linux-kernel - RE: [PATCH] Make efi-pstore return a unique id

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Date:	Wed, 20 Nov 2013 15:17:55 +0000
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	Madper Xie <cxie@...hat.com>, Richard Weinberger <richard@....at>
CC:	Tony Luck <tony.luck@...il.com>,
	"matt.fleming@...el.com" <matt.fleming@...el.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"Linux EFI" <linux-efi@...r.kernel.org>,
	谢成骏 <bbboson@...il.com>
Subject: RE: [PATCH] Make efi-pstore return a unique id


> Then will lost the sequence of our log. We will get lots of entries like
> "dmesg-efi-`unique but meaningless number here`" in pstore fs. Who will
> know which file is the latest record?

Ah, that's good point.

> And another side, the combin of timestamp, count and part is unique. Why
> we generate a unique number from a unique number?
> if you think "making a string from three ints and then a parse it to a
> int again" is odd, i'd like to use ((timestamp * 100 + part) * 100 +
> count.

How about calculating the number of digit of part /count, instead of using fixed "100"?
We can ensure the uniqueness of each id by doing it.

digit_num = log2(part)/log2(10) + 1
timestamp * 10^(digit_num + 1)

Seiji