linux-kernel - Re: linux-next: OOPS at boot time

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Message-ID: <20100721174952.GT31073@ZenIV.linux.org.uk>
Date:	Wed, 21 Jul 2010 18:49:52 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Jan Kara <jack@...e.cz>
Cc:	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Chinner <david@...morbit.com>, linux-next@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>
Subject: Re: linux-next: OOPS at boot time

On Wed, Jul 21, 2010 at 02:11:17PM +0200, Jan Kara wrote:
>   Thanks for bisecting this. The patch series indeed seems to uncover
> some discrepancies.
>   Ext3 has always dirtied inode in it's ->delete_inode method (via quota
> code). But previously clear_inode() just overwrote the state with I_CLEAR
> and thus we never saw the BUG_ON. After Al's patches, i_state is set in
> end_writeback() which happens earlier. In particular it happens before
> ext3_free_inode() which dirties the inode through quota code while freeing
> xattrs - they are accounted in i_blocks, so i_blocks are updated during
> freeing and inode is dirtied.
>   Actually, ext3_mark_inode_dirty() called during each mark_inode_dirty()
> call writes the inode state to the journal so the dirty flag in the inode
> state is in fact stale and overwriting it with I_CLEAR never mattered. In
> this sense, the BUG_ON triggered is a false positive. But I believe this is
> a separate story.
>   I'm not sure how to really fix this. It seems a bit premature to me to
> mark inode as I_CLEAR before the filesystem is actually done with it. So
> maybe the line
>   inode->i_state = I_FREEING | I_CLEAR;
> should be moved to evict() fuction?

Nope.  I_CLEAR is "no async calls from vfs anymore; it's under complete
fs control and is about to die now".

In any case, I'll post a dumb replacement for ext3 after I verify it on
the laptop I have with me.  Should be in an hour or so (the damn thing is
_slow_).
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