Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 5dc37642 authored by Naoya Horiguchi's avatar Naoya Horiguchi Committed by Linus Torvalds
Browse files

mm hugetlb: add hugepage support to pagemap 



This patch enables extraction of the pfn of a hugepage from
/proc/pid/pagemap in an architecture independent manner.

Details
-------
My test program (leak_pagemap) works as follows:
 - creat() and mmap() a file on hugetlbfs (file size is 200MB == 100 hugepages,)
 - read()/write() something on it,
 - call page-types with option -p,
 - munmap() and unlink() the file on hugetlbfs

Without my patches
------------------
$ ./leak_pagemap
             flags page-count       MB  symbolic-flags                     long-symbolic-flags
0x0000000000000000          1        0  __________________________________
0x0000000000000804          1        0  __R________M______________________ referenced,mmap
0x000000000000086c         81        0  __RU_lA____M______________________ referenced,uptodate,lru,active,mmap
0x0000000000005808          5        0  ___U_______Ma_b___________________ uptodate,mmap,anonymous,swapbacked
0x0000000000005868         12        0  ___U_lA____Ma_b___________________ uptodate,lru,active,mmap,anonymous,swapbacked
0x000000000000586c          1        0  __RU_lA____Ma_b___________________ referenced,uptodate,lru,active,mmap,anonymous,swapbacked
             total        101        0

The output of page-types don't show any hugepage.

With my patches
---------------
$ ./leak_pagemap
             flags page-count       MB  symbolic-flags                     long-symbolic-flags
0x0000000000000000          1        0  __________________________________
0x0000000000030000      51100      199  ________________TG________________ compound_tail,huge
0x0000000000028018        100        0  ___UD__________H_G________________ uptodate,dirty,compound_head,huge
0x0000000000000804          1        0  __R________M______________________ referenced,mmap
0x000000000000080c          1        0  __RU_______M______________________ referenced,uptodate,mmap
0x000000000000086c         80        0  __RU_lA____M______________________ referenced,uptodate,lru,active,mmap
0x0000000000005808          4        0  ___U_______Ma_b___________________ uptodate,mmap,anonymous,swapbacked
0x0000000000005868         12        0  ___U_lA____Ma_b___________________ uptodate,lru,active,mmap,anonymous,swapbacked
0x000000000000586c          1        0  __RU_lA____Ma_b___________________ referenced,uptodate,lru,active,mmap,anonymous,swapbacked
             total      51300      200

The output of page-types shows 51200 pages contributing to hugepages,
containing 100 head pages and 51100 tail pages as expected.

[akpm@linux-foundation.org: build fix]
Signed-off-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d33b9f45

fs/proc/task_mmu.c

+45 −0
Original line number Diff line number Diff line
@@ -650,6 +650,50 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 
	return err;

}



static u64 huge_pte_to_pagemap_entry(pte_t pte, int offset)

{

	u64 pme = 0;

	if (pte_present(pte))

		pme = PM_PFRAME(pte_pfn(pte) + offset)

			| PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT;

	return pme;

}



static int pagemap_hugetlb_range(pte_t *pte, unsigned long addr,

				 unsigned long end, struct mm_walk *walk)

{

	struct vm_area_struct *vma;

	struct pagemapread *pm = walk->private;

	struct hstate *hs = NULL;

	int err = 0;



	vma = find_vma(walk->mm, addr);

	if (vma)

		hs = hstate_vma(vma);

	for (; addr != end; addr += PAGE_SIZE) {

		u64 pfn = PM_NOT_PRESENT;



		if (vma && (addr >= vma->vm_end)) {

			vma = find_vma(walk->mm, addr);

			if (vma)

				hs = hstate_vma(vma);

		}



		if (vma && (vma->vm_start <= addr) && is_vm_hugetlb_page(vma)) {

			/* calculate pfn of the "raw" page in the hugepage. */

			int offset = (addr & ~huge_page_mask(hs)) >> PAGE_SHIFT;

			pfn = huge_pte_to_pagemap_entry(*pte, offset);

		}

		err = add_to_pagemap(addr, pfn, pm);

		if (err)

			return err;

	}



	cond_resched();



	return err;

}



/*

 * /proc/pid/pagemap - an array mapping virtual pages to pfns

 *
@@ -742,6 +786,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf, 


	pagemap_walk.pmd_entry = pagemap_pte_range;

	pagemap_walk.pte_hole = pagemap_pte_hole;

	pagemap_walk.hugetlb_entry = pagemap_hugetlb_range;

	pagemap_walk.mm = mm;

	pagemap_walk.private = &pm;

include/linux/mm.h

+3 −0
Original line number Diff line number Diff line
@@ -770,6 +770,7 @@ unsigned long unmap_vmas(struct mmu_gather **tlb, 
 * @pmd_entry: if set, called for each non-empty PMD (3rd-level) entry

 * @pte_entry: if set, called for each non-empty PTE (4th-level) entry

 * @pte_hole: if set, called for each hole at all levels

 * @hugetlb_entry: if set, called for each hugetlb entry

 *

 * (see walk_page_range for more details)

 */
@@ -779,6 +780,8 @@ struct mm_walk { 
	int (*pmd_entry)(pmd_t *, unsigned long, unsigned long, struct mm_walk *);

	int (*pte_entry)(pte_t *, unsigned long, unsigned long, struct mm_walk *);

	int (*pte_hole)(unsigned long, unsigned long, struct mm_walk *);

	int (*hugetlb_entry)(pte_t *, unsigned long, unsigned long,

			     struct mm_walk *);

	struct mm_struct *mm;

	void *private;

};

mm/pagewalk.c

+19 −3
Original line number Diff line number Diff line
@@ -120,15 +120,31 @@ int walk_page_range(unsigned long addr, unsigned long end, 
	do {

		next = pgd_addr_end(addr, end);



		/* skip hugetlb vma to avoid hugepage PMD being cleared

		 * in pmd_none_or_clear_bad(). */

		/*

		 * handle hugetlb vma individually because pagetable walk for

		 * the hugetlb page is dependent on the architecture and

		 * we can't handled it in the same manner as non-huge pages.

		 */

		vma = find_vma(walk->mm, addr);

#ifdef CONFIG_HUGETLB_PAGE

		if (vma && is_vm_hugetlb_page(vma)) {

			pte_t *pte;

			struct hstate *hs;



			if (vma->vm_end < next)

				next = vma->vm_end;

			hs = hstate_vma(vma);

			pte = huge_pte_offset(walk->mm,

					      addr & huge_page_mask(hs));

			if (pte && !huge_pte_none(huge_ptep_get(pte))

			    && walk->hugetlb_entry)

				err = walk->hugetlb_entry(pte, addr,

							  next, walk);

			if (err)

				break;

			continue;

		}



#endif

		if (pgd_none_or_clear_bad(pgd)) {

			if (walk->pte_hole)

				err = walk->pte_hole(addr, next, walk);