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/*
* arch/arm/mm/gup.c
*
* Copyright (C) 2013 Linaro Ltd.
*
* Based on arch/powerpc/mm/gup.c which is:
* Copyright (C) 2008 Nick Piggin
* Copyright (C) 2008 Novell Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/rwsem.h>
#include <linux/hugetlb.h>
#include <asm/pgtable.h>
static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
int write, struct page **pages, int *nr)
{
pte_t *ptep, *ptem;
int ret = 0;
ptem = ptep = pte_offset_map(&pmd, addr);
do {
pte_t pte = ACCESS_ONCE(*ptep);
struct page *page;
if (!pte_present_user(pte) || pte_protnone(pte)
|| (write && !pte_write(pte)))
goto pte_unmap;
VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
page = pte_page(pte);
if (!page_cache_get_speculative(page))
goto pte_unmap;
if (unlikely(pte_val(pte) != pte_val(*ptep))) {
put_page(page);
goto pte_unmap;
}
pages[*nr] = page;
(*nr)++;
} while (ptep++, addr += PAGE_SIZE, addr != end);
ret = 1;
pte_unmap:
pte_unmap(ptem);
return ret;
}
static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
unsigned long end, int write, struct page **pages, int *nr)
{
struct page *head, *page, *tail;
int refs;
if (!pmd_present(orig) || pmd_protnone(orig)
|| (write && !pmd_write(orig)))
return 0;
refs = 0;
head = pmd_page(orig);
page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
tail = page;
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(pmd_val(orig) != pmd_val(*pmdp))) {
*nr -= refs;
while (refs--)
put_page(head);
return 0;
}
/*
* Tail pages have their _mapcount bumped, see
* __get_page_tail_foll for more information.
*/
while (refs--) {
if (PageTail(tail))
get_huge_page_tail(tail);
tail++;
}
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 = ACCESS_ONCE(*pmdp);
next = pmd_addr_end(addr, end);
if (pmd_none(pmd) || pmd_trans_splitting(pmd))
return 0;
if (unlikely(pmd_huge(pmd) || pmd_trans_huge(pmd))) {
if (!gup_huge_pmd(pmd, pmdp, 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 int gup_pud_range(pgd_t *pgdp, unsigned long addr, unsigned long end,
int write, struct page **pages, int *nr)
{
unsigned long next;
pud_t *pudp;
pudp = pud_offset(pgdp, addr);
do {
pud_t pud = ACCESS_ONCE(*pudp);
next = pud_addr_end(addr, end);
if (pud_none(pud))
return 0;
else if (!gup_pmd_range(pud, addr, next, write, pages, nr))
return 0;
} while (pudp++, 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;
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,
start, len)))
return 0;
/*
* A non-zero gup_readers value will block page table pages
* from being freed and also block THP splitting.
* This allows us to walk the page tables and pin pages.
*/
inc_gup_readers(mm);
pgdp = pgd_offset(mm, addr);
do {
next = pgd_addr_end(addr, end);
if (pgd_none(*pgdp))
break;
else if (!gup_pud_range(pgdp, addr, next, write, pages, &nr))
break;
} while (pgdp++, addr = next, addr != end);
dec_gup_readers(mm);
return nr;
}
int get_user_pages_fast(unsigned long start, int nr_pages, int write,
struct page **pages)
{
struct mm_struct *mm = current->mm;
int nr, ret;
start &= PAGE_MASK;
nr = __get_user_pages_fast(start, nr_pages, write, pages);
ret = nr;
if (nr < nr_pages) {
/* 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,
nr_pages - nr, 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;
}
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