Re: [PATCH v6 06/15] mm/khugepaged: pipe enum scan_result codes back to callers

["Zach O'Keefe" <zokeefe@google.com>]

On Mon, Jun 6, 2022 at 3:40 PM Yang Shi <shy828301@gmail.com> wrote:
>
> On Fri, Jun 3, 2022 at 5:40 PM Zach O'Keefe <zokeefe@google.com> wrote:
> >
> > Pipe enum scan_result codes back through return values of functions
> > downstream of khugepaged_scan_file() and khugepaged_scan_pmd() to
> > inform callers if the operation was successful, and if not, why.
> >
> > Since khugepaged_scan_pmd()'s return value already has a specific
> > meaning (whether mmap_lock was unlocked or not), add a bool* argument
> > to khugepaged_scan_pmd() to retrieve this information.
> >
> > Change khugepaged to take action based on the return values of
> > khugepaged_scan_file() and khugepaged_scan_pmd() instead of acting
> > deep within the collapsing functions themselves.
> >
> > Remove dependency on error pointers to communicate to khugepaged that
> > allocation failed and it should sleep; instead just use the result of
> > the scan (SCAN_ALLOC_HUGE_PAGE_FAIL if allocation fails).
> >
> > Signed-off-by: Zach O'Keefe <zokeefe@google.com>
>
> Reviewed-by: Yang Shi <shy828301@gmail.com>

Hey Yang,

Thanks for taking the time to review this series. Very much appreciated!

> A couple of minor nits below...
>
> > ---
> >  mm/khugepaged.c | 192 ++++++++++++++++++++++++------------------------
> >  1 file changed, 96 insertions(+), 96 deletions(-)
> >
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index ba722347bebd..03e0da0008f1 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -722,13 +722,13 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> >                 result = SCAN_SUCCEED;
> >                 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
> >                                                     referenced, writable, result);
> > -               return 1;
> > +               return SCAN_SUCCEED;
>
> You could do "return result" too.

Thanks for catching. Done.

> >         }
> >  out:
> >         release_pte_pages(pte, _pte, compound_pagelist);
> >         trace_mm_collapse_huge_page_isolate(page, none_or_zero,
> >                                             referenced, writable, result);
> > -       return 0;
> > +       return result;
> >  }
> >
> >  static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> > @@ -850,14 +850,13 @@ static int khugepaged_find_target_node(struct collapse_control *cc)
> >  #endif
> >
> >  /* Sleep for the first alloc fail, break the loop for the second fail */
> > -static bool alloc_fail_should_sleep(struct page **hpage, bool *wait)
> > +static bool alloc_fail_should_sleep(int result, bool *wait)
> >  {
> > -       if (IS_ERR(*hpage)) {
> > +       if (result == SCAN_ALLOC_HUGE_PAGE_FAIL) {
> >                 if (!*wait)
> >                         return true;
> >
> >                 *wait = false;
> > -               *hpage = NULL;
> >                 khugepaged_alloc_sleep();
> >         }
> >         return false;
> > @@ -868,7 +867,6 @@ static bool khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
> >         *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
> >         if (unlikely(!*hpage)) {
> >                 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
> > -               *hpage = ERR_PTR(-ENOMEM);
> >                 return false;
> >         }
> >
> > @@ -1010,17 +1008,17 @@ static int alloc_charge_hpage(struct mm_struct *mm, struct page **hpage,
> >         return SCAN_SUCCEED;
> >  }
> >
> > -static void collapse_huge_page(struct mm_struct *mm, unsigned long address,
> > -                              struct page **hpage, int referenced,
> > -                              int unmapped, struct collapse_control *cc)
> > +static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
> > +                             int referenced, int unmapped,
> > +                             struct collapse_control *cc)
> >  {
> >         LIST_HEAD(compound_pagelist);
> >         pmd_t *pmd, _pmd;
> >         pte_t *pte;
> >         pgtable_t pgtable;
> > -       struct page *new_page;
> > +       struct page *hpage;
> >         spinlock_t *pmd_ptl, *pte_ptl;
> > -       int isolated = 0, result = 0;
> > +       int result = SCAN_FAIL;
> >         struct vm_area_struct *vma;
> >         struct mmu_notifier_range range;
> >
> > @@ -1034,12 +1032,10 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address,
> >          */
> >         mmap_read_unlock(mm);
> >
> > -       result = alloc_charge_hpage(mm, hpage, cc);
> > +       result = alloc_charge_hpage(mm, &hpage, cc);
> >         if (result != SCAN_SUCCEED)
> >                 goto out_nolock;
> >
> > -       new_page = *hpage;
> > -
> >         mmap_read_lock(mm);
> >         result = hugepage_vma_revalidate(mm, address, &vma);
> >         if (result) {
> > @@ -1100,11 +1096,11 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address,
> >         mmu_notifier_invalidate_range_end(&range);
> >
> >         spin_lock(pte_ptl);
> > -       isolated = __collapse_huge_page_isolate(vma, address, pte,
> > -                       &compound_pagelist);
> > +       result =  __collapse_huge_page_isolate(vma, address, pte,
> > +                                              &compound_pagelist);
> >         spin_unlock(pte_ptl);
> >
> > -       if (unlikely(!isolated)) {
> > +       if (unlikely(result != SCAN_SUCCEED)) {
> >                 pte_unmap(pte);
> >                 spin_lock(pmd_ptl);
> >                 BUG_ON(!pmd_none(*pmd));
> > @@ -1116,7 +1112,6 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address,
> >                 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
> >                 spin_unlock(pmd_ptl);
> >                 anon_vma_unlock_write(vma->anon_vma);
> > -               result = SCAN_FAIL;
> >                 goto out_up_write;
> >         }
> >
> > @@ -1126,8 +1121,8 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address,
> >          */
> >         anon_vma_unlock_write(vma->anon_vma);
> >
> > -       __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl,
> > -                       &compound_pagelist);
> > +       __collapse_huge_page_copy(pte, hpage, vma, address, pte_ptl,
> > +                                 &compound_pagelist);
> >         pte_unmap(pte);
> >         /*
> >          * spin_lock() below is not the equivalent of smp_wmb(), but
> > @@ -1135,43 +1130,42 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address,
> >          * avoid the copy_huge_page writes to become visible after
> >          * the set_pmd_at() write.
> >          */
> > -       __SetPageUptodate(new_page);
> > +       __SetPageUptodate(hpage);
> >         pgtable = pmd_pgtable(_pmd);
> >
> > -       _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
> > +       _pmd = mk_huge_pmd(hpage, vma->vm_page_prot);
> >         _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
> >
> >         spin_lock(pmd_ptl);
> >         BUG_ON(!pmd_none(*pmd));
> > -       page_add_new_anon_rmap(new_page, vma, address);
> > -       lru_cache_add_inactive_or_unevictable(new_page, vma);
> > +       page_add_new_anon_rmap(hpage, vma, address);
> > +       lru_cache_add_inactive_or_unevictable(hpage, vma);
> >         pgtable_trans_huge_deposit(mm, pmd, pgtable);
> >         set_pmd_at(mm, address, pmd, _pmd);
> >         update_mmu_cache_pmd(vma, address, pmd);
> >         spin_unlock(pmd_ptl);
> >
> > -       *hpage = NULL;
> > +       hpage = NULL;
> >
> > -       khugepaged_pages_collapsed++;
> >         result = SCAN_SUCCEED;
> >  out_up_write:
> >         mmap_write_unlock(mm);
> >  out_nolock:
> > -       if (!IS_ERR_OR_NULL(*hpage)) {
> > -               mem_cgroup_uncharge(page_folio(*hpage));
> > -               put_page(*hpage);
> > +       if (hpage) {
> > +               mem_cgroup_uncharge(page_folio(hpage));
> > +               put_page(hpage);
> >         }
> > -       trace_mm_collapse_huge_page(mm, isolated, result);
> > -       return;
> > +       trace_mm_collapse_huge_page(mm, result == SCAN_SUCCEED, result);
> > +       return result;
> >  }
> >
> >  static int khugepaged_scan_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
> > -                              unsigned long address, struct page **hpage,
> > +                              unsigned long address, bool *mmap_locked,
> >                                struct collapse_control *cc)
> >  {
> >         pmd_t *pmd;
> >         pte_t *pte, *_pte;
> > -       int ret = 0, result = 0, referenced = 0;
> > +       int result = SCAN_FAIL, referenced = 0;
> >         int none_or_zero = 0, shared = 0;
> >         struct page *page = NULL;
> >         unsigned long _address;
> > @@ -1306,19 +1300,19 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
> >                 result = SCAN_LACK_REFERENCED_PAGE;
> >         } else {
> >                 result = SCAN_SUCCEED;
> > -               ret = 1;
> >         }
> >  out_unmap:
> >         pte_unmap_unlock(pte, ptl);
> > -       if (ret) {
> > +       if (result == SCAN_SUCCEED) {
> >                 /* collapse_huge_page will return with the mmap_lock released */
> > -               collapse_huge_page(mm, address, hpage, referenced, unmapped,
> > -                                  cc);
> > +               *mmap_locked = false;
> > +               result = collapse_huge_page(mm, address, referenced,
> > +                                           unmapped, cc);
>
> Shall move "*mmap_locked = false" after collapse_huge_page() call? No
> functional change, but seems more consistent.

Done.

> >         }
> >  out:
> >         trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
> >                                      none_or_zero, result, unmapped);
> > -       return ret;
> > +       return result;
> >  }
> >
> >  static void collect_mm_slot(struct mm_slot *mm_slot)
> > @@ -1581,7 +1575,6 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
> >   * @mm: process address space where collapse happens
> >   * @file: file that collapse on
> >   * @start: collapse start address
> > - * @hpage: new allocated huge page for collapse
> >   * @cc: collapse context and scratchpad
> >   *
> >   * Basic scheme is simple, details are more complex:
> > @@ -1599,12 +1592,11 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
> >   *    + restore gaps in the page cache;
> >   *    + unlock and free huge page;
> >   */
> > -static void collapse_file(struct mm_struct *mm, struct file *file,
> > -                         pgoff_t start, struct page **hpage,
> > -                         struct collapse_control *cc)
> > +static int collapse_file(struct mm_struct *mm, struct file *file,
> > +                        pgoff_t start, struct collapse_control *cc)
> >  {
> >         struct address_space *mapping = file->f_mapping;
> > -       struct page *new_page;
> > +       struct page *hpage;
> >         pgoff_t index, end = start + HPAGE_PMD_NR;
> >         LIST_HEAD(pagelist);
> >         XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
> > @@ -1615,12 +1607,10 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
> >         VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
> >         VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
> >
> > -       result = alloc_charge_hpage(mm, hpage, cc);
> > +       result = alloc_charge_hpage(mm, &hpage, cc);
> >         if (result != SCAN_SUCCEED)
> >                 goto out;
> >
> > -       new_page = *hpage;
> > -
> >         /*
> >          * Ensure we have slots for all the pages in the range.  This is
> >          * almost certainly a no-op because most of the pages must be present
> > @@ -1637,14 +1627,14 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
> >                 }
> >         } while (1);
> >
> > -       __SetPageLocked(new_page);
> > +       __SetPageLocked(hpage);
> >         if (is_shmem)
> > -               __SetPageSwapBacked(new_page);
> > -       new_page->index = start;
> > -       new_page->mapping = mapping;
> > +               __SetPageSwapBacked(hpage);
> > +       hpage->index = start;
> > +       hpage->mapping = mapping;
> >
> >         /*
> > -        * At this point the new_page is locked and not up-to-date.
> > +        * At this point the hpage is locked and not up-to-date.
> >          * It's safe to insert it into the page cache, because nobody would
> >          * be able to map it or use it in another way until we unlock it.
> >          */
> > @@ -1672,7 +1662,7 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
> >                                         result = SCAN_FAIL;
> >                                         goto xa_locked;
> >                                 }
> > -                               xas_store(&xas, new_page);
> > +                               xas_store(&xas, hpage);
> >                                 nr_none++;
> >                                 continue;
> >                         }
> > @@ -1814,19 +1804,19 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
> >                 list_add_tail(&page->lru, &pagelist);
> >
> >                 /* Finally, replace with the new page. */
> > -               xas_store(&xas, new_page);
> > +               xas_store(&xas, hpage);
> >                 continue;
> >  out_unlock:
> >                 unlock_page(page);
> >                 put_page(page);
> >                 goto xa_unlocked;
> >         }
> > -       nr = thp_nr_pages(new_page);
> > +       nr = thp_nr_pages(hpage);
> >
> >         if (is_shmem)
> > -               __mod_lruvec_page_state(new_page, NR_SHMEM_THPS, nr);
> > +               __mod_lruvec_page_state(hpage, NR_SHMEM_THPS, nr);
> >         else {
> > -               __mod_lruvec_page_state(new_page, NR_FILE_THPS, nr);
> > +               __mod_lruvec_page_state(hpage, NR_FILE_THPS, nr);
> >                 filemap_nr_thps_inc(mapping);
> >                 /*
> >                  * Paired with smp_mb() in do_dentry_open() to ensure
> > @@ -1837,21 +1827,21 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
> >                 smp_mb();
> >                 if (inode_is_open_for_write(mapping->host)) {
> >                         result = SCAN_FAIL;
> > -                       __mod_lruvec_page_state(new_page, NR_FILE_THPS, -nr);
> > +                       __mod_lruvec_page_state(hpage, NR_FILE_THPS, -nr);
> >                         filemap_nr_thps_dec(mapping);
> >                         goto xa_locked;
> >                 }
> >         }
> >
> >         if (nr_none) {
> > -               __mod_lruvec_page_state(new_page, NR_FILE_PAGES, nr_none);
> > +               __mod_lruvec_page_state(hpage, NR_FILE_PAGES, nr_none);
> >                 if (is_shmem)
> > -                       __mod_lruvec_page_state(new_page, NR_SHMEM, nr_none);
> > +                       __mod_lruvec_page_state(hpage, NR_SHMEM, nr_none);
> >         }
> >
> >         /* Join all the small entries into a single multi-index entry */
> >         xas_set_order(&xas, start, HPAGE_PMD_ORDER);
> > -       xas_store(&xas, new_page);
> > +       xas_store(&xas, hpage);
> >  xa_locked:
> >         xas_unlock_irq(&xas);
> >  xa_unlocked:
> > @@ -1873,11 +1863,11 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
> >                 index = start;
> >                 list_for_each_entry_safe(page, tmp, &pagelist, lru) {
> >                         while (index < page->index) {
> > -                               clear_highpage(new_page + (index % HPAGE_PMD_NR));
> > +                               clear_highpage(hpage + (index % HPAGE_PMD_NR));
> >                                 index++;
> >                         }
> > -                       copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
> > -                                       page);
> > +                       copy_highpage(hpage + (page->index % HPAGE_PMD_NR),
> > +                                     page);
> >                         list_del(&page->lru);
> >                         page->mapping = NULL;
> >                         page_ref_unfreeze(page, 1);
> > @@ -1888,23 +1878,23 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
> >                         index++;
> >                 }
> >                 while (index < end) {
> > -                       clear_highpage(new_page + (index % HPAGE_PMD_NR));
> > +                       clear_highpage(hpage + (index % HPAGE_PMD_NR));
> >                         index++;
> >                 }
> >
> > -               SetPageUptodate(new_page);
> > -               page_ref_add(new_page, HPAGE_PMD_NR - 1);
> > +               SetPageUptodate(hpage);
> > +               page_ref_add(hpage, HPAGE_PMD_NR - 1);
> >                 if (is_shmem)
> > -                       set_page_dirty(new_page);
> > -               lru_cache_add(new_page);
> > +                       set_page_dirty(hpage);
> > +               lru_cache_add(hpage);
> >
> >                 /*
> >                  * Remove pte page tables, so we can re-fault the page as huge.
> >                  */
> >                 retract_page_tables(mapping, start);
> > -               *hpage = NULL;
> > -
> > -               khugepaged_pages_collapsed++;
> > +               unlock_page(hpage);
> > +               hpage = NULL;
> > +               goto out;
>
> Maybe just set hpage to NULL here, then later...
>
> >         } else {
> >                 struct page *page;
> >
> > @@ -1943,22 +1933,22 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
> >                 VM_BUG_ON(nr_none);
> >                 xas_unlock_irq(&xas);
> >
> > -               new_page->mapping = NULL;
> > +               hpage->mapping = NULL;
> >         }
> >
> > -       unlock_page(new_page);
> > +       unlock_page(hpage);
>
> do
> if (hpage)
>     unlock_page(hpage);

I don't have a strong preference here. Done.


> >  out:
> >         VM_BUG_ON(!list_empty(&pagelist));
> > -       if (!IS_ERR_OR_NULL(*hpage)) {
> > -               mem_cgroup_uncharge(page_folio(*hpage));
> > -               put_page(*hpage);
> > +       if (hpage) {
> > +               mem_cgroup_uncharge(page_folio(hpage));
> > +               put_page(hpage);
> >         }
> >         /* TODO: tracepoints */
> > +       return result;
> >  }
> >
> > -static void khugepaged_scan_file(struct mm_struct *mm, struct file *file,
> > -                                pgoff_t start, struct page **hpage,
> > -                                struct collapse_control *cc)
> > +static int khugepaged_scan_file(struct mm_struct *mm, struct file *file,
> > +                               pgoff_t start, struct collapse_control *cc)
> >  {
> >         struct page *page = NULL;
> >         struct address_space *mapping = file->f_mapping;
> > @@ -2031,15 +2021,16 @@ static void khugepaged_scan_file(struct mm_struct *mm, struct file *file,
> >                         result = SCAN_EXCEED_NONE_PTE;
> >                         count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
> >                 } else {
> > -                       collapse_file(mm, file, start, hpage, cc);
> > +                       result = collapse_file(mm, file, start, cc);
> >                 }
> >         }
> >
> >         /* TODO: tracepoints */
> > +       return result;
> >  }
> >  #else
> > -static void khugepaged_scan_file(struct mm_struct *mm, struct file *file,
> > -                                pgoff_t start, struct collapse_control *cc)
> > +static int khugepaged_scan_file(struct mm_struct *mm, struct file *file, pgoff_t start,
> > +                               struct collapse_control *cc)
> >  {
> >         BUILD_BUG();
> >  }
> > @@ -2049,8 +2040,7 @@ static void khugepaged_collapse_pte_mapped_thps(struct mm_slot *mm_slot)
> >  }
> >  #endif
> >
> > -static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
> > -                                           struct page **hpage,
> > +static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
> >                                             struct collapse_control *cc)
> >         __releases(&khugepaged_mm_lock)
> >         __acquires(&khugepaged_mm_lock)
> > @@ -2064,6 +2054,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
> >
> >         VM_BUG_ON(!pages);
> >         lockdep_assert_held(&khugepaged_mm_lock);
> > +       *result = SCAN_FAIL;
> >
> >         if (khugepaged_scan.mm_slot)
> >                 mm_slot = khugepaged_scan.mm_slot;
> > @@ -2117,7 +2108,8 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
> >                         goto skip;
> >
> >                 while (khugepaged_scan.address < hend) {
> > -                       int ret;
> > +                       bool mmap_locked = true;
> > +
> >                         cond_resched();
> >                         if (unlikely(khugepaged_test_exit(mm)))
> >                                 goto breakouterloop;
> > @@ -2134,20 +2126,28 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
> >                                                 khugepaged_scan.address);
> >
> >                                 mmap_read_unlock(mm);
> > -                               ret = 1;
> > -                               khugepaged_scan_file(mm, file, pgoff, hpage,
> > -                                                    cc);
> > +                               mmap_locked = false;
> > +                               *result = khugepaged_scan_file(mm, file, pgoff,
> > +                                                              cc);
> >                                 fput(file);
> >                         } else {
> > -                               ret = khugepaged_scan_pmd(mm, vma,
> > -                                               khugepaged_scan.address,
> > -                                               hpage, cc);
> > +                               *result = khugepaged_scan_pmd(mm, vma,
> > +                                                             khugepaged_scan.address,
> > +                                                             &mmap_locked, cc);
> >                         }
> > +                       if (*result == SCAN_SUCCEED)
> > +                               ++khugepaged_pages_collapsed;
> >                         /* move to next address */
> >                         khugepaged_scan.address += HPAGE_PMD_SIZE;
> >                         progress += HPAGE_PMD_NR;
> > -                       if (ret)
> > -                               /* we released mmap_lock so break loop */
> > +                       if (!mmap_locked)
> > +                               /*
> > +                                * We released mmap_lock so break loop.  Note
> > +                                * that we drop mmap_lock before all hugepage
> > +                                * allocations, so if allocation fails, we are
> > +                                * guaranteed to break here and report the
> > +                                * correct result back to caller.
> > +                                */
> >                                 goto breakouterloop_mmap_lock;
> >                         if (progress >= pages)
> >                                 goto breakouterloop;
> > @@ -2199,15 +2199,15 @@ static int khugepaged_wait_event(void)
> >
> >  static void khugepaged_do_scan(struct collapse_control *cc)
> >  {
> > -       struct page *hpage = NULL;
> >         unsigned int progress = 0, pass_through_head = 0;
> >         unsigned int pages = READ_ONCE(khugepaged_pages_to_scan);
> >         bool wait = true;
> > +       int result = SCAN_SUCCEED;
> >
> >         lru_add_drain_all();
> >
> >         while (progress < pages) {
> > -               if (alloc_fail_should_sleep(&hpage, &wait))
> > +               if (alloc_fail_should_sleep(result, &wait))
> >                         break;
> >
> >                 cond_resched();
> > @@ -2221,7 +2221,7 @@ static void khugepaged_do_scan(struct collapse_control *cc)
> >                 if (khugepaged_has_work() &&
> >                     pass_through_head < 2)
> >                         progress += khugepaged_scan_mm_slot(pages - progress,
> > -                                                           &hpage, cc);
> > +                                                           &result, cc);
> >                 else
> >                         progress = pages;
> >                 spin_unlock(&khugepaged_mm_lock);
> > --
> > 2.36.1.255.ge46751e96f-goog
> >