Re: Linux 2.4.30-rc3 md/ext3 problems (ext3 gurus : please check)

[Stephen C. Tweedie]

Hi,

On Wed, 2005-04-06 at 21:10, Stephen C. Tweedie wrote:

> However, 2.6 is suspected of still having leaks in ext3.  To be certain
> that we're not just backporting one of those to 2.4, we need to
> understand who exactly is going to clean up these bh's if they are in
> fact unused once we complete this code and do the final put_bh().  
> 
> I'll give this patch a spin with Andrew's fsx-based leak stress and see
> if anything unpleasant appears.  

I'm currently running with the buffer-trace debug patch, on 2.4, with a
custom patch to put every buffer jbd ever sees onto a per-superblock
list, and remove it only when the bh is destroyed in
put_unused_buffer_head().  At unmount time, we can walk that list to
find stale buffers attached to data pages (invalidate_buffers() already
does such a walk for metadata.)

I just ran it with a quick test and it found 300,000 buffers still
present at unmount.  Whoops, I guess I need to move the check to _after_
the final invalidate_inodes() call. :-)

But this method ought to allow us to test for this sort of leak a lot
more reliably, and to report via the usual buffer history tracing the
most recent activity on any bh that does leak.

Andrew, I'll give this a try on 2.6 once I've got this 2.4 patch tested
for Marcelo.  I've got uptodate buffer_trace for 2.6 anyway, so it
shouldn't be too hard.

--Stephen

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