Re: [PATCH 3/3] mm: thp: relocate flush_cache_range() in migrate_misplaced_transhuge_page()

[kbuild test robot <lkp@intel.com>]

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Hi Andrea,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linux-sof-driver/master]
[also build test ERROR on v4.19-rc7 next-20181012]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Andrea-Arcangeli/mm-thp-fix-MADV_DONTNEED-vs-migrate_misplaced_transhuge_page-race-condition/20181014-143004
base:   https://github.com/thesofproject/linux master
config: arm64-defconfig (attached as .config)
compiler: aarch64-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.2.0 make.cross ARCH=arm64 

All errors (new ones prefixed by >>):

   mm/migrate.c: In function 'migrate_misplaced_transhuge_page':
>> mm/migrate.c:2054:32: error: 'end' undeclared (first use in this function); did you mean '_end'?
     flush_cache_range(vma, start, end + HPAGE_PMD_SIZE);
                                   ^~~
                                   _end
   mm/migrate.c:2054:32: note: each undeclared identifier is reported only once for each function it appears in

vim +2054 mm/migrate.c

  2005	
  2006	#if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
  2007	/*
  2008	 * Migrates a THP to a given target node. page must be locked and is unlocked
  2009	 * before returning.
  2010	 */
  2011	int migrate_misplaced_transhuge_page(struct mm_struct *mm,
  2012					struct vm_area_struct *vma,
  2013					pmd_t *pmd, pmd_t entry,
  2014					unsigned long address,
  2015					struct page *page, int node)
  2016	{
  2017		spinlock_t *ptl;
  2018		pg_data_t *pgdat = NODE_DATA(node);
  2019		int isolated = 0;
  2020		struct page *new_page = NULL;
  2021		int page_lru = page_is_file_cache(page);
  2022		unsigned long start = address & HPAGE_PMD_MASK;
  2023	
  2024		/*
  2025		 * Rate-limit the amount of data that is being migrated to a node.
  2026		 * Optimal placement is no good if the memory bus is saturated and
  2027		 * all the time is being spent migrating!
  2028		 */
  2029		if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR))
  2030			goto out_dropref;
  2031	
  2032		new_page = alloc_pages_node(node,
  2033			(GFP_TRANSHUGE_LIGHT | __GFP_THISNODE),
  2034			HPAGE_PMD_ORDER);
  2035		if (!new_page)
  2036			goto out_fail;
  2037		prep_transhuge_page(new_page);
  2038	
  2039		isolated = numamigrate_isolate_page(pgdat, page);
  2040		if (!isolated) {
  2041			put_page(new_page);
  2042			goto out_fail;
  2043		}
  2044	
  2045		/* Prepare a page as a migration target */
  2046		__SetPageLocked(new_page);
  2047		if (PageSwapBacked(page))
  2048			__SetPageSwapBacked(new_page);
  2049	
  2050		/* anon mapping, we can simply copy page->mapping to the new page: */
  2051		new_page->mapping = page->mapping;
  2052		new_page->index = page->index;
  2053		/* flush the cache before copying using the kernel virtual address */
> 2054		flush_cache_range(vma, start, end + HPAGE_PMD_SIZE);
  2055		migrate_page_copy(new_page, page);
  2056		WARN_ON(PageLRU(new_page));
  2057	
  2058		/* Recheck the target PMD */
  2059		ptl = pmd_lock(mm, pmd);
  2060		if (unlikely(!pmd_same(*pmd, entry) || !page_ref_freeze(page, 2))) {
  2061			spin_unlock(ptl);
  2062	
  2063			/* Reverse changes made by migrate_page_copy() */
  2064			if (TestClearPageActive(new_page))
  2065				SetPageActive(page);
  2066			if (TestClearPageUnevictable(new_page))
  2067				SetPageUnevictable(page);
  2068	
  2069			unlock_page(new_page);
  2070			put_page(new_page);		/* Free it */
  2071	
  2072			/* Retake the callers reference and putback on LRU */
  2073			get_page(page);
  2074			putback_lru_page(page);
  2075			mod_node_page_state(page_pgdat(page),
  2076				 NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
  2077	
  2078			goto out_unlock;
  2079		}
  2080	
  2081		entry = mk_huge_pmd(new_page, vma->vm_page_prot);
  2082		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
  2083	
  2084		/*
  2085		 * Overwrite the old entry under pagetable lock and establish
  2086		 * the new PTE. Any parallel GUP will either observe the old
  2087		 * page blocking on the page lock, block on the page table
  2088		 * lock or observe the new page. The SetPageUptodate on the
  2089		 * new page and page_add_new_anon_rmap guarantee the copy is
  2090		 * visible before the pagetable update.
  2091		 */
  2092		page_add_anon_rmap(new_page, vma, start, true);
  2093		/*
  2094		 * At this point the pmd is numa/protnone (i.e. non present)
  2095		 * and the TLB has already been flushed globally. So no TLB
  2096		 * can be currently caching this non present pmd mapping.
  2097		 * There's no need of clearing the pmd before doing
  2098		 * set_pmd_at(), nor to flush the TLB after
  2099		 * set_pmd_at(). Clearing the pmd here would introduce a race
  2100		 * condition against MADV_DONTNEED, beacuse MADV_DONTNEED only
  2101		 * holds the mmap_sem for reading. If the pmd is set to NULL
  2102		 * at any given time, MADV_DONTNEED won't wait on the pmd lock
  2103		 * and it'll skip clearing this pmd.
  2104		 */
  2105		set_pmd_at(mm, start, pmd, entry);
  2106		update_mmu_cache_pmd(vma, address, &entry);
  2107	
  2108		page_ref_unfreeze(page, 2);
  2109		mlock_migrate_page(new_page, page);
  2110		page_remove_rmap(page, true);
  2111		set_page_owner_migrate_reason(new_page, MR_NUMA_MISPLACED);
  2112	
  2113		spin_unlock(ptl);
  2114	
  2115		/* Take an "isolate" reference and put new page on the LRU. */
  2116		get_page(new_page);
  2117		putback_lru_page(new_page);
  2118	
  2119		unlock_page(new_page);
  2120		unlock_page(page);
  2121		put_page(page);			/* Drop the rmap reference */
  2122		put_page(page);			/* Drop the LRU isolation reference */
  2123	
  2124		count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
  2125		count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
  2126	
  2127		mod_node_page_state(page_pgdat(page),
  2128				NR_ISOLATED_ANON + page_lru,
  2129				-HPAGE_PMD_NR);
  2130		return isolated;
  2131	
  2132	out_fail:
  2133		count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
  2134	out_dropref:
  2135		ptl = pmd_lock(mm, pmd);
  2136		if (pmd_same(*pmd, entry)) {
  2137			entry = pmd_modify(entry, vma->vm_page_prot);
  2138			set_pmd_at(mm, start, pmd, entry);
  2139			update_mmu_cache_pmd(vma, address, &entry);
  2140		}
  2141		spin_unlock(ptl);
  2142	
  2143	out_unlock:
  2144		unlock_page(page);
  2145		put_page(page);
  2146		return 0;
  2147	}
  2148	#endif /* CONFIG_NUMA_BALANCING */
  2149	

---
0-DAY kernel test infrastructure                Open Source Technology Center
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