Hi Jérôme,

I love your patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v4.20-rc5]
[cannot apply to next-20181206]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/jglisse-redhat-com/mmu-notifier-contextual-informations/20181207-031930
config: i386-randconfig-x007-201848 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   kernel/events/uprobes.c: In function '__replace_page':
   kernel/events/uprobes.c:174:28: error: storage size of 'range' isn't known
     struct mmu_notifier_range range;
                               ^~~~~
>> kernel/events/uprobes.c:177:16: error: 'MMU_NOTIFY_CLEAR' undeclared (first use in this function); did you mean 'VM_ARCH_CLEAR'?
     range.event = MMU_NOTIFY_CLEAR;
                   ^~~~~~~~~~~~~~~~
                   VM_ARCH_CLEAR
   kernel/events/uprobes.c:177:16: note: each undeclared identifier is reported only once for each function it appears in
   kernel/events/uprobes.c:174:28: warning: unused variable 'range' [-Wunused-variable]
     struct mmu_notifier_range range;
                               ^~~~~

vim +177 kernel/events/uprobes.c

   152	
   153	/**
   154	 * __replace_page - replace page in vma by new page.
   155	 * based on replace_page in mm/ksm.c
   156	 *
   157	 * @vma:      vma that holds the pte pointing to page
   158	 * @addr:     address the old @page is mapped at
   159	 * @page:     the cowed page we are replacing by kpage
   160	 * @kpage:    the modified page we replace page by
   161	 *
   162	 * Returns 0 on success, -EFAULT on failure.
   163	 */
   164	static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
   165					struct page *old_page, struct page *new_page)
   166	{
   167		struct mm_struct *mm = vma->vm_mm;
   168		struct page_vma_mapped_walk pvmw = {
   169			.page = old_page,
   170			.vma = vma,
   171			.address = addr,
   172		};
   173		int err;
 > 174		struct mmu_notifier_range range;
   175		struct mem_cgroup *memcg;
   176	
 > 177		range.event = MMU_NOTIFY_CLEAR;
   178		range.start = addr;
   179		range.end = addr + PAGE_SIZE;
   180		range.mm = mm;
   181	
   182		VM_BUG_ON_PAGE(PageTransHuge(old_page), old_page);
   183	
   184		err = mem_cgroup_try_charge(new_page, vma->vm_mm, GFP_KERNEL, &memcg,
   185				false);
   186		if (err)
   187			return err;
   188	
   189		/* For try_to_free_swap() and munlock_vma_page() below */
   190		lock_page(old_page);
   191	
   192		mmu_notifier_invalidate_range_start(&range);
   193		err = -EAGAIN;
   194		if (!page_vma_mapped_walk(&pvmw)) {
   195			mem_cgroup_cancel_charge(new_page, memcg, false);
   196			goto unlock;
   197		}
   198		VM_BUG_ON_PAGE(addr != pvmw.address, old_page);
   199	
   200		get_page(new_page);
   201		page_add_new_anon_rmap(new_page, vma, addr, false);
   202		mem_cgroup_commit_charge(new_page, memcg, false, false);
   203		lru_cache_add_active_or_unevictable(new_page, vma);
   204	
   205		if (!PageAnon(old_page)) {
   206			dec_mm_counter(mm, mm_counter_file(old_page));
   207			inc_mm_counter(mm, MM_ANONPAGES);
   208		}
   209	
   210		flush_cache_page(vma, addr, pte_pfn(*pvmw.pte));
   211		ptep_clear_flush_notify(vma, addr, pvmw.pte);
   212		set_pte_at_notify(mm, addr, pvmw.pte,
   213				mk_pte(new_page, vma->vm_page_prot));
   214	
   215		page_remove_rmap(old_page, false);
   216		if (!page_mapped(old_page))
   217			try_to_free_swap(old_page);
   218		page_vma_mapped_walk_done(&pvmw);
   219	
   220		if (vma->vm_flags & VM_LOCKED)
   221			munlock_vma_page(old_page);
   222		put_page(old_page);
   223	
   224		err = 0;
   225	 unlock:
   226		mmu_notifier_invalidate_range_end(&range);
   227		unlock_page(old_page);
   228		return err;
   229	}
   230	

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