Date: Wed, 13 Feb 2008 01:01:45 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Bart Dopheide <dopheide@fmf.nl>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
       linux-kernel@vger.kernel.org,
       OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>,
       Jens Axboe <jens.axboe@oracle.com>,
       Bartlomiej Zolnierkiewicz <mzolnier@gmail.com>
Subject: Re: Kernel BUG at fs/mpage.c:489
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	<200802131205.45493.nickpiggin@yahoo.com.au>
	<20080213072627.GB2174@fmf.nl>
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On Wed, 13 Feb 2008 08:26:27 +0100 Bart Dopheide <dopheide@fmf.nl> wrote:

> On Wed, Feb 13, 2008 at 12:05:45PM +1100, Nick Piggin wrote:
> :)On Wednesday 13 February 2008 08:50, Alan Cox wrote:
> :)> Almost certainly a hardware fail of some sort.
> :)
> :)Right, but the kernel shouldn't go bug...
> 
> Indeed, that's why I'm reporting.
> 
> 
> :)I don't have a copy of your exact source code... which condition in
> :)__mpage_writepage went BUG?
> 
> BUG_ON(buffer_locked(bh));
> 
> In a bit of context:
> 482:    if (page_has_buffers(page)) {
> 483:            struct buffer_head *head = page_buffers(page);
> 484:            struct buffer_head *bh = head;
> 485:
> 486:            /* If they're all mapped and dirty, do it */
> 487:            page_block = 0;
> 488:            do {
> 489:                    BUG_ON(buffer_locked(bh));
> 490:                    if (!buffer_mapped(bh)) {
> 491:                            /*
> 492:                             * unmapped dirty buffers are created by
> 493:                             * __set_page_dirty_buffers -> mmapped data
> 494:                             */
> 495:                            if (buffer_dirty(bh))
> 496:                                    goto confused;
> 497:                            if (first_unmapped == blocks_per_page)
> 498:                                    first_unmapped = page_block;
> 499:                            continue;
> 500:                    }
> 

Probably means that either fat, IDE, block or fs/buffer.c failed to unlock a buffer_head
when the IO error happened.  It's unlikely to be fat.

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