Re: [PATCH -V9 04/15] hugetlb: use mmu_gather instead of a temporary linked list for accumulating pages

["Aneesh Kumar K.V" <aneesh.kumar-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>]

Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org> writes:

> On Wed 13-06-12 15:57:23, Aneesh Kumar K.V wrote:
>> From: "Aneesh Kumar K.V" <aneesh.kumar-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
>> 
>> Use a mmu_gather instead of a temporary linked list for accumulating
>> pages when we unmap a hugepage range
>
> Sorry for coming up with the comment that late but you owe us an
> explanation _why_ you are doing this.
>
> I assume that this fixes a real problem when we take i_mmap_mutex
> already up in 
> unmap_mapping_range
>   mutex_lock(&mapping->i_mmap_mutex);
>   unmap_mapping_range_tree | unmap_mapping_range_list 
>     unmap_mapping_range_vma
>       zap_page_range_single
>         unmap_single_vma
> 	  unmap_hugepage_range
> 	    mutex_lock(&vma->vm_file->f_mapping->i_mmap_mutex);
>
> And that this should have been marked for stable as well (I haven't
> checked when this has been introduced).

Switch to mmu_gather is to get rid of the use of page->lru so that i can use it for
active list.


-aneesh