[akpm-mm:mm-unstable 83/143] mm/khugepaged.c:1704:9: error: implicit declaration of function 'vma_try_start_write' is invalid in C99

[akpm-mm:mm-unstable 83/143] mm/khugepaged.c:1704:9: error: implicit declaration of function 'vma_try_start_write' is invalid in C99

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable
head:   df3ae4347aff9be1e9763ffa3b1015fca348bfbd
commit: 92e3612279f925881e96dcc89acfb6bf96a2bb2a [83/143] mm/khugepaged: fix vm_lock/i_mmap_rwsem inversion in retract_page_tables
config: i386-randconfig-a002 (https://download.01.org/0day-ci/archive/20230304/202303042159.qPwZsZsh-lkp@intel.com/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/commit/?id=92e3612279f925881e96dcc89acfb6bf96a2bb2a
        git remote add akpm-mm https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git
        git fetch --no-tags akpm-mm mm-unstable
        git checkout 92e3612279f925881e96dcc89acfb6bf96a2bb2a
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202303042159.qPwZsZsh-lkp@intel.com/

All errors (new ones prefixed by >>):

>> mm/khugepaged.c:1704:9: error: implicit declaration of function 'vma_try_start_write' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
                           if (!vma_try_start_write(vma))
                                ^
   mm/khugepaged.c:1704:9: note: did you mean 'vma_start_write'?
   include/linux/mm.h:719:20: note: 'vma_start_write' declared here
   static inline void vma_start_write(struct vm_area_struct *vma) {}
                      ^
   1 error generated.


vim +/vma_try_start_write +1704 mm/khugepaged.c

  1641	
  1642	static int retract_page_tables(struct address_space *mapping, pgoff_t pgoff,
  1643				       struct mm_struct *target_mm,
  1644				       unsigned long target_addr, struct page *hpage,
  1645				       struct collapse_control *cc)
  1646	{
  1647		struct vm_area_struct *vma;
  1648		int target_result = SCAN_FAIL;
  1649	
  1650		i_mmap_lock_write(mapping);
  1651		vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
  1652			int result = SCAN_FAIL;
  1653			struct mm_struct *mm = NULL;
  1654			unsigned long addr = 0;
  1655			pmd_t *pmd;
  1656			bool is_target = false;
  1657	
  1658			/*
  1659			 * Check vma->anon_vma to exclude MAP_PRIVATE mappings that
  1660			 * got written to. These VMAs are likely not worth investing
  1661			 * mmap_write_lock(mm) as PMD-mapping is likely to be split
  1662			 * later.
  1663			 *
  1664			 * Note that vma->anon_vma check is racy: it can be set up after
  1665			 * the check but before we took mmap_lock by the fault path.
  1666			 * But page lock would prevent establishing any new ptes of the
  1667			 * page, so we are safe.
  1668			 *
  1669			 * An alternative would be drop the check, but check that page
  1670			 * table is clear before calling pmdp_collapse_flush() under
  1671			 * ptl. It has higher chance to recover THP for the VMA, but
  1672			 * has higher cost too. It would also probably require locking
  1673			 * the anon_vma.
  1674			 */
  1675			if (READ_ONCE(vma->anon_vma)) {
  1676				result = SCAN_PAGE_ANON;
  1677				goto next;
  1678			}
  1679			addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
  1680			if (addr & ~HPAGE_PMD_MASK ||
  1681			    vma->vm_end < addr + HPAGE_PMD_SIZE) {
  1682				result = SCAN_VMA_CHECK;
  1683				goto next;
  1684			}
  1685			mm = vma->vm_mm;
  1686			is_target = mm == target_mm && addr == target_addr;
  1687			result = find_pmd_or_thp_or_none(mm, addr, &pmd);
  1688			if (result != SCAN_SUCCEED)
  1689				goto next;
  1690			/*
  1691			 * We need exclusive mmap_lock to retract page table.
  1692			 *
  1693			 * We use trylock due to lock inversion: we need to acquire
  1694			 * mmap_lock while holding page lock. Fault path does it in
  1695			 * reverse order. Trylock is a way to avoid deadlock.
  1696			 *
  1697			 * Also, it's not MADV_COLLAPSE's job to collapse other
  1698			 * mappings - let khugepaged take care of them later.
  1699			 */
  1700			result = SCAN_PTE_MAPPED_HUGEPAGE;
  1701			if ((cc->is_khugepaged || is_target) &&
  1702			    mmap_write_trylock(mm)) {
  1703				/* trylock for the same lock inversion as above */
> 1704				if (!vma_try_start_write(vma))
  1705					goto unlock_next;
  1706	
  1707				/*
  1708				 * Re-check whether we have an ->anon_vma, because
  1709				 * collapse_and_free_pmd() requires that either no
  1710				 * ->anon_vma exists or the anon_vma is locked.
  1711				 * We already checked ->anon_vma above, but that check
  1712				 * is racy because ->anon_vma can be populated under the
  1713				 * mmap lock in read mode.
  1714				 */
  1715				if (vma->anon_vma) {
  1716					result = SCAN_PAGE_ANON;
  1717					goto unlock_next;
  1718				}
  1719				/*
  1720				 * When a vma is registered with uffd-wp, we can't
  1721				 * recycle the pmd pgtable because there can be pte
  1722				 * markers installed.  Skip it only, so the rest mm/vma
  1723				 * can still have the same file mapped hugely, however
  1724				 * it'll always mapped in small page size for uffd-wp
  1725				 * registered ranges.
  1726				 */
  1727				if (hpage_collapse_test_exit(mm)) {
  1728					result = SCAN_ANY_PROCESS;
  1729					goto unlock_next;
  1730				}
  1731				if (userfaultfd_wp(vma)) {
  1732					result = SCAN_PTE_UFFD_WP;
  1733					goto unlock_next;
  1734				}
  1735				collapse_and_free_pmd(mm, vma, addr, pmd);
  1736				if (!cc->is_khugepaged && is_target)
  1737					result = set_huge_pmd(vma, addr, pmd, hpage);
  1738				else
  1739					result = SCAN_SUCCEED;
  1740	
  1741	unlock_next:
  1742				mmap_write_unlock(mm);
  1743				goto next;
  1744			}
  1745			/*
  1746			 * Calling context will handle target mm/addr. Otherwise, let
  1747			 * khugepaged try again later.
  1748			 */
  1749			if (!is_target) {
  1750				khugepaged_add_pte_mapped_thp(mm, addr);
  1751				continue;
  1752			}
  1753	next:
  1754			if (is_target)
  1755				target_result = result;
  1756		}
  1757		i_mmap_unlock_write(mapping);
  1758		return target_result;
  1759	}
  1760	

-- 
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https://github.com/intel/lkp-tests