diff mbox series

[v3,13/14] mm/gup: grab head page refcount once for group of subpages

Message ID 20210714193542.21857-14-joao.m.martins@oracle.com (mailing list archive)
State New
Headers show
Series mm, sparse-vmemmap: Introduce compound pagemaps | expand

Commit Message

Joao Martins July 14, 2021, 7:35 p.m. UTC
Use try_grab_compound_head() for device-dax GUP when configured with a
compound pagemap.

Rather than incrementing the refcount for each page, do one atomic
addition for all the pages to be pinned.

Performance measured by gup_benchmark improves considerably
get_user_pages_fast() and pin_user_pages_fast() with NVDIMMs:

 $ gup_test -f /dev/dax1.0 -m 16384 -r 10 -S [-u,-a] -n 512 -w
(get_user_pages_fast 2M pages) ~59 ms -> ~6.1 ms
(pin_user_pages_fast 2M pages) ~87 ms -> ~6.2 ms
[altmap]
(get_user_pages_fast 2M pages) ~494 ms -> ~9 ms
(pin_user_pages_fast 2M pages) ~494 ms -> ~10 ms

 $ gup_test -f /dev/dax1.0 -m 129022 -r 10 -S [-u,-a] -n 512 -w
(get_user_pages_fast 2M pages) ~492 ms -> ~49 ms
(pin_user_pages_fast 2M pages) ~493 ms -> ~50 ms
[altmap with -m 127004]
(get_user_pages_fast 2M pages) ~3.91 sec -> ~70 ms
(pin_user_pages_fast 2M pages) ~3.97 sec -> ~74 ms

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
 mm/gup.c | 53 +++++++++++++++++++++++++++++++++--------------------
 1 file changed, 33 insertions(+), 20 deletions(-)

Comments

Dan Williams July 28, 2021, 7:55 p.m. UTC | #1
On Wed, Jul 14, 2021 at 12:36 PM Joao Martins <joao.m.martins@oracle.com> wrote:
>
> Use try_grab_compound_head() for device-dax GUP when configured with a
> compound pagemap.
>
> Rather than incrementing the refcount for each page, do one atomic
> addition for all the pages to be pinned.
>
> Performance measured by gup_benchmark improves considerably
> get_user_pages_fast() and pin_user_pages_fast() with NVDIMMs:
>
>  $ gup_test -f /dev/dax1.0 -m 16384 -r 10 -S [-u,-a] -n 512 -w
> (get_user_pages_fast 2M pages) ~59 ms -> ~6.1 ms
> (pin_user_pages_fast 2M pages) ~87 ms -> ~6.2 ms
> [altmap]
> (get_user_pages_fast 2M pages) ~494 ms -> ~9 ms
> (pin_user_pages_fast 2M pages) ~494 ms -> ~10 ms
>
>  $ gup_test -f /dev/dax1.0 -m 129022 -r 10 -S [-u,-a] -n 512 -w
> (get_user_pages_fast 2M pages) ~492 ms -> ~49 ms
> (pin_user_pages_fast 2M pages) ~493 ms -> ~50 ms
> [altmap with -m 127004]
> (get_user_pages_fast 2M pages) ~3.91 sec -> ~70 ms
> (pin_user_pages_fast 2M pages) ~3.97 sec -> ~74 ms
>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> ---
>  mm/gup.c | 53 +++++++++++++++++++++++++++++++++--------------------
>  1 file changed, 33 insertions(+), 20 deletions(-)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index 42b8b1fa6521..9baaa1c0b7f3 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -2234,31 +2234,55 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
>  }
>  #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
>
> +
> +static int record_subpages(struct page *page, unsigned long addr,
> +                          unsigned long end, struct page **pages)
> +{
> +       int nr;
> +
> +       for (nr = 0; addr != end; addr += PAGE_SIZE)
> +               pages[nr++] = page++;
> +
> +       return nr;
> +}
> +
>  #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
>  static int __gup_device_huge(unsigned long pfn, unsigned long addr,
>                              unsigned long end, unsigned int flags,
>                              struct page **pages, int *nr)
>  {
> -       int nr_start = *nr;
> +       int refs, nr_start = *nr;
>         struct dev_pagemap *pgmap = NULL;
>
>         do {
> -               struct page *page = pfn_to_page(pfn);
> +               struct page *pinned_head, *head, *page = pfn_to_page(pfn);
> +               unsigned long next;
>
>                 pgmap = get_dev_pagemap(pfn, pgmap);
>                 if (unlikely(!pgmap)) {
>                         undo_dev_pagemap(nr, nr_start, flags, pages);
>                         return 0;
>                 }
> -               SetPageReferenced(page);
> -               pages[*nr] = page;
> -               if (unlikely(!try_grab_page(page, flags))) {
> -                       undo_dev_pagemap(nr, nr_start, flags, pages);
> +
> +               head = compound_head(page);
> +               /* @end is assumed to be limited at most one compound page */
> +               next = PageCompound(head) ? end : addr + PAGE_SIZE;

Please no ternary operator for this check, but otherwise this patch
looks good to me.

Reviewed-by: Dan Williams <dan.j.williams@intel.com>


> +               refs = record_subpages(page, addr, next, pages + *nr);
> +
> +               SetPageReferenced(head);
> +               pinned_head = try_grab_compound_head(head, refs, flags);
> +               if (!pinned_head) {
> +                       if (PageCompound(head)) {
> +                               ClearPageReferenced(head);
> +                               put_dev_pagemap(pgmap);
> +                       } else {
> +                               undo_dev_pagemap(nr, nr_start, flags, pages);
> +                       }
>                         return 0;
>                 }
> -               (*nr)++;
> -               pfn++;
> -       } while (addr += PAGE_SIZE, addr != end);
> +               *nr += refs;
> +               pfn += refs;
> +       } while (addr += (refs << PAGE_SHIFT), addr != end);
>
>         if (pgmap)
>                 put_dev_pagemap(pgmap);
> @@ -2318,17 +2342,6 @@ static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
>  }
>  #endif
>
> -static int record_subpages(struct page *page, unsigned long addr,
> -                          unsigned long end, struct page **pages)
> -{
> -       int nr;
> -
> -       for (nr = 0; addr != end; addr += PAGE_SIZE)
> -               pages[nr++] = page++;
> -
> -       return nr;
> -}
> -
>  #ifdef CONFIG_ARCH_HAS_HUGEPD
>  static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
>                                       unsigned long sz)
> --
> 2.17.1
>
Joao Martins July 28, 2021, 8:07 p.m. UTC | #2
On 7/28/21 8:55 PM, Dan Williams wrote:
> On Wed, Jul 14, 2021 at 12:36 PM Joao Martins <joao.m.martins@oracle.com> wrote:
>>
>> Use try_grab_compound_head() for device-dax GUP when configured with a
>> compound pagemap.
>>
>> Rather than incrementing the refcount for each page, do one atomic
>> addition for all the pages to be pinned.
>>
>> Performance measured by gup_benchmark improves considerably
>> get_user_pages_fast() and pin_user_pages_fast() with NVDIMMs:
>>
>>  $ gup_test -f /dev/dax1.0 -m 16384 -r 10 -S [-u,-a] -n 512 -w
>> (get_user_pages_fast 2M pages) ~59 ms -> ~6.1 ms
>> (pin_user_pages_fast 2M pages) ~87 ms -> ~6.2 ms
>> [altmap]
>> (get_user_pages_fast 2M pages) ~494 ms -> ~9 ms
>> (pin_user_pages_fast 2M pages) ~494 ms -> ~10 ms
>>
>>  $ gup_test -f /dev/dax1.0 -m 129022 -r 10 -S [-u,-a] -n 512 -w
>> (get_user_pages_fast 2M pages) ~492 ms -> ~49 ms
>> (pin_user_pages_fast 2M pages) ~493 ms -> ~50 ms
>> [altmap with -m 127004]
>> (get_user_pages_fast 2M pages) ~3.91 sec -> ~70 ms
>> (pin_user_pages_fast 2M pages) ~3.97 sec -> ~74 ms
>>
>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>> ---
>>  mm/gup.c | 53 +++++++++++++++++++++++++++++++++--------------------
>>  1 file changed, 33 insertions(+), 20 deletions(-)
>>
>> diff --git a/mm/gup.c b/mm/gup.c
>> index 42b8b1fa6521..9baaa1c0b7f3 100644
>> --- a/mm/gup.c
>> +++ b/mm/gup.c
>> @@ -2234,31 +2234,55 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
>>  }
>>  #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
>>
>> +
>> +static int record_subpages(struct page *page, unsigned long addr,
>> +                          unsigned long end, struct page **pages)
>> +{
>> +       int nr;
>> +
>> +       for (nr = 0; addr != end; addr += PAGE_SIZE)
>> +               pages[nr++] = page++;
>> +
>> +       return nr;
>> +}
>> +
>>  #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
>>  static int __gup_device_huge(unsigned long pfn, unsigned long addr,
>>                              unsigned long end, unsigned int flags,
>>                              struct page **pages, int *nr)
>>  {
>> -       int nr_start = *nr;
>> +       int refs, nr_start = *nr;
>>         struct dev_pagemap *pgmap = NULL;
>>
>>         do {
>> -               struct page *page = pfn_to_page(pfn);
>> +               struct page *pinned_head, *head, *page = pfn_to_page(pfn);
>> +               unsigned long next;
>>
>>                 pgmap = get_dev_pagemap(pfn, pgmap);
>>                 if (unlikely(!pgmap)) {
>>                         undo_dev_pagemap(nr, nr_start, flags, pages);
>>                         return 0;
>>                 }
>> -               SetPageReferenced(page);
>> -               pages[*nr] = page;
>> -               if (unlikely(!try_grab_page(page, flags))) {
>> -                       undo_dev_pagemap(nr, nr_start, flags, pages);
>> +
>> +               head = compound_head(page);
>> +               /* @end is assumed to be limited at most one compound page */
>> +               next = PageCompound(head) ? end : addr + PAGE_SIZE;
> 
> Please no ternary operator for this check, but otherwise this patch
> looks good to me.
> 
OK. I take that you prefer this instead:

unsigned long next = addr + PAGE_SIZE;

[...]

/* @end is assumed to be limited at most one compound page */
if (PageCompound(head))
	next = end;

> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> 
Thanks!
Dan Williams July 28, 2021, 8:23 p.m. UTC | #3
On Wed, Jul 28, 2021 at 1:08 PM Joao Martins <joao.m.martins@oracle.com> wrote:
>
>
>
> On 7/28/21 8:55 PM, Dan Williams wrote:
> > On Wed, Jul 14, 2021 at 12:36 PM Joao Martins <joao.m.martins@oracle.com> wrote:
> >>
> >> Use try_grab_compound_head() for device-dax GUP when configured with a
> >> compound pagemap.
> >>
> >> Rather than incrementing the refcount for each page, do one atomic
> >> addition for all the pages to be pinned.
> >>
> >> Performance measured by gup_benchmark improves considerably
> >> get_user_pages_fast() and pin_user_pages_fast() with NVDIMMs:
> >>
> >>  $ gup_test -f /dev/dax1.0 -m 16384 -r 10 -S [-u,-a] -n 512 -w
> >> (get_user_pages_fast 2M pages) ~59 ms -> ~6.1 ms
> >> (pin_user_pages_fast 2M pages) ~87 ms -> ~6.2 ms
> >> [altmap]
> >> (get_user_pages_fast 2M pages) ~494 ms -> ~9 ms
> >> (pin_user_pages_fast 2M pages) ~494 ms -> ~10 ms
> >>
> >>  $ gup_test -f /dev/dax1.0 -m 129022 -r 10 -S [-u,-a] -n 512 -w
> >> (get_user_pages_fast 2M pages) ~492 ms -> ~49 ms
> >> (pin_user_pages_fast 2M pages) ~493 ms -> ~50 ms
> >> [altmap with -m 127004]
> >> (get_user_pages_fast 2M pages) ~3.91 sec -> ~70 ms
> >> (pin_user_pages_fast 2M pages) ~3.97 sec -> ~74 ms
> >>
> >> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> >> ---
> >>  mm/gup.c | 53 +++++++++++++++++++++++++++++++++--------------------
> >>  1 file changed, 33 insertions(+), 20 deletions(-)
> >>
> >> diff --git a/mm/gup.c b/mm/gup.c
> >> index 42b8b1fa6521..9baaa1c0b7f3 100644
> >> --- a/mm/gup.c
> >> +++ b/mm/gup.c
> >> @@ -2234,31 +2234,55 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
> >>  }
> >>  #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
> >>
> >> +
> >> +static int record_subpages(struct page *page, unsigned long addr,
> >> +                          unsigned long end, struct page **pages)
> >> +{
> >> +       int nr;
> >> +
> >> +       for (nr = 0; addr != end; addr += PAGE_SIZE)
> >> +               pages[nr++] = page++;
> >> +
> >> +       return nr;
> >> +}
> >> +
> >>  #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
> >>  static int __gup_device_huge(unsigned long pfn, unsigned long addr,
> >>                              unsigned long end, unsigned int flags,
> >>                              struct page **pages, int *nr)
> >>  {
> >> -       int nr_start = *nr;
> >> +       int refs, nr_start = *nr;
> >>         struct dev_pagemap *pgmap = NULL;
> >>
> >>         do {
> >> -               struct page *page = pfn_to_page(pfn);
> >> +               struct page *pinned_head, *head, *page = pfn_to_page(pfn);
> >> +               unsigned long next;
> >>
> >>                 pgmap = get_dev_pagemap(pfn, pgmap);
> >>                 if (unlikely(!pgmap)) {
> >>                         undo_dev_pagemap(nr, nr_start, flags, pages);
> >>                         return 0;
> >>                 }
> >> -               SetPageReferenced(page);
> >> -               pages[*nr] = page;
> >> -               if (unlikely(!try_grab_page(page, flags))) {
> >> -                       undo_dev_pagemap(nr, nr_start, flags, pages);
> >> +
> >> +               head = compound_head(page);
> >> +               /* @end is assumed to be limited at most one compound page */
> >> +               next = PageCompound(head) ? end : addr + PAGE_SIZE;
> >
> > Please no ternary operator for this check, but otherwise this patch
> > looks good to me.
> >
> OK. I take that you prefer this instead:
>
> unsigned long next = addr + PAGE_SIZE;
>
> [...]
>
> /* @end is assumed to be limited at most one compound page */
> if (PageCompound(head))
>         next = end;

Yup.
Joao Martins Aug. 25, 2021, 7:10 p.m. UTC | #4
On 7/28/21 9:23 PM, Dan Williams wrote:
> On Wed, Jul 28, 2021 at 1:08 PM Joao Martins <joao.m.martins@oracle.com> wrote:
>> On 7/28/21 8:55 PM, Dan Williams wrote:
>>> On Wed, Jul 14, 2021 at 12:36 PM Joao Martins <joao.m.martins@oracle.com> wrote:
>>>>
>>>> Use try_grab_compound_head() for device-dax GUP when configured with a
>>>> compound pagemap.
>>>>
>>>> Rather than incrementing the refcount for each page, do one atomic
>>>> addition for all the pages to be pinned.
>>>>
>>>> Performance measured by gup_benchmark improves considerably
>>>> get_user_pages_fast() and pin_user_pages_fast() with NVDIMMs:
>>>>
>>>>  $ gup_test -f /dev/dax1.0 -m 16384 -r 10 -S [-u,-a] -n 512 -w
>>>> (get_user_pages_fast 2M pages) ~59 ms -> ~6.1 ms
>>>> (pin_user_pages_fast 2M pages) ~87 ms -> ~6.2 ms
>>>> [altmap]
>>>> (get_user_pages_fast 2M pages) ~494 ms -> ~9 ms
>>>> (pin_user_pages_fast 2M pages) ~494 ms -> ~10 ms
>>>>
>>>>  $ gup_test -f /dev/dax1.0 -m 129022 -r 10 -S [-u,-a] -n 512 -w
>>>> (get_user_pages_fast 2M pages) ~492 ms -> ~49 ms
>>>> (pin_user_pages_fast 2M pages) ~493 ms -> ~50 ms
>>>> [altmap with -m 127004]
>>>> (get_user_pages_fast 2M pages) ~3.91 sec -> ~70 ms
>>>> (pin_user_pages_fast 2M pages) ~3.97 sec -> ~74 ms
>>>>
>>>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>>>> ---
>>>>  mm/gup.c | 53 +++++++++++++++++++++++++++++++++--------------------
>>>>  1 file changed, 33 insertions(+), 20 deletions(-)
>>>>
>>>> diff --git a/mm/gup.c b/mm/gup.c
>>>> index 42b8b1fa6521..9baaa1c0b7f3 100644
>>>> --- a/mm/gup.c
>>>> +++ b/mm/gup.c
>>>> @@ -2234,31 +2234,55 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
>>>>  }
>>>>  #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
>>>>
>>>> +
>>>> +static int record_subpages(struct page *page, unsigned long addr,
>>>> +                          unsigned long end, struct page **pages)
>>>> +{
>>>> +       int nr;
>>>> +
>>>> +       for (nr = 0; addr != end; addr += PAGE_SIZE)
>>>> +               pages[nr++] = page++;
>>>> +
>>>> +       return nr;
>>>> +}
>>>> +
>>>>  #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
>>>>  static int __gup_device_huge(unsigned long pfn, unsigned long addr,
>>>>                              unsigned long end, unsigned int flags,
>>>>                              struct page **pages, int *nr)
>>>>  {
>>>> -       int nr_start = *nr;
>>>> +       int refs, nr_start = *nr;
>>>>         struct dev_pagemap *pgmap = NULL;
>>>>
>>>>         do {
>>>> -               struct page *page = pfn_to_page(pfn);
>>>> +               struct page *pinned_head, *head, *page = pfn_to_page(pfn);
>>>> +               unsigned long next;
>>>>
>>>>                 pgmap = get_dev_pagemap(pfn, pgmap);
>>>>                 if (unlikely(!pgmap)) {
>>>>                         undo_dev_pagemap(nr, nr_start, flags, pages);
>>>>                         return 0;
>>>>                 }
>>>> -               SetPageReferenced(page);
>>>> -               pages[*nr] = page;
>>>> -               if (unlikely(!try_grab_page(page, flags))) {
>>>> -                       undo_dev_pagemap(nr, nr_start, flags, pages);
>>>> +
>>>> +               head = compound_head(page);
>>>> +               /* @end is assumed to be limited at most one compound page */
>>>> +               next = PageCompound(head) ? end : addr + PAGE_SIZE;
>>>
>>> Please no ternary operator for this check, but otherwise this patch
>>> looks good to me.
>>>
>> OK. I take that you prefer this instead:
>>
>> unsigned long next = addr + PAGE_SIZE;
>>
>> [...]
>>
>> /* @end is assumed to be limited at most one compound page */
>> if (PageCompound(head))
>>         next = end;
> 
> Yup.
> 
In addition to abiove, I'll be remove @pinned_head variable and retain the
current style that was with try_grab_page() while retaining the unlikely
that was there before. I'm assuming I can retain the Reviewed-by tag, but let
me know of otherwise (diff below).

diff --git a/mm/gup.c b/mm/gup.c
index ca64bc0b339e..398bee74105a 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2256,7 +2256,7 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr,
        int ret = 1;

        do {
-               struct page *pinned_head, *head, *page = pfn_to_page(pfn);
+               struct page *head, *page = pfn_to_page(pfn);
                unsigned long next = addr + PAGE_SIZE;

                pgmap = get_dev_pagemap(pfn, pgmap);
@@ -2273,8 +2273,7 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr,
                refs = record_subpages(page, addr, next, pages + *nr);

                SetPageReferenced(head);
-               pinned_head = try_grab_compound_head(head, refs, flags);
-               if (unlikely(!pinned_head)) {
+               if (unlikely(!try_grab_compound_head(head, refs, flags))) {
                        if (PageCompound(head))
                                ClearPageReferenced(head);
                        else
Matthew Wilcox Aug. 25, 2021, 7:15 p.m. UTC | #5
On Wed, Aug 25, 2021 at 08:10:39PM +0100, Joao Martins wrote:
> @@ -2273,8 +2273,7 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr,
>                 refs = record_subpages(page, addr, next, pages + *nr);
> 
>                 SetPageReferenced(head);
> -               pinned_head = try_grab_compound_head(head, refs, flags);
> -               if (unlikely(!pinned_head)) {
> +               if (unlikely(!try_grab_compound_head(head, refs, flags))) {
>                         if (PageCompound(head))

BTW, you can just check PageHead(head).  We know it can't be PageTail ...
Joao Martins Aug. 25, 2021, 7:26 p.m. UTC | #6
On 8/25/21 8:15 PM, Matthew Wilcox wrote:
> On Wed, Aug 25, 2021 at 08:10:39PM +0100, Joao Martins wrote:
>> @@ -2273,8 +2273,7 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr,
>>                 refs = record_subpages(page, addr, next, pages + *nr);
>>
>>                 SetPageReferenced(head);
>> -               pinned_head = try_grab_compound_head(head, refs, flags);
>> -               if (unlikely(!pinned_head)) {
>> +               if (unlikely(!try_grab_compound_head(head, refs, flags))) {
>>                         if (PageCompound(head))
> 
> BTW, you can just check PageHead(head).  We know it can't be PageTail ...
> 
Ugh, yes. Your comment is also applicable to the other PageCompound() added before, as
it's done on the compound head. I've fixed it on both, thanks!
diff mbox series

Patch

diff --git a/mm/gup.c b/mm/gup.c
index 42b8b1fa6521..9baaa1c0b7f3 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2234,31 +2234,55 @@  static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 }
 #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
 
+
+static int record_subpages(struct page *page, unsigned long addr,
+			   unsigned long end, struct page **pages)
+{
+	int nr;
+
+	for (nr = 0; addr != end; addr += PAGE_SIZE)
+		pages[nr++] = page++;
+
+	return nr;
+}
+
 #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
 static int __gup_device_huge(unsigned long pfn, unsigned long addr,
 			     unsigned long end, unsigned int flags,
 			     struct page **pages, int *nr)
 {
-	int nr_start = *nr;
+	int refs, nr_start = *nr;
 	struct dev_pagemap *pgmap = NULL;
 
 	do {
-		struct page *page = pfn_to_page(pfn);
+		struct page *pinned_head, *head, *page = pfn_to_page(pfn);
+		unsigned long next;
 
 		pgmap = get_dev_pagemap(pfn, pgmap);
 		if (unlikely(!pgmap)) {
 			undo_dev_pagemap(nr, nr_start, flags, pages);
 			return 0;
 		}
-		SetPageReferenced(page);
-		pages[*nr] = page;
-		if (unlikely(!try_grab_page(page, flags))) {
-			undo_dev_pagemap(nr, nr_start, flags, pages);
+
+		head = compound_head(page);
+		/* @end is assumed to be limited at most one compound page */
+		next = PageCompound(head) ? end : addr + PAGE_SIZE;
+		refs = record_subpages(page, addr, next, pages + *nr);
+
+		SetPageReferenced(head);
+		pinned_head = try_grab_compound_head(head, refs, flags);
+		if (!pinned_head) {
+			if (PageCompound(head)) {
+				ClearPageReferenced(head);
+				put_dev_pagemap(pgmap);
+			} else {
+				undo_dev_pagemap(nr, nr_start, flags, pages);
+			}
 			return 0;
 		}
-		(*nr)++;
-		pfn++;
-	} while (addr += PAGE_SIZE, addr != end);
+		*nr += refs;
+		pfn += refs;
+	} while (addr += (refs << PAGE_SHIFT), addr != end);
 
 	if (pgmap)
 		put_dev_pagemap(pgmap);
@@ -2318,17 +2342,6 @@  static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
 }
 #endif
 
-static int record_subpages(struct page *page, unsigned long addr,
-			   unsigned long end, struct page **pages)
-{
-	int nr;
-
-	for (nr = 0; addr != end; addr += PAGE_SIZE)
-		pages[nr++] = page++;
-
-	return nr;
-}
-
 #ifdef CONFIG_ARCH_HAS_HUGEPD
 static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
 				      unsigned long sz)