Re: [BLOCK] bh: Ensure bh fits within a page

From: Badari Pulavarty
Date: Thu Aug 17 2006 - 19:09:46 EST

On Wed, 2006-08-02 at 09:30 +1000, Herbert Xu wrote:
> Jens Axboe <axboe@xxxxxxx> wrote:
> >
> > That looks really dangerous, I'd prefer that to be a BUG_ON() as well to
> > prevent nastiness further down.
> OK, I used a WARN_ON mainly because ext3 has been doing this for years
> without killing anyone until now :)
> [BLOCK] bh: Ensure bh fits within a page
> There is a bug in jbd with slab debugging enabled where it was submitting
> a bh obtained via jbd_rep_kmalloc which crossed a page boundary. A lot
> of time was spent on tracking this down because the symptoms were far off
> from where the problem was.
> This patch adds a sanity check to submit_bh so we can immediately spot
> anyone doing similar things in future.
> Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Cheers,


I am working on a fix to address this problem. Do you have any testcases
to reproduce the problem ? I have been running bunch of tests with
CONFIG_DEBUG_SLAB with WARN_ON() and I haven't seen it yet :(

Wondering, if there is any special thing I need to do to reproduce
the problem ? Please let me know.


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