[kas:uffd/v2 7/14] include/linux/mm.h:4618 gup_can_follow_protnone() warn: bitwise AND condition is false here

[kas:uffd/v2 7/14] include/linux/mm.h:4618 gup_can_follow_protnone() warn: bitwise AND condition is false here

[kernel test robot]

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
TO: "Kiryl Shutsemau (Meta)" <kas@kernel.org>

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/kas/linux.git uffd/v2
head:   0b6f87fd4809245f9eebee73f34e2fb14230330c
commit: c88e78ffb2cc5ca81f5a6319b7e3c4ffd8baefe1 [7/14] mm: handle VM_UFFD_RWP in khugepaged, rmap, and GUP
:::::: branch date: 26 hours ago
:::::: commit date: 26 hours ago
config: m68k-randconfig-r073-20260509 (https://download.01.org/0day-ci/archive/20260510/202605100132.U77SlLEg-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 12.5.0
smatch: v0.5.0-9065-ge9cc34fd

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 <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202605100132.U77SlLEg-lkp@intel.com/

smatch warnings:
include/linux/mm.h:4618 gup_can_follow_protnone() warn: bitwise AND condition is false here

vim +4618 include/linux/mm.h

9a291a7c9428155 James Morse            2017-06-02  4605  
474098edac262ae David Hildenbrand      2022-08-25  4606  /*
474098edac262ae David Hildenbrand      2022-08-25  4607   * Indicates whether GUP can follow a PROT_NONE mapped page, or whether
c88e78ffb2cc5ca Kiryl Shutsemau (Meta  2026-04-22  4608)  * a (NUMA hinting or userfaultfd RWP) fault is required.
474098edac262ae David Hildenbrand      2022-08-25  4609   */
da0045587d59d4f Max Kellermann         2025-09-01  4610  static inline bool gup_can_follow_protnone(const struct vm_area_struct *vma,
d74943a2f3cdade David Hildenbrand      2023-08-03  4611  					   unsigned int flags)
474098edac262ae David Hildenbrand      2022-08-25  4612  {
c88e78ffb2cc5ca Kiryl Shutsemau (Meta  2026-04-22  4613) 	/*
c88e78ffb2cc5ca Kiryl Shutsemau (Meta  2026-04-22  4614) 	 * VM_UFFD_RWP uses protnone as an access-tracking marker, not for
c88e78ffb2cc5ca Kiryl Shutsemau (Meta  2026-04-22  4615) 	 * NUMA hinting. GUP must always take a fault so the access is
c88e78ffb2cc5ca Kiryl Shutsemau (Meta  2026-04-22  4616) 	 * delivered to userfaultfd, regardless of FOLL_HONOR_NUMA_FAULT.
c88e78ffb2cc5ca Kiryl Shutsemau (Meta  2026-04-22  4617) 	 */
c88e78ffb2cc5ca Kiryl Shutsemau (Meta  2026-04-22 @4618) 	if (vma->vm_flags & VM_UFFD_RWP)
c88e78ffb2cc5ca Kiryl Shutsemau (Meta  2026-04-22  4619) 		return false;
c88e78ffb2cc5ca Kiryl Shutsemau (Meta  2026-04-22  4620) 
474098edac262ae David Hildenbrand      2022-08-25  4621  	/*
d74943a2f3cdade David Hildenbrand      2023-08-03  4622  	 * If callers don't want to honor NUMA hinting faults, no need to
d74943a2f3cdade David Hildenbrand      2023-08-03  4623  	 * determine if we would actually have to trigger a NUMA hinting fault.
474098edac262ae David Hildenbrand      2022-08-25  4624  	 */
d74943a2f3cdade David Hildenbrand      2023-08-03  4625  	if (!(flags & FOLL_HONOR_NUMA_FAULT))
d74943a2f3cdade David Hildenbrand      2023-08-03  4626  		return true;
d74943a2f3cdade David Hildenbrand      2023-08-03  4627  
d74943a2f3cdade David Hildenbrand      2023-08-03  4628  	/*
d74943a2f3cdade David Hildenbrand      2023-08-03  4629  	 * NUMA hinting faults don't apply in inaccessible (PROT_NONE) VMAs.
d74943a2f3cdade David Hildenbrand      2023-08-03  4630  	 *
d74943a2f3cdade David Hildenbrand      2023-08-03  4631  	 * Requiring a fault here even for inaccessible VMAs would mean that
d74943a2f3cdade David Hildenbrand      2023-08-03  4632  	 * FOLL_FORCE cannot make any progress, because handle_mm_fault()
d74943a2f3cdade David Hildenbrand      2023-08-03  4633  	 * refuses to process NUMA hinting faults in inaccessible VMAs.
d74943a2f3cdade David Hildenbrand      2023-08-03  4634  	 */
d74943a2f3cdade David Hildenbrand      2023-08-03  4635  	return !vma_is_accessible(vma);
474098edac262ae David Hildenbrand      2022-08-25  4636  }
474098edac262ae David Hildenbrand      2022-08-25  4637  

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