Messages in this thread | | | Date | Mon, 16 Feb 2009 18:03:20 -0500 | From | Mark Lord <> | Subject | Re: [PATCH] libata: Don't trust current capacity values in identify words 57-58 |
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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. ..
Mind you, one can do better than that, too.
The "10% solution" in there right now is a bit of a (working) hack. It really probably just needs to check for a flipped-LBA that is within +/- one full cylinder of the CHS capacity.
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