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Commit 5c7fb56e authored by Dan Williams's avatar Dan Williams Committed by Linus Torvalds
Browse files

mm, dax: dax-pmd vs thp-pmd vs hugetlbfs-pmd 



A dax-huge-page mapping while it uses some thp helpers is ultimately not
a transparent huge page.  The distinction is especially important in the
get_user_pages() path.  pmd_devmap() is used to distinguish dax-pmds
from pmd_huge() and pmd_trans_huge() which have slightly different
semantics.

Explicitly mark the pmd_trans_huge() helpers that dax needs by adding
pmd_devmap() checks.

[kirill.shutemov@linux.intel.com: fix regression in handling mlocked pages in  __split_huge_pmd()]
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5c2c2587

arch/x86/include/asm/pgtable.h

+8 −1
Original line number Diff line number Diff line
@@ -164,13 +164,20 @@ static inline int pmd_large(pmd_t pte) 
#ifdef CONFIG_TRANSPARENT_HUGEPAGE

static inline int pmd_trans_huge(pmd_t pmd)

{

	return pmd_val(pmd) & _PAGE_PSE;

	return (pmd_val(pmd) & (_PAGE_PSE|_PAGE_DEVMAP)) == _PAGE_PSE;

}



static inline int has_transparent_hugepage(void)

{

	return cpu_has_pse;

}



#ifdef __HAVE_ARCH_PTE_DEVMAP

static inline int pmd_devmap(pmd_t pmd)

{

	return !!(pmd_val(pmd) & _PAGE_DEVMAP);

}

#endif

#endif /* CONFIG_TRANSPARENT_HUGEPAGE */



static inline pte_t pte_set_flags(pte_t pte, pteval_t set)

include/linux/huge_mm.h

+3 −2
Original line number Diff line number Diff line
@@ -104,7 +104,8 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 
#define split_huge_pmd(__vma, __pmd, __address)				\

	do {								\

		pmd_t *____pmd = (__pmd);				\

		if (pmd_trans_huge(*____pmd))				\

		if (pmd_trans_huge(*____pmd)				\

					|| pmd_devmap(*____pmd))	\

			__split_huge_pmd(__vma, __pmd, __address);	\

	}  while (0)
@@ -124,7 +125,7 @@ static inline bool pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma, 
		spinlock_t **ptl)

{

	VM_BUG_ON_VMA(!rwsem_is_locked(&vma->vm_mm->mmap_sem), vma);

	if (pmd_trans_huge(*pmd))

	if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd))

		return __pmd_trans_huge_lock(pmd, vma, ptl);

	else

		return false;

include/linux/mm.h

+7 −0
Original line number Diff line number Diff line
@@ -329,6 +329,13 @@ struct inode; 
#define page_private(page)		((page)->private)

#define set_page_private(page, v)	((page)->private = (v))



#if !defined(__HAVE_ARCH_PTE_DEVMAP) || !defined(CONFIG_TRANSPARENT_HUGEPAGE)

static inline int pmd_devmap(pmd_t pmd)

{

	return 0;

}

#endif



/*

 * FIXME: take this include out, include page-flags.h in

 * files which need it (119 of them)

mm/huge_memory.c

+21 −17
Original line number Diff line number Diff line
@@ -995,7 +995,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 


	ret = -EAGAIN;

	pmd = *src_pmd;

	if (unlikely(!pmd_trans_huge(pmd))) {

	if (unlikely(!pmd_trans_huge(pmd) && !pmd_devmap(pmd))) {

		pte_free(dst_mm, pgtable);

		goto out_unlock;

	}
@@ -1018,17 +1018,20 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 
		goto out_unlock;

	}



	if (pmd_trans_huge(pmd)) {

		/* thp accounting separate from pmd_devmap accounting */

		src_page = pmd_page(pmd);

		VM_BUG_ON_PAGE(!PageHead(src_page), src_page);

		get_page(src_page);

		page_dup_rmap(src_page, true);

		add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);

		atomic_long_inc(&dst_mm->nr_ptes);

		pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);

	}



	pmdp_set_wrprotect(src_mm, addr, src_pmd);

	pmd = pmd_mkold(pmd_wrprotect(pmd));

	pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);

	set_pmd_at(dst_mm, addr, dst_pmd, pmd);

	atomic_long_inc(&dst_mm->nr_ptes);



	ret = 0;

out_unlock:
@@ -1716,7 +1719,7 @@ bool __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma, 
		spinlock_t **ptl)

{

	*ptl = pmd_lock(vma->vm_mm, pmd);

	if (likely(pmd_trans_huge(*pmd)))

	if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))

		return true;

	spin_unlock(*ptl);

	return false;
@@ -2788,7 +2791,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 
	VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);

	VM_BUG_ON_VMA(vma->vm_start > haddr, vma);

	VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);

	VM_BUG_ON(!pmd_trans_huge(*pmd));

	VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));



	count_vm_event(THP_SPLIT_PMD);
@@ -2901,14 +2904,15 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 


	mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);

	ptl = pmd_lock(mm, pmd);

	if (unlikely(!pmd_trans_huge(*pmd)))

		goto out;

	if (pmd_trans_huge(*pmd)) {

		page = pmd_page(*pmd);

	__split_huge_pmd_locked(vma, pmd, haddr, false);

		if (PageMlocked(page))

			get_page(page);

		else

			page = NULL;

	} else if (!pmd_devmap(*pmd))

		goto out;

	__split_huge_pmd_locked(vma, pmd, haddr, false);

out:

	spin_unlock(ptl);

	mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
@@ -2938,7 +2942,7 @@ static void split_huge_pmd_address(struct vm_area_struct *vma, 
		return;



	pmd = pmd_offset(pud, address);

	if (!pmd_present(*pmd) || !pmd_trans_huge(*pmd))

	if (!pmd_present(*pmd) || (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd)))

		return;

	/*

	 * Caller holds the mmap_sem write mode, so a huge pmd cannot

mm/memory.c

+4 −4
Original line number Diff line number Diff line
@@ -950,7 +950,7 @@ static inline int copy_pmd_range(struct mm_struct *dst_mm, struct mm_struct *src 
	src_pmd = pmd_offset(src_pud, addr);

	do {

		next = pmd_addr_end(addr, end);

		if (pmd_trans_huge(*src_pmd)) {

		if (pmd_trans_huge(*src_pmd) || pmd_devmap(*src_pmd)) {

			int err;

			VM_BUG_ON(next-addr != HPAGE_PMD_SIZE);

			err = copy_huge_pmd(dst_mm, src_mm,
@@ -1177,7 +1177,7 @@ static inline unsigned long zap_pmd_range(struct mmu_gather *tlb, 
	pmd = pmd_offset(pud, addr);

	do {

		next = pmd_addr_end(addr, end);

		if (pmd_trans_huge(*pmd)) {

		if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {

			if (next - addr != HPAGE_PMD_SIZE) {

#ifdef CONFIG_DEBUG_VM

				if (!rwsem_is_locked(&tlb->mm->mmap_sem)) {
@@ -3375,7 +3375,7 @@ static int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma, 
		int ret;



		barrier();

		if (pmd_trans_huge(orig_pmd)) {

		if (pmd_trans_huge(orig_pmd) || pmd_devmap(orig_pmd)) {

			unsigned int dirty = flags & FAULT_FLAG_WRITE;



			if (pmd_protnone(orig_pmd))
@@ -3404,7 +3404,7 @@ static int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma, 
	    unlikely(__pte_alloc(mm, vma, pmd, address)))

		return VM_FAULT_OOM;

	/* if an huge pmd materialized from under us just retry later */

	if (unlikely(pmd_trans_huge(*pmd)))

	if (unlikely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))

		return 0;

	/*

	 * A regular pmd is established and it can't morph into a huge pmd