From mboxrd@z Thu Jan  1 00:00:00 1970
Subject: Re: iounmap() - can't always unmap memory I've mappedt
Date: Fri, 29 Sep 2000 23:00:16 +0100 (BST)
In-Reply-To: <20000929221109Z129234-481+1111@vger.kernel.org> from "Timur Tabi" at Sep 29, 2000 04:56:00 PM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
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To: Timur Tabi <ttabi@interactivesi.com>
Cc: Linux Kernel Mailing list <linux-kernel@vger.kernel.org>, Linux MM mailing list <linux-mm@kvack.org>
List-ID: <linux-mm.kvack.org>

> "num_pages" is usually just equal to 1.  This code appears to work very well.
> However, when I call the iounmap function on the memory obtained via
> ioremap_nocache, sometimes I hit a kernel BUG().  The code which causes the bug
> is in page_alloc.c, line 85 (in function  __free_pages_ok):
> 
> 	if (page->buffers)
> 		BUG();

This sounds like you are trying to do maps on pages that are in use. No can do

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