RE: [PATCH v6 2/2] mm: fix the handling Non-LRU pages returned by follow_page

[Wang, Haiyue]

> -----Original Message-----
> From: David Hildenbrand <david@xxxxxxxxxx>
> Sent: Tuesday, August 23, 2022 21:28
> To: Wang, Haiyue <haiyue.wang@xxxxxxxxx>; Miaohe Lin <linmiaohe@xxxxxxxxxx>; linux-mm@xxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> Cc: akpm@xxxxxxxxxxxxxxxxxxxx; apopple@xxxxxxxxxx; Huang, Ying <ying.huang@xxxxxxxxx>;
> songmuchun@xxxxxxxxxxxxx; naoya.horiguchi@xxxxxxxxx; alex.sierra@xxxxxxx; Felix Kuehling
> <Felix.Kuehling@xxxxxxx>
> Subject: Re: [PATCH v6 2/2] mm: fix the handling Non-LRU pages returned by follow_page
> 
> On 23.08.22 15:26, Wang, Haiyue wrote:
> >> -----Original Message-----
> >> From: David Hildenbrand <david@xxxxxxxxxx>
> >> Sent: Tuesday, August 23, 2022 18:07
> >> To: Miaohe Lin <linmiaohe@xxxxxxxxxx>; Wang, Haiyue <haiyue.wang@xxxxxxxxx>; linux-mm@xxxxxxxxx;
> >> linux-kernel@xxxxxxxxxxxxxxx
> >> Cc: akpm@xxxxxxxxxxxxxxxxxxxx; apopple@xxxxxxxxxx; Huang, Ying <ying.huang@xxxxxxxxx>;
> >> songmuchun@xxxxxxxxxxxxx; naoya.horiguchi@xxxxxxxxx; alex.sierra@xxxxxxx; Felix Kuehling
> >> <Felix.Kuehling@xxxxxxx>
> >> Subject: Re: [PATCH v6 2/2] mm: fix the handling Non-LRU pages returned by follow_page
> >>
> >> On 17.08.22 04:34, Miaohe Lin wrote:
> >>> On 2022/8/16 10:21, Haiyue Wang wrote:
> >>>> The handling Non-LRU pages returned by follow_page() jumps directly, it
> >>>> doesn't call put_page() to handle the reference count, since 'FOLL_GET'
> >>>> flag for follow_page() has get_page() called. Fix the zone device page
> >>>> check by handling the page reference count correctly before returning.
> >>>>
> >>>> And as David reviewed, "device pages are never PageKsm pages". Drop this
> >>>> zone device page check for break_ksm().
> >>>>
> >>>> Fixes: 3218f8712d6b ("mm: handling Non-LRU pages returned by vm_normal_pages")
> >>>> Signed-off-by: Haiyue Wang <haiyue.wang@xxxxxxxxx>
> >>>> Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
> >>>> Reviewed-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>
> >>>
> >>> Thanks for your fixing. LGTM with one nit below. But I have no strong opinion on it.
> >>> So with or without fixing below nit:
> >>>
> >>> Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> >>>
> >>>> ---
> >>>>  mm/huge_memory.c |  4 ++--
> >>>>  mm/ksm.c         | 12 +++++++++---
> >>>>  mm/migrate.c     | 19 ++++++++++++-------
> >>>>  3 files changed, 23 insertions(+), 12 deletions(-)
> >>>>
> >>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> >>>> index 8a7c1b344abe..b2ba17c3dcd7 100644
> >>>> --- a/mm/huge_memory.c
> >>>> +++ b/mm/huge_memory.c
> >>>> @@ -2963,10 +2963,10 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
> >>>>  		/* FOLL_DUMP to ignore special (like zero) pages */
> >>>>  		page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
> >>>>
> >>>> -		if (IS_ERR_OR_NULL(page) || is_zone_device_page(page))
> >>>> +		if (IS_ERR_OR_NULL(page))
> >>>>  			continue;
> >>>>
> >>>> -		if (!is_transparent_hugepage(page))
> >>>> +		if (is_zone_device_page(page) || !is_transparent_hugepage(page))
> >>>
> >>> !is_transparent_hugepage should already do the work here? IIRC, zone_device_page can't be
> >>> a transhuge page anyway. And only transparent_hugepage is cared here.
> >>
> >> I agree.
> >
> > OK, will remove it in next version.
> >
> >>
> >> Can we avoid sending a new version of a patch series as reply to another
> >> patch series (previous version)?
> >
> > Don't use '--in-reply-to=' when running 'git send-email' ?
> 
> Yes. That makes it easier top identify versions of patch series, without
> having to dig down into an ever-growing thread.

Got it, thanks. ;-)

> 
> --
> Thanks,
> 
> David / dhildenb