linux-kernel - Re: [next-20101038] Call trace in ext4

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Message-ID: <20101028200548.GC28126@thunk.org>
Date:	Thu, 28 Oct 2010 16:05:48 -0400
From:	Ted Ts'o <tytso@....edu>
To:	sedat.dilek@...il.com
Cc:	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	LKML <linux-kernel@...r.kernel.org>, linux-ext4@...r.kernel.org,
	sfr@...b.auug.org.au, Arnd Bergmann <arnd@...db.de>,
	Avinash Kurup <kurup.avinash@...il.com>
Subject: Re: [next-20101038] Call trace in ext4

On Thu, Oct 28, 2010 at 09:54:23PM +0200, Sedat Dilek wrote:
> 
> Hm, unfortunately NO (see logs).
> 
> I have compiled via M=fs/ext4 in an already compiled build-tree with
> these 3 patches.

Ok, stupid question.  You did make sure the new ext4 module was
loaded, right?

> [  100.884524] ------------[ cut here ]------------
> [  100.884718] kernel BUG at /home/sd/src/linux-2.6/linux-2.6.36/debian/build/source_i386_none/fs/ext4/inode.c:2721!

OK, so after the patch, line 2721: changed from page_buffers() to:

    if (!page_has_buffers(page))

page_has_buffers() expands to:

#define page_has_buffers(page)	PagePrivate(page)

which expands to test_bit() call to see if PG_private1 is set in
page->flags.  There is no BUG_ON anywhere there as far as I can tell.

Line 2721 in the older kernel was page_has_buffers() which does have a
BUG_ON check.

					- Ted
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