Commit 28093f9f authored by Gerald Schaefer's avatar Gerald Schaefer Committed by Linus Torvalds
Browse files

numa: fix /proc/<pid>/numa_maps for THP 



In gather_pte_stats() a THP pmd is cast into a pte, which is wrong
because the layouts may differ depending on the architecture.  On s390
this will lead to inaccurate numa_maps accounting in /proc because of
misguided pte_present() and pte_dirty() checks on the fake pte.

On other architectures pte_present() and pte_dirty() may work by chance,
but there may be an issue with direct-access (dax) mappings w/o
underlying struct pages when HAVE_PTE_SPECIAL is set and THP is
available.  In vm_normal_page() the fake pte will be checked with
pte_special() and because there is no "special" bit in a pmd, this will
always return false and the VM_PFNMAP | VM_MIXEDMAP checking will be
skipped.  On dax mappings w/o struct pages, an invalid struct page
pointer would then be returned that can crash the kernel.

This patch fixes the numa_maps THP handling by introducing new "_pmd"
variants of the can_gather_numa_stats() and vm_normal_page() functions.

Signed-off-by: default avatarGerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org>	[4.3+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3486b85a

fs/proc/task_mmu.c

+30 −3
Original line number Diff line number Diff line
@@ -1518,6 +1518,32 @@ static struct page *can_gather_numa_stats(pte_t pte, struct vm_area_struct *vma, 
	return page;

}



#ifdef CONFIG_TRANSPARENT_HUGEPAGE

static struct page *can_gather_numa_stats_pmd(pmd_t pmd,

					      struct vm_area_struct *vma,

					      unsigned long addr)

{

	struct page *page;

	int nid;



	if (!pmd_present(pmd))

		return NULL;



	page = vm_normal_page_pmd(vma, addr, pmd);

	if (!page)

		return NULL;



	if (PageReserved(page))

		return NULL;



	nid = page_to_nid(page);

	if (!node_isset(nid, node_states[N_MEMORY]))

		return NULL;



	return page;

}

#endif



static int gather_pte_stats(pmd_t *pmd, unsigned long addr,

		unsigned long end, struct mm_walk *walk)

{
@@ -1527,14 +1553,14 @@ static int gather_pte_stats(pmd_t *pmd, unsigned long addr, 
	pte_t *orig_pte;

	pte_t *pte;



#ifdef CONFIG_TRANSPARENT_HUGEPAGE

	ptl = pmd_trans_huge_lock(pmd, vma);

	if (ptl) {

		pte_t huge_pte = *(pte_t *)pmd;

		struct page *page;



		page = can_gather_numa_stats(huge_pte, vma, addr);

		page = can_gather_numa_stats_pmd(*pmd, vma, addr);

		if (page)

			gather_stats(page, md, pte_dirty(huge_pte),

			gather_stats(page, md, pmd_dirty(*pmd),

				     HPAGE_PMD_SIZE/PAGE_SIZE);

		spin_unlock(ptl);

		return 0;
@@ -1542,6 +1568,7 @@ static int gather_pte_stats(pmd_t *pmd, unsigned long addr, 


	if (pmd_trans_unstable(pmd))

		return 0;

#endif

	orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);

	do {

		struct page *page = can_gather_numa_stats(*pte, vma, addr);

include/linux/mm.h

+2 −0
Original line number Diff line number Diff line
@@ -1140,6 +1140,8 @@ struct zap_details { 


struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,

		pte_t pte);

struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,

				pmd_t pmd);



int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,

		unsigned long size);

mm/memory.c

+40 −0
Original line number Diff line number Diff line
@@ -789,6 +789,46 @@ out: 
	return pfn_to_page(pfn);

}



#ifdef CONFIG_TRANSPARENT_HUGEPAGE

struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,

				pmd_t pmd)

{

	unsigned long pfn = pmd_pfn(pmd);



	/*

	 * There is no pmd_special() but there may be special pmds, e.g.

	 * in a direct-access (dax) mapping, so let's just replicate the

	 * !HAVE_PTE_SPECIAL case from vm_normal_page() here.

	 */

	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {

		if (vma->vm_flags & VM_MIXEDMAP) {

			if (!pfn_valid(pfn))

				return NULL;

			goto out;

		} else {

			unsigned long off;

			off = (addr - vma->vm_start) >> PAGE_SHIFT;

			if (pfn == vma->vm_pgoff + off)

				return NULL;

			if (!is_cow_mapping(vma->vm_flags))

				return NULL;

		}

	}



	if (is_zero_pfn(pfn))

		return NULL;

	if (unlikely(pfn > highest_memmap_pfn))

		return NULL;



	/*

	 * NOTE! We still have PageReserved() pages in the page tables.

	 * eg. VDSO mappings can cause them to exist.

	 */

out:

	return pfn_to_page(pfn);

}

#endif



/*

 * copy one vm_area from one task to the other. Assumes the page tables

 * already present in the new task to be cleared in the whole range

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