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

kernel test robot
2024-05-30T06:37:15Z

Hi Baolin,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on next-20240529]
[cannot apply to linus/master v6.10-rc1]
[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/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: riscv-defconfig (https://download.01.org/0day-ci/archive/20240530/202405301430.0NRLTOWU-lkp@intel.com/config)
compiler: clang version 19.0.0git (https://github.com/llvm/llvm-project bafda89a0944d947fc4b3b5663185e07a397ac30)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240530/202405301430.0NRLTOWU-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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202405301430.0NRLTOWU-lkp@intel.com/

All warnings (new ones prefixed by >>):

In file included from mm/shmem.c:28:
In file included from include/linux/ramfs.h:5:
In file included from include/linux/fs_parser.h:11:
In file included from include/linux/fs_context.h:14:
In file included from include/linux/security.h:33:
In file included from include/linux/mm.h:2245:
include/linux/vmstat.h:514:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
514 | return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
| ~~~~~~~~~~~ ^ ~~~
>> mm/shmem.c:1748:14: warning: variable 'suitable_orders' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
1748 | } else if (orders & BIT(HPAGE_PMD_ORDER)) {
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mm/shmem.c:1766:25: note: uninitialized use occurs here
1766 | order = highest_order(suitable_orders);
| ^~~~~~~~~~~~~~~
mm/shmem.c:1748:10: note: remove the 'if' if its condition is always true
1748 | } else if (orders & BIT(HPAGE_PMD_ORDER)) {
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mm/shmem.c:1736:31: note: initialize the variable 'suitable_orders' to silence this warning
1736 | unsigned long suitable_orders;
| ^
| = 0
2 warnings generated.

vim +1748 mm/shmem.c

1728
1729 static struct folio *shmem_alloc_and_add_folio(struct vm_fault *vmf,
1730 gfp_t gfp, struct inode *inode, pgoff_t index,
1731 struct mm_struct *fault_mm, unsigned long orders)
1732 {
1733 struct address_space *mapping = inode->i_mapping;
1734 struct shmem_inode_info *info = SHMEM_I(inode);
1735 struct vm_area_struct *vma = vmf ? vmf->vma : NULL;
1736 unsigned long suitable_orders;
1737 struct folio *folio = NULL;
1738 long pages;
1739 int error, order;
1740
1741 if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
1742 orders = 0;
1743
1744 if (orders > 0) {
1745 if (vma && vma_is_anon_shmem(vma)) {
1746 suitable_orders = anon_shmem_suitable_orders(inode, vmf,
1747 mapping, index, orders);
> 1748 } else if (orders & BIT(HPAGE_PMD_ORDER)) {
1749 pages = HPAGE_PMD_NR;
1750 suitable_orders = BIT(HPAGE_PMD_ORDER);
1751 index = round_down(index, HPAGE_PMD_NR);
1752
1753 /*
1754 * Check for conflict before waiting on a huge allocation.
1755 * Conflict might be that a huge page has just been allocated
1756 * and added to page cache by a racing thread, or that there
1757 * is already at least one small page in the huge extent.
1758 * Be careful to retry when appropriate, but not forever!
1759 * Elsewhere -EEXIST would be the right code, but not here.
1760 */
1761 if (xa_find(&mapping->i_pages, &index,
1762 index + HPAGE_PMD_NR - 1, XA_PRESENT))
1763 return ERR_PTR(-E2BIG);
1764 }
1765
1766 order = highest_order(suitable_orders);
1767 while (suitable_orders) {
1768 pages = 1UL << order;
1769 index = round_down(index, pages);
1770 folio = shmem_alloc_folio(gfp, order, info, index);
1771 if (folio)
1772 goto allocated;
1773
1774 if (pages == HPAGE_PMD_NR)
1775 count_vm_event(THP_FILE_FALLBACK);
1776 order = next_order(&suitable_orders, order);
1777 }
1778 } else {
1779 pages = 1;
1780 folio = shmem_alloc_folio(gfp, 0, info, index);
1781 }
1782 if (!folio)
1783 return ERR_PTR(-ENOMEM);
1784
1785 allocated:
1786 __folio_set_locked(folio);
1787 __folio_set_swapbacked(folio);
1788
1789 gfp &= GFP_RECLAIM_MASK;
1790 error = mem_cgroup_charge(folio, fault_mm, gfp);
1791 if (error) {
1792 if (xa_find(&mapping->i_pages, &index,
1793 index + pages - 1, XA_PRESENT)) {
1794 error = -EEXIST;
1795 } else if (pages == HPAGE_PMD_NR) {
1796 count_vm_event(THP_FILE_FALLBACK);
1797 count_vm_event(THP_FILE_FALLBACK_CHARGE);
1798 }
1799 goto unlock;
1800 }
1801
1802 error = shmem_add_to_page_cache(folio, mapping, index, NULL, gfp);
1803 if (error)
1804 goto unlock;
1805
1806 error = shmem_inode_acct_blocks(inode, pages);
1807 if (error) {
1808 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1809 long freed;
1810 /*
1811 * Try to reclaim some space by splitting a few
1812 * large folios beyond i_size on the filesystem.
1813 */
1814 shmem_unused_huge_shrink(sbinfo, NULL, 2);
1815 /*
1816 * And do a shmem_recalc_inode() to account for freed pages:
1817 * except our folio is there in cache, so not quite balanced.
1818 */
1819 spin_lock(&info->lock);
1820 freed = pages + info->alloced - info->swapped -
1821 READ_ONCE(mapping->nrpages);
1822 if (freed > 0)
1823 info->alloced -= freed;
1824 spin_unlock(&info->lock);
1825 if (freed > 0)
1826 shmem_inode_unacct_blocks(inode, freed);
1827 error = shmem_inode_acct_blocks(inode, pages);
1828 if (error) {
1829 filemap_remove_folio(folio);
1830 goto unlock;
1831 }
1832 }
1833
1834 shmem_recalc_inode(inode, pages, 0);
1835 folio_add_lru(folio);
1836 return folio;
1837
1838 unlock:
1839 folio_unlock(folio);
1840 folio_put(folio);
1841 return ERR_PTR(error);
1842 }
1843

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