Subject: Re: [PATCH] scsi/sd: Fix capacity output to show MB/GB/TB/...
From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Simon Arlott <simon@fire.lp0.eu>
Cc: Matthew Wilcox <matthew@wil.cx>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       linux-scsi <linux-scsi@vger.kernel.org>
In-Reply-To: <48B9B588.7060709@simon.arlott.org.uk>
References: <48B9546B.4010004@simon.arlott.org.uk>
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	 <48B9B552.8060406@simon.arlott.org.uk>
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Date: Sat, 30 Aug 2008 20:59:07 -0500
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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.

James


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