Re: mm: BUG in __munlock_pagevec

[Kirill A. Shutemov]

On Mon, Nov 30, 2015 at 09:24:56AM -0500, Sasha Levin wrote:
> Hi all,
> 
> I've hit the following while fuzzing with trinity on the latest -next kernel:
> 
> 
> [  850.305385] page:ffffea001a5a0f00 count:0 mapcount:1 mapping:dead000000000400 index:0x1ffffffffff
> [  850.306773] flags: 0x2fffff80000000()
> [  850.307175] page dumped because: VM_BUG_ON_PAGE(1 && PageTail(page))
> [  850.308027] page_owner info is not active (free page?)

Could you check this completely untested patch:

diff --git a/mm/mlock.c b/mm/mlock.c
index af421d8bd6da..9197b6721a1e 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -393,6 +393,13 @@ static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
 		if (!page || page_zone_id(page) != zoneid)
 			break;
 
+		/*
+		 * Do not use pagevec for PTE-mapped THP,
+		 * munlock_vma_pages_range() will handle them.
+		 */
+		if (PageTransCompound(page))
+			break;
+
 		get_page(page);
 		/*
 		 * Increase the address that will be returned *before* the
-- 
 Kirill A. Shutemov
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