RE: vmcore not getting created on linux-4.7

[Steve Wise]

> >
> > Updating to 1.6.0 of makedumpfile didn't help. :(
> >
> 
> Does anyone else have suggestions on how to debug this?  From my original
> post, the dump kernel just reboots and I'm not sure why.  Where can I add
> printks to gather more info on why the dump kernel gives on on the dump?

Seems this issue was a bug in makedumpfile that is fixed with this commit:

commit 2c21d4656e8d3c2af2b1e14809d076941ae69e96
Author: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Date:   Fri Jun 17 18:41:26 2016 +0900

    [PATCH v2] Support _count -> _refcount rename in struct page
    
    _count member was renamed to _refcount in linux commit 0139aa7b7fa12
    ("mm: rename _count, field of the struct page, to _refcount") and this
    broke makedumpfile. The reason for making the change was to find all users
    accessing it directly and not through the recommended API. I tried
    suggesting to revert the change but failed, I see no other choice than to
    start supporting both _count and _refcount in makedumpfile.
    
    Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>

I found this fix in the devel branch of
git://git.code.sf.net/p/makedumpfile/code.

I'm surprised others aren't seeing this?  All 6 of my development systems stop
being able to get vmcore dumps with 4.7-rc...

Steve.