Date: Thu, 7 Dec 2000 20:05:58 +0100
From: Jan Niehusmann <jan@gondor.com>
To: linux-kernel@vger.kernel.org, adilger@turbolinux.com
Subject: Re: fs corruption with invalidate_buffers()
Message-ID: <20001207200558.A976@gondor.com>
In-Reply-To: <20001206030723.A1136@gondor.com>
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In-Reply-To: <20001206030723.A1136@gondor.com>; from jan@gondor.com on Wed, Dec 06, 2000 at 03:07:23AM +0100
Sender: linux-kernel-owner@vger.kernel.org

On Wed, Dec 06, 2000 at 03:07:23AM +0100, Jan Niehusmann wrote:
> While resizing the filesystem, invalidate_buffers() is called from the
> lvm code. (lvm.c, line 2251, in lvm_do_lv_extend_reduce()) 
> If I remove this call, the corruption goes away. But this is probably not
> the correct fix, as it can cause problems when reducing the lv size.

Some more details:

I added the following code to put_last_free(bh) in buffer.c:

--- buffer.c.orig	Wed Dec  6 17:19:57 2000
+++ buffer.c	Thu Dec  7 19:55:39 2000
@@ -500,6 +500,11 @@
 	struct bh_free_head *head = &free_list[BUFSIZE_INDEX(bh->b_size)];
 	struct buffer_head **bhp = &head->list;
 
+	if(bh->b_page && Page_Uptodate(bh->b_page)
+			&& bh->b_page->mapping) { // XXX ???
+		BUG();
+	}
+
 	bh->b_state = 0;
 
 	spin_lock(&head->lock);


That is, if I want to put a buffer to the free list, I check if it is 
mapped and uptodate. If I understand the memory management correctly, this
is a Bad Thing and should not happen. But guess what? It does, in
invalidate_buffers. 

I think invalidate_buffers should check if the buffer belongs to a 
mapped page, and if it does, invalidate this mapping.

Jan


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