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

[Nick Piggin <nickpiggin@yahoo.com.au>]

Andrea Gelmini wrote:
> On Fri, Dec 29, 2006 at 06:59:02PM +0000, Linux Kernel Mailing List wrote:
>
> > Gitweb:     http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=7658cc289288b8ae7dd2c2224549a048431222b3
> > Commit:     7658cc289288b8ae7dd2c2224549a048431222b3
> > Parent:     3bf8ba38f38d3647368e4edcf7d019f9f8d9184a
> > Author:     Linus Torvalds <torvalds@macmini.osdl.org>
> > AuthorDate: Fri Dec 29 10:00:58 2006 -0800
> > Committer:  Linus Torvalds <torvalds@macmini.osdl.org>
> > CommitDate: Fri Dec 29 10:00:58 2006 -0800
> >
> >    VM: Fix nasty and subtle race in shared mmap'ed page writeback
>
>
> With 2.6.20-rc2-git1, which contain this patch, I have no more Berkeley
> DB corruption with Klibido.
> I'm afraid a lot of software project switched to Sqlite, from BDB,
> because the bug this patch fix (ie. http://bogofilter.sourceforge.net/).
> I've also thought, since years, it was an userland problem.

This bug was only introduced in 2.6.19, due to a change that caused pte
dirty bits to be discarded without a subsequent set_page_dirty() (nowhere
else in the kernel should have done this).

So if your corruption is years old, then it must be something else.
Maybe it is hidden by a timing change, or BDB isn't using msync properly.

--
SUSE Labs, Novell Inc.
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