Re: [PATCH v3 4/6] mm: shmem: add mTHP support for anonymous shmem

Dan Carpenter
2024-06-04T09:23:50Z

Hi Baolin,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url: https://github.com/intel-lab-lkp/linux/commits/Baolin-Wang/mm-memory-extend-finish_fault-to-support-large-folio/20240530-100805
base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link: https://lore.kernel.org/r/ec35a23026dd016705d211e85163cabe07681516.1717033868.git.baolin.wang%40linux.alibaba.com
patch subject: [PATCH v3 4/6] mm: shmem: add mTHP support for anonymous shmem
config: powerpc64-randconfig-r071-20240531 (https://download.01.org/0day-ci/archive/20240602/202406020203.14sT311e-lkp@intel.com/config)
compiler: clang version 19.0.0git (https://github.com/llvm/llvm-project bafda89a0944d947fc4b3b5663185e07a397ac30)

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@intel.com>
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
| Closes: https://lore.kernel.org/r/202406020203.14sT311e-lkp@intel.com/

smatch warnings:
mm/shmem.c:1766 shmem_alloc_and_add_folio() error: uninitialized symbol 'suitable_orders'.

vim +/suitable_orders +1766 mm/shmem.c

ededbc2c2f28a1 Baolin Wang 2024-05-30 1729 static struct folio *shmem_alloc_and_add_folio(struct vm_fault *vmf,
ededbc2c2f28a1 Baolin Wang 2024-05-30 1730 gfp_t gfp, struct inode *inode, pgoff_t index,
ededbc2c2f28a1 Baolin Wang 2024-05-30 1731 struct mm_struct *fault_mm, unsigned long orders)
800d8c63b2e989 Kirill A. Shutemov 2016-07-26 1732 {
3022fd7af9604d Hugh Dickins 2023-09-29 1733 struct address_space *mapping = inode->i_mapping;
0f0796945614b7 Mike Rapoport 2017-09-06 1734 struct shmem_inode_info *info = SHMEM_I(inode);
ededbc2c2f28a1 Baolin Wang 2024-05-30 1735 struct vm_area_struct *vma = vmf ? vmf->vma : NULL;
ededbc2c2f28a1 Baolin Wang 2024-05-30 1736 unsigned long suitable_orders;
ededbc2c2f28a1 Baolin Wang 2024-05-30 1737 struct folio *folio = NULL;
3022fd7af9604d Hugh Dickins 2023-09-29 1738 long pages;
ededbc2c2f28a1 Baolin Wang 2024-05-30 1739 int error, order;
800d8c63b2e989 Kirill A. Shutemov 2016-07-26 1740
396bcc5299c281 Matthew Wilcox (Oracle 2020-04-06 1741) if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
ededbc2c2f28a1 Baolin Wang 2024-05-30 1742 orders = 0;
800d8c63b2e989 Kirill A. Shutemov 2016-07-26 1743
ededbc2c2f28a1 Baolin Wang 2024-05-30 1744 if (orders > 0) {
ededbc2c2f28a1 Baolin Wang 2024-05-30 1745 if (vma && vma_is_anon_shmem(vma)) {
ededbc2c2f28a1 Baolin Wang 2024-05-30 1746 suitable_orders = anon_shmem_suitable_orders(inode, vmf,
ededbc2c2f28a1 Baolin Wang 2024-05-30 1747 mapping, index, orders);
ededbc2c2f28a1 Baolin Wang 2024-05-30 1748 } else if (orders & BIT(HPAGE_PMD_ORDER)) {
3022fd7af9604d Hugh Dickins 2023-09-29 1749 pages = HPAGE_PMD_NR;
ededbc2c2f28a1 Baolin Wang 2024-05-30 1750 suitable_orders = BIT(HPAGE_PMD_ORDER);
3022fd7af9604d Hugh Dickins 2023-09-29 1751 index = round_down(index, HPAGE_PMD_NR);
3022fd7af9604d Hugh Dickins 2023-09-29 1752
3022fd7af9604d Hugh Dickins 2023-09-29 1753 /*
3022fd7af9604d Hugh Dickins 2023-09-29 1754 * Check for conflict before waiting on a huge allocation.
3022fd7af9604d Hugh Dickins 2023-09-29 1755 * Conflict might be that a huge page has just been allocated
3022fd7af9604d Hugh Dickins 2023-09-29 1756 * and added to page cache by a racing thread, or that there
3022fd7af9604d Hugh Dickins 2023-09-29 1757 * is already at least one small page in the huge extent.
3022fd7af9604d Hugh Dickins 2023-09-29 1758 * Be careful to retry when appropriate, but not forever!
3022fd7af9604d Hugh Dickins 2023-09-29 1759 * Elsewhere -EEXIST would be the right code, but not here.
3022fd7af9604d Hugh Dickins 2023-09-29 1760 */
3022fd7af9604d Hugh Dickins 2023-09-29 1761 if (xa_find(&mapping->i_pages, &index,
3022fd7af9604d Hugh Dickins 2023-09-29 1762 index + HPAGE_PMD_NR - 1, XA_PRESENT))
3022fd7af9604d Hugh Dickins 2023-09-29 1763 return ERR_PTR(-E2BIG);
ededbc2c2f28a1 Baolin Wang 2024-05-30 1764 }

suitable_orders uninitialized on else path.

52cd3b074050dd Lee Schermerhorn 2008-04-28 1765
ededbc2c2f28a1 Baolin Wang 2024-05-30 @1766 order = highest_order(suitable_orders);
ededbc2c2f28a1 Baolin Wang 2024-05-30 1767 while (suitable_orders) {
ededbc2c2f28a1 Baolin Wang 2024-05-30 1768 pages = 1UL << order;
ededbc2c2f28a1 Baolin Wang 2024-05-30 1769 index = round_down(index, pages);
ededbc2c2f28a1 Baolin Wang 2024-05-30 1770 folio = shmem_alloc_folio(gfp, order, info, index);
ededbc2c2f28a1 Baolin Wang 2024-05-30 1771 if (folio)
ededbc2c2f28a1 Baolin Wang 2024-05-30 1772 goto allocated;
ededbc2c2f28a1 Baolin Wang 2024-05-30 1773
ededbc2c2f28a1 Baolin Wang 2024-05-30 1774 if (pages == HPAGE_PMD_NR)
3022fd7af9604d Hugh Dickins 2023-09-29 1775 count_vm_event(THP_FILE_FALLBACK);
ededbc2c2f28a1 Baolin Wang 2024-05-30 1776 order = next_order(&suitable_orders, order);
ededbc2c2f28a1 Baolin Wang 2024-05-30 1777 }
3022fd7af9604d Hugh Dickins 2023-09-29 1778 } else {
3022fd7af9604d Hugh Dickins 2023-09-29 1779 pages = 1;

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