Re: [PATCH 15/18] mm, hugetlb: move up anon_vma_prepare()

[Naoya Horiguchi]

On Mon, Jul 29, 2013 at 03:05:37PM -0400, Naoya Horiguchi wrote:
> On Mon, Jul 29, 2013 at 02:32:06PM +0900, Joonsoo Kim wrote:
> > If we fail with a allocated hugepage, it is hard to recover properly.
> > One such example is reserve count. We don't have any method to recover
> > reserve count. Although, I will introduce a function to recover reserve
> > count in following patch, it is better not to allocate a hugepage
> > as much as possible. So move up anon_vma_prepare() which can be failed
> > in OOM situation.
> > 
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> 
> Reviewed-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>

Sorry, let me suspend this Reviewed for a question.
If alloc_huge_page failed after we succeeded anon_vma_parepare,
the allocated anon_vma_chain and/or anon_vma are safely freed?
Or don't we have to free them?

Thanks,
Naoya Horiguchi

> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 683fd38..bb8a45f 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -2536,6 +2536,15 @@ retry_avoidcopy:
> >  	/* Drop page_table_lock as buddy allocator may be called */
> >  	spin_unlock(&mm->page_table_lock);
> >  
> > +	/*
> > +	 * When the original hugepage is shared one, it does not have
> > +	 * anon_vma prepared.
> > +	 */
> > +	if (unlikely(anon_vma_prepare(vma))) {
> > +		ret = VM_FAULT_OOM;
> > +		goto out_old_page;
> > +	}
> > +
> >  	use_reserve = vma_has_reserves(h, vma, address);
> >  	if (use_reserve == -ENOMEM) {
> >  		ret = VM_FAULT_OOM;
> > @@ -2590,15 +2599,6 @@ retry_avoidcopy:
> >  		goto out_lock;
> >  	}
> >  
> > -	/*
> > -	 * When the original hugepage is shared one, it does not have
> > -	 * anon_vma prepared.
> > -	 */
> > -	if (unlikely(anon_vma_prepare(vma))) {
> > -		ret = VM_FAULT_OOM;
> > -		goto out_new_page;
> > -	}
> > -
> >  	copy_user_huge_page(new_page, old_page, address, vma,
> >  			    pages_per_huge_page(h));
> >  	__SetPageUptodate(new_page);
> > @@ -2625,7 +2625,6 @@ retry_avoidcopy:
> >  	spin_unlock(&mm->page_table_lock);
> >  	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
> >  
> > -out_new_page:
> >  	page_cache_release(new_page);
> >  out_old_page:
> >  	page_cache_release(old_page);
> > -- 
> > 1.7.9.5
> > 
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