Re: VM: Fix nasty and subtle race in shared mmap'ed page writeback

[David Miller]

From: Andrew Morton <akpm@xxxxxxxx>
Date: Wed, 3 Jan 2007 22:12:20 -0800

> On Thu, 04 Jan 2007 17:03:43 +1100
> Nick Piggin <nickpiggin@xxxxxxxxxxxx> wrote:
> 
> > > That bug was introduced in 2.6.19, with the dirty page tracking patches.
> > > 
> > > 2.6.18 and earlier used ->private_lock coverage in try_to_free_buffers() to
> > > prevent it.
> > 
> > Ohh, right you are, I was looking at 2.6.19 sources. The comments above
> > ttfb match that as well. Curious that the dirty page patches were allowed
> > to mess with this...
> 
> Frankly, those patches scared the crap out of me, specifically because of
> the delicacy and complexity of the various dirtiness state coherencies. 
> But I just didn't have the bandwidth to go through them with a sufficiently
> fine toothcomb, sorry.
> 
> > Anyway that leaves us with the question of why Andrea's database is getting
> > corrupted. Hopefully he can give us a minimal test-case.
> 
> It'd odd that stories of pre-2.6.19 BerkeleyDB corruption are now coming
> out of the woodwork.  It's the first I've ever heard of them.

Note that the original rtorrent debian bug report was against 2.6.18
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