linux/mm/mincore.c
Johannes Weiner f488401076 mincore: break do_mincore() into logical pieces
Split out functions to handle hugetlb ranges, pte ranges and unmapped
ranges, to improve readability but also to prepare the file structure for
nested page table walks.

No semantic changes intended.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-05-25 08:06:58 -07:00

268 lines
6.5 KiB
C

/*
* linux/mm/mincore.c
*
* Copyright (C) 1994-2006 Linus Torvalds
*/
/*
* The mincore() system call.
*/
#include <linux/pagemap.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/syscalls.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/hugetlb.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
static void mincore_hugetlb_page_range(struct vm_area_struct *vma,
unsigned long addr, unsigned long nr,
unsigned char *vec)
{
#ifdef CONFIG_HUGETLB_PAGE
struct hstate *h;
int i;
i = 0;
h = hstate_vma(vma);
while (1) {
unsigned char present;
pte_t *ptep;
/*
* Huge pages are always in RAM for now, but
* theoretically it needs to be checked.
*/
ptep = huge_pte_offset(current->mm,
addr & huge_page_mask(h));
present = ptep && !huge_pte_none(huge_ptep_get(ptep));
while (1) {
vec[i++] = present;
addr += PAGE_SIZE;
/* reach buffer limit */
if (i == nr)
return;
/* check hugepage border */
if (!(addr & ~huge_page_mask(h)))
break;
}
}
#else
BUG();
#endif
}
/*
* Later we can get more picky about what "in core" means precisely.
* For now, simply check to see if the page is in the page cache,
* and is up to date; i.e. that no page-in operation would be required
* at this time if an application were to map and access this page.
*/
static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
{
unsigned char present = 0;
struct page *page;
/*
* When tmpfs swaps out a page from a file, any process mapping that
* file will not get a swp_entry_t in its pte, but rather it is like
* any other file mapping (ie. marked !present and faulted in with
* tmpfs's .fault). So swapped out tmpfs mappings are tested here.
*
* However when tmpfs moves the page from pagecache and into swapcache,
* it is still in core, but the find_get_page below won't find it.
* No big deal, but make a note of it.
*/
page = find_get_page(mapping, pgoff);
if (page) {
present = PageUptodate(page);
page_cache_release(page);
}
return present;
}
static void mincore_unmapped_range(struct vm_area_struct *vma,
unsigned long addr, unsigned long nr,
unsigned char *vec)
{
int i;
if (vma->vm_file) {
pgoff_t pgoff;
pgoff = linear_page_index(vma, addr);
for (i = 0; i < nr; i++, pgoff++)
vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
} else {
for (i = 0; i < nr; i++)
vec[i] = 0;
}
}
static void mincore_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, unsigned long nr,
unsigned char *vec)
{
spinlock_t *ptl;
pte_t *ptep;
int i;
ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
for (i = 0; i < nr; i++, ptep++, addr += PAGE_SIZE) {
pte_t pte = *ptep;
pgoff_t pgoff;
if (pte_none(pte))
mincore_unmapped_range(vma, addr, 1, vec);
else if (pte_present(pte))
vec[i] = 1;
else if (pte_file(pte)) {
pgoff = pte_to_pgoff(pte);
vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
} else { /* pte is a swap entry */
swp_entry_t entry = pte_to_swp_entry(pte);
if (is_migration_entry(entry)) {
/* migration entries are always uptodate */
vec[i] = 1;
} else {
#ifdef CONFIG_SWAP
pgoff = entry.val;
vec[i] = mincore_page(&swapper_space, pgoff);
#else
WARN_ON(1);
vec[i] = 1;
#endif
}
}
}
pte_unmap_unlock(ptep - 1, ptl);
}
/*
* Do a chunk of "sys_mincore()". We've already checked
* all the arguments, we hold the mmap semaphore: we should
* just return the amount of info we're asked for.
*/
static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec)
{
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
unsigned long nr;
struct vm_area_struct *vma;
vma = find_vma(current->mm, addr);
if (!vma || addr < vma->vm_start)
return -ENOMEM;
nr = min(pages, (vma->vm_end - addr) >> PAGE_SHIFT);
if (is_vm_hugetlb_page(vma)) {
mincore_hugetlb_page_range(vma, addr, nr, vec);
return nr;
}
/*
* Calculate how many pages there are left in the last level of the
* PTE array for our address.
*/
nr = min(nr, PTRS_PER_PTE - ((addr >> PAGE_SHIFT) & (PTRS_PER_PTE-1)));
pgd = pgd_offset(vma->vm_mm, addr);
if (pgd_none_or_clear_bad(pgd))
goto none_mapped;
pud = pud_offset(pgd, addr);
if (pud_none_or_clear_bad(pud))
goto none_mapped;
pmd = pmd_offset(pud, addr);
if (pmd_none_or_clear_bad(pmd))
goto none_mapped;
mincore_pte_range(vma, pmd, addr, nr, vec);
return nr;
none_mapped:
mincore_unmapped_range(vma, addr, nr, vec);
return nr;
}
/*
* The mincore(2) system call.
*
* mincore() returns the memory residency status of the pages in the
* current process's address space specified by [addr, addr + len).
* The status is returned in a vector of bytes. The least significant
* bit of each byte is 1 if the referenced page is in memory, otherwise
* it is zero.
*
* Because the status of a page can change after mincore() checks it
* but before it returns to the application, the returned vector may
* contain stale information. Only locked pages are guaranteed to
* remain in memory.
*
* return values:
* zero - success
* -EFAULT - vec points to an illegal address
* -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE
* -ENOMEM - Addresses in the range [addr, addr + len] are
* invalid for the address space of this process, or
* specify one or more pages which are not currently
* mapped
* -EAGAIN - A kernel resource was temporarily unavailable.
*/
SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
unsigned char __user *, vec)
{
long retval;
unsigned long pages;
unsigned char *tmp;
/* Check the start address: needs to be page-aligned.. */
if (start & ~PAGE_CACHE_MASK)
return -EINVAL;
/* ..and we need to be passed a valid user-space range */
if (!access_ok(VERIFY_READ, (void __user *) start, len))
return -ENOMEM;
/* This also avoids any overflows on PAGE_CACHE_ALIGN */
pages = len >> PAGE_SHIFT;
pages += (len & ~PAGE_MASK) != 0;
if (!access_ok(VERIFY_WRITE, vec, pages))
return -EFAULT;
tmp = (void *) __get_free_page(GFP_USER);
if (!tmp)
return -EAGAIN;
retval = 0;
while (pages) {
/*
* Do at most PAGE_SIZE entries per iteration, due to
* the temporary buffer size.
*/
down_read(&current->mm->mmap_sem);
retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);
up_read(&current->mm->mmap_sem);
if (retval <= 0)
break;
if (copy_to_user(vec, tmp, retval)) {
retval = -EFAULT;
break;
}
pages -= retval;
vec += retval;
start += retval << PAGE_SHIFT;
retval = 0;
}
free_page((unsigned long) tmp);
return retval;
}