[ljs:project/cow-context 1/18] kernel/fork.c:738:2: error: call to undeclared function 'drop_cow_context'; ISO C99 and later do not support implicit function declarations

[ljs:project/cow-context 1/18] kernel/fork.c:738:2: error: call to undeclared function 'drop_cow_context'; ISO C99 and later do not support implicit function declarations

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/ljs/linux.git project/cow-context
head:   e02aa02fef8128743869032cb20d26f752cd9154
commit: 1be9d553f4be97b754471cc04735f215e75c4bf2 [1/18] mm/rmap: add cow_context data structure and assign to mm
config: arm-allnoconfig (https://download.01.org/0day-ci/archive/20260507/202605071818.oG5849si-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/20260507/202605071818.oG5849si-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/202605071818.oG5849si-lkp@intel.com/

All errors (new ones prefixed by >>):

>> kernel/fork.c:738:2: error: call to undeclared function 'drop_cow_context'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     738 |         drop_cow_context(mm);
         |         ^
>> kernel/fork.c:1097:2: error: call to undeclared function 'mm_init_cow_context'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
    1097 |         mm_init_cow_context(mm);
         |         ^
   kernel/fork.c:1097:2: note: did you mean 'init_new_context'?
   include/asm-generic/mmu_context.h:34:19: note: 'init_new_context' declared here
      34 | static inline int init_new_context(struct task_struct *tsk,
         |                   ^
   2 errors generated.


vim +/drop_cow_context +738 kernel/fork.c

   714	
   715	/*
   716	 * Called when the last reference to the mm
   717	 * is dropped: either by a lazy thread or by
   718	 * mmput. Free the page directory and the mm.
   719	 */
   720	void __mmdrop(struct mm_struct *mm)
   721	{
   722		BUG_ON(mm == &init_mm);
   723		WARN_ON_ONCE(mm == current->mm);
   724	
   725		/* Ensure no CPUs are using this as their lazy tlb mm */
   726		cleanup_lazy_tlbs(mm);
   727	
   728		WARN_ON_ONCE(mm == current->active_mm);
   729		mm_free_pgd(mm);
   730		mm_free_id(mm);
   731		destroy_context(mm);
   732		mmu_notifier_subscriptions_destroy(mm);
   733		check_mm(mm);
   734		put_user_ns(mm->user_ns);
   735		mm_pasid_drop(mm);
   736		mm_destroy_cid(mm);
   737		percpu_counter_destroy_many(mm->rss_stat, NR_MM_COUNTERS);
 > 738		drop_cow_context(mm);
   739	
   740		free_mm(mm);
   741	}
   742	EXPORT_SYMBOL_GPL(__mmdrop);
   743	

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