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: x86_64-randconfig-x017-201848 (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=x86_64 

All errors (new ones prefixed by >>):

   fs//proc/task_mmu.c: In function 'clear_refs_write':
>> fs//proc/task_mmu.c:1099:29: error: storage size of 'range' isn't known
      struct mmu_notifier_range range;
                                ^~~~~
   fs//proc/task_mmu.c:1099:29: warning: unused variable 'range' [-Wunused-variable]

vim +1099 fs//proc/task_mmu.c

  1069	
  1070	static ssize_t clear_refs_write(struct file *file, const char __user *buf,
  1071					size_t count, loff_t *ppos)
  1072	{
  1073		struct task_struct *task;
  1074		char buffer[PROC_NUMBUF];
  1075		struct mm_struct *mm;
  1076		struct vm_area_struct *vma;
  1077		enum clear_refs_types type;
  1078		struct mmu_gather tlb;
  1079		int itype;
  1080		int rv;
  1081	
  1082		memset(buffer, 0, sizeof(buffer));
  1083		if (count > sizeof(buffer) - 1)
  1084			count = sizeof(buffer) - 1;
  1085		if (copy_from_user(buffer, buf, count))
  1086			return -EFAULT;
  1087		rv = kstrtoint(strstrip(buffer), 10, &itype);
  1088		if (rv < 0)
  1089			return rv;
  1090		type = (enum clear_refs_types)itype;
  1091		if (type < CLEAR_REFS_ALL || type >= CLEAR_REFS_LAST)
  1092			return -EINVAL;
  1093	
  1094		task = get_proc_task(file_inode(file));
  1095		if (!task)
  1096			return -ESRCH;
  1097		mm = get_task_mm(task);
  1098		if (mm) {
> 1099			struct mmu_notifier_range range;
  1100			struct clear_refs_private cp = {
  1101				.type = type,
  1102			};
  1103			struct mm_walk clear_refs_walk = {
  1104				.pmd_entry = clear_refs_pte_range,
  1105				.test_walk = clear_refs_test_walk,
  1106				.mm = mm,
  1107				.private = &cp,
  1108			};
  1109	
  1110			if (type == CLEAR_REFS_MM_HIWATER_RSS) {
  1111				if (down_write_killable(&mm->mmap_sem)) {
  1112					count = -EINTR;
  1113					goto out_mm;
  1114				}
  1115	
  1116				/*
  1117				 * Writing 5 to /proc/pid/clear_refs resets the peak
  1118				 * resident set size to this mm's current rss value.
  1119				 */
  1120				reset_mm_hiwater_rss(mm);
  1121				up_write(&mm->mmap_sem);
  1122				goto out_mm;
  1123			}
  1124	
  1125			down_read(&mm->mmap_sem);
  1126			tlb_gather_mmu(&tlb, mm, 0, -1);
  1127			if (type == CLEAR_REFS_SOFT_DIRTY) {
  1128				for (vma = mm->mmap; vma; vma = vma->vm_next) {
  1129					if (!(vma->vm_flags & VM_SOFTDIRTY))
  1130						continue;
  1131					up_read(&mm->mmap_sem);
  1132					if (down_write_killable(&mm->mmap_sem)) {
  1133						count = -EINTR;
  1134						goto out_mm;
  1135					}
  1136					for (vma = mm->mmap; vma; vma = vma->vm_next) {
  1137						vma->vm_flags &= ~VM_SOFTDIRTY;
  1138						vma_set_page_prot(vma);
  1139					}
  1140					downgrade_write(&mm->mmap_sem);
  1141					break;
  1142				}
  1143	
  1144				range.start = 0;
  1145				range.end = -1UL;
  1146				range.mm = mm;
  1147				mmu_notifier_invalidate_range_start(&range);
  1148			}
  1149			walk_page_range(0, mm->highest_vm_end, &clear_refs_walk);
  1150			if (type == CLEAR_REFS_SOFT_DIRTY)
  1151				mmu_notifier_invalidate_range_end(&range);
  1152			tlb_finish_mmu(&tlb, 0, -1);
  1153			up_read(&mm->mmap_sem);
  1154	out_mm:
  1155			mmput(mm);
  1156		}
  1157		put_task_struct(task);
  1158	
  1159		return count;
  1160	}
  1161	

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