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

From: Nick Piggin
Date: Sat Dec 30 2006 - 22:59:22 EST

Andrea Gelmini wrote:
On Fri, Dec 29, 2006 at 06:59:02PM +0000, Linux Kernel Mailing List wrote:

Commit: 7658cc289288b8ae7dd2c2224549a048431222b3
Parent: 3bf8ba38f38d3647368e4edcf7d019f9f8d9184a
Author: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxx>
AuthorDate: Fri Dec 29 10:00:58 2006 -0800
Committer: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxx>
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.
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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