Re: [PATCH v2 1/1] mm/mmu_notifier: Add async OOM cleanup via call_srcu()

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

Hi shaikh.kamal,

kernel test robot noticed the following build errors:

[auto build test ERROR on v7.0]
[cannot apply to akpm-mm/mm-everything kvm/queue kvm/next kvm/linux-next v7.1-rc1 linus/master next-20260430]
[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/shaikh-kamal/mm-mmu_notifier-Add-async-OOM-cleanup-via-call_srcu/20260430-202943
base:   v7.0
patch link:    https://lore.kernel.org/r/20260429222548.25475-1-shaikhkamal2012%40gmail.com
patch subject: [PATCH v2 1/1] mm/mmu_notifier: Add async OOM cleanup via call_srcu()
config: hexagon-allnoconfig (https://download.01.org/0day-ci/archive/20260503/202605031115.qmkkOLQc-lkp@intel.com/config)
compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project 5bac06718f502014fade905512f1d26d578a18f3)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260503/202605031115.qmkkOLQc-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/202605031115.qmkkOLQc-lkp@intel.com/

All errors (new ones prefixed by >>):

>> mm/oom_kill.c:523:2: error: call to undeclared function 'mmu_notifier_oom_enter'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     523 |         mmu_notifier_oom_enter(mm);
         |         ^
   mm/oom_kill.c:523:2: note: did you mean 'mmu_notifier_release'?
   include/linux/mmu_notifier.h:610:20: note: 'mmu_notifier_release' declared here
     610 | static inline void mmu_notifier_release(struct mm_struct *mm)
         |                    ^
   mm/oom_kill.c:511:28: warning: variable 'oom_reaper_th' set but not used [-Wunused-but-set-global]
     511 | static struct task_struct *oom_reaper_th;
         |                            ^
   1 warning and 1 error generated.


vim +/mmu_notifier_oom_enter +523 mm/oom_kill.c

   515	
   516	static bool __oom_reap_task_mm(struct mm_struct *mm)
   517	{
   518		struct vm_area_struct *vma;
   519		bool ret = true;
   520		MA_STATE(mas, &mm->mm_mt, ULONG_MAX, ULONG_MAX);
   521	
   522		/* Notify MMU notifiers about the OOM event */
 > 523		mmu_notifier_oom_enter(mm);
   524	
   525		/*
   526		 * Tell all users of get_user/copy_from_user etc... that the content
   527		 * is no longer stable. No barriers really needed because unmapping
   528		 * should imply barriers already and the reader would hit a page fault
   529		 * if it stumbled over a reaped memory.
   530		 */
   531		mm_flags_set(MMF_UNSTABLE, mm);
   532	
   533		/*
   534		 * It might start racing with the dying task and compete for shared
   535		 * resources - e.g. page table lock contention has been observed.
   536		 * Reduce those races by reaping the oom victim from the other end
   537		 * of the address space.
   538		 */
   539		mas_for_each_rev(&mas, vma, 0) {
   540			if (vma->vm_flags & (VM_HUGETLB|VM_PFNMAP))
   541				continue;
   542	
   543			/*
   544			 * Only anonymous pages have a good chance to be dropped
   545			 * without additional steps which we cannot afford as we
   546			 * are OOM already.
   547			 *
   548			 * We do not even care about fs backed pages because all
   549			 * which are reclaimable have already been reclaimed and
   550			 * we do not want to block exit_mmap by keeping mm ref
   551			 * count elevated without a good reason.
   552			 */
   553			if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
   554				struct mmu_notifier_range range;
   555				struct mmu_gather tlb;
   556	
   557				mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0,
   558							mm, vma->vm_start,
   559							vma->vm_end);
   560				tlb_gather_mmu(&tlb, mm);
   561				if (mmu_notifier_invalidate_range_start_nonblock(&range)) {
   562					tlb_finish_mmu(&tlb);
   563					ret = false;
   564					continue;
   565				}
   566				unmap_page_range(&tlb, vma, range.start, range.end, NULL);
   567				mmu_notifier_invalidate_range_end(&range);
   568				tlb_finish_mmu(&tlb);
   569			}
   570		}
   571	
   572		return ret;
   573	}
   574	

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