linux-kernel - Re: [PATCH v2] libata: Don't trust current capacity values in identify words 57-58

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Message-ID: <499AA047.70502@ru.mvista.com>
Date:	Tue, 17 Feb 2009 14:32:23 +0300
From:	Sergei Shtylyov <sshtylyov@...mvista.com>
To:	Robert Hancock <hancockrwd@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	ide <linux-ide@...r.kernel.org>, Jeff Garzik <jeff@...zik.org>,
	Mark Lord <liml@....ca>,
	Hanno Böck <hanno@...eck.de>
Subject: Re: [PATCH v2] libata: Don't trust current capacity values in identify
 words 57-58

Hello.

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.
>
> While we're at it, clean up this function to use named constants for the
> identify word values.
>
> Signed-off-by: Robert Hancock <hancockrwd@...il.com>
>   

Acked-by: Sergei Shtylyov <sshtylyov@...mvista.com>

   ... though I'm not sure that the rename should be a part of this patch.

> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
> index 9fbf059..33b5549 100644
> --- a/drivers/ata/libata-core.c
> +++ b/drivers/ata/libata-core.c
> @@ -1322,14 +1322,16 @@ static u64 ata_id_n_sectors(const u16 *id)
>  {
>  	if (ata_id_has_lba(id)) {
>  		if (ata_id_has_lba48(id))
> -			return ata_id_u64(id, 100);
> +			return ata_id_u64(id, ATA_ID_LBA_CAPACITY_2);
>  		else
> -			return ata_id_u32(id, 60);
> +			return ata_id_u32(id, ATA_ID_LBA_CAPACITY);
>  	} else {
>  		if (ata_id_current_chs_valid(id))
> -			return ata_id_u32(id, 57);
> +			return id[ATA_ID_CUR_CYLS] * id[ATA_ID_CUR_HEADS] *
> +			       id[ATA_ID_CUR_SECTORS];
>   

   It won't hurt to comment on why the capacity is ignored. 
Unfortunately, the IDE code lacks such comment.

MBR, Sergei


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