diff --git a/mm/Kconfig b/mm/Kconfig index f88be1cbcfb26b925d274e40de99ac9145c441f5..a5dae9a7eb510af8f5ae45ae5fc91d2c53a57a91 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -712,6 +712,17 @@ config GUP_BENCHMARK config GUP_GET_PTE_LOW_HIGH bool +config READ_ONLY_THP_FOR_FS + bool "Read-only THP for filesystems (EXPERIMENTAL)" + depends on TRANSPARENT_HUGE_PAGECACHE && SHMEM + + help + Allow khugepaged to put read-only file-backed pages in THP. + + This is marked experimental because it is a new feature. Write + support of file THPs will be developed in the next few release + cycles. + config ARCH_HAS_PTE_SPECIAL bool diff --git a/mm/filemap.c b/mm/filemap.c index f4d2971abd7c6b188de4fd7c4592c75d1a795a1b..91fe3a08ca4a31cca4ad1bc92733287f87b44437 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -203,8 +203,8 @@ static void unaccount_page_cache_page(struct address_space *mapping, __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr); if (PageTransHuge(page)) __dec_node_page_state(page, NR_SHMEM_THPS); - } else { - VM_BUG_ON_PAGE(PageTransHuge(page), page); + } else if (PageTransHuge(page)) { + __dec_node_page_state(page, NR_FILE_THPS); } /* diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 7e36cc893f25ca4977fcbce08146e0211b3dbbe7..8607c77431b3e03e57cde1e6ae19d8adddc78e06 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -48,6 +48,7 @@ enum scan_result { SCAN_CGROUP_CHARGE_FAIL, SCAN_EXCEED_SWAP_PTE, SCAN_TRUNCATED, + SCAN_PAGE_HAS_PRIVATE, }; #define CREATE_TRACE_POINTS @@ -404,7 +405,11 @@ static bool hugepage_vma_check(struct vm_area_struct *vma, (vm_flags & VM_NOHUGEPAGE) || test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) return false; - if (shmem_file(vma->vm_file)) { + + if (shmem_file(vma->vm_file) || + (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && + vma->vm_file && + (vm_flags & VM_DENYWRITE))) { if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) return false; return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, @@ -456,8 +461,9 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma, unsigned long hstart, hend; /* - * khugepaged does not yet work on non-shmem files or special - * mappings. And file-private shmem THP is not supported. + * khugepaged only supports read-only files for non-shmem files. + * khugepaged does not yet work on special mappings. And + * file-private shmem THP is not supported. */ if (!hugepage_vma_check(vma, vm_flags)) return 0; @@ -1287,12 +1293,12 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) } /** - * collapse_file - collapse small tmpfs/shmem pages into huge one. + * collapse_file - collapse filemap/tmpfs/shmem pages into huge one. * * Basic scheme is simple, details are more complex: * - allocate and lock a new huge page; * - scan page cache replacing old pages with the new one - * + swap in pages if necessary; + * + swap/gup in pages if necessary; * + fill in gaps; * + keep old pages around in case rollback is required; * - if replacing succeeds: @@ -1316,7 +1322,9 @@ static void collapse_file(struct mm_struct *mm, LIST_HEAD(pagelist); XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER); int nr_none = 0, result = SCAN_SUCCEED; + bool is_shmem = shmem_file(file); + VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem); VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); /* Only allocate from the target node */ @@ -1348,7 +1356,8 @@ static void collapse_file(struct mm_struct *mm, } while (1); __SetPageLocked(new_page); - __SetPageSwapBacked(new_page); + if (is_shmem) + __SetPageSwapBacked(new_page); new_page->index = start; new_page->mapping = mapping; @@ -1363,41 +1372,75 @@ static void collapse_file(struct mm_struct *mm, struct page *page = xas_next(&xas); VM_BUG_ON(index != xas.xa_index); - if (!page) { - /* - * Stop if extent has been truncated or hole-punched, - * and is now completely empty. - */ - if (index == start) { - if (!xas_next_entry(&xas, end - 1)) { - result = SCAN_TRUNCATED; + if (is_shmem) { + if (!page) { + /* + * Stop if extent has been truncated or + * hole-punched, and is now completely + * empty. + */ + if (index == start) { + if (!xas_next_entry(&xas, end - 1)) { + result = SCAN_TRUNCATED; + goto xa_locked; + } + xas_set(&xas, index); + } + if (!shmem_charge(mapping->host, 1)) { + result = SCAN_FAIL; goto xa_locked; } - xas_set(&xas, index); + xas_store(&xas, new_page); + nr_none++; + continue; } - if (!shmem_charge(mapping->host, 1)) { - result = SCAN_FAIL; + + if (xa_is_value(page) || !PageUptodate(page)) { + xas_unlock_irq(&xas); + /* swap in or instantiate fallocated page */ + if (shmem_getpage(mapping->host, index, &page, + SGP_NOHUGE)) { + result = SCAN_FAIL; + goto xa_unlocked; + } + } else if (trylock_page(page)) { + get_page(page); + xas_unlock_irq(&xas); + } else { + result = SCAN_PAGE_LOCK; goto xa_locked; } - xas_store(&xas, new_page); - nr_none++; - continue; - } - - if (xa_is_value(page) || !PageUptodate(page)) { - xas_unlock_irq(&xas); - /* swap in or instantiate fallocated page */ - if (shmem_getpage(mapping->host, index, &page, - SGP_NOHUGE)) { + } else { /* !is_shmem */ + if (!page || xa_is_value(page)) { + xas_unlock_irq(&xas); + page_cache_sync_readahead(mapping, &file->f_ra, + file, index, + PAGE_SIZE); + /* drain pagevecs to help isolate_lru_page() */ + lru_add_drain(); + page = find_lock_page(mapping, index); + if (unlikely(page == NULL)) { + result = SCAN_FAIL; + goto xa_unlocked; + } + } else if (!PageUptodate(page)) { + xas_unlock_irq(&xas); + wait_on_page_locked(page); + if (!trylock_page(page)) { + result = SCAN_PAGE_LOCK; + goto xa_unlocked; + } + get_page(page); + } else if (PageDirty(page)) { result = SCAN_FAIL; - goto xa_unlocked; + goto xa_locked; + } else if (trylock_page(page)) { + get_page(page); + xas_unlock_irq(&xas); + } else { + result = SCAN_PAGE_LOCK; + goto xa_locked; } - } else if (trylock_page(page)) { - get_page(page); - xas_unlock_irq(&xas); - } else { - result = SCAN_PAGE_LOCK; - goto xa_locked; } /* @@ -1426,6 +1469,12 @@ static void collapse_file(struct mm_struct *mm, goto out_unlock; } + if (page_has_private(page) && + !try_to_release_page(page, GFP_KERNEL)) { + result = SCAN_PAGE_HAS_PRIVATE; + goto out_unlock; + } + if (page_mapped(page)) unmap_mapping_pages(mapping, index, 1, false); @@ -1463,12 +1512,18 @@ static void collapse_file(struct mm_struct *mm, goto xa_unlocked; } - __inc_node_page_state(new_page, NR_SHMEM_THPS); + if (is_shmem) + __inc_node_page_state(new_page, NR_SHMEM_THPS); + else + __inc_node_page_state(new_page, NR_FILE_THPS); + if (nr_none) { struct zone *zone = page_zone(new_page); __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none); - __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none); + if (is_shmem) + __mod_node_page_state(zone->zone_pgdat, + NR_SHMEM, nr_none); } xa_locked: @@ -1506,10 +1561,15 @@ static void collapse_file(struct mm_struct *mm, SetPageUptodate(new_page); page_ref_add(new_page, HPAGE_PMD_NR - 1); - set_page_dirty(new_page); mem_cgroup_commit_charge(new_page, memcg, false, true); + + if (is_shmem) { + set_page_dirty(new_page); + lru_cache_add_anon(new_page); + } else { + lru_cache_add_file(new_page); + } count_memcg_events(memcg, THP_COLLAPSE_ALLOC, 1); - lru_cache_add_anon(new_page); /* * Remove pte page tables, so we can re-fault the page as huge. @@ -1524,7 +1584,9 @@ static void collapse_file(struct mm_struct *mm, /* Something went wrong: roll back page cache changes */ xas_lock_irq(&xas); mapping->nrpages -= nr_none; - shmem_uncharge(mapping->host, nr_none); + + if (is_shmem) + shmem_uncharge(mapping->host, nr_none); xas_set(&xas, start); xas_for_each(&xas, page, end - 1) { @@ -1607,7 +1669,8 @@ static void khugepaged_scan_file(struct mm_struct *mm, break; } - if (page_count(page) != 1 + page_mapcount(page)) { + if (page_count(page) != + 1 + page_mapcount(page) + page_has_private(page)) { result = SCAN_PAGE_COUNT; break; } @@ -1713,11 +1776,13 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, VM_BUG_ON(khugepaged_scan.address < hstart || khugepaged_scan.address + HPAGE_PMD_SIZE > hend); - if (shmem_file(vma->vm_file)) { + if (IS_ENABLED(CONFIG_SHMEM) && vma->vm_file) { struct file *file; pgoff_t pgoff = linear_page_index(vma, khugepaged_scan.address); - if (!shmem_huge_enabled(vma)) + + if (shmem_file(vma->vm_file) + && !shmem_huge_enabled(vma)) goto skip; file = get_file(vma->vm_file); up_read(&mm->mmap_sem); diff --git a/mm/rmap.c b/mm/rmap.c index 26006445c8b520c75d3a5acf21da27132453de15..d9a23bb773bf7997773cb94952fbf73c313a0bf3 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1189,8 +1189,10 @@ void page_add_file_rmap(struct page *page, bool compound) } if (!atomic_inc_and_test(compound_mapcount_ptr(page))) goto out; - VM_BUG_ON_PAGE(!PageSwapBacked(page), page); - __inc_node_page_state(page, NR_SHMEM_PMDMAPPED); + if (PageSwapBacked(page)) + __inc_node_page_state(page, NR_SHMEM_PMDMAPPED); + else + __inc_node_page_state(page, NR_FILE_PMDMAPPED); } else { if (PageTransCompound(page) && page_mapping(page)) { VM_WARN_ON_ONCE(!PageLocked(page)); @@ -1229,8 +1231,10 @@ static void page_remove_file_rmap(struct page *page, bool compound) } if (!atomic_add_negative(-1, compound_mapcount_ptr(page))) goto out; - VM_BUG_ON_PAGE(!PageSwapBacked(page), page); - __dec_node_page_state(page, NR_SHMEM_PMDMAPPED); + if (PageSwapBacked(page)) + __dec_node_page_state(page, NR_SHMEM_PMDMAPPED); + else + __dec_node_page_state(page, NR_FILE_PMDMAPPED); } else { if (!atomic_add_negative(-1, &page->_mapcount)) goto out;