On 12/09/2013 09:26 PM, Sasha Levin wrote:
> On 12/09/2013 12:12 PM, Vlastimil Babka wrote:
>> On 12/09/2013 06:05 PM, Sasha Levin wrote:
>>> On 12/09/2013 04:34 AM, Vlastimil Babka wrote:
>>>> Hello, I will look at it, thanks.
>>>> Do you have specific reproduction instructions?
>>>
>>> Not really, the fuzzer hit it once and I've been unable to trigger it
>>> again. Looking at
>>> the piece of code involved it might have had something to do with
>>> hugetlbfs, so I'll crank
>>> up testing on that part.
>>
>> Thanks. Do you have trinity log and the .config file? I'm currently unable
>> to even boot linux-next
>> with my config/setup due to a GPF.
>> Looking at code I wouldn't expect that it could encounter a tail page,
>> without first encountering a
>> head page and skipping the whole huge page. At least in THP case, as TLB
>> pages should be split when
>> a vma is split. As for hugetlbfs, it should be skipped for mlock/munlock
>> operations completely. One
>> of these assumptions is probably failing here...
>
> If it helps, I've added a dump_page() in case we hit a tail page there and
> got:
>
> [ 980.172299] page:ffffea003e5e8040 count:0 mapcount:1 mapping:
> (null) index:0
> x0
> [ 980.173412] page flags: 0x2fffff80008000(tail)
>
> I can also add anything else in there to get other debug output if you think
> of something else useful.
Please try the following. Thanks in advance.
------8<------
diff --git a/mm/mlock.c b/mm/mlock.c
index d480cd6..c81b7c3 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -436,11 +436,14 @@ static unsigned long __munlock_pagevec_fill(struct
pagevec *pvec,
void munlock_vma_pages_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end)
{
+ unsigned long orig_start = start;
+ unsigned int page_increm = 0;
+
vma->vm_flags &= ~VM_LOCKED;
while (start < end) {
struct page *page = NULL;
- unsigned int page_mask, page_increm;
+ unsigned int page_mask;
struct pagevec pvec;
struct zone *zone;
int zoneid;
@@ -457,6 +460,22 @@ void munlock_vma_pages_range(struct vm_area_struct *vma,
&page_mask);
if (page && !IS_ERR(page)) {
+ if (PageTail(page)) {
+ struct page *first_page;
+ dump_page(page);
+ printk("start=%lu pfn=%lu orig_start=%lu "
+ "page_increm=%d "
+ "vm_start=%lu vm_end=%lu vm_flags=%lu\n",
+ start, page_to_pfn(page), orig_start,
+ page_increm,
+ vma->vm_start, vma->vm_end,
+ vma->vm_flags);
+ first_page = page->first_page;
+ printk("first_page pfn=%lu\n",
+ page_to_pfn(first_page));
+ dump_page(first_page);
+ VM_BUG_ON(true);
+ }
if (PageTransHuge(page)) {
lock_page(page);
/*
--
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