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Commit 84c3fc4e authored by Zi Yan's avatar Zi Yan Committed by Linus Torvalds
Browse files

mm: thp: check pmd migration entry in common path 



When THP migration is being used, memory management code needs to handle
pmd migration entries properly.  This patch uses !pmd_present() or
is_swap_pmd() (depending on whether pmd_none() needs separate code or
not) to check pmd migration entries at the places where a pmd entry is
present.

Since pmd-related code uses split_huge_page(), split_huge_pmd(),
pmd_trans_huge(), pmd_trans_unstable(), or
pmd_none_or_trans_huge_or_clear_bad(), this patch:

1. adds pmd migration entry split code in split_huge_pmd(),

2. takes care of pmd migration entries whenever pmd_trans_huge() is present,

3. makes pmd_none_or_trans_huge_or_clear_bad() pmd migration entry aware.

Since split_huge_page() uses split_huge_pmd() and pmd_trans_unstable()
is equivalent to pmd_none_or_trans_huge_or_clear_bad(), we do not change
them.

Until this commit, a pmd entry should be:
1. pointing to a pte page,
2. is_swap_pmd(),
3. pmd_trans_huge(),
4. pmd_devmap(), or
5. pmd_none().

Signed-off-by: default avatarZi Yan <zi.yan@cs.rutgers.edu>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Nellans <dnellans@nvidia.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 616b8371

fs/proc/task_mmu.c

+21 −11
Original line number Diff line number Diff line
@@ -608,6 +608,7 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 


	ptl = pmd_trans_huge_lock(pmd, vma);

	if (ptl) {

		if (pmd_present(*pmd))

			smaps_pmd_entry(pmd, addr, walk);

		spin_unlock(ptl);

		return 0;
@@ -1012,6 +1013,9 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr, 
			goto out;

		}



		if (!pmd_present(*pmd))

			goto out;



		page = pmd_page(*pmd);



		/* Clear accessed and referenced bits. */
@@ -1293,27 +1297,33 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end, 
	if (ptl) {

		u64 flags = 0, frame = 0;

		pmd_t pmd = *pmdp;

		struct page *page = NULL;



		if ((vma->vm_flags & VM_SOFTDIRTY) || pmd_soft_dirty(pmd))

			flags |= PM_SOFT_DIRTY;



		/*

		 * Currently pmd for thp is always present because thp

		 * can not be swapped-out, migrated, or HWPOISONed

		 * (split in such cases instead.)

		 * This if-check is just to prepare for future implementation.

		 */

		if (pmd_present(pmd)) {

			struct page *page = pmd_page(pmd);



			if (page_mapcount(page) == 1)

				flags |= PM_MMAP_EXCLUSIVE;

			page = pmd_page(pmd);



			flags |= PM_PRESENT;

			if (pm->show_pfn)

				frame = pmd_pfn(pmd) +

					((addr & ~PMD_MASK) >> PAGE_SHIFT);

		}

#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION

		else if (is_swap_pmd(pmd)) {

			swp_entry_t entry = pmd_to_swp_entry(pmd);



			frame = swp_type(entry) |

				(swp_offset(entry) << MAX_SWAPFILES_SHIFT);

			flags |= PM_SWAP;

			VM_BUG_ON(!is_pmd_migration_entry(pmd));

			page = migration_entry_to_page(entry);

		}

#endif



		if (page && page_mapcount(page) == 1)

			flags |= PM_MMAP_EXCLUSIVE;



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

			pagemap_entry_t pme = make_pme(frame, flags);

include/asm-generic/pgtable.h

+17 −1
Original line number Diff line number Diff line
@@ -846,7 +846,23 @@ static inline int pmd_none_or_trans_huge_or_clear_bad(pmd_t *pmd) 
#ifdef CONFIG_TRANSPARENT_HUGEPAGE

	barrier();

#endif

	if (pmd_none(pmdval) || pmd_trans_huge(pmdval))

	/*

	 * !pmd_present() checks for pmd migration entries

	 *

	 * The complete check uses is_pmd_migration_entry() in linux/swapops.h

	 * But using that requires moving current function and pmd_trans_unstable()

	 * to linux/swapops.h to resovle dependency, which is too much code move.

	 *

	 * !pmd_present() is equivalent to is_pmd_migration_entry() currently,

	 * because !pmd_present() pages can only be under migration not swapped

	 * out.

	 *

	 * pmd_none() is preseved for future condition checks on pmd migration

	 * entries and not confusing with this function name, although it is

	 * redundant with !pmd_present().

	 */

	if (pmd_none(pmdval) || pmd_trans_huge(pmdval) ||

		(IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION) && !pmd_present(pmdval)))

		return 1;

	if (unlikely(pmd_bad(pmdval))) {

		pmd_clear_bad(pmd);

include/linux/huge_mm.h

+12 −2
Original line number Diff line number Diff line
@@ -147,7 +147,7 @@ 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 (is_swap_pmd(*____pmd) || pmd_trans_huge(*____pmd)	\

					|| pmd_devmap(*____pmd))	\

			__split_huge_pmd(__vma, __pmd, __address,	\

						false, NULL);		\
@@ -178,12 +178,18 @@ extern spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, 
		struct vm_area_struct *vma);

extern spinlock_t *__pud_trans_huge_lock(pud_t *pud,

		struct vm_area_struct *vma);



static inline int is_swap_pmd(pmd_t pmd)

{

	return !pmd_none(pmd) && !pmd_present(pmd);

}



/* mmap_sem must be held on entry */

static inline spinlock_t *pmd_trans_huge_lock(pmd_t *pmd,

		struct vm_area_struct *vma)

{

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

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

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

		return __pmd_trans_huge_lock(pmd, vma);

	else

		return NULL;
@@ -299,6 +305,10 @@ static inline void vma_adjust_trans_huge(struct vm_area_struct *vma, 
					 long adjust_next)

{

}

static inline int is_swap_pmd(pmd_t pmd)

{

	return 0;

}

static inline spinlock_t *pmd_trans_huge_lock(pmd_t *pmd,

		struct vm_area_struct *vma)

{

mm/gup.c

+20 −2
Original line number Diff line number Diff line
@@ -234,6 +234,16 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, 
			return page;

		return no_page_table(vma, flags);

	}

retry:

	if (!pmd_present(*pmd)) {

		if (likely(!(flags & FOLL_MIGRATION)))

			return no_page_table(vma, flags);

		VM_BUG_ON(thp_migration_supported() &&

				  !is_pmd_migration_entry(*pmd));

		if (is_pmd_migration_entry(*pmd))

			pmd_migration_entry_wait(mm, pmd);

		goto retry;

	}

	if (pmd_devmap(*pmd)) {

		ptl = pmd_lock(mm, pmd);

		page = follow_devmap_pmd(vma, address, pmd, flags);
@@ -247,7 +257,15 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, 
	if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))

		return no_page_table(vma, flags);



retry_locked:

	ptl = pmd_lock(mm, pmd);

	if (unlikely(!pmd_present(*pmd))) {

		spin_unlock(ptl);

		if (likely(!(flags & FOLL_MIGRATION)))

			return no_page_table(vma, flags);

		pmd_migration_entry_wait(mm, pmd);

		goto retry_locked;

	}

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

		spin_unlock(ptl);

		return follow_page_pte(vma, address, pmd, flags);
@@ -424,7 +442,7 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address, 
	pud = pud_offset(p4d, address);

	BUG_ON(pud_none(*pud));

	pmd = pmd_offset(pud, address);

	if (pmd_none(*pmd))

	if (!pmd_present(*pmd))

		return -EFAULT;

	VM_BUG_ON(pmd_trans_huge(*pmd));

	pte = pte_offset_map(pmd, address);
@@ -1534,7 +1552,7 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, 
		pmd_t pmd = READ_ONCE(*pmdp);



		next = pmd_addr_end(addr, end);

		if (pmd_none(pmd))

		if (!pmd_present(pmd))

			return 0;



		if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) {

mm/huge_memory.c

+59 −6
Original line number Diff line number Diff line
@@ -928,6 +928,23 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, 


	ret = -EAGAIN;

	pmd = *src_pmd;



#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION

	if (unlikely(is_swap_pmd(pmd))) {

		swp_entry_t entry = pmd_to_swp_entry(pmd);



		VM_BUG_ON(!is_pmd_migration_entry(pmd));

		if (is_write_migration_entry(entry)) {

			make_migration_entry_read(&entry);

			pmd = swp_entry_to_pmd(entry);

			set_pmd_at(src_mm, addr, src_pmd, pmd);

		}

		set_pmd_at(dst_mm, addr, dst_pmd, pmd);

		ret = 0;

		goto out_unlock;

	}

#endif



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

		pte_free(dst_mm, pgtable);

		goto out_unlock;
@@ -1599,6 +1616,12 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, 
	if (is_huge_zero_pmd(orig_pmd))

		goto out;



	if (unlikely(!pmd_present(orig_pmd))) {

		VM_BUG_ON(thp_migration_supported() &&

				  !is_pmd_migration_entry(orig_pmd));

		goto out;

	}



	page = pmd_page(orig_pmd);

	/*

	 * If other processes are mapping this page, we couldn't discard
@@ -1810,6 +1833,25 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 
	preserve_write = prot_numa && pmd_write(*pmd);

	ret = 1;



#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION

	if (is_swap_pmd(*pmd)) {

		swp_entry_t entry = pmd_to_swp_entry(*pmd);



		VM_BUG_ON(!is_pmd_migration_entry(*pmd));

		if (is_write_migration_entry(entry)) {

			pmd_t newpmd;

			/*

			 * A protection check is difficult so

			 * just be safe and disable write

			 */

			make_migration_entry_read(&entry);

			newpmd = swp_entry_to_pmd(entry);

			set_pmd_at(mm, addr, pmd, newpmd);

		}

		goto unlock;

	}

#endif



	/*

	 * Avoid trapping faults against the zero page. The read-only

	 * data is likely to be read-cached on the local CPU and
@@ -1875,7 +1917,8 @@ spinlock_t *__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) || pmd_devmap(*pmd)))

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

			pmd_devmap(*pmd)))

		return ptl;

	spin_unlock(ptl);

	return NULL;
@@ -1993,14 +2036,15 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 
	struct page *page;

	pgtable_t pgtable;

	pmd_t _pmd;

	bool young, write, dirty, soft_dirty;

	bool young, write, dirty, soft_dirty, pmd_migration = false;

	unsigned long addr;

	int i;



	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) && !pmd_devmap(*pmd));

	VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)

				&& !pmd_devmap(*pmd));



	count_vm_event(THP_SPLIT_PMD);
@@ -2025,6 +2069,15 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 
		return __split_huge_zero_page_pmd(vma, haddr, pmd);

	}



#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION

	pmd_migration = is_pmd_migration_entry(*pmd);

	if (pmd_migration) {

		swp_entry_t entry;



		entry = pmd_to_swp_entry(*pmd);

		page = pfn_to_page(swp_offset(entry));

	} else

#endif

		page = pmd_page(*pmd);

	VM_BUG_ON_PAGE(!page_count(page), page);

	page_ref_add(page, HPAGE_PMD_NR - 1);
@@ -2044,7 +2097,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 
		 * transferred to avoid any possibility of altering

		 * permissions across VMAs.

		 */

		if (freeze) {

		if (freeze || pmd_migration) {

			swp_entry_t swp_entry;

			swp_entry = make_migration_entry(page + i, write);

			entry = swp_entry_to_pte(swp_entry);
@@ -2143,7 +2196,7 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 
		page = pmd_page(*pmd);

		if (PageMlocked(page))

			clear_page_mlock(page);

	} else if (!pmd_devmap(*pmd))

	} else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))

		goto out;

	__split_huge_pmd_locked(vma, pmd, haddr, freeze);

out: