linux-kernel - Re: [PATCH] scsi/sd: Fix capacity output to show MB/GB/TB/...

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Message-ID: <48BAB3FB.1050809@simon.arlott.org.uk>
Date:	Sun, 31 Aug 2008 16:08:43 +0100
From:	Simon Arlott <simon@...e.lp0.eu>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
CC:	Matthew Wilcox <matthew@....cx>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-scsi <linux-scsi@...r.kernel.org>
Subject: Re: [PATCH] scsi/sd: Fix capacity output to show MB/GB/TB/...

On 31/08/08 02:59, James Bottomley wrote:
> On Sat, 2008-08-30 at 22:03 +0100, Simon Arlott wrote:
>> The capacity printk'd in bytes is divided by 1000000,
>> whereas 1048576 would be more consistent with the rest
>> of the OS and disk-related utilities ('df' etc.).
>> 
>> This change replaces the (sz - (sz/625 - 974))/1950
>> calculation with a simple right shift to output with
>> five significant digits the capacity in KB, MB, GB, TB,
>> PB, or EB. Anything beyond this becomes too large...
> 
> Well, still needs to be dividing by 1000 not 1024 for SCSI and ATA.
> However, I'm afraid it needs to be a bit more sophisticated:  for
> instance, under these calculations, a 1.75TB disk will show up as 1TB.
> Thus, I think we need to print the capacity to 3 significant figures to
> cope with this case.

Actually it'll show up as 1629GB, as my patch shows up to 5 digits 
(not five significant digits, which would require outputting a 
non-integer value).

Isn't outputting "1.75" unnecessarily complicated, and "1750" would 
work better?

-- 
Simon Arlott
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