RE: [PATCH] Add /proc/PID/{smaps, numa_maps} support for DAX

[Du, Fan]

>-----Original Message-----
>From: Dan Williams [mailto:dan.j.williams@xxxxxxxxx]
>Sent: Tuesday, October 24, 2017 4:47 PM
>To: Du, Fan <fan.du@xxxxxxxxx>
>Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>; Christoph Hellwig
><hch@xxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; Dave Hansen
><dave.hansen@xxxxxxxxxxxxxxx>
>Subject: Re: [PATCH] Add /proc/PID/{smaps, numa_maps} support for DAX
>
>On Tue, Oct 24, 2017 at 12:52 AM, Fan Du <fan.du@xxxxxxxxx> wrote:
>>
>> So user could check those interface for more detailed
>> information about how much DAX mappings are currently
>> created.
>>
>> Here we use vma_is_dax method to find specific page
>> struture with DAX {huge, normal}page mappings,
>> vm_normal_page routine works as before without any
>> impact on the existing logical where _vm_normal_page
>> are called.
>>
>> Signed-off-by: Fan Du <fan.du@xxxxxxxxx>
>> ---
>>  fs/proc/task_mmu.c | 25 +++++++++++++++++++------
>>  1 file changed, 19 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
>> index 5589b4b..ba2e58c 100644
>> --- a/fs/proc/task_mmu.c
>> +++ b/fs/proc/task_mmu.c
>> @@ -528,7 +528,11 @@ static void smaps_pte_entry(pte_t *pte, unsigned
>long addr,
>>         struct page *page = NULL;
>>
>>         if (pte_present(*pte)) {
>> -               page = vm_normal_page(vma, addr, *pte);
>> +               if (!vma_is_dax(vma))
>> +                       page = vm_normal_page(vma, addr, *pte);
>> +               else
>> +                       page = pte_page(*pte);
>
>See usage of pte_devmap, pmd_devmap, and pud_devmap in mm/gup.c. You
>need to check for that bit to know that there is a 'struct page' entry
>associated with a DAX mapping.  

Thanks Dan for your review, got it!


>I believe we just need to fix up and
>resend his approach from last year:
>
>    https://marc.info/?l=linux-kernel&m=148045064103357&w=2

Sure, I will rebase Dave's patch and send v2 soon.