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Date: Thu, 12 Jan 2006 11:02:49 +0900 (JST)
Message-Id: <20060112.110249.46098125.psbfan@po.harenet.ne.jp>
To: linux-kernel@vger.kernel.org
Subject: about sanitize_e820_map()
From: Toshiyuki Ishii <psbfan@po.harenet.ne.jp>
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Good evening.
I am Toshiyuki Ishii at Kurashiki in Japan.

I am a beginner of kernel source code,
so sorry if I am misunderstanding.

In sanitize_e820_map(),
When sorting change_point[] by address and swapping
two maps that represets the same memory region
and have a different address, end address for privious change_point
and start address for current change_point,
"if" statement is

if ((change_point[i]->addr < change_point[i-1]->addr) ||

     ((change_point[i]->addr == change_point[i-1]->addr) &&
      (change_point[i]->addr == change_point[i]->pbios->addr) &&
      (change_point[i-1]->addr != change_point[i-1]->pbios->addr))

There are two conditions and I think the first one is sorting by address.
I have a qestion in the second condition.

I think second line

change_point[i]->addr == change_point[i]->pbios->addr

checks that current change_point represents start address.
and third line

change_point[i-1]->addr != change_point[i-1]->pbios->addr

checks that previous change_point represents end address.
If this "if" statement intends to swap maps for "the same" region
that match these condition, the first line should be

change_point[i]->pbios->addr == change_point[i-1]->pbios->addr

I think.

Am I wrong?