Re: [PATCH] mm/hugetlb: fix gigantic page initialization/allocation

[David Rientjes]

On Tue, 2 Feb 2016, Mike Kravetz wrote:

> Attempting to preallocate 1G gigantic huge pages at boot time with
> "hugepagesz=1G hugepages=1" on the kernel command line will prevent
> booting with the following:
> 
> kernel BUG at mm/hugetlb.c:1218!
> 
> When mapcount accounting was reworked, the setting of compound_mapcount_ptr
> in prep_compound_gigantic_page was overlooked.  As a result, the validation
> of mapcount in free_huge_page fails.
> 
> The "BUG_ON" checks in free_huge_page were also changed to "VM_BUG_ON_PAGE"
> to assist with debugging.
> 
> Fixes: af5642a8af ("mm: rework mapcount accounting to enable 4k mapping of THPs")
> Suggested-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>

I'm not sure whether this should have a "From: Naoya Horiguchi" line with 
an accompanying sign-off or not, since Naoya debugged and wrote the actual 
fix to prep_compound_gigantic_page().

Acked-by: David Rientjes <rientjes@xxxxxxxxxx>