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Commit a5430dda authored by Jérôme Glisse's avatar Jérôme Glisse Committed by Linus Torvalds
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mm/migrate: support un-addressable ZONE_DEVICE page in migration 

Allow to unmap and restore special swap entry of un-addressable
ZONE_DEVICE memory.

Link: http://lkml.kernel.org/r/20170817000548.32038-17-jglisse@redhat.com


Signed-off-by: default avatarJérôme Glisse <jglisse@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Nellans <dnellans@nvidia.com>
Cc: Evgeny Baskakov <ebaskakov@nvidia.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Mark Hairgrove <mhairgrove@nvidia.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Sherry Cheung <SCheung@nvidia.com>
Cc: Subhash Gutti <sgutti@nvidia.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Bob Liu <liubo95@huawei.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8c3328f1

include/linux/migrate.h

+8 −2
Original line number Diff line number Diff line
@@ -159,12 +159,18 @@ static inline int migrate_misplaced_transhuge_page(struct mm_struct *mm, 


#ifdef CONFIG_MIGRATION



/*

 * Watch out for PAE architecture, which has an unsigned long, and might not

 * have enough bits to store all physical address and flags. So far we have

 * enough room for all our flags.

 */

#define MIGRATE_PFN_VALID	(1UL << 0)

#define MIGRATE_PFN_MIGRATE	(1UL << 1)

#define MIGRATE_PFN_LOCKED	(1UL << 2)

#define MIGRATE_PFN_WRITE	(1UL << 3)

#define MIGRATE_PFN_ERROR	(1UL << 4)

#define MIGRATE_PFN_SHIFT	5

#define MIGRATE_PFN_DEVICE	(1UL << 4)

#define MIGRATE_PFN_ERROR	(1UL << 5)

#define MIGRATE_PFN_SHIFT	6



static inline struct page *migrate_pfn_to_page(unsigned long mpfn)

{

mm/migrate.c

+121 −28
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ 
#include <linux/hugetlb.h>

#include <linux/hugetlb_cgroup.h>

#include <linux/gfp.h>

#include <linux/memremap.h>

#include <linux/balloon_compaction.h>

#include <linux/mmu_notifier.h>

#include <linux/page_idle.h>
@@ -237,7 +238,13 @@ static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma, 
		if (is_write_migration_entry(entry))

			pte = maybe_mkwrite(pte, vma);



		if (unlikely(is_zone_device_page(new)) &&

		    is_device_private_page(new)) {

			entry = make_device_private_entry(new, pte_write(pte));

			pte = swp_entry_to_pte(entry);

		} else

			flush_dcache_page(new);



#ifdef CONFIG_HUGETLB_PAGE

		if (PageHuge(new)) {

			pte = pte_mkhuge(pte);
@@ -2205,17 +2212,40 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, 
		pte = *ptep;

		pfn = pte_pfn(pte);



		if (pte_none(pte)) {

			mpfn = pfn = 0;

			goto next;

		}



		if (!pte_present(pte)) {

			mpfn = pfn = 0;



			/*

			 * Only care about unaddressable device page special

			 * page table entry. Other special swap entries are not

			 * migratable, and we ignore regular swapped page.

			 */

			entry = pte_to_swp_entry(pte);

			if (!is_device_private_entry(entry))

				goto next;



			page = device_private_entry_to_page(entry);

			mpfn = migrate_pfn(page_to_pfn(page))|

				MIGRATE_PFN_DEVICE | MIGRATE_PFN_MIGRATE;

			if (is_write_device_private_entry(entry))

				mpfn |= MIGRATE_PFN_WRITE;

		} else {

			page = vm_normal_page(migrate->vma, addr, pte);

			mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;

			mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;

		}



		/* FIXME support THP */

		page = vm_normal_page(migrate->vma, addr, pte);

		if (!page || !page->mapping || PageTransCompound(page)) {

			mpfn = pfn = 0;

			goto next;

		}

		pfn = page_to_pfn(page);



		/*

		 * By getting a reference on the page we pin it and that blocks
@@ -2228,8 +2258,6 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, 
		 */

		get_page(page);

		migrate->cpages++;

		mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;

		mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;



		/*

		 * Optimize for the common case where page is only mapped once
@@ -2256,10 +2284,13 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, 
			 */

			page_remove_rmap(page, false);

			put_page(page);



			if (pte_present(pte))

				unmapped++;

		}



next:

		migrate->dst[migrate->npages] = 0;

		migrate->src[migrate->npages++] = mpfn;

	}

	arch_leave_lazy_mmu_mode();
@@ -2329,6 +2360,28 @@ static bool migrate_vma_check_page(struct page *page) 
	if (PageCompound(page))

		return false;



	/* Page from ZONE_DEVICE have one extra reference */

	if (is_zone_device_page(page)) {

		/*

		 * Private page can never be pin as they have no valid pte and

		 * GUP will fail for those. Yet if there is a pending migration

		 * a thread might try to wait on the pte migration entry and

		 * will bump the page reference count. Sadly there is no way to

		 * differentiate a regular pin from migration wait. Hence to

		 * avoid 2 racing thread trying to migrate back to CPU to enter

		 * infinite loop (one stoping migration because the other is

		 * waiting on pte migration entry). We always return true here.

		 *

		 * FIXME proper solution is to rework migration_entry_wait() so

		 * it does not need to take a reference on page.

		 */

		if (is_device_private_page(page))

			return true;



		/* Other ZONE_DEVICE memory type are not supported */

		return false;

	}



	if ((page_count(page) - extra) > page_mapcount(page))

		return false;
@@ -2379,6 +2432,8 @@ static void migrate_vma_prepare(struct migrate_vma *migrate) 
			migrate->src[i] |= MIGRATE_PFN_LOCKED;

		}



		/* ZONE_DEVICE pages are not on LRU */

		if (!is_zone_device_page(page)) {

			if (!PageLRU(page) && allow_drain) {

				/* Drain CPU's pagevec */

				lru_add_drain_all();
@@ -2399,20 +2454,29 @@ static void migrate_vma_prepare(struct migrate_vma *migrate) 
				continue;

			}



			/* Drop the reference we took in collect */

			put_page(page);

		}



		if (!migrate_vma_check_page(page)) {

			if (remap) {

				migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;

				migrate->cpages--;

				restore++;



				if (!is_zone_device_page(page)) {

					get_page(page);

					putback_lru_page(page);

				}

			} else {

				migrate->src[i] = 0;

				unlock_page(page);

				migrate->cpages--;



				if (!is_zone_device_page(page))

					putback_lru_page(page);

				else

					put_page(page);

			}

		}

	}
@@ -2483,6 +2547,9 @@ static void migrate_vma_unmap(struct migrate_vma *migrate) 
		unlock_page(page);

		restore--;



		if (is_zone_device_page(page))

			put_page(page);

		else

			putback_lru_page(page);

	}

}
@@ -2514,6 +2581,26 @@ static void migrate_vma_pages(struct migrate_vma *migrate) 


		mapping = page_mapping(page);



		if (is_zone_device_page(newpage)) {

			if (is_device_private_page(newpage)) {

				/*

				 * For now only support private anonymous when

				 * migrating to un-addressable device memory.

				 */

				if (mapping) {

					migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;

					continue;

				}

			} else {

				/*

				 * Other types of ZONE_DEVICE page are not

				 * supported.

				 */

				migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;

				continue;

			}

		}



		r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY);

		if (r != MIGRATEPAGE_SUCCESS)

			migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
@@ -2554,10 +2641,16 @@ static void migrate_vma_finalize(struct migrate_vma *migrate) 
		unlock_page(page);

		migrate->cpages--;



		if (is_zone_device_page(page))

			put_page(page);

		else

			putback_lru_page(page);



		if (newpage != page) {

			unlock_page(newpage);

			if (is_zone_device_page(newpage))

				put_page(newpage);

			else

				putback_lru_page(newpage);

		}

	}

mm/page_vma_mapped.c

+10 −0
Original line number Diff line number Diff line
@@ -48,6 +48,7 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw) 
		if (!is_swap_pte(*pvmw->pte))

			return false;

		entry = pte_to_swp_entry(*pvmw->pte);



		if (!is_migration_entry(entry))

			return false;

		if (migration_entry_to_page(entry) - pvmw->page >=
@@ -60,6 +61,15 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw) 
		WARN_ON_ONCE(1);

#endif

	} else {

		if (is_swap_pte(*pvmw->pte)) {

			swp_entry_t entry;



			entry = pte_to_swp_entry(*pvmw->pte);

			if (is_device_private_entry(entry) &&

			    device_private_entry_to_page(entry) == pvmw->page)

				return true;

		}



		if (!pte_present(*pvmw->pte))

			return false;

mm/rmap.c

+26 −0
Original line number Diff line number Diff line
@@ -63,6 +63,7 @@ 
#include <linux/hugetlb.h>

#include <linux/backing-dev.h>

#include <linux/page_idle.h>

#include <linux/memremap.h>



#include <asm/tlbflush.h>
@@ -1346,6 +1347,10 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, 
	if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED))

		return true;



	if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) &&

	    is_zone_device_page(page) && !is_device_private_page(page))

		return true;



	if (flags & TTU_SPLIT_HUGE_PMD) {

		split_huge_pmd_address(vma, address,

				flags & TTU_SPLIT_FREEZE, page);
@@ -1403,6 +1408,27 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, 
		address = pvmw.address;





		if (IS_ENABLED(CONFIG_MIGRATION) &&

		    (flags & TTU_MIGRATION) &&

		    is_zone_device_page(page)) {

			swp_entry_t entry;

			pte_t swp_pte;



			pteval = ptep_get_and_clear(mm, pvmw.address, pvmw.pte);



			/*

			 * Store the pfn of the page in a special migration

			 * pte. do_swap_page() will wait until the migration

			 * pte is removed and then restart fault handling.

			 */

			entry = make_migration_entry(page, 0);

			swp_pte = swp_entry_to_pte(entry);

			if (pte_soft_dirty(pteval))

				swp_pte = pte_swp_mksoft_dirty(swp_pte);

			set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);

			goto discard;

		}



		if (!(flags & TTU_IGNORE_ACCESS)) {

			if (ptep_clear_flush_young_notify(vma, address,

						pvmw.pte)) {