mm/mincore.c - kernel/prism - Git at Google

 /*
  *	linux/mm/mincore.c
  *
  * Copyright (C) 1994-2006  Linus Torvalds
  */

 /*
  * The mincore() system call.
  */
 #include <linux/slab.h>
 #include <linux/pagemap.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>

 /*
  * 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;
 }

 /*
  * 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 char *vec, unsigned long pages)
 {
 	pgd_t *pgd;
 	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *ptep;
 	spinlock_t *ptl;
 	unsigned long nr;
 	int i;
 	pgoff_t pgoff;
 	struct vm_area_struct *vma = find_vma(current->mm, addr);

 	/*
 	 * find_vma() didn't find anything above us, or we're
 	 * in an unmapped hole in the address space: ENOMEM.
 	 */
 	if (!vma || addr < vma->vm_start)
 		return -ENOMEM;

 #ifdef CONFIG_HUGETLB_PAGE
 	if (is_vm_hugetlb_page(vma)) {
 		struct hstate *h;
 		unsigned long nr_huge;
 		unsigned char present;

 		i = 0;
 		nr = min(pages, (vma->vm_end - addr) >> PAGE_SHIFT);
 		h = hstate_vma(vma);
 		nr_huge = ((addr + pages * PAGE_SIZE - 1) >> huge_page_shift(h))
 			  - (addr >> huge_page_shift(h)) + 1;
 		nr_huge = min(nr_huge,
 			      (vma->vm_end - addr) >> huge_page_shift(h));
 		while (1) {
 			/* hugepage always in RAM for now,
 			 * but generally it needs to be check */
 			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 nr;
 				/* check hugepage border */
 				if (!((addr & ~huge_page_mask(h))
 				      >> PAGE_SHIFT))
 					break;
 			}
 		}
 		return nr;
 	}
 #endif

 	/*
 	 * Calculate how many pages there are left in the last level of the
 	 * PTE array for our address.
 	 */
 	nr = PTRS_PER_PTE - ((addr >> PAGE_SHIFT) & (PTRS_PER_PTE-1));

 	/*
 	 * Don't overrun this vma
 	 */
 	nr = min(nr, (vma->vm_end - addr) >> PAGE_SHIFT);

 	/*
 	 * Don't return more than the caller asked for
 	 */
 	nr = min(nr, pages);

 	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;

 	ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
 	for (i = 0; i < nr; i++, ptep++, addr += PAGE_SIZE) {
 		unsigned char present;
 		pte_t pte = *ptep;

 		if (pte_present(pte)) {
 			present = 1;

 		} else if (pte_none(pte)) {
 			if (vma->vm_file) {
 				pgoff = linear_page_index(vma, addr);
 				present = mincore_page(vma->vm_file->f_mapping,
 							pgoff);
 			} else
 				present = 0;

 		} else if (pte_file(pte)) {
 			pgoff = pte_to_pgoff(pte);
 			present = 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 */
 				present = 1;
 			} else {
 #ifdef CONFIG_SWAP
 				pgoff = entry.val;
 				present = mincore_page(&swapper_space, pgoff);
 #else
 				WARN_ON(1);
 				present = 1;
 #endif
 			}
 		}

 		vec[i] = present;
 	}
 	pte_unmap_unlock(ptep-1, ptl);

 	return nr;

 none_mapped:
 	if (vma->vm_file) {
 		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;
 	}

 	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, tmp, min(pages, PAGE_SIZE));
 		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;
 }
	/*
	* linux/mm/mincore.c
	*
	* Copyright (C) 1994-2006 Linus Torvalds
	*/

	/*
	* The mincore() system call.
	*/
	#include <linux/slab.h>
	#include <linux/pagemap.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>

	/*
	* 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;
	}

	/*
	* 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 char *vec, unsigned long pages)
	{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *ptep;
	spinlock_t *ptl;
	unsigned long nr;
	int i;
	pgoff_t pgoff;
	struct vm_area_struct *vma = find_vma(current->mm, addr);

	/*
	* find_vma() didn't find anything above us, or we're
	* in an unmapped hole in the address space: ENOMEM.
	*/
	if (!vma \|\| addr < vma->vm_start)
	return -ENOMEM;

	#ifdef CONFIG_HUGETLB_PAGE
	if (is_vm_hugetlb_page(vma)) {
	struct hstate *h;
	unsigned long nr_huge;
	unsigned char present;

	i = 0;
	nr = min(pages, (vma->vm_end - addr) >> PAGE_SHIFT);
	h = hstate_vma(vma);
	nr_huge = ((addr + pages * PAGE_SIZE - 1) >> huge_page_shift(h))
	- (addr >> huge_page_shift(h)) + 1;
	nr_huge = min(nr_huge,
	(vma->vm_end - addr) >> huge_page_shift(h));
	while (1) {
	/* hugepage always in RAM for now,
	* but generally it needs to be check */
	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 nr;
	/* check hugepage border */
	if (!((addr & ~huge_page_mask(h))
	>> PAGE_SHIFT))
	break;
	}
	}
	return nr;
	}
	#endif

	/*
	* Calculate how many pages there are left in the last level of the
	* PTE array for our address.
	*/
	nr = PTRS_PER_PTE - ((addr >> PAGE_SHIFT) & (PTRS_PER_PTE-1));

	/*
	* Don't overrun this vma
	*/
	nr = min(nr, (vma->vm_end - addr) >> PAGE_SHIFT);

	/*
	* Don't return more than the caller asked for
	*/
	nr = min(nr, pages);

	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;

	ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
	for (i = 0; i < nr; i++, ptep++, addr += PAGE_SIZE) {
	unsigned char present;
	pte_t pte = *ptep;

	if (pte_present(pte)) {
	present = 1;

	} else if (pte_none(pte)) {
	if (vma->vm_file) {
	pgoff = linear_page_index(vma, addr);
	present = mincore_page(vma->vm_file->f_mapping,
	pgoff);
	} else
	present = 0;

	} else if (pte_file(pte)) {
	pgoff = pte_to_pgoff(pte);
	present = 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 */
	present = 1;
	} else {
	#ifdef CONFIG_SWAP
	pgoff = entry.val;
	present = mincore_page(&swapper_space, pgoff);
	#else
	WARN_ON(1);
	present = 1;
	#endif
	}
	}

	vec[i] = present;
	}
	pte_unmap_unlock(ptep-1, ptl);

	return nr;

	none_mapped:
	if (vma->vm_file) {
	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;
	}

	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, tmp, min(pages, PAGE_SIZE));
	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;
	}