>> } else {
>> if (ata_id_current_chs_valid(id))
>> - return ata_id_u32(id, 57);
>> + return id[54] * id[55] * id[56];
>> else
>> return id[1] * id[3] * id[6];
> ..
>
> NAK. That's not quite correct, either.
>
> The LBA capacity can be larger than the CHS capacity,
> so we have to use the reported LBA values if at all possible.
>
> That's why ata_id_is_lba_capacity_ok() exists,
> and why it looks so peculiar.
>
> Some of those early drives really did require that kind of logic.

This is the !ata_id_has_lba code path. If the drive supports LBA then
the LBA capacity will always be used, that hasn't changed.