From 50ad2f24b3b48c7123e0d61a467baf35875a9ba5 Mon Sep 17 00:00:00 2001 From: Zach O'Keefe Date: Wed, 6 Jul 2022 16:59:23 -0700 Subject: [PATCH] mm/khugepaged: propagate enum scan_result codes back to callers Propagate 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. hugepage_vma_revalidate() now returns SCAN_SUCCEED on success to be more consistent with enum scan_result propagation. 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). Link: https://lkml.kernel.org/r/20220706235936.2197195-6-zokeefe@google.com Signed-off-by: Zach O'Keefe Reviewed-by: Yang Shi Cc: Alex Shi Cc: Andrea Arcangeli Cc: Arnd Bergmann Cc: Axel Rasmussen Cc: Chris Kennelly Cc: Chris Zankel Cc: David Hildenbrand Cc: David Rientjes Cc: Helge Deller Cc: Hugh Dickins Cc: Ivan Kokshaysky Cc: James Bottomley Cc: Jens Axboe Cc: "Kirill A. Shutemov" Cc: Matthew Wilcox Cc: Matt Turner Cc: Max Filippov Cc: Miaohe Lin Cc: Michal Hocko Cc: Minchan Kim Cc: Pasha Tatashin Cc: Pavel Begunkov Cc: Peter Xu Cc: Rongwei Wang Cc: SeongJae Park Cc: Song Liu Cc: Thomas Bogendoerfer Cc: Vlastimil Babka Cc: Zi Yan Cc: Dan Carpenter Cc: "Souptick Joarder (HPE)" Signed-off-by: Andrew Morton --- mm/khugepaged.c | 233 ++++++++++++++++++++++++------------------------ 1 file changed, 117 insertions(+), 116 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index c0133816a3fa..849f70af557f 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -558,7 +558,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, { struct page *page = NULL; pte_t *_pte; - int none_or_zero = 0, shared = 0, result = 0, referenced = 0; + int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0; bool writable = false; for (_pte = pte; _pte < pte + HPAGE_PMD_NR; @@ -672,13 +672,13 @@ next: result = SCAN_SUCCEED; trace_mm_collapse_huge_page_isolate(page, none_or_zero, referenced, writable, result); - return 1; + return result; } 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, @@ -818,7 +818,6 @@ 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; } @@ -830,8 +829,7 @@ static bool khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) /* * If mmap_lock temporarily dropped, revalidate vma * before taking mmap_lock. - * Return 0 if succeeds, otherwise return none-zero - * value (scan code). + * Returns enum scan_result value. */ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, @@ -859,7 +857,7 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, */ if (!vma->anon_vma || !vma_is_anonymous(vma)) return SCAN_VMA_CHECK; - return 0; + return SCAN_SUCCEED; } /* @@ -870,10 +868,10 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, * Note that if false is returned, mmap_lock will be released. */ -static bool __collapse_huge_page_swapin(struct mm_struct *mm, - struct vm_area_struct *vma, - unsigned long haddr, pmd_t *pmd, - int referenced) +static int __collapse_huge_page_swapin(struct mm_struct *mm, + struct vm_area_struct *vma, + unsigned long haddr, pmd_t *pmd, + int referenced) { int swapped_in = 0; vm_fault_t ret = 0; @@ -904,12 +902,13 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, */ if (ret & VM_FAULT_RETRY) { trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); - return false; + /* Likely, but not guaranteed, that page lock failed */ + return SCAN_PAGE_LOCK; } if (ret & VM_FAULT_ERROR) { mmap_read_unlock(mm); trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); - return false; + return SCAN_FAIL; } swapped_in++; } @@ -919,7 +918,7 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, lru_add_drain(); trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); - return true; + return SCAN_SUCCEED; } static int alloc_charge_hpage(struct page **hpage, struct mm_struct *mm, @@ -937,17 +936,17 @@ static int alloc_charge_hpage(struct page **hpage, struct mm_struct *mm, 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; @@ -961,15 +960,13 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address, */ mmap_read_unlock(mm); - result = alloc_charge_hpage(hpage, mm, cc); + result = alloc_charge_hpage(&hpage, mm, cc); if (result != SCAN_SUCCEED) goto out_nolock; - new_page = *hpage; - mmap_read_lock(mm); result = hugepage_vma_revalidate(mm, address, &vma); - if (result) { + if (result != SCAN_SUCCEED) { mmap_read_unlock(mm); goto out_nolock; } @@ -981,14 +978,16 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address, goto out_nolock; } - /* - * __collapse_huge_page_swapin will return with mmap_lock released - * when it fails. So we jump out_nolock directly in that case. - * Continuing to collapse causes inconsistency. - */ - if (unmapped && !__collapse_huge_page_swapin(mm, vma, address, - pmd, referenced)) { - goto out_nolock; + if (unmapped) { + /* + * __collapse_huge_page_swapin will return with mmap_lock + * released when it fails. So we jump out_nolock directly in + * that case. Continuing to collapse causes inconsistency. + */ + result = __collapse_huge_page_swapin(mm, vma, address, pmd, + referenced); + if (result != SCAN_SUCCEED) + goto out_nolock; } mmap_read_unlock(mm); @@ -999,7 +998,7 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address, */ mmap_write_lock(mm); result = hugepage_vma_revalidate(mm, address, &vma); - if (result) + if (result != SCAN_SUCCEED) goto out_up_write; /* check if the pmd is still valid */ if (mm_find_pmd(mm, address) != pmd) @@ -1026,11 +1025,11 @@ 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)); @@ -1042,7 +1041,6 @@ 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; } @@ -1052,8 +1050,8 @@ 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 @@ -1061,43 +1059,42 @@ 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; @@ -1234,19 +1231,19 @@ 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) { + result = collapse_huge_page(mm, address, referenced, + unmapped, cc); /* collapse_huge_page will return with the mmap_lock released */ - collapse_huge_page(mm, address, hpage, referenced, unmapped, - cc); + *mmap_locked = false; } 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) @@ -1508,7 +1505,6 @@ 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: @@ -1526,12 +1522,11 @@ 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); @@ -1542,12 +1537,10 @@ 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(hpage, mm, cc); + result = alloc_charge_hpage(&hpage, mm, 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 @@ -1564,14 +1557,14 @@ 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. */ @@ -1599,7 +1592,7 @@ 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; } @@ -1741,19 +1734,19 @@ 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 @@ -1764,21 +1757,21 @@ out_unlock: 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); /* nr_none is always 0 for non-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: @@ -1800,11 +1793,11 @@ xa_unlocked: 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); @@ -1815,23 +1808,22 @@ xa_unlocked: 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; } else { struct page *page; @@ -1870,22 +1862,23 @@ xa_unlocked: VM_BUG_ON(nr_none); xas_unlock_irq(&xas); - new_page->mapping = NULL; + hpage->mapping = NULL; } - unlock_page(new_page); + if (hpage) + unlock_page(hpage); 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; @@ -1958,16 +1951,16 @@ 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 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) { BUILD_BUG(); } @@ -1977,8 +1970,7 @@ 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) @@ -1990,6 +1982,7 @@ 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; @@ -2036,7 +2029,8 @@ skip: VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); while (khugepaged_scan.address < hend) { - int ret; + bool mmap_locked = true; + cond_resched(); if (unlikely(khugepaged_test_exit(mm))) goto breakouterloop; @@ -2050,20 +2044,28 @@ skip: khugepaged_scan.address); mmap_read_unlock(mm); - ret = 1; - khugepaged_scan_file(mm, file, pgoff, hpage, - cc); + *result = khugepaged_scan_file(mm, file, pgoff, + cc); + mmap_locked = false; 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; @@ -2115,10 +2117,10 @@ 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(); @@ -2134,7 +2136,7 @@ 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); @@ -2142,7 +2144,7 @@ static void khugepaged_do_scan(struct collapse_control *cc) if (progress >= pages) break; - if (IS_ERR(hpage)) { + if (result == SCAN_ALLOC_HUGE_PAGE_FAIL) { /* * If fail to allocate the first time, try to sleep for * a while. When hit again, cancel the scan. @@ -2150,7 +2152,6 @@ static void khugepaged_do_scan(struct collapse_control *cc) if (!wait) break; wait = false; - hpage = NULL; khugepaged_alloc_sleep(); } }