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x86/mm/gup: Switch GUP to the generic get_user_page_fast() implementation

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This patch provides all required callbacks required by the generic
get_user_pages_fast() code and switches x86 over - and removes
the platform specific implementation.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20170606113133.22974-2-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Kirill A. Shutemov 2017-06-06 14:31:20 +03:00 committed by Ingo Molnar
parent 6c690ee103
commit e585513b76
12 changed files with 128 additions and 519 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

2
arch/arm/Kconfig
View file

@ -1637,7 +1637,7 @@ config ARCH_SELECT_MEMORY_MODEL
config HAVE_ARCH_PFN_VALID
def_bool ARCH_HAS_HOLES_MEMORYMODEL || !SPARSEMEM
config HAVE_GENERIC_RCU_GUP
config HAVE_GENERIC_GUP
def_bool y
depends on ARM_LPAE

2
arch/arm64/Kconfig
View file

@ -205,7 +205,7 @@ config GENERIC_CALIBRATE_DELAY
config ZONE_DMA
def_bool y
config HAVE_GENERIC_RCU_GUP
config HAVE_GENERIC_GUP
def_bool y
config ARCH_DMA_ADDR_T_64BIT

2
arch/powerpc/Kconfig
View file

@ -184,7 +184,7 @@ config PPC
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER
select HAVE_GCC_PLUGINS
select HAVE_GENERIC_RCU_GUP
select HAVE_GENERIC_GUP
select HAVE_HW_BREAKPOINT if PERF_EVENTS && (PPC_BOOK3S || PPC_8xx)
select HAVE_IDE
select HAVE_IOREMAP_PROT

3
arch/x86/Kconfig
View file

@ -2797,6 +2797,9 @@ config X86_DMA_REMAP
bool
depends on STA2X11
config HAVE_GENERIC_GUP
def_bool y
source "net/Kconfig"
source "drivers/Kconfig"

12
arch/x86/include/asm/mmu_context.h
View file

@ -218,18 +218,6 @@ static inline int vma_pkey(struct vm_area_struct *vma)
}
#endif
static inline bool __pkru_allows_pkey(u16 pkey, bool write)
{
u32 pkru = read_pkru();
if (!__pkru_allows_read(pkru, pkey))
return false;
if (write && !__pkru_allows_write(pkru, pkey))
return false;
return true;
}
/*
* We only want to enforce protection keys on the current process
* because we effectively have no access to PKRU for other

47
arch/x86/include/asm/pgtable-3level.h
View file

@ -212,4 +212,51 @@ static inline pud_t native_pudp_get_and_clear(pud_t *pudp)
#define __pte_to_swp_entry(pte) ((swp_entry_t){ (pte).pte_high })
#define __swp_entry_to_pte(x) ((pte_t){ { .pte_high = (x).val } })
#define gup_get_pte gup_get_pte
/*
* WARNING: only to be used in the get_user_pages_fast() implementation.
*
* With get_user_pages_fast(), we walk down the pagetables without taking
* any locks. For this we would like to load the pointers atomically,
* but that is not possible (without expensive cmpxchg8b) on PAE. What
* we do have is the guarantee that a PTE will only either go from not
* present to present, or present to not present or both -- it will not
* switch to a completely different present page without a TLB flush in
* between; something that we are blocking by holding interrupts off.
*
* Setting ptes from not present to present goes:
*
* ptep->pte_high = h;
* smp_wmb();
* ptep->pte_low = l;
*
* And present to not present goes:
*
* ptep->pte_low = 0;
* smp_wmb();
* ptep->pte_high = 0;
*
* We must ensure here that the load of pte_low sees 'l' iff pte_high
* sees 'h'. We load pte_high *after* loading pte_low, which ensures we
* don't see an older value of pte_high. *Then* we recheck pte_low,
* which ensures that we haven't picked up a changed pte high. We might
* have gotten rubbish values from pte_low and pte_high, but we are
* guaranteed that pte_low will not have the present bit set *unless*
* it is 'l'. Because get_user_pages_fast() only operates on present ptes
* we're safe.
*/
static inline pte_t gup_get_pte(pte_t *ptep)
{
pte_t pte;
do {
pte.pte_low = ptep->pte_low;
smp_rmb();
pte.pte_high = ptep->pte_high;
smp_rmb();
} while (unlikely(pte.pte_low != ptep->pte_low));
return pte;
}
#endif /* _ASM_X86_PGTABLE_3LEVEL_H */

53
arch/x86/include/asm/pgtable.h
View file

@ -244,6 +244,11 @@ static inline int pud_devmap(pud_t pud)
return 0;
}
#endif
static inline int pgd_devmap(pgd_t pgd)
{
return 0;
}
#endif
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
@ -1185,6 +1190,54 @@ static inline u16 pte_flags_pkey(unsigned long pte_flags)
#endif
}
static inline bool __pkru_allows_pkey(u16 pkey, bool write)
{
u32 pkru = read_pkru();
if (!__pkru_allows_read(pkru, pkey))
return false;
if (write && !__pkru_allows_write(pkru, pkey))
return false;
return true;
}
/*
* 'pteval' can come from a PTE, PMD or PUD. We only check
* _PAGE_PRESENT, _PAGE_USER, and _PAGE_RW in here which are the
* same value on all 3 types.
*/
static inline bool __pte_access_permitted(unsigned long pteval, bool write)
{
unsigned long need_pte_bits = _PAGE_PRESENT|_PAGE_USER;
if (write)
need_pte_bits |= _PAGE_RW;
if ((pteval & need_pte_bits) != need_pte_bits)
return 0;
return __pkru_allows_pkey(pte_flags_pkey(pteval), write);
}
#define pte_access_permitted pte_access_permitted
static inline bool pte_access_permitted(pte_t pte, bool write)
{
return __pte_access_permitted(pte_val(pte), write);
}
#define pmd_access_permitted pmd_access_permitted
static inline bool pmd_access_permitted(pmd_t pmd, bool write)
{
return __pte_access_permitted(pmd_val(pmd), write);
}
#define pud_access_permitted pud_access_permitted
static inline bool pud_access_permitted(pud_t pud, bool write)
{
return __pte_access_permitted(pud_val(pud), write);
}
#include <asm-generic/pgtable.h>
#endif /* __ASSEMBLY__ */

16
arch/x86/include/asm/pgtable_64.h
View file

@ -227,6 +227,20 @@ extern void cleanup_highmap(void);
extern void init_extra_mapping_uc(unsigned long phys, unsigned long size);
extern void init_extra_mapping_wb(unsigned long phys, unsigned long size);
#endif /* !__ASSEMBLY__ */
#define gup_fast_permitted gup_fast_permitted
static inline bool gup_fast_permitted(unsigned long start, int nr_pages,
int write)
{
unsigned long len, end;
len = (unsigned long)nr_pages << PAGE_SHIFT;
end = start + len;
if (end < start)
return false;
if (end >> __VIRTUAL_MASK_SHIFT)
return false;
return true;
}
#endif /* !__ASSEMBLY__ */
#endif /* _ASM_X86_PGTABLE_64_H */

2
arch/x86/mm/Makefile
View file

@ -2,7 +2,7 @@
KCOV_INSTRUMENT_tlb.o := n
obj-y := init.o init_$(BITS).o fault.o ioremap.o extable.o pageattr.o mmap.o \
pat.o pgtable.o physaddr.o gup.o setup_nx.o tlb.o
pat.o pgtable.o physaddr.o setup_nx.o tlb.o
# Make sure __phys_addr has no stackprotector
nostackp := $(call cc-option, -fno-stack-protector)

496
arch/x86/mm/gup.c
View file

@ -1,496 +0,0 @@
/*
* Lockless get_user_pages_fast for x86
*
* Copyright (C) 2008 Nick Piggin
* Copyright (C) 2008 Novell Inc.
*/
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/vmstat.h>
#include <linux/highmem.h>
#include <linux/swap.h>
#include <linux/memremap.h>
#include <asm/mmu_context.h>
#include <asm/pgtable.h>
static inline pte_t gup_get_pte(pte_t *ptep)
{
#ifndef CONFIG_X86_PAE
return READ_ONCE(*ptep);
#else
/*
* With get_user_pages_fast, we walk down the pagetables without taking
* any locks. For this we would like to load the pointers atomically,
* but that is not possible (without expensive cmpxchg8b) on PAE. What
* we do have is the guarantee that a pte will only either go from not
* present to present, or present to not present or both -- it will not
* switch to a completely different present page without a TLB flush in
* between; something that we are blocking by holding interrupts off.
*
* Setting ptes from not present to present goes:
* ptep->pte_high = h;
* smp_wmb();
* ptep->pte_low = l;
*
* And present to not present goes:
* ptep->pte_low = 0;
* smp_wmb();
* ptep->pte_high = 0;
*
* We must ensure here that the load of pte_low sees l iff pte_high
* sees h. We load pte_high *after* loading pte_low, which ensures we
* don't see an older value of pte_high. *Then* we recheck pte_low,
* which ensures that we haven't picked up a changed pte high. We might
* have got rubbish values from pte_low and pte_high, but we are
* guaranteed that pte_low will not have the present bit set *unless*
* it is 'l'. And get_user_pages_fast only operates on present ptes, so
* we're safe.
*
* gup_get_pte should not be used or copied outside gup.c without being
* very careful -- it does not atomically load the pte or anything that
* is likely to be useful for you.
*/
pte_t pte;
retry:
pte.pte_low = ptep->pte_low;
smp_rmb();
pte.pte_high = ptep->pte_high;
smp_rmb();
if (unlikely(pte.pte_low != ptep->pte_low))
goto retry;
return pte;
#endif
}
static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages)
{
while ((*nr) - nr_start) {
struct page *page = pages[--(*nr)];
ClearPageReferenced(page);
put_page(page);
}
}
/*
* 'pteval' can come from a pte, pmd, pud or p4d. We only check
* _PAGE_PRESENT, _PAGE_USER, and _PAGE_RW in here which are the
* same value on all 4 types.
*/
static inline int pte_allows_gup(unsigned long pteval, int write)
{
unsigned long need_pte_bits = _PAGE_PRESENT|_PAGE_USER;
if (write)
need_pte_bits |= _PAGE_RW;
if ((pteval & need_pte_bits) != need_pte_bits)
return 0;
/* Check memory protection keys permissions. */
if (!__pkru_allows_pkey(pte_flags_pkey(pteval), write))
return 0;
return 1;
}
/*
* The performance critical leaf functions are made noinline otherwise gcc
* inlines everything into a single function which results in too much
* register pressure.
*/
static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
unsigned long end, int write, struct page **pages, int *nr)
{
struct dev_pagemap *pgmap = NULL;
int nr_start = *nr, ret = 0;
pte_t *ptep, *ptem;
/*
* Keep the original mapped PTE value (ptem) around since we
* might increment ptep off the end of the page when finishing
* our loop iteration.
*/
ptem = ptep = pte_offset_map(&pmd, addr);
do {
pte_t pte = gup_get_pte(ptep);
struct page *page;
/* Similar to the PMD case, NUMA hinting must take slow path */
if (pte_protnone(pte))
break;
if (!pte_allows_gup(pte_val(pte), write))
break;
if (pte_devmap(pte)) {
pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
if (unlikely(!pgmap)) {
undo_dev_pagemap(nr, nr_start, pages);
break;
}
} else if (pte_special(pte))
break;
VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
page = pte_page(pte);
get_page(page);
put_dev_pagemap(pgmap);
SetPageReferenced(page);
pages[*nr] = page;
(*nr)++;
} while (ptep++, addr += PAGE_SIZE, addr != end);
if (addr == end)
ret = 1;
pte_unmap(ptem);
return ret;
}
static inline void get_head_page_multiple(struct page *page, int nr)
{
VM_BUG_ON_PAGE(page != compound_head(page), page);
VM_BUG_ON_PAGE(page_count(page) == 0, page);
page_ref_add(page, nr);
SetPageReferenced(page);
}
static int __gup_device_huge(unsigned long pfn, unsigned long addr,
unsigned long end, struct page **pages, int *nr)
{
int nr_start = *nr;
struct dev_pagemap *pgmap = NULL;
do {
struct page *page = pfn_to_page(pfn);
pgmap = get_dev_pagemap(pfn, pgmap);
if (unlikely(!pgmap)) {
undo_dev_pagemap(nr, nr_start, pages);
return 0;
}
SetPageReferenced(page);
pages[*nr] = page;
get_page(page);
put_dev_pagemap(pgmap);
(*nr)++;
pfn++;
} while (addr += PAGE_SIZE, addr != end);
return 1;
}
static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
unsigned long end, struct page **pages, int *nr)
{
unsigned long fault_pfn;
fault_pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
return __gup_device_huge(fault_pfn, addr, end, pages, nr);
}
static int __gup_device_huge_pud(pud_t pud, unsigned long addr,
unsigned long end, struct page **pages, int *nr)
{
unsigned long fault_pfn;
fault_pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
return __gup_device_huge(fault_pfn, addr, end, pages, nr);
}
static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
unsigned long end, int write, struct page **pages, int *nr)
{
struct page *head, *page;
int refs;
if (!pte_allows_gup(pmd_val(pmd), write))
return 0;
VM_BUG_ON(!pfn_valid(pmd_pfn(pmd)));
if (pmd_devmap(pmd))
return __gup_device_huge_pmd(pmd, addr, end, pages, nr);
/* hugepages are never "special" */
VM_BUG_ON(pmd_flags(pmd) & _PAGE_SPECIAL);
refs = 0;
head = pmd_page(pmd);
page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
do {
VM_BUG_ON_PAGE(compound_head(page) != head, page);
pages[*nr] = page;
(*nr)++;
page++;
refs++;
} while (addr += PAGE_SIZE, addr != end);
get_head_page_multiple(head, refs);
return 1;
}
static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
int write, struct page **pages, int *nr)
{
unsigned long next;
pmd_t *pmdp;
pmdp = pmd_offset(&pud, addr);
do {
pmd_t pmd = *pmdp;
next = pmd_addr_end(addr, end);
if (pmd_none(pmd))
return 0;
if (unlikely(pmd_large(pmd) || !pmd_present(pmd))) {
/*
* NUMA hinting faults need to be handled in the GUP
* slowpath for accounting purposes and so that they
* can be serialised against THP migration.
*/
if (pmd_protnone(pmd))
return 0;
if (!gup_huge_pmd(pmd, addr, next, write, pages, nr))
return 0;
} else {
if (!gup_pte_range(pmd, addr, next, write, pages, nr))
return 0;
}
} while (pmdp++, addr = next, addr != end);
return 1;
}
static noinline int gup_huge_pud(pud_t pud, unsigned long addr,
unsigned long end, int write, struct page **pages, int *nr)
{
struct page *head, *page;
int refs;
if (!pte_allows_gup(pud_val(pud), write))
return 0;
VM_BUG_ON(!pfn_valid(pud_pfn(pud)));
if (pud_devmap(pud))
return __gup_device_huge_pud(pud, addr, end, pages, nr);
/* hugepages are never "special" */
VM_BUG_ON(pud_flags(pud) & _PAGE_SPECIAL);
refs = 0;
head = pud_page(pud);
page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
do {
VM_BUG_ON_PAGE(compound_head(page) != head, page);
pages[*nr] = page;
(*nr)++;
page++;
refs++;
} while (addr += PAGE_SIZE, addr != end);
get_head_page_multiple(head, refs);
return 1;
}
static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end,
int write, struct page **pages, int *nr)
{
unsigned long next;
pud_t *pudp;
pudp = pud_offset(&p4d, addr);
do {
pud_t pud = *pudp;
next = pud_addr_end(addr, end);
if (pud_none(pud))
return 0;
if (unlikely(pud_large(pud))) {
if (!gup_huge_pud(pud, addr, next, write, pages, nr))
return 0;
} else {
if (!gup_pmd_range(pud, addr, next, write, pages, nr))
return 0;
}
} while (pudp++, addr = next, addr != end);
return 1;
}
static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end,
int write, struct page **pages, int *nr)
{
unsigned long next;
p4d_t *p4dp;
p4dp = p4d_offset(&pgd, addr);
do {
p4d_t p4d = *p4dp;
next = p4d_addr_end(addr, end);
if (p4d_none(p4d))
return 0;
BUILD_BUG_ON(p4d_large(p4d));
if (!gup_pud_range(p4d, addr, next, write, pages, nr))
return 0;
} while (p4dp++, addr = next, addr != end);
return 1;
}
/*
* Like get_user_pages_fast() except its IRQ-safe in that it won't fall
* back to the regular GUP.
*/
int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
struct page **pages)
{
struct mm_struct *mm = current->mm;
unsigned long addr, len, end;
unsigned long next;
unsigned long flags;
pgd_t *pgdp;
int nr = 0;
start &= PAGE_MASK;
addr = start;
len = (unsigned long) nr_pages << PAGE_SHIFT;
end = start + len;
if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
(void __user *)start, len)))
return 0;
/*
* XXX: batch / limit 'nr', to avoid large irq off latency
* needs some instrumenting to determine the common sizes used by
* important workloads (eg. DB2), and whether limiting the batch size
* will decrease performance.
*
* It seems like we're in the clear for the moment. Direct-IO is
* the main guy that batches up lots of get_user_pages, and even
* they are limited to 64-at-a-time which is not so many.
*/
/*
* This doesn't prevent pagetable teardown, but does prevent
* the pagetables and pages from being freed on x86.
*
* So long as we atomically load page table pointers versus teardown
* (which we do on x86, with the above PAE exception), we can follow the
* address down to the the page and take a ref on it.
*/
local_irq_save(flags);
pgdp = pgd_offset(mm, addr);
do {
pgd_t pgd = *pgdp;
next = pgd_addr_end(addr, end);
if (pgd_none(pgd))
break;
if (!gup_p4d_range(pgd, addr, next, write, pages, &nr))
break;
} while (pgdp++, addr = next, addr != end);
local_irq_restore(flags);
return nr;
}
/**
* get_user_pages_fast() - pin user pages in memory
* @start: starting user address
* @nr_pages: number of pages from start to pin
* @write: whether pages will be written to
* @pages: array that receives pointers to the pages pinned.
* Should be at least nr_pages long.
*
* Attempt to pin user pages in memory without taking mm->mmap_sem.
* If not successful, it will fall back to taking the lock and
* calling get_user_pages().
*
* Returns number of pages pinned. This may be fewer than the number
* requested. If nr_pages is 0 or negative, returns 0. If no pages
* were pinned, returns -errno.
*/
int get_user_pages_fast(unsigned long start, int nr_pages, int write,
struct page **pages)
{
struct mm_struct *mm = current->mm;
unsigned long addr, len, end;
unsigned long next;
pgd_t *pgdp;
int nr = 0;
start &= PAGE_MASK;
addr = start;
len = (unsigned long) nr_pages << PAGE_SHIFT;
end = start + len;
if (end < start)
goto slow_irqon;
#ifdef CONFIG_X86_64
if (end >> __VIRTUAL_MASK_SHIFT)
goto slow_irqon;
#endif
/*
* XXX: batch / limit 'nr', to avoid large irq off latency
* needs some instrumenting to determine the common sizes used by
* important workloads (eg. DB2), and whether limiting the batch size
* will decrease performance.
*
* It seems like we're in the clear for the moment. Direct-IO is
* the main guy that batches up lots of get_user_pages, and even
* they are limited to 64-at-a-time which is not so many.
*/
/*
* This doesn't prevent pagetable teardown, but does prevent
* the pagetables and pages from being freed on x86.
*
* So long as we atomically load page table pointers versus teardown
* (which we do on x86, with the above PAE exception), we can follow the
* address down to the the page and take a ref on it.
*/
local_irq_disable();
pgdp = pgd_offset(mm, addr);
do {
pgd_t pgd = *pgdp;
next = pgd_addr_end(addr, end);
if (pgd_none(pgd))
goto slow;
if (!gup_p4d_range(pgd, addr, next, write, pages, &nr))
goto slow;
} while (pgdp++, addr = next, addr != end);
local_irq_enable();
VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
return nr;
{
int ret;
slow:
local_irq_enable();
slow_irqon:
/* Try to get the remaining pages with get_user_pages */
start += nr << PAGE_SHIFT;
pages += nr;
ret = get_user_pages_unlocked(start,
(end - start) >> PAGE_SHIFT,
pages, write ? FOLL_WRITE : 0);
/* Have to be a bit careful with return values */
if (nr > 0) {
if (ret < 0)
ret = nr;
else
ret += nr;
}
return ret;
}
}

2
mm/Kconfig
View file

@ -137,7 +137,7 @@ config HAVE_MEMBLOCK_NODE_MAP
config HAVE_MEMBLOCK_PHYS_MAP
bool
config HAVE_GENERIC_RCU_GUP
config HAVE_GENERIC_GUP
bool
config ARCH_DISCARD_MEMBLOCK

10
mm/gup.c
View file

@ -1151,7 +1151,7 @@ struct page *get_dump_page(unsigned long addr)
#endif /* CONFIG_ELF_CORE */
/*
* Generic RCU Fast GUP
* Generic Fast GUP
*
* get_user_pages_fast attempts to pin user pages by walking the page
* tables directly and avoids taking locks. Thus the walker needs to be
@ -1172,8 +1172,8 @@ struct page *get_dump_page(unsigned long addr)
* Before activating this code, please be aware that the following assumptions
* are currently made:
*
* *) HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table is used to free
* pages containing page tables.
* *) Either HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to
* free pages containing page tables or TLB flushing requires IPI broadcast.
*
* *) ptes can be read atomically by the architecture.
*
@ -1183,7 +1183,7 @@ struct page *get_dump_page(unsigned long addr)
*
* This code is based heavily on the PowerPC implementation by Nick Piggin.
*/
#ifdef CONFIG_HAVE_GENERIC_RCU_GUP
#ifdef CONFIG_HAVE_GENERIC_GUP
#ifndef gup_get_pte
/*
@ -1673,4 +1673,4 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write,
return ret;
}
#endif /* CONFIG_HAVE_GENERIC_RCU_GUP */
#endif /* CONFIG_HAVE_GENERIC_GUP */