296 lines
6.8 KiB
C
296 lines
6.8 KiB
C
/*
|
|
* Lockless get_user_pages_fast for powerpc
|
|
*
|
|
* Copyright (C) 2008 Nick Piggin
|
|
* Copyright (C) 2008 Novell Inc.
|
|
*/
|
|
#undef DEBUG
|
|
|
|
#include <linux/sched.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/hugetlb.h>
|
|
#include <linux/vmstat.h>
|
|
#include <linux/pagemap.h>
|
|
#include <linux/rwsem.h>
|
|
#include <asm/pgtable.h>
|
|
|
|
#ifdef __HAVE_ARCH_PTE_SPECIAL
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
unsigned long mask, result;
|
|
pte_t *ptep;
|
|
|
|
result = _PAGE_PRESENT|_PAGE_USER;
|
|
if (write)
|
|
result |= _PAGE_RW;
|
|
mask = result | _PAGE_SPECIAL;
|
|
|
|
ptep = pte_offset_kernel(&pmd, addr);
|
|
do {
|
|
pte_t pte = *ptep;
|
|
struct page *page;
|
|
|
|
if ((pte_val(pte) & mask) != result)
|
|
return 0;
|
|
VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
|
|
page = pte_page(pte);
|
|
if (!page_cache_get_speculative(page))
|
|
return 0;
|
|
if (unlikely(pte_val(pte) != pte_val(*ptep))) {
|
|
put_page(page);
|
|
return 0;
|
|
}
|
|
pages[*nr] = page;
|
|
(*nr)++;
|
|
|
|
} while (ptep++, addr += PAGE_SIZE, addr != end);
|
|
|
|
return 1;
|
|
}
|
|
|
|
#ifdef CONFIG_HUGETLB_PAGE
|
|
static noinline int gup_huge_pte(pte_t *ptep, struct hstate *hstate,
|
|
unsigned long *addr, unsigned long end,
|
|
int write, struct page **pages, int *nr)
|
|
{
|
|
unsigned long mask;
|
|
unsigned long pte_end;
|
|
struct page *head, *page;
|
|
pte_t pte;
|
|
int refs;
|
|
|
|
pte_end = (*addr + huge_page_size(hstate)) & huge_page_mask(hstate);
|
|
if (pte_end < end)
|
|
end = pte_end;
|
|
|
|
pte = *ptep;
|
|
mask = _PAGE_PRESENT|_PAGE_USER;
|
|
if (write)
|
|
mask |= _PAGE_RW;
|
|
if ((pte_val(pte) & mask) != mask)
|
|
return 0;
|
|
/* hugepages are never "special" */
|
|
VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
|
|
|
|
refs = 0;
|
|
head = pte_page(pte);
|
|
page = head + ((*addr & ~huge_page_mask(hstate)) >> PAGE_SHIFT);
|
|
do {
|
|
VM_BUG_ON(compound_head(page) != head);
|
|
pages[*nr] = page;
|
|
(*nr)++;
|
|
page++;
|
|
refs++;
|
|
} while (*addr += PAGE_SIZE, *addr != end);
|
|
|
|
if (!page_cache_add_speculative(head, refs)) {
|
|
*nr -= refs;
|
|
return 0;
|
|
}
|
|
if (unlikely(pte_val(pte) != pte_val(*ptep))) {
|
|
/* Could be optimized better */
|
|
while (*nr) {
|
|
put_page(page);
|
|
(*nr)--;
|
|
}
|
|
}
|
|
|
|
return 1;
|
|
}
|
|
#endif /* CONFIG_HUGETLB_PAGE */
|
|
|
|
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 (!gup_pte_range(pmd, addr, next, write, pages, nr))
|
|
return 0;
|
|
} while (pmdp++, addr = next, addr != end);
|
|
|
|
return 1;
|
|
}
|
|
|
|
static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
|
|
int write, struct page **pages, int *nr)
|
|
{
|
|
unsigned long next;
|
|
pud_t *pudp;
|
|
|
|
pudp = pud_offset(&pgd, addr);
|
|
do {
|
|
pud_t pud = *pudp;
|
|
|
|
next = pud_addr_end(addr, end);
|
|
if (pud_none(pud))
|
|
return 0;
|
|
if (!gup_pmd_range(pud, addr, next, write, pages, nr))
|
|
return 0;
|
|
} while (pudp++, addr = next, addr != end);
|
|
|
|
return 1;
|
|
}
|
|
|
|
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;
|
|
#ifdef CONFIG_PPC64
|
|
unsigned int shift;
|
|
int psize;
|
|
#endif
|
|
|
|
pr_debug("%s(%lx,%x,%s)\n", __func__, start, nr_pages, write ? "write" : "read");
|
|
|
|
start &= PAGE_MASK;
|
|
addr = start;
|
|
len = (unsigned long) nr_pages << PAGE_SHIFT;
|
|
end = start + len;
|
|
|
|
if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
|
|
start, len)))
|
|
goto slow_irqon;
|
|
|
|
pr_debug(" aligned: %lx .. %lx\n", start, end);
|
|
|
|
#ifdef CONFIG_HUGETLB_PAGE
|
|
/* We bail out on slice boundary crossing when hugetlb is
|
|
* enabled in order to not have to deal with two different
|
|
* page table formats
|
|
*/
|
|
if (addr < SLICE_LOW_TOP) {
|
|
if (end > SLICE_LOW_TOP)
|
|
goto slow_irqon;
|
|
|
|
if (unlikely(GET_LOW_SLICE_INDEX(addr) !=
|
|
GET_LOW_SLICE_INDEX(end - 1)))
|
|
goto slow_irqon;
|
|
} else {
|
|
if (unlikely(GET_HIGH_SLICE_INDEX(addr) !=
|
|
GET_HIGH_SLICE_INDEX(end - 1)))
|
|
goto slow_irqon;
|
|
}
|
|
#endif /* CONFIG_HUGETLB_PAGE */
|
|
|
|
/*
|
|
* 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 from being freed on powerpc.
|
|
*
|
|
* So long as we atomically load page table pointers versus teardown,
|
|
* we can follow the address down to the the page and take a ref on it.
|
|
*/
|
|
local_irq_disable();
|
|
|
|
#ifdef CONFIG_PPC64
|
|
/* Those bits are related to hugetlbfs implementation and only exist
|
|
* on 64-bit for now
|
|
*/
|
|
psize = get_slice_psize(mm, addr);
|
|
shift = mmu_psize_defs[psize].shift;
|
|
#endif /* CONFIG_PPC64 */
|
|
|
|
#ifdef CONFIG_HUGETLB_PAGE
|
|
if (unlikely(mmu_huge_psizes[psize])) {
|
|
pte_t *ptep;
|
|
unsigned long a = addr;
|
|
unsigned long sz = ((1UL) << shift);
|
|
struct hstate *hstate = size_to_hstate(sz);
|
|
|
|
BUG_ON(!hstate);
|
|
/*
|
|
* XXX: could be optimized to avoid hstate
|
|
* lookup entirely (just use shift)
|
|
*/
|
|
|
|
do {
|
|
VM_BUG_ON(shift != mmu_psize_defs[get_slice_psize(mm, a)].shift);
|
|
ptep = huge_pte_offset(mm, a);
|
|
pr_debug(" %016lx: huge ptep %p\n", a, ptep);
|
|
if (!ptep || !gup_huge_pte(ptep, hstate, &a, end, write, pages,
|
|
&nr))
|
|
goto slow;
|
|
} while (a != end);
|
|
} else
|
|
#endif /* CONFIG_HUGETLB_PAGE */
|
|
{
|
|
pgdp = pgd_offset(mm, addr);
|
|
do {
|
|
pgd_t pgd = *pgdp;
|
|
|
|
#ifdef CONFIG_PPC64
|
|
VM_BUG_ON(shift != mmu_psize_defs[get_slice_psize(mm, addr)].shift);
|
|
#endif
|
|
pr_debug(" %016lx: normal pgd %p\n", addr,
|
|
(void *)pgd_val(pgd));
|
|
next = pgd_addr_end(addr, end);
|
|
if (pgd_none(pgd))
|
|
goto slow;
|
|
if (!gup_pud_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:
|
|
pr_debug(" slow path ! nr = %d\n", nr);
|
|
|
|
/* Try to get the remaining pages with get_user_pages */
|
|
start += nr << PAGE_SHIFT;
|
|
pages += nr;
|
|
|
|
down_read(&mm->mmap_sem);
|
|
ret = get_user_pages(current, mm, start,
|
|
(end - start) >> PAGE_SHIFT, write, 0, pages, NULL);
|
|
up_read(&mm->mmap_sem);
|
|
|
|
/* Have to be a bit careful with return values */
|
|
if (nr > 0) {
|
|
if (ret < 0)
|
|
ret = nr;
|
|
else
|
|
ret += nr;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
}
|
|
|
|
#endif /* __HAVE_ARCH_PTE_SPECIAL */
|