Re: Recent mm changes leading to filesystem corruption?

Re: Recent mm changes leading to filesystem corruption?

[Hugh Dickins]

On Sat, 16 Dec 2006, Martin Michlmayr wrote:

> Debian recently applied a number of mm changes that went into 2.6.19
> to their 2.6.18 kernel for LSB 3.1 compliance (msync() had problems
> before).  Since then, some filesystem corruption has been observed
> which can be traced back to these mm changes.  Is anyone aware of
> problems with these patches?

Very disturbing.  I'm not aware of any problem with them, and we
surely wouldn't have released 2.6.19 with any known-corrupting patches
in.  There's some doubts about 2.6.19 itself in the links below: were
it not for those, I'd suspect a mismerge of the pieces into 2.6.18,
perhaps a hidden dependency on something else.  I'll ponder a little,
but let's CC linux-mm in case someone there has an idea.

Hugh

> 
> The patches that were applied are:
> 
>    - mm: tracking shared dirty pages
>    - mm: balance dirty pages
>    - mm: optimize the new mprotect() code a bit
>    - mm: small cleanup of install_page()
>    - mm: fixup do_wp_page()
>    - mm: msync() cleanup
> 
> With these applied to 2.6.18, the Debian installer on a slow ARM
> system fails because a program segfaults due to filesystem corruption:
> http://bugs.debian.org/401980  This problem also occurs if you only
> apply the "mm: tracking shared dirty pages" patch to 2.6.18 from the
> series of 5 patches listed above.
> 
> Another problem has been reported related to libtorrent: according to
> http://bugs.debian.org/402707 someone also saw this with non-Debian
> 2.6.19 but obviously it's hard to say whether the bugs are really
> related.
> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=394392;msg=24 shows
> some dmesg messages but again it's not 100% clear it's the same bug.
> 
> Has anyone else seen problems or is aware of a fix to the patches
> listed above that I'm unaware of?  It's possible the problem only
> shows up on slow systems. (The corruption is reproducible on a slow
> NSLU2 ARM system with 32 MB ram, but it doesn't happen on a faster ARM
> box with more RAM.)
> -- 
> Martin Michlmayr
> http://www.cyrius.com/

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: Recent mm changes leading to filesystem corruption?

[Martin Michlmayr]

* Hugh Dickins <hugh@veritas.com> [2006-12-16 18:20]:
> Very disturbing.  I'm not aware of any problem with them, and we
> surely wouldn't have released 2.6.19 with any known-corrupting patches
> in.  There's some doubts about 2.6.19 itself in the links below: were
> it not for those, I'd suspect a mismerge of the pieces into 2.6.18,
> perhaps a hidden dependency on something else.  I'll ponder a little,
> but let's CC linux-mm in case someone there has an idea.

Do you think http://article.gmane.org/gmane.linux.kernel/473710 might
be related?
-- 
Martin Michlmayr
http://www.cyrius.com/

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: Recent mm changes leading to filesystem corruption?

[Hugh Dickins]

On Sat, 16 Dec 2006, Martin Michlmayr wrote:
> * Hugh Dickins <hugh@veritas.com> [2006-12-16 18:20]:
> > Very disturbing.  I'm not aware of any problem with them, and we
> > surely wouldn't have released 2.6.19 with any known-corrupting patches
> > in.  There's some doubts about 2.6.19 itself in the links below: were
> > it not for those, I'd suspect a mismerge of the pieces into 2.6.18,
> > perhaps a hidden dependency on something else.  I'll ponder a little,
> > but let's CC linux-mm in case someone there has an idea.
> 
> Do you think http://article.gmane.org/gmane.linux.kernel/473710 might
> be related?

Sounds like it.  Let's CC Jan Kara on your other thread,
he seems to have delved into it a little.

Hugh

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: Recent mm changes leading to filesystem corruption?

[Peter Zijlstra]

On Sat, 2006-12-16 at 16:50 +0100, Martin Michlmayr wrote:
> Debian recently applied a number of mm changes that went into 2.6.19
> to their 2.6.18 kernel for LSB 3.1 compliance (msync() had problems
> before).  Since then, some filesystem corruption has been observed
> which can be traced back to these mm changes.  Is anyone aware of
> problems with these patches?

As said by Hugh, no we were not.

> The patches that were applied are:
> 
>    - mm: tracking shared dirty pages
>    - mm: balance dirty pages
>    - mm: optimize the new mprotect() code a bit
>    - mm: small cleanup of install_page()
>    - mm: fixup do_wp_page()
>    - mm: msync() cleanup
> 
> With these applied to 2.6.18, the Debian installer on a slow ARM
> system fails because a program segfaults due to filesystem corruption:
> http://bugs.debian.org/401980  This problem also occurs if you only
> apply the "mm: tracking shared dirty pages" patch to 2.6.18 from the
> series of 5 patches listed above.

This made me think of a blog entry by DaveM from some time ago:
  http://vger.kernel.org/~davem/cgi-bin/blog.cgi/2006/06/09

> Another problem has been reported related to libtorrent: according to
> http://bugs.debian.org/402707 someone also saw this with non-Debian
> 2.6.19 but obviously it's hard to say whether the bugs are really
> related.
> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=394392;msg=24 shows
> some dmesg messages but again it's not 100% clear it's the same bug.
> 
> Has anyone else seen problems or is aware of a fix to the patches
> listed above that I'm unaware of?  It's possible the problem only
> shows up on slow systems. (The corruption is reproducible on a slow
> NSLU2 ARM system with 32 MB ram, but it doesn't happen on a faster ARM
> box with more RAM.)

What is not clear from all these reports is what architectures this is
seen on. I suspect some of them are i686, which together with the
explicit mention of ARM make it a cross platform issue.



--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: Recent mm changes leading to filesystem corruption?

[Martin Michlmayr]

* Peter Zijlstra <a.p.zijlstra@chello.nl> [2006-12-16 21:55]:
> What is not clear from all these reports is what architectures this is
> seen on. I suspect some of them are i686, which together with the
> explicit mention of ARM make it a cross platform issue.

Problems have been seen at least on x86, x86_64 and arm.
-- 
Martin Michlmayr
tbm@cyrius.com

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>