Re: [BUG, TOT] xfs w/ dax failure in __follow_pte_pmd()

[Matthew Wilcox <willy@infradead.org>]

On Wed, Jan 02, 2019 at 01:25:31PM -0800, Matthew Wilcox wrote:
> On Thu, Jan 03, 2019 at 08:13:32AM +1100, Dave Chinner wrote:
> > Hi folks,
> > 
> > An overnight test run on a current TOT kernel failed generic/413
> > with the following dmesg output:
> > 
> > [ 9487.276402] RIP: 0010:__follow_pte_pmd+0x22d/0x340
> > [ 9487.305065] Call Trace:
> > [ 9487.307310]  dax_entry_mkclean+0xbb/0x1f0
> 
> We've only got one commit touching dax_entry_mkclean and it's Jerome's.
> Looking through ac46d4f3c43241ffa23d5bf36153a0830c0e02cc, I'd say
> it's missing a call to mmu_notifier_range_init().

Could I persuade you to give this a try?

diff --git a/mm/memory.c b/mm/memory.c
index 2dd2f9ab57f4..21a650368be0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4078,8 +4078,8 @@ static int __follow_pte_pmd(struct mm_struct *mm, unsigned long address,
 		goto out;
 
 	if (range) {
-		range->start = address & PAGE_MASK;
-		range->end = range->start + PAGE_SIZE;
+		mmu_notifier_range_init(range, mm, address & PAGE_MASK,
+				     (address & PAGE_MASK) + PAGE_SIZE);
 		mmu_notifier_invalidate_range_start(range);
 	}
 	ptep = pte_offset_map_lock(mm, pmd, address, ptlp);