Re: [RFC/PATCH 3/5] mm: get_user_pages: use NON-MOVABLE pages when FOLL_DURABLE flag is set

[Marek Szyprowski <m.szyprowski@samsung.com>]

Hello,

On 5/6/2013 9:19 AM, Tang Chen wrote:
> Hi Marek,
>
> It has been a long time since this patch-set was sent.
> And I'm pushing memory hot-remove works. I think I need your
> [patch3/5] to fix a problem I met.
>
> We have sent a similar patch before. But I think yours may be better. :)
> https://lkml.org/lkml/2013/2/21/126
>
> So would you please update and resend your patch again ?
> Or do you have your own plan to push it ?
>

I don't think that there was any conclusion after my patch, so I really see
no point in submitting it again now. If you need it for Your patchset, You
can include it directly. Just please keep my signed-off-by tag.

> Thanks. :)
>
> On 03/05/2013 02:57 PM, Marek Szyprowski wrote:
>> Ensure that newly allocated pages, which are faulted in in FOLL_DURABLE
>> mode comes from non-movalbe pageblocks, to workaround migration failures
>> with Contiguous Memory Allocator.
>>
>> Signed-off-by: Marek Szyprowski<m.szyprowski@samsung.com>
>> Signed-off-by: Kyungmin Park<kyungmin.park@samsung.com>
>> ---
>>   include/linux/highmem.h |   12 ++++++++++--
>>   include/linux/mm.h      |    2 ++
>>   mm/memory.c             |   24 ++++++++++++++++++------
>>   3 files changed, 30 insertions(+), 8 deletions(-)
>>
>> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
>> index 7fb31da..cf0b9d8 100644
>> --- a/include/linux/highmem.h
>> +++ b/include/linux/highmem.h
>> @@ -168,7 +168,8 @@ __alloc_zeroed_user_highpage(gfp_t movableflags,
>>   #endif
>>
>>   /**
>> - * alloc_zeroed_user_highpage_movable - Allocate a zeroed HIGHMEM 
>> page for a VMA that the caller knows can move
>> + * alloc_zeroed_user_highpage_movable - Allocate a zeroed HIGHMEM 
>> page for
>> + *                    a VMA that the caller knows can move
>>    * @vma: The VMA the page is to be allocated for
>>    * @vaddr: The virtual address the page will be inserted into
>>    *
>> @@ -177,11 +178,18 @@ __alloc_zeroed_user_highpage(gfp_t movableflags,
>>    */
>>   static inline struct page *
>>   alloc_zeroed_user_highpage_movable(struct vm_area_struct *vma,
>> -                    unsigned long vaddr)
>> +                   unsigned long vaddr)
>>   {
>>       return __alloc_zeroed_user_highpage(__GFP_MOVABLE, vma, vaddr);
>>   }
>>
>> +static inline struct page *
>> +alloc_zeroed_user_highpage(gfp_t gfp, struct vm_area_struct *vma,
>> +               unsigned long vaddr)
>> +{
>> +    return __alloc_zeroed_user_highpage(gfp, vma, vaddr);
>> +}
>> +
>>   static inline void clear_highpage(struct page *page)
>>   {
>>       void *kaddr = kmap_atomic(page);
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 9806e54..c11f58f 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -165,6 +165,7 @@ extern pgprot_t protection_map[16];
>>   #define FAULT_FLAG_RETRY_NOWAIT    0x10    /* Don't drop mmap_sem 
>> and wait when retrying */
>>   #define FAULT_FLAG_KILLABLE    0x20    /* The fault task is in 
>> SIGKILL killable region */
>>   #define FAULT_FLAG_TRIED    0x40    /* second try */
>> +#define FAULT_FLAG_NO_CMA    0x80    /* don't use CMA pages */
>>
>>   /*
>>    * vm_fault is filled by the the pagefault handler and passed to 
>> the vma's
>> @@ -1633,6 +1634,7 @@ static inline struct page *follow_page(struct 
>> vm_area_struct *vma,
>>   #define FOLL_HWPOISON    0x100    /* check page is hwpoisoned */
>>   #define FOLL_NUMA    0x200    /* force NUMA hinting page fault */
>>   #define FOLL_MIGRATION    0x400    /* wait for page to replace 
>> migration entry */
>> +#define FOLL_DURABLE    0x800    /* get the page reference for a 
>> long time */
>>
>>   typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long 
>> addr,
>>               void *data);
>> diff --git a/mm/memory.c b/mm/memory.c
>> index 42dfd8e..2b9c2dd 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -1816,6 +1816,9 @@ long __get_user_pages(struct task_struct *tsk, 
>> struct mm_struct *mm,
>>                   int ret;
>>                   unsigned int fault_flags = 0;
>>
>> +                if (gup_flags&  FOLL_DURABLE)
>> +                    fault_flags = FAULT_FLAG_NO_CMA;
>> +
>>                   /* For mlock, just skip the stack guard page. */
>>                   if (foll_flags&  FOLL_MLOCK) {
>>                       if (stack_guard_page(vma, start))
>> @@ -2495,7 +2498,7 @@ static inline void cow_user_page(struct page 
>> *dst, struct page *src, unsigned lo
>>    */
>>   static int do_wp_page(struct mm_struct *mm, struct vm_area_struct 
>> *vma,
>>           unsigned long address, pte_t *page_table, pmd_t *pmd,
>> -        spinlock_t *ptl, pte_t orig_pte)
>> +        spinlock_t *ptl, pte_t orig_pte, unsigned int flags)
>>       __releases(ptl)
>>   {
>>       struct page *old_page, *new_page = NULL;
>> @@ -2505,6 +2508,10 @@ static int do_wp_page(struct mm_struct *mm, 
>> struct vm_area_struct *vma,
>>       struct page *dirty_page = NULL;
>>       unsigned long mmun_start = 0;    /* For mmu_notifiers */
>>       unsigned long mmun_end = 0;    /* For mmu_notifiers */
>> +    gfp_t gfp = GFP_HIGHUSER_MOVABLE;
>> +
>> +    if (IS_ENABLED(CONFIG_CMA)&&  (flags& FAULT_FLAG_NO_CMA))
>> +        gfp&= ~__GFP_MOVABLE;
>>
>>       old_page = vm_normal_page(vma, address, orig_pte);
>>       if (!old_page) {
>> @@ -2668,11 +2675,11 @@ gotten:
>>           goto oom;
>>
>>       if (is_zero_pfn(pte_pfn(orig_pte))) {
>> -        new_page = alloc_zeroed_user_highpage_movable(vma, address);
>> +        new_page = alloc_zeroed_user_highpage(gfp, vma, address);
>>           if (!new_page)
>>               goto oom;
>>       } else {
>> -        new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
>> +        new_page = alloc_page_vma(gfp, vma, address);
>>           if (!new_page)
>>               goto oom;
>>           cow_user_page(new_page, old_page, address, vma);
>> @@ -3032,7 +3039,7 @@ static int do_swap_page(struct mm_struct *mm, 
>> struct vm_area_struct *vma,
>>       }
>>
>>       if (flags&  FAULT_FLAG_WRITE) {
>> -        ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
>> +        ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, 
>> pte, flags);
>>           if (ret&  VM_FAULT_ERROR)
>>               ret&= VM_FAULT_ERROR;
>>           goto out;
>> @@ -3187,6 +3194,11 @@ static int __do_fault(struct mm_struct *mm, 
>> struct vm_area_struct *vma,
>>       struct vm_fault vmf;
>>       int ret;
>>       int page_mkwrite = 0;
>> +    gfp_t gfp = GFP_HIGHUSER_MOVABLE;
>> +
>> +    if (IS_ENABLED(CONFIG_CMA)&&  (flags& FAULT_FLAG_NO_CMA))
>> +        gfp&= ~__GFP_MOVABLE;
>> +
>>
>>       /*
>>        * If we do COW later, allocate page befor taking lock_page()
>> @@ -3197,7 +3209,7 @@ static int __do_fault(struct mm_struct *mm, 
>> struct vm_area_struct *vma,
>>           if (unlikely(anon_vma_prepare(vma)))
>>               return VM_FAULT_OOM;
>>
>> -        cow_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
>> +        cow_page = alloc_page_vma(gfp, vma, address);
>>           if (!cow_page)
>>               return VM_FAULT_OOM;
>>
>> @@ -3614,7 +3626,7 @@ int handle_pte_fault(struct mm_struct *mm,
>>       if (flags&  FAULT_FLAG_WRITE) {
>>           if (!pte_write(entry))
>>               return do_wp_page(mm, vma, address,
>> -                    pte, pmd, ptl, entry);
>> +                    pte, pmd, ptl, entry, flags);
>>           entry = pte_mkdirty(entry);
>>       }
>>       entry = pte_mkyoung(entry);
>

Best regards
-- 
Marek Szyprowski
Samsung Poland R&D Center


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