[Crash-utility] makedumpfile: 4.5 kernel commit breaks page filtering

[Joe Lawrence]

On 02/25/2016 07:35 PM, Atsushi Kumagai wrote:
> Hello Dave,
>
>>> Note that PAGE_MAPPING_ANON is now only set in the compound_head page,
>>> so when makedumpfile walks though the pages, it will have to look
>>> at each page's head page for the bit setting.
>>
>> Thanks for your report.
>> As you said, it seems checking the head page like kernel does is necessary.
>> I'll try to work it out, please give me some time.
>
> Reading head page's page->mapping for each tail page will take extra time,
> so I contrived another way.
>
> It's just skipping compound tail pages for filtering.
> If makedumpfile excludes compound pages, it will be done at a time by
> exclude_range() at the time of checking the compound head page. We don't
> need to check compound tail pages individually.
>
> I made the patch, could you test the *compound* branch below ?
> This version requires a new unexported symbol, you need to specify
> -x vmlinux for now.
>
>    https://sourceforge.net/p/makedumpfile/code/ci/compound/tree/

Hi Atsushi, Dave,

Running the makedumpfile compound branch on 4.5-rc5 and this kdump.conf 
setting:

core_collector makedumpfile -l --message-level 1 -d 31 -x 
/kdumproot/var/crash/vmlinux

I was able to collect and successfully read a few test dumps without 
incident.  This was inside a VM without any interesting system load, but 
was regularly giving me issues before the patch.

Regards,

-- Joe