Re: [PATCH v4 4/4] mm: introduce MADV_PAGEOUT
On Fri, Jul 12, 2019 at 09:58:09AM -0400, Johannes Weiner wrote:
> On Fri, Jul 12, 2019 at 02:18:28PM +0900, Minchan Kim wrote:
> > Hi Johannes,
> >
> > On Thu, Jul 11, 2019 at 02:42:23PM -0400, Johannes Weiner wrote:
> > > On Thu, Jul 11, 2019 at 10:25:28AM +0900, Minchan Kim wrote:
> > > > @@ -480,6 +482,198 @@ static long madvise_cold(struct vm_area_struct
> > > > *vma,
> > > > return 0;
> > > > }
> > > >
> > > > +static int madvise_pageout_pte_range(pmd_t *pmd, unsigned long addr,
> > > > + unsigned long end, struct mm_walk *walk)
> > > > +{
> > > > + struct mmu_gather *tlb = walk->private;
> > > > + struct mm_struct *mm = tlb->mm;
> > > > + struct vm_area_struct *vma = walk->vma;
> > > > + pte_t *orig_pte, *pte, ptent;
> > > > + spinlock_t *ptl;
> > > > + LIST_HEAD(page_list);
> > > > + struct page *page;
> > > > + unsigned long next;
> > > > +
> > > > + if (fatal_signal_pending(current))
> > > > + return -EINTR;
> > > > +
> > > > + next = pmd_addr_end(addr, end);
> > > > + if (pmd_trans_huge(*pmd)) {
> > > > + pmd_t orig_pmd;
> > > > +
> > > > + tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
> > > > + ptl = pmd_trans_huge_lock(pmd, vma);
> > > > + if (!ptl)
> > > > + return 0;
> > > > +
> > > > + orig_pmd = *pmd;
> > > > + if (is_huge_zero_pmd(orig_pmd))
> > > > + goto huge_unlock;
> > > > +
> > > > + if (unlikely(!pmd_present(orig_pmd))) {
> > > > + VM_BUG_ON(thp_migration_supported() &&
> > > > +
> > > > !is_pmd_migration_entry(orig_pmd));
> > > > + goto huge_unlock;
> > > > + }
> > > > +
> > > > + page = pmd_page(orig_pmd);
> > > > + if (next - addr != HPAGE_PMD_SIZE) {
> > > > + int err;
> > > > +
> > > > + if (page_mapcount(page) != 1)
> > > > + goto huge_unlock;
> > > > + get_page(page);
> > > > + spin_unlock(ptl);
> > > > + lock_page(page);
> > > > + err = split_huge_page(page);
> > > > + unlock_page(page);
> > > > + put_page(page);
> > > > + if (!err)
> > > > + goto regular_page;
> > > > + return 0;
> > > > + }
> > > > +
> > > > + if (isolate_lru_page(page))
> > > > + goto huge_unlock;
> > > > +
> > > > + if (pmd_young(orig_pmd)) {
> > > > + pmdp_invalidate(vma, addr, pmd);
> > > > + orig_pmd = pmd_mkold(orig_pmd);
> > > > +
> > > > + set_pmd_at(mm, addr, pmd, orig_pmd);
> > > > + tlb_remove_tlb_entry(tlb, pmd, addr);
> > > > + }
> > > > +
> > > > + ClearPageReferenced(page);
> > > > + test_and_clear_page_young(page);
> > > > + list_add(>lru, _list);
> > > > +huge_unlock:
> > > > + spin_unlock(ptl);
> > > > + reclaim_pages(_list);
> > > > + return 0;
> > > > + }
> > > > +
> > > > + if (pmd_trans_unstable(pmd))
> > > > + return 0;
> > > > +regular_page:
> > > > + tlb_change_page_size(tlb, PAGE_SIZE);
> > > > + orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr,
> > > > );
> > > > + flush_tlb_batched_pending(mm);
> > > > + arch_enter_lazy_mmu_mode();
> > > > + for (; addr < end; pte++, addr += PAGE_SIZE) {
> > > > + ptent = *pte;
> > > > + if (!pte_present(ptent))
> > > > + continue;
> > > > +
> > > > + page = vm_normal_page(vma, addr, ptent);
> > > > + if (!page)
> > > > + continue;
> > > > +
> > > > + /*
> > > > +* creating a THP page is expensive so split it only if
> > > > we
> > > > +* are sure it's worth. Split it if we are only owner.
> > > > +*/
> > > > + if (PageTransCompound(page)) {
> > > > + if (page_mapcount(page) != 1)
> > > > + break;
> > > > + get_page(page);
> > > > + if (!trylock_page(page)) {
> > > > + put_page(page);
> > > > + break;
> > > > + }
> > > > + pte_unmap_unlock(orig_pte, ptl);
> > > > + if (split_huge_page(page)) {
> > > > + unlock_page(page);
> > > > +
Re: [PATCH v4 4/4] mm: introduce MADV_PAGEOUT
On Fri 12-07-19 09:58:09, Johannes Weiner wrote:
[...]
> > @@ -423,6 +445,12 @@ static int madvise_cold_pte_range(pmd_t *pmd, unsigned
> > long addr,
> >
> > VM_BUG_ON_PAGE(PageTransCompound(page), page);
> >
> > + if (pageout) {
> > + if (isolate_lru_page(page))
> > + continue;
> > + list_add(>lru, _list);
> > + }
> > +
> > if (pte_young(ptent)) {
> > ptent = ptep_get_and_clear_full(mm, addr, pte,
> > tlb->fullmm);
>
> One thought on the ordering here.
>
> When LRU isolation fails, it would still make sense to clear the young
> bit: we cannot reclaim the page as we wanted to, but the user still
> provided a clear hint that the page is cold and she won't be touching
> it for a while. MADV_PAGEOUT is basically MADV_COLD + try_to_reclaim.
> So IMO isolation should go to the end next to deactivate_page().
Make sense to me
--
Michal Hocko
SUSE Labs
Re: [PATCH v4 4/4] mm: introduce MADV_PAGEOUT
On Fri, Jul 12, 2019 at 02:18:28PM +0900, Minchan Kim wrote:
> Hi Johannes,
>
> On Thu, Jul 11, 2019 at 02:42:23PM -0400, Johannes Weiner wrote:
> > On Thu, Jul 11, 2019 at 10:25:28AM +0900, Minchan Kim wrote:
> > > @@ -480,6 +482,198 @@ static long madvise_cold(struct vm_area_struct *vma,
> > > return 0;
> > > }
> > >
> > > +static int madvise_pageout_pte_range(pmd_t *pmd, unsigned long addr,
> > > + unsigned long end, struct mm_walk *walk)
> > > +{
> > > + struct mmu_gather *tlb = walk->private;
> > > + struct mm_struct *mm = tlb->mm;
> > > + struct vm_area_struct *vma = walk->vma;
> > > + pte_t *orig_pte, *pte, ptent;
> > > + spinlock_t *ptl;
> > > + LIST_HEAD(page_list);
> > > + struct page *page;
> > > + unsigned long next;
> > > +
> > > + if (fatal_signal_pending(current))
> > > + return -EINTR;
> > > +
> > > + next = pmd_addr_end(addr, end);
> > > + if (pmd_trans_huge(*pmd)) {
> > > + pmd_t orig_pmd;
> > > +
> > > + tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
> > > + ptl = pmd_trans_huge_lock(pmd, vma);
> > > + if (!ptl)
> > > + return 0;
> > > +
> > > + orig_pmd = *pmd;
> > > + if (is_huge_zero_pmd(orig_pmd))
> > > + goto huge_unlock;
> > > +
> > > + if (unlikely(!pmd_present(orig_pmd))) {
> > > + VM_BUG_ON(thp_migration_supported() &&
> > > + !is_pmd_migration_entry(orig_pmd));
> > > + goto huge_unlock;
> > > + }
> > > +
> > > + page = pmd_page(orig_pmd);
> > > + if (next - addr != HPAGE_PMD_SIZE) {
> > > + int err;
> > > +
> > > + if (page_mapcount(page) != 1)
> > > + goto huge_unlock;
> > > + get_page(page);
> > > + spin_unlock(ptl);
> > > + lock_page(page);
> > > + err = split_huge_page(page);
> > > + unlock_page(page);
> > > + put_page(page);
> > > + if (!err)
> > > + goto regular_page;
> > > + return 0;
> > > + }
> > > +
> > > + if (isolate_lru_page(page))
> > > + goto huge_unlock;
> > > +
> > > + if (pmd_young(orig_pmd)) {
> > > + pmdp_invalidate(vma, addr, pmd);
> > > + orig_pmd = pmd_mkold(orig_pmd);
> > > +
> > > + set_pmd_at(mm, addr, pmd, orig_pmd);
> > > + tlb_remove_tlb_entry(tlb, pmd, addr);
> > > + }
> > > +
> > > + ClearPageReferenced(page);
> > > + test_and_clear_page_young(page);
> > > + list_add(>lru, _list);
> > > +huge_unlock:
> > > + spin_unlock(ptl);
> > > + reclaim_pages(_list);
> > > + return 0;
> > > + }
> > > +
> > > + if (pmd_trans_unstable(pmd))
> > > + return 0;
> > > +regular_page:
> > > + tlb_change_page_size(tlb, PAGE_SIZE);
> > > + orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, );
> > > + flush_tlb_batched_pending(mm);
> > > + arch_enter_lazy_mmu_mode();
> > > + for (; addr < end; pte++, addr += PAGE_SIZE) {
> > > + ptent = *pte;
> > > + if (!pte_present(ptent))
> > > + continue;
> > > +
> > > + page = vm_normal_page(vma, addr, ptent);
> > > + if (!page)
> > > + continue;
> > > +
> > > + /*
> > > + * creating a THP page is expensive so split it only if we
> > > + * are sure it's worth. Split it if we are only owner.
> > > + */
> > > + if (PageTransCompound(page)) {
> > > + if (page_mapcount(page) != 1)
> > > + break;
> > > + get_page(page);
> > > + if (!trylock_page(page)) {
> > > + put_page(page);
> > > + break;
> > > + }
> > > + pte_unmap_unlock(orig_pte, ptl);
> > > + if (split_huge_page(page)) {
> > > + unlock_page(page);
> > > + put_page(page);
> > > + pte_offset_map_lock(mm, pmd, addr, );
> > > + break;
> > > + }
> > > + unlock_page(page);
> > > + put_page(page);
> > > + pte = pte_offset_map_lock(mm, pmd, addr, );
> > > + pte--;
> > > + addr -= PAGE_SIZE;
> > > + continue;
> > > + }
> > > +
> > > + VM_BUG_ON_PAGE(PageTransCompound(page), page);
> > > +
> > > + if (isolate_lru_page(page))
> > > + continue;
> > > +
> > > + if (pte_young(ptent)) {
> > > + ptent = ptep_get_and_clear_full(mm, addr, pte,
> > > + tlb->fullmm);
> > > + ptent = pte_mkold(ptent);
> > > +
Re: [PATCH v4 4/4] mm: introduce MADV_PAGEOUT
On Fri 12-07-19 14:18:28, Minchan Kim wrote:
[...]
> >From 41592f23e876ec21e49dc3c76dc89538e2bb16be Mon Sep 17 00:00:00 2001
> From: Minchan Kim
> Date: Fri, 12 Jul 2019 14:05:36 +0900
> Subject: [PATCH] mm: factor out common parts between MADV_COLD and
> MADV_PAGEOUT
>
> There are many common parts between MADV_COLD and MADV_PAGEOUT.
> This patch factor them out to save code duplication.
This looks better indeed. I still hope that this can get improved even
further but let's do that in a follow up patch.
> Signed-off-by: Minchan Kim
Acked-by: Michal Hocko
> ---
> mm/madvise.c | 201 +--
> 1 file changed, 52 insertions(+), 149 deletions(-)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index bc2f0138982e..3d3d14517cc8 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -30,6 +30,11 @@
>
> #include "internal.h"
>
> +struct madvise_walk_private {
> + struct mmu_gather *tlb;
> + bool pageout;
> +};
> +
> /*
> * Any behaviour which results in changes to the vma->vm_flags needs to
> * take mmap_sem for writing. Others, which simply traverse vmas, need
> @@ -310,16 +315,23 @@ static long madvise_willneed(struct vm_area_struct *vma,
> return 0;
> }
>
> -static int madvise_cold_pte_range(pmd_t *pmd, unsigned long addr,
> - unsigned long end, struct mm_walk *walk)
> +static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
> + unsigned long addr, unsigned long end,
> + struct mm_walk *walk)
> {
> - struct mmu_gather *tlb = walk->private;
> + struct madvise_walk_private *private = walk->private;
> + struct mmu_gather *tlb = private->tlb;
> + bool pageout = private->pageout;
> struct mm_struct *mm = tlb->mm;
> struct vm_area_struct *vma = walk->vma;
> pte_t *orig_pte, *pte, ptent;
> spinlock_t *ptl;
> - struct page *page;
> unsigned long next;
> + struct page *page = NULL;
> + LIST_HEAD(page_list);
> +
> + if (fatal_signal_pending(current))
> + return -EINTR;
>
> next = pmd_addr_end(addr, end);
> if (pmd_trans_huge(*pmd)) {
> @@ -358,6 +370,12 @@ static int madvise_cold_pte_range(pmd_t *pmd, unsigned
> long addr,
> return 0;
> }
>
> + if (pageout) {
> + if (isolate_lru_page(page))
> + goto huge_unlock;
> + list_add(>lru, _list);
> + }
> +
> if (pmd_young(orig_pmd)) {
> pmdp_invalidate(vma, addr, pmd);
> orig_pmd = pmd_mkold(orig_pmd);
> @@ -366,10 +384,14 @@ static int madvise_cold_pte_range(pmd_t *pmd, unsigned
> long addr,
> tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
> }
>
> + ClearPageReferenced(page);
> test_and_clear_page_young(page);
> - deactivate_page(page);
> huge_unlock:
> spin_unlock(ptl);
> + if (pageout)
> + reclaim_pages(_list);
> + else
> + deactivate_page(page);
> return 0;
> }
>
> @@ -423,6 +445,12 @@ static int madvise_cold_pte_range(pmd_t *pmd, unsigned
> long addr,
>
> VM_BUG_ON_PAGE(PageTransCompound(page), page);
>
> + if (pageout) {
> + if (isolate_lru_page(page))
> + continue;
> + list_add(>lru, _list);
> + }
> +
> if (pte_young(ptent)) {
> ptent = ptep_get_and_clear_full(mm, addr, pte,
> tlb->fullmm);
> @@ -437,12 +465,16 @@ static int madvise_cold_pte_range(pmd_t *pmd, unsigned
> long addr,
>* As a side effect, it makes confuse idle-page tracking
>* because they will miss recent referenced history.
>*/
> + ClearPageReferenced(page);
> test_and_clear_page_young(page);
> - deactivate_page(page);
> + if (!pageout)
> + deactivate_page(page);
> }
>
> arch_enter_lazy_mmu_mode();
> pte_unmap_unlock(orig_pte, ptl);
> + if (pageout)
> + reclaim_pages(_list);
> cond_resched();
>
> return 0;
> @@ -452,10 +484,15 @@ static void madvise_cold_page_range(struct mmu_gather
> *tlb,
>struct vm_area_struct *vma,
>unsigned long addr, unsigned long end)
> {
> + struct madvise_walk_private walk_private = {
> + .tlb = tlb,
> + .pageout = false,
> + };
> +
> struct mm_walk cold_walk = {
> - .pmd_entry = madvise_cold_pte_range,
> + .pmd_entry = madvise_cold_or_pageout_pte_range,
> .mm = vma->vm_mm,
> -
Re: [PATCH v4 4/4] mm: introduce MADV_PAGEOUT
Hi Johannes,
On Thu, Jul 11, 2019 at 02:42:23PM -0400, Johannes Weiner wrote:
> On Thu, Jul 11, 2019 at 10:25:28AM +0900, Minchan Kim wrote:
> > @@ -480,6 +482,198 @@ static long madvise_cold(struct vm_area_struct *vma,
> > return 0;
> > }
> >
> > +static int madvise_pageout_pte_range(pmd_t *pmd, unsigned long addr,
> > + unsigned long end, struct mm_walk *walk)
> > +{
> > + struct mmu_gather *tlb = walk->private;
> > + struct mm_struct *mm = tlb->mm;
> > + struct vm_area_struct *vma = walk->vma;
> > + pte_t *orig_pte, *pte, ptent;
> > + spinlock_t *ptl;
> > + LIST_HEAD(page_list);
> > + struct page *page;
> > + unsigned long next;
> > +
> > + if (fatal_signal_pending(current))
> > + return -EINTR;
> > +
> > + next = pmd_addr_end(addr, end);
> > + if (pmd_trans_huge(*pmd)) {
> > + pmd_t orig_pmd;
> > +
> > + tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
> > + ptl = pmd_trans_huge_lock(pmd, vma);
> > + if (!ptl)
> > + return 0;
> > +
> > + orig_pmd = *pmd;
> > + if (is_huge_zero_pmd(orig_pmd))
> > + goto huge_unlock;
> > +
> > + if (unlikely(!pmd_present(orig_pmd))) {
> > + VM_BUG_ON(thp_migration_supported() &&
> > + !is_pmd_migration_entry(orig_pmd));
> > + goto huge_unlock;
> > + }
> > +
> > + page = pmd_page(orig_pmd);
> > + if (next - addr != HPAGE_PMD_SIZE) {
> > + int err;
> > +
> > + if (page_mapcount(page) != 1)
> > + goto huge_unlock;
> > + get_page(page);
> > + spin_unlock(ptl);
> > + lock_page(page);
> > + err = split_huge_page(page);
> > + unlock_page(page);
> > + put_page(page);
> > + if (!err)
> > + goto regular_page;
> > + return 0;
> > + }
> > +
> > + if (isolate_lru_page(page))
> > + goto huge_unlock;
> > +
> > + if (pmd_young(orig_pmd)) {
> > + pmdp_invalidate(vma, addr, pmd);
> > + orig_pmd = pmd_mkold(orig_pmd);
> > +
> > + set_pmd_at(mm, addr, pmd, orig_pmd);
> > + tlb_remove_tlb_entry(tlb, pmd, addr);
> > + }
> > +
> > + ClearPageReferenced(page);
> > + test_and_clear_page_young(page);
> > + list_add(>lru, _list);
> > +huge_unlock:
> > + spin_unlock(ptl);
> > + reclaim_pages(_list);
> > + return 0;
> > + }
> > +
> > + if (pmd_trans_unstable(pmd))
> > + return 0;
> > +regular_page:
> > + tlb_change_page_size(tlb, PAGE_SIZE);
> > + orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, );
> > + flush_tlb_batched_pending(mm);
> > + arch_enter_lazy_mmu_mode();
> > + for (; addr < end; pte++, addr += PAGE_SIZE) {
> > + ptent = *pte;
> > + if (!pte_present(ptent))
> > + continue;
> > +
> > + page = vm_normal_page(vma, addr, ptent);
> > + if (!page)
> > + continue;
> > +
> > + /*
> > +* creating a THP page is expensive so split it only if we
> > +* are sure it's worth. Split it if we are only owner.
> > +*/
> > + if (PageTransCompound(page)) {
> > + if (page_mapcount(page) != 1)
> > + break;
> > + get_page(page);
> > + if (!trylock_page(page)) {
> > + put_page(page);
> > + break;
> > + }
> > + pte_unmap_unlock(orig_pte, ptl);
> > + if (split_huge_page(page)) {
> > + unlock_page(page);
> > + put_page(page);
> > + pte_offset_map_lock(mm, pmd, addr, );
> > + break;
> > + }
> > + unlock_page(page);
> > + put_page(page);
> > + pte = pte_offset_map_lock(mm, pmd, addr, );
> > + pte--;
> > + addr -= PAGE_SIZE;
> > + continue;
> > + }
> > +
> > + VM_BUG_ON_PAGE(PageTransCompound(page), page);
> > +
> > + if (isolate_lru_page(page))
> > + continue;
> > +
> > + if (pte_young(ptent)) {
> > + ptent = ptep_get_and_clear_full(mm, addr, pte,
> > + tlb->fullmm);
> > + ptent = pte_mkold(ptent);
> > + set_pte_at(mm, addr, pte, ptent);
> > + tlb_remove_tlb_entry(tlb, pte, addr);
> > +
Re: [PATCH v4 4/4] mm: introduce MADV_PAGEOUT
On Thu, Jul 11, 2019 at 10:25:28AM +0900, Minchan Kim wrote:
> @@ -480,6 +482,198 @@ static long madvise_cold(struct vm_area_struct *vma,
> return 0;
> }
>
> +static int madvise_pageout_pte_range(pmd_t *pmd, unsigned long addr,
> + unsigned long end, struct mm_walk *walk)
> +{
> + struct mmu_gather *tlb = walk->private;
> + struct mm_struct *mm = tlb->mm;
> + struct vm_area_struct *vma = walk->vma;
> + pte_t *orig_pte, *pte, ptent;
> + spinlock_t *ptl;
> + LIST_HEAD(page_list);
> + struct page *page;
> + unsigned long next;
> +
> + if (fatal_signal_pending(current))
> + return -EINTR;
> +
> + next = pmd_addr_end(addr, end);
> + if (pmd_trans_huge(*pmd)) {
> + pmd_t orig_pmd;
> +
> + tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
> + ptl = pmd_trans_huge_lock(pmd, vma);
> + if (!ptl)
> + return 0;
> +
> + orig_pmd = *pmd;
> + if (is_huge_zero_pmd(orig_pmd))
> + goto huge_unlock;
> +
> + if (unlikely(!pmd_present(orig_pmd))) {
> + VM_BUG_ON(thp_migration_supported() &&
> + !is_pmd_migration_entry(orig_pmd));
> + goto huge_unlock;
> + }
> +
> + page = pmd_page(orig_pmd);
> + if (next - addr != HPAGE_PMD_SIZE) {
> + int err;
> +
> + if (page_mapcount(page) != 1)
> + goto huge_unlock;
> + get_page(page);
> + spin_unlock(ptl);
> + lock_page(page);
> + err = split_huge_page(page);
> + unlock_page(page);
> + put_page(page);
> + if (!err)
> + goto regular_page;
> + return 0;
> + }
> +
> + if (isolate_lru_page(page))
> + goto huge_unlock;
> +
> + if (pmd_young(orig_pmd)) {
> + pmdp_invalidate(vma, addr, pmd);
> + orig_pmd = pmd_mkold(orig_pmd);
> +
> + set_pmd_at(mm, addr, pmd, orig_pmd);
> + tlb_remove_tlb_entry(tlb, pmd, addr);
> + }
> +
> + ClearPageReferenced(page);
> + test_and_clear_page_young(page);
> + list_add(>lru, _list);
> +huge_unlock:
> + spin_unlock(ptl);
> + reclaim_pages(_list);
> + return 0;
> + }
> +
> + if (pmd_trans_unstable(pmd))
> + return 0;
> +regular_page:
> + tlb_change_page_size(tlb, PAGE_SIZE);
> + orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, );
> + flush_tlb_batched_pending(mm);
> + arch_enter_lazy_mmu_mode();
> + for (; addr < end; pte++, addr += PAGE_SIZE) {
> + ptent = *pte;
> + if (!pte_present(ptent))
> + continue;
> +
> + page = vm_normal_page(vma, addr, ptent);
> + if (!page)
> + continue;
> +
> + /*
> + * creating a THP page is expensive so split it only if we
> + * are sure it's worth. Split it if we are only owner.
> + */
> + if (PageTransCompound(page)) {
> + if (page_mapcount(page) != 1)
> + break;
> + get_page(page);
> + if (!trylock_page(page)) {
> + put_page(page);
> + break;
> + }
> + pte_unmap_unlock(orig_pte, ptl);
> + if (split_huge_page(page)) {
> + unlock_page(page);
> + put_page(page);
> + pte_offset_map_lock(mm, pmd, addr, );
> + break;
> + }
> + unlock_page(page);
> + put_page(page);
> + pte = pte_offset_map_lock(mm, pmd, addr, );
> + pte--;
> + addr -= PAGE_SIZE;
> + continue;
> + }
> +
> + VM_BUG_ON_PAGE(PageTransCompound(page), page);
> +
> + if (isolate_lru_page(page))
> + continue;
> +
> + if (pte_young(ptent)) {
> + ptent = ptep_get_and_clear_full(mm, addr, pte,
> + tlb->fullmm);
> + ptent = pte_mkold(ptent);
> + set_pte_at(mm, addr, pte, ptent);
> + tlb_remove_tlb_entry(tlb, pte, addr);
> + }
> + ClearPageReferenced(page);
> + test_and_clear_page_young(page);
> + list_add(>lru,
