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Message-ID: <202512160619.3Ut4sxaJ-lkp@intel.com>
Date: Tue, 16 Dec 2025 07:01:18 +0800
From: kernel test robot <lkp@...el.com>
To: Vernon Yang <vernon2gm@...il.com>, akpm@...ux-foundation.org,
david@...nel.org, lorenzo.stoakes@...cle.com
Cc: oe-kbuild-all@...ts.linux.dev, ziy@...dia.com, npache@...hat.com,
baohua@...nel.org, lance.yang@...ux.dev, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, Vernon Yang <yanglincheng@...inos.cn>
Subject: Re: [PATCH 2/4] mm: khugepaged: remove mm when all memory has been
collapsed
Hi Vernon,
kernel test robot noticed the following build errors:
[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on linus/master v6.19-rc1 next-20251215]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Vernon-Yang/mm-khugepaged-add-trace_mm_khugepaged_scan-event/20251215-171046
base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link: https://lore.kernel.org/r/20251215090419.174418-3-yanglincheng%40kylinos.cn
patch subject: [PATCH 2/4] mm: khugepaged: remove mm when all memory has been collapsed
config: x86_64-rhel-9.4 (https://download.01.org/0day-ci/archive/20251216/202512160619.3Ut4sxaJ-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251216/202512160619.3Ut4sxaJ-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202512160619.3Ut4sxaJ-lkp@intel.com/
All errors (new ones prefixed by >>):
mm/khugepaged.c: In function 'khugepaged_scan_mm_slot':
>> mm/khugepaged.c:2490:30: error: 'SCAN_PMD_NULL' undeclared (first use in this function); did you mean 'SCAN_VMA_NULL'?
2490 | case SCAN_PMD_NULL:
| ^~~~~~~~~~~~~
| SCAN_VMA_NULL
mm/khugepaged.c:2490:30: note: each undeclared identifier is reported only once for each function it appears in
>> mm/khugepaged.c:2491:30: error: 'SCAN_PMD_NONE' undeclared (first use in this function)
2491 | case SCAN_PMD_NONE:
| ^~~~~~~~~~~~~
vim +2490 mm/khugepaged.c
2392
2393 static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
2394 struct collapse_control *cc)
2395 __releases(&khugepaged_mm_lock)
2396 __acquires(&khugepaged_mm_lock)
2397 {
2398 struct vma_iterator vmi;
2399 struct mm_slot *slot;
2400 struct mm_struct *mm;
2401 struct vm_area_struct *vma;
2402 int progress = 0;
2403
2404 VM_BUG_ON(!pages);
2405 lockdep_assert_held(&khugepaged_mm_lock);
2406 *result = SCAN_FAIL;
2407
2408 if (khugepaged_scan.mm_slot) {
2409 slot = khugepaged_scan.mm_slot;
2410 } else {
2411 slot = list_first_entry(&khugepaged_scan.mm_head,
2412 struct mm_slot, mm_node);
2413 khugepaged_scan.address = 0;
2414 khugepaged_scan.mm_slot = slot;
2415 khugepaged_scan.maybe_collapse = false;
2416 }
2417 spin_unlock(&khugepaged_mm_lock);
2418
2419 mm = slot->mm;
2420 /*
2421 * Don't wait for semaphore (to avoid long wait times). Just move to
2422 * the next mm on the list.
2423 */
2424 vma = NULL;
2425 if (unlikely(!mmap_read_trylock(mm)))
2426 goto breakouterloop_mmap_lock;
2427
2428 progress++;
2429 if (unlikely(hpage_collapse_test_exit_or_disable(mm)))
2430 goto breakouterloop;
2431
2432 vma_iter_init(&vmi, mm, khugepaged_scan.address);
2433 for_each_vma(vmi, vma) {
2434 unsigned long hstart, hend;
2435
2436 cond_resched();
2437 if (unlikely(hpage_collapse_test_exit_or_disable(mm))) {
2438 progress++;
2439 break;
2440 }
2441 if (!thp_vma_allowable_order(vma, vma->vm_flags, TVA_KHUGEPAGED, PMD_ORDER)) {
2442 skip:
2443 progress++;
2444 continue;
2445 }
2446 hstart = round_up(vma->vm_start, HPAGE_PMD_SIZE);
2447 hend = round_down(vma->vm_end, HPAGE_PMD_SIZE);
2448 if (khugepaged_scan.address > hend)
2449 goto skip;
2450 if (khugepaged_scan.address < hstart)
2451 khugepaged_scan.address = hstart;
2452 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2453
2454 while (khugepaged_scan.address < hend) {
2455 bool mmap_locked = true;
2456
2457 cond_resched();
2458 if (unlikely(hpage_collapse_test_exit_or_disable(mm)))
2459 goto breakouterloop;
2460
2461 VM_BUG_ON(khugepaged_scan.address < hstart ||
2462 khugepaged_scan.address + HPAGE_PMD_SIZE >
2463 hend);
2464 if (!vma_is_anonymous(vma)) {
2465 struct file *file = get_file(vma->vm_file);
2466 pgoff_t pgoff = linear_page_index(vma,
2467 khugepaged_scan.address);
2468
2469 mmap_read_unlock(mm);
2470 mmap_locked = false;
2471 *result = hpage_collapse_scan_file(mm,
2472 khugepaged_scan.address, file, pgoff, cc);
2473 fput(file);
2474 if (*result == SCAN_PTE_MAPPED_HUGEPAGE) {
2475 mmap_read_lock(mm);
2476 if (hpage_collapse_test_exit_or_disable(mm))
2477 goto breakouterloop;
2478 *result = collapse_pte_mapped_thp(mm,
2479 khugepaged_scan.address, false);
2480 if (*result == SCAN_PMD_MAPPED)
2481 *result = SCAN_SUCCEED;
2482 mmap_read_unlock(mm);
2483 }
2484 } else {
2485 *result = hpage_collapse_scan_pmd(mm, vma,
2486 khugepaged_scan.address, &mmap_locked, cc);
2487 }
2488
2489 switch (*result) {
> 2490 case SCAN_PMD_NULL:
> 2491 case SCAN_PMD_NONE:
2492 case SCAN_PMD_MAPPED:
2493 case SCAN_PTE_MAPPED_HUGEPAGE:
2494 break;
2495 case SCAN_SUCCEED:
2496 ++khugepaged_pages_collapsed;
2497 fallthrough;
2498 default:
2499 khugepaged_scan.maybe_collapse = true;
2500 }
2501
2502 /* move to next address */
2503 khugepaged_scan.address += HPAGE_PMD_SIZE;
2504 progress += HPAGE_PMD_NR;
2505 if (!mmap_locked)
2506 /*
2507 * We released mmap_lock so break loop. Note
2508 * that we drop mmap_lock before all hugepage
2509 * allocations, so if allocation fails, we are
2510 * guaranteed to break here and report the
2511 * correct result back to caller.
2512 */
2513 goto breakouterloop_mmap_lock;
2514 if (progress >= pages)
2515 goto breakouterloop;
2516 }
2517 }
2518 breakouterloop:
2519 mmap_read_unlock(mm); /* exit_mmap will destroy ptes after this */
2520 breakouterloop_mmap_lock:
2521
2522 spin_lock(&khugepaged_mm_lock);
2523 VM_BUG_ON(khugepaged_scan.mm_slot != slot);
2524 /*
2525 * Release the current mm_slot if this mm is about to die, or
2526 * if we scanned all vmas of this mm.
2527 */
2528 if (hpage_collapse_test_exit(mm) || !vma) {
2529 bool maybe_collapse = khugepaged_scan.maybe_collapse;
2530
2531 if (mm_flags_test(MMF_DISABLE_THP_COMPLETELY, mm))
2532 maybe_collapse = true;
2533
2534 /*
2535 * Make sure that if mm_users is reaching zero while
2536 * khugepaged runs here, khugepaged_exit will find
2537 * mm_slot not pointing to the exiting mm.
2538 */
2539 if (!list_is_last(&slot->mm_node, &khugepaged_scan.mm_head)) {
2540 khugepaged_scan.mm_slot = list_next_entry(slot, mm_node);
2541 khugepaged_scan.address = 0;
2542 khugepaged_scan.maybe_collapse = false;
2543 } else {
2544 khugepaged_scan.mm_slot = NULL;
2545 khugepaged_full_scans++;
2546 }
2547
2548 collect_mm_slot(slot, maybe_collapse);
2549 }
2550
2551 trace_mm_khugepaged_scan(mm, progress, khugepaged_scan.mm_slot == NULL);
2552
2553 return progress;
2554 }
2555
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
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