Re: [PATCH v2 6/7] mm: Batch around can_change_pte_writable()

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

Hi Dev,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on arm64/for-next/core linus/master v6.15-rc4 next-20250429]
[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/Dev-Jain/mm-Refactor-code-in-mprotect/20250429-133151
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20250429052336.18912-7-dev.jain%40arm.com
patch subject: [PATCH v2 6/7] mm: Batch around can_change_pte_writable()
config: arm64-randconfig-002-20250430 (https://download.01.org/0day-ci/archive/20250430/202504301306.AU2G1yvg-lkp@intel.com/config)
compiler: clang version 21.0.0git (https://github.com/llvm/llvm-project f819f46284f2a79790038e1f6649172789734ae8)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250430/202504301306.AU2G1yvg-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/202504301306.AU2G1yvg-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> mm/mprotect.c:46:15: warning: unused variable 'page' [-Wunused-variable]
      46 |         struct page *page;
         |                      ^~~~
   mm/mprotect.c:226:51: error: use of undeclared identifier 'folio'
     226 |                             can_change_ptes_writable(vma, addr, ptent, folio, 1))
         |                                                                        ^
   1 warning and 1 error generated.


vim +/page +46 mm/mprotect.c

36f881883c5794 Kirill A. Shutemov 2015-06-24  42  
695112a1385b39 Dev Jain           2025-04-29  43  bool can_change_ptes_writable(struct vm_area_struct *vma, unsigned long addr,
695112a1385b39 Dev Jain           2025-04-29  44  			      pte_t pte, struct folio *folio, unsigned int nr)
64fe24a3e05e5f David Hildenbrand  2022-06-14  45  {
64fe24a3e05e5f David Hildenbrand  2022-06-14 @46  	struct page *page;
64fe24a3e05e5f David Hildenbrand  2022-06-14  47  
7ea7e333842ed5 David Hildenbrand  2022-11-08  48  	if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE)))
7ea7e333842ed5 David Hildenbrand  2022-11-08  49  		return false;
64fe24a3e05e5f David Hildenbrand  2022-06-14  50  
7ea7e333842ed5 David Hildenbrand  2022-11-08  51  	/* Don't touch entries that are not even readable. */
d84887739d5c98 Nadav Amit         2022-11-08  52  	if (pte_protnone(pte))
64fe24a3e05e5f David Hildenbrand  2022-06-14  53  		return false;
64fe24a3e05e5f David Hildenbrand  2022-06-14  54  
64fe24a3e05e5f David Hildenbrand  2022-06-14  55  	/* Do we need write faults for softdirty tracking? */
f38ee285191813 Barry Song         2024-06-08  56  	if (pte_needs_soft_dirty_wp(vma, pte))
64fe24a3e05e5f David Hildenbrand  2022-06-14  57  		return false;
64fe24a3e05e5f David Hildenbrand  2022-06-14  58  
64fe24a3e05e5f David Hildenbrand  2022-06-14  59  	/* Do we need write faults for uffd-wp tracking? */
64fe24a3e05e5f David Hildenbrand  2022-06-14  60  	if (userfaultfd_pte_wp(vma, pte))
64fe24a3e05e5f David Hildenbrand  2022-06-14  61  		return false;
64fe24a3e05e5f David Hildenbrand  2022-06-14  62  
64fe24a3e05e5f David Hildenbrand  2022-06-14  63  	if (!(vma->vm_flags & VM_SHARED)) {
64fe24a3e05e5f David Hildenbrand  2022-06-14  64  		/*
7ea7e333842ed5 David Hildenbrand  2022-11-08  65  		 * Writable MAP_PRIVATE mapping: We can only special-case on
7ea7e333842ed5 David Hildenbrand  2022-11-08  66  		 * exclusive anonymous pages, because we know that our
7ea7e333842ed5 David Hildenbrand  2022-11-08  67  		 * write-fault handler similarly would map them writable without
7ea7e333842ed5 David Hildenbrand  2022-11-08  68  		 * any additional checks while holding the PT lock.
64fe24a3e05e5f David Hildenbrand  2022-06-14  69  		 */
695112a1385b39 Dev Jain           2025-04-29  70  		if (!folio)
695112a1385b39 Dev Jain           2025-04-29  71  			folio = vm_normal_folio(vma, addr, pte);
695112a1385b39 Dev Jain           2025-04-29  72  		return folio_test_anon(folio) && !folio_maybe_mapped_shared(folio);
64fe24a3e05e5f David Hildenbrand  2022-06-14  73  	}
64fe24a3e05e5f David Hildenbrand  2022-06-14  74  
fce831c92092ad David Hildenbrand  2024-05-22  75  	VM_WARN_ON_ONCE(is_zero_pfn(pte_pfn(pte)) && pte_dirty(pte));
fce831c92092ad David Hildenbrand  2024-05-22  76  
7ea7e333842ed5 David Hildenbrand  2022-11-08  77  	/*
7ea7e333842ed5 David Hildenbrand  2022-11-08  78  	 * Writable MAP_SHARED mapping: "clean" might indicate that the FS still
7ea7e333842ed5 David Hildenbrand  2022-11-08  79  	 * needs a real write-fault for writenotify
7ea7e333842ed5 David Hildenbrand  2022-11-08  80  	 * (see vma_wants_writenotify()). If "dirty", the assumption is that the
7ea7e333842ed5 David Hildenbrand  2022-11-08  81  	 * FS was already notified and we can simply mark the PTE writable
7ea7e333842ed5 David Hildenbrand  2022-11-08  82  	 * just like the write-fault handler would do.
7ea7e333842ed5 David Hildenbrand  2022-11-08  83  	 */
d84887739d5c98 Nadav Amit         2022-11-08  84  	return pte_dirty(pte);
64fe24a3e05e5f David Hildenbrand  2022-06-14  85  }
64fe24a3e05e5f David Hildenbrand  2022-06-14  86  

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