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s390/mm: implement __get_user_pages_fast() 

This patch introduces the __get_user_pages_fast() function on s390,
which will be needed with CONFIG_TRANSPARENT_HUGEPAGE and futex.

Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Gerald Schaefer 2012-09-04 15:37:55 +02:00 committed by Martin Schwidefsky
parent 25502f0015
commit 34cda99260
1 changed files with 37 additions and 0 deletions
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37
arch/s390/mm/gup.c
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@ -154,6 +154,43 @@ static inline int gup_pud_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr,
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, flags;
pgd_t *pgdp, pgd;
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;
local_irq_save(flags);
pgdp = pgd_offset(mm, addr);
do {
pgd = *pgdp;
barrier();
next = pgd_addr_end(addr, end);
if (pgd_none(pgd))
break;
if (!gup_pud_range(pgdp, 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