linux-kernel - Re: ext4 crash on 2.6.37: NULL ptr in ext4_discard

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Message-ID: <20110220061552.GB8765@thunk.org>
Date:	Sun, 20 Feb 2011 01:15:52 -0500
From:	Ted Ts'o <tytso@....edu>
To:	Mark Lord <kernel@...savvy.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-ext4@...r.kernel.org
Subject: Re: ext4 crash on 2.6.37: NULL ptr in ext4_discard_preallocations

On Sun, Feb 20, 2011 at 12:05:27AM -0500, Mark Lord wrote:
> I suppose it must be, as there's no other 0x3c offset in that function.
> Which means it's probably this line that's crashing:
> 
>              BUG_ON(pa->pa_obj_lock != &ei->i_prealloc_lock);
> 
> ...which could only happen if "pa" was NULL there.
> I wonder how that happened ?

Which could only happen if ei->i_prealloc_list were not properly
initialized (i..e, it was still NULL).  Which shouldn't ever
happen...., since all ext4_inodes are initialized in
ext4_alloc_inode().

Hmm, can you replicate the crash?

					- Ted
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