Re: [PATCH v1 2/2] mm: remove extra ZONE_DEVICE struct page refcount

["Sierra Guiza, Alejandro (Alex)" <alex.sierra@amd.com>]

On 10/14/2021 3:57 PM, Ralph Campbell wrote:
>
> On 10/14/21 11:01 AM, Jason Gunthorpe wrote:
>> On Thu, Oct 14, 2021 at 10:35:27AM -0700, Ralph Campbell wrote:
>>
>>> I ran xfstests-dev using the kernel boot option to "fake" a pmem device
>>> when I first posted this patch. The tests ran OK (or at least the same
>>> tests passed with and without my patch).
>> Hmm. I know nothing of xfstests but
>>
>> tests/generic/413
>>
>> Looks kind of like it might cover this situation?
>>
>> Did it run for you?
>>
>> Jason
>
> I don't remember. I'll have to rerun the test which might take a day 
> or two
> to set up again.
>
I just ran this generic/413 on my side using pmem fake device. It does fail.
I remember we proposed a fix on this patch before try_get_page was removed.
@@ -1186,7 +1153,7 @@ bool __must_check try_grab_page(struct page *page, 
unsigned int flags);
  static inline __must_check bool try_get_page(struct page *page)
  {
         page = compound_head(page);
-       if (WARN_ON_ONCE(page_ref_count(page) <= 0))
+       if (WARN_ON_ONCE(page_ref_count(page) < 
(int)!is_zone_device_page(page)))
                 return false;
         page_ref_inc(page);
         return true;

Alex