Re: btrfs GPF in read_extent_buffer() while scrubbing with kernel 3.4.2

[Chris Mason <chris.mason@fusionio.com>]

On Fri, Jul 06, 2012 at 09:02:34AM -0600, Jan Schmidt wrote:
> On Fri, July 06, 2012 at 16:40 (+0200), Chris Mason wrote:
> > On Fri, Jul 06, 2012 at 08:33:51AM -0600, Sami Liedes wrote:
> >> On Fri, Jul 06, 2012 at 12:42:50PM +0200, Jan Schmidt wrote:
> >>> I've no good idea at the moment how to go on. It might help to get a feeling if
> >>> it's shifting around at least a little bit or really constant in the timing of
> >>> occurrence. So can you please apply the next patch on top of the other two and
> >>> give it some more failure tries? The "checksum mismatch [1234]" line will be of
> >>> most interest. I'm also curious what the additional debug variables will say in
> >>> the extended version of the very first printk. You can leave out the stack
> >>> traces if you like, they won't matter much anyway.
> >>
> >> Ok. Also turned on CONFIG_DEBUG_PAGEALLOC and CONFIG_SLUB_DEBUG_ON as
> >> suggested by Chris Mason.
> >>
> >> With those and the latest patch, there's an oops already at boot. I
> >> don't have netconsole yet at that point, but here's the important
> >> parts (sure I can capture it fully if you need).
> >>
> >> By the way, something seems to be untabifying your patches. I don't
> >> know if it's on my side or yours, but at least some other patches I
> >> receive via linux-btrfs contain tabs. Doing a M-x tabify in emacs
> >> mostly makes them apply cleanly for me.
> >>
> >> 	Sami
> >>
> >>
> >> ------------------------------------------------------------
> >> btrfs: disk space caching is enabled
> >> BUG: unable to handle kernel NULL pointer dereference at 0000000000000150
> >> IP: [<ffffffffa0223568>] check_node+0x138/0x250 [btrfs]
> > 
> > This isn't from any of the new debugging.  Can you please try it on an
> > unpatched kernel?
> 
> You're confusing that with check_leaf. I added check_node along the way, see my
> mail from Thu, July 05, 2012 at 15:41 (+0200). I'd really like to add something
> similar for the 3.6 series.
> 
> Checking for the null pointer dereference.

Sorry, I wasn't clear.  I meant it wasn't from slab debug or
DEBUG_PAGEALLOC, so it must be new in your patches ;)

-chris