From: Jérôme Glisse <jglisse@xxxxxxxxxx> Subject: 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@xxxxxxxxxx Signed-off-by: Jérôme Glisse <jglisse@xxxxxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Aneesh Kumar <aneesh.kumar@xxxxxxxxxxxxxxxxxx> Cc: Balbir Singh <bsingharora@xxxxxxxxx> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: David Nellans <dnellans@xxxxxxxxxx> Cc: Evgeny Baskakov <ebaskakov@xxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: John Hubbard <jhubbard@xxxxxxxxxx> Cc: Mark Hairgrove <mhairgrove@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> Cc: Sherry Cheung <SCheung@xxxxxxxxxx> Cc: Subhash Gutti <sgutti@xxxxxxxxxx> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> Cc: Bob Liu <liubo95@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/migrate.h | 10 ++ mm/migrate.c | 149 ++++++++++++++++++++++++++++++-------- mm/page_vma_mapped.c | 10 ++ mm/rmap.c | 26 ++++++ 4 files changed, 165 insertions(+), 30 deletions(-) diff -puN include/linux/migrate.h~mm-migrate-support-un-addressable-zone_device-page-in-migration-v3 include/linux/migrate.h --- a/include/linux/migrate.h~mm-migrate-support-un-addressable-zone_device-page-in-migration-v3 +++ a/include/linux/migrate.h @@ -159,12 +159,18 @@ static inline int migrate_misplaced_tran #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) { diff -puN mm/migrate.c~mm-migrate-support-un-addressable-zone_device-page-in-migration-v3 mm/migrate.c --- a/mm/migrate.c~mm-migrate-support-un-addressable-zone_device-page-in-migration-v3 +++ a/mm/migrate.c @@ -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 if (is_write_migration_entry(entry)) pte = maybe_mkwrite(pte, vma); - flush_dcache_page(new); + 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 @@ again: pte = *ptep; pfn = pte_pfn(pte); - if (!pte_present(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 @@ again: */ 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 @@ again: */ page_remove_rmap(page, false); put_page(page); - unmapped++; + + 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(struc 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; @@ -2379,24 +2432,30 @@ static void migrate_vma_prepare(struct m migrate->src[i] |= MIGRATE_PFN_LOCKED; } - if (!PageLRU(page) && allow_drain) { - /* Drain CPU's pagevec */ - lru_add_drain_all(); - allow_drain = false; - } + /* 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(); + allow_drain = false; + } - if (isolate_lru_page(page)) { - if (remap) { - migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; - migrate->cpages--; - restore++; - } else { - migrate->src[i] = 0; - unlock_page(page); - migrate->cpages--; - put_page(page); + if (isolate_lru_page(page)) { + if (remap) { + migrate->src[i] &= ~MIGRATE_PFN_MIGRATE; + migrate->cpages--; + restore++; + } else { + migrate->src[i] = 0; + unlock_page(page); + migrate->cpages--; + put_page(page); + } + continue; } - continue; + + /* Drop the reference we took in collect */ + put_page(page); } if (!migrate_vma_check_page(page)) { @@ -2405,14 +2464,19 @@ static void migrate_vma_prepare(struct m migrate->cpages--; restore++; - get_page(page); - putback_lru_page(page); + if (!is_zone_device_page(page)) { + get_page(page); + putback_lru_page(page); + } } else { migrate->src[i] = 0; unlock_page(page); migrate->cpages--; - putback_lru_page(page); + if (!is_zone_device_page(page)) + putback_lru_page(page); + else + put_page(page); } } } @@ -2483,7 +2547,10 @@ restore: unlock_page(page); restore--; - putback_lru_page(page); + if (is_zone_device_page(page)) + put_page(page); + else + putback_lru_page(page); } } @@ -2514,6 +2581,26 @@ static void migrate_vma_pages(struct mig 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; @@ -2554,11 +2641,17 @@ static void migrate_vma_finalize(struct unlock_page(page); migrate->cpages--; - putback_lru_page(page); + if (is_zone_device_page(page)) + put_page(page); + else + putback_lru_page(page); if (newpage != page) { unlock_page(newpage); - putback_lru_page(newpage); + if (is_zone_device_page(newpage)) + put_page(newpage); + else + putback_lru_page(newpage); } } } diff -puN mm/page_vma_mapped.c~mm-migrate-support-un-addressable-zone_device-page-in-migration-v3 mm/page_vma_mapped.c --- a/mm/page_vma_mapped.c~mm-migrate-support-un-addressable-zone_device-page-in-migration-v3 +++ a/mm/page_vma_mapped.c @@ -48,6 +48,7 @@ static bool check_pte(struct page_vma_ma 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_ma 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; diff -puN mm/rmap.c~mm-migrate-support-un-addressable-zone_device-page-in-migration-v3 mm/rmap.c --- a/mm/rmap.c~mm-migrate-support-un-addressable-zone_device-page-in-migration-v3 +++ a/mm/rmap.c @@ -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 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 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)) { _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
