Re: [RFC PATCH 2/4] mm: unified fault and migrate device page paths

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

Hi Mika,

[This is a private test report for your RFC patch.]
kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on akpm-mm/mm-nonmm-unstable linus/master v6.17-rc1 next-20250814]
[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/Mika-Penttil/mm-use-current-as-mmu-notifier-s-owner/20250814-152712
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20250814072045.3637192-4-mpenttil%40redhat.com
patch subject: [RFC PATCH 2/4] mm: unified fault and migrate device page paths
config: arc-randconfig-002-20250815 (https://download.01.org/0day-ci/archive/20250815/202508150505.ioccTtkU-lkp@intel.com/config)
compiler: arc-linux-gcc (GCC) 9.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250815/202508150505.ioccTtkU-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/202508150505.ioccTtkU-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from include/linux/pagewalk.h:5,
                    from mm/hmm.c:11:
   include/linux/mm.h:80: warning: "PAGES_TO_MB" redefined
      80 | #define PAGES_TO_MB(pages) ((pages) >> (20 - PAGE_SHIFT))
         | 
   In file included from arch/arc/include/asm/irqflags-compact.h:16,
                    from arch/arc/include/asm/irqflags.h:11,
                    from include/linux/irqflags.h:18,
                    from include/linux/spinlock.h:59,
                    from include/linux/mmzone.h:8,
                    from include/linux/gfp.h:7,
                    from include/linux/mm.h:7,
                    from include/linux/pagewalk.h:5,
                    from mm/hmm.c:11:
   arch/arc/include/asm/arcregs.h:155: note: this is the location of the previous definition
     155 | #define PAGES_TO_MB(n_pages) (PAGES_TO_KB(n_pages) >> 10)
         | 
   mm/hmm.c:55:30: error: return type is an incomplete type
      55 | static enum migrate_vma_info hmm_want_migrate(struct hmm_range *range)
         |                              ^~~~~~~~~~~~~~~~
   mm/hmm.c: In function 'hmm_want_migrate':
   mm/hmm.c:57:24: error: storage size of 'minfo' isn't known
      57 |  enum migrate_vma_info minfo;
         |                        ^~~~~
   mm/hmm.c:59:41: error: dereferencing pointer to incomplete type 'struct migrate_vma'
      59 |  minfo = range->migrate ? range->migrate->flags : 0;
         |                                         ^~
   mm/hmm.c:61:3: error: 'MIGRATE_VMA_SELECT_SYSTEM' undeclared (first use in this function)
      61 |   MIGRATE_VMA_SELECT_SYSTEM : 0;
         |   ^~~~~~~~~~~~~~~~~~~~~~~~~
   mm/hmm.c:61:3: note: each undeclared identifier is reported only once for each function it appears in
>> mm/hmm.c:63:9: warning: 'return' with a value, in function returning void [-Wreturn-type]
      63 |  return minfo;
         |         ^~~~~
   mm/hmm.c:55:30: note: declared here
      55 | static enum migrate_vma_info hmm_want_migrate(struct hmm_range *range)
         |                              ^~~~~~~~~~~~~~~~
>> mm/hmm.c:57:24: warning: unused variable 'minfo' [-Wunused-variable]
      57 |  enum migrate_vma_info minfo;
         |                        ^~~~~
   mm/hmm.c: In function 'hmm_pfns_fill':
   mm/hmm.c:73:7: error: void value not ignored as it ought to be
      73 |   if (hmm_want_migrate(range) &&
         |       ^~~~~~~~~~~~~~~~~~~~~~~
   mm/hmm.c: In function 'hmm_vma_handle_migrate_prepare':
   mm/hmm.c:367:24: error: storage size of 'minfo' isn't known
     367 |  enum migrate_vma_info minfo;
         |                        ^~~~~
   mm/hmm.c:415:17: error: 'MIGRATE_VMA_SELECT_DEVICE_PRIVATE' undeclared (first use in this function)
     415 |   if (!(minfo & MIGRATE_VMA_SELECT_DEVICE_PRIVATE))
         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   mm/hmm.c:425:16: error: 'MIGRATE_VMA_SELECT_SYSTEM' undeclared (first use in this function)
     425 |       (minfo & MIGRATE_VMA_SELECT_SYSTEM)) {
         |                ^~~~~~~~~~~~~~~~~~~~~~~~~
   mm/hmm.c:437:10: error: 'MIGRATE_VMA_SELECT_DEVICE_COHERENT' undeclared (first use in this function)
     437 |          MIGRATE_VMA_SELECT_DEVICE_COHERENT) ||
         |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   mm/hmm.c:519:4: error: implicit declaration of function 'flush_tlb_range'; did you mean 'flush_pmd_tlb_range'? [-Werror=implicit-function-declaration]
     519 |    flush_tlb_range(walk->vma, addr, addr + PAGE_SIZE);
         |    ^~~~~~~~~~~~~~~
         |    flush_pmd_tlb_range
   mm/hmm.c:367:24: warning: unused variable 'minfo' [-Wunused-variable]
     367 |  enum migrate_vma_info minfo;
         |                        ^~~~~
   mm/hmm.c: In function 'hmm_vma_capture_migrate_range':
   mm/hmm.c:580:6: error: invalid use of void expression
     580 |  if (!hmm_want_migrate(range))
         |      ^
   mm/hmm.c: In function 'hmm_vma_walk_pmd':
   mm/hmm.c:637:6: error: void value not ignored as it ought to be
     637 |  if (hmm_want_migrate(range) &&
         |      ^~~~~~~~~~~~~~~~~~~~~~~
   mm/hmm.c: In function 'hmm_range_fault':
   mm/hmm.c:937:6: error: void value not ignored as it ought to be
     937 |  if (hmm_want_migrate(range) && range->migrate &&
         |      ^~~~~~~~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors


vim +/return +63 mm/hmm.c

    54	
    55	static enum migrate_vma_info hmm_want_migrate(struct hmm_range *range)
    56	{
  > 57		enum migrate_vma_info minfo;
    58	
    59		minfo = range->migrate ? range->migrate->flags : 0;
    60		minfo |= (range->default_flags & HMM_PFN_REQ_MIGRATE) ?
    61			MIGRATE_VMA_SELECT_SYSTEM : 0;
    62	
  > 63		return minfo;
    64	}
    65	

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