[PATCH 13/27] mm: move the migrate_vma_* device migration code into it's own file
From: Christoph Hellwig
Date: Thu Feb 10 2022 - 02:29:46 EST
Split the code used to migrate to and from ZONE_DEVICE memory from
migrate.c into a new file.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
mm/Kconfig | 3 +
mm/Makefile | 1 +
mm/migrate.c | 753 -------------------------------------------
mm/migrate_device.c | 765 ++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 769 insertions(+), 753 deletions(-)
create mode 100644 mm/migrate_device.c
diff --git a/mm/Kconfig b/mm/Kconfig
index a1901ae6d06293..6391d8d3a616f3 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -249,6 +249,9 @@ config MIGRATION
pages as migration can relocate pages to satisfy a huge page
allocation instead of reclaiming.
+config DEVICE_MIGRATION
+ def_bool MIGRATION && DEVICE_PRIVATE
+
config ARCH_ENABLE_HUGEPAGE_MIGRATION
bool
diff --git a/mm/Makefile b/mm/Makefile
index 70d4309c9ce338..4cc13f3179a518 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -92,6 +92,7 @@ obj-$(CONFIG_KFENCE) += kfence/
obj-$(CONFIG_FAILSLAB) += failslab.o
obj-$(CONFIG_MEMTEST) += memtest.o
obj-$(CONFIG_MIGRATION) += migrate.o
+obj-$(CONFIG_DEVICE_MIGRATION) += migrate_device.o
obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o khugepaged.o
obj-$(CONFIG_PAGE_COUNTER) += page_counter.o
obj-$(CONFIG_MEMCG) += memcontrol.o vmpressure.o
diff --git a/mm/migrate.c b/mm/migrate.c
index 746e1230886ddb..c31d04b46a5e17 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -38,12 +38,10 @@
#include <linux/hugetlb.h>
#include <linux/hugetlb_cgroup.h>
#include <linux/gfp.h>
-#include <linux/pagewalk.h>
#include <linux/pfn_t.h>
#include <linux/memremap.h>
#include <linux/userfaultfd_k.h>
#include <linux/balloon_compaction.h>
-#include <linux/mmu_notifier.h>
#include <linux/page_idle.h>
#include <linux/page_owner.h>
#include <linux/sched/mm.h>
@@ -2125,757 +2123,6 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_NUMA */
-#ifdef CONFIG_DEVICE_PRIVATE
-static int migrate_vma_collect_skip(unsigned long start,
- unsigned long end,
- struct mm_walk *walk)
-{
- struct migrate_vma *migrate = walk->private;
- unsigned long addr;
-
- for (addr = start; addr < end; addr += PAGE_SIZE) {
- migrate->dst[migrate->npages] = 0;
- migrate->src[migrate->npages++] = 0;
- }
-
- return 0;
-}
-
-static int migrate_vma_collect_hole(unsigned long start,
- unsigned long end,
- __always_unused int depth,
- struct mm_walk *walk)
-{
- struct migrate_vma *migrate = walk->private;
- unsigned long addr;
-
- /* Only allow populating anonymous memory. */
- if (!vma_is_anonymous(walk->vma))
- return migrate_vma_collect_skip(start, end, walk);
-
- for (addr = start; addr < end; addr += PAGE_SIZE) {
- migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
- migrate->dst[migrate->npages] = 0;
- migrate->npages++;
- migrate->cpages++;
- }
-
- return 0;
-}
-
-static int migrate_vma_collect_pmd(pmd_t *pmdp,
- unsigned long start,
- unsigned long end,
- struct mm_walk *walk)
-{
- struct migrate_vma *migrate = walk->private;
- struct vm_area_struct *vma = walk->vma;
- struct mm_struct *mm = vma->vm_mm;
- unsigned long addr = start, unmapped = 0;
- spinlock_t *ptl;
- pte_t *ptep;
-
-again:
- if (pmd_none(*pmdp))
- return migrate_vma_collect_hole(start, end, -1, walk);
-
- if (pmd_trans_huge(*pmdp)) {
- struct page *page;
-
- ptl = pmd_lock(mm, pmdp);
- if (unlikely(!pmd_trans_huge(*pmdp))) {
- spin_unlock(ptl);
- goto again;
- }
-
- page = pmd_page(*pmdp);
- if (is_huge_zero_page(page)) {
- spin_unlock(ptl);
- split_huge_pmd(vma, pmdp, addr);
- if (pmd_trans_unstable(pmdp))
- return migrate_vma_collect_skip(start, end,
- walk);
- } else {
- int ret;
-
- get_page(page);
- spin_unlock(ptl);
- if (unlikely(!trylock_page(page)))
- return migrate_vma_collect_skip(start, end,
- walk);
- ret = split_huge_page(page);
- unlock_page(page);
- put_page(page);
- if (ret)
- return migrate_vma_collect_skip(start, end,
- walk);
- if (pmd_none(*pmdp))
- return migrate_vma_collect_hole(start, end, -1,
- walk);
- }
- }
-
- if (unlikely(pmd_bad(*pmdp)))
- return migrate_vma_collect_skip(start, end, walk);
-
- ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
- arch_enter_lazy_mmu_mode();
-
- for (; addr < end; addr += PAGE_SIZE, ptep++) {
- unsigned long mpfn = 0, pfn;
- struct page *page;
- swp_entry_t entry;
- pte_t pte;
-
- pte = *ptep;
-
- if (pte_none(pte)) {
- if (vma_is_anonymous(vma)) {
- mpfn = MIGRATE_PFN_MIGRATE;
- migrate->cpages++;
- }
- goto next;
- }
-
- if (!pte_present(pte)) {
- /*
- * 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 = pfn_swap_entry_to_page(entry);
- if (!(migrate->flags &
- MIGRATE_VMA_SELECT_DEVICE_PRIVATE) ||
- page->pgmap->owner != migrate->pgmap_owner)
- goto next;
-
- mpfn = migrate_pfn(page_to_pfn(page)) |
- MIGRATE_PFN_MIGRATE;
- if (is_writable_device_private_entry(entry))
- mpfn |= MIGRATE_PFN_WRITE;
- } else {
- if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
- goto next;
- pfn = pte_pfn(pte);
- if (is_zero_pfn(pfn)) {
- mpfn = MIGRATE_PFN_MIGRATE;
- migrate->cpages++;
- goto next;
- }
- 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 */
- if (!page || !page->mapping || PageTransCompound(page)) {
- mpfn = 0;
- goto next;
- }
-
- /*
- * By getting a reference on the page we pin it and that blocks
- * any kind of migration. Side effect is that it "freezes" the
- * pte.
- *
- * We drop this reference after isolating the page from the lru
- * for non device page (device page are not on the lru and thus
- * can't be dropped from it).
- */
- get_page(page);
-
- /*
- * Optimize for the common case where page is only mapped once
- * in one process. If we can lock the page, then we can safely
- * set up a special migration page table entry now.
- */
- if (trylock_page(page)) {
- pte_t swp_pte;
-
- migrate->cpages++;
- ptep_get_and_clear(mm, addr, ptep);
-
- /* Setup special migration page table entry */
- if (mpfn & MIGRATE_PFN_WRITE)
- entry = make_writable_migration_entry(
- page_to_pfn(page));
- else
- entry = make_readable_migration_entry(
- page_to_pfn(page));
- swp_pte = swp_entry_to_pte(entry);
- if (pte_present(pte)) {
- if (pte_soft_dirty(pte))
- swp_pte = pte_swp_mksoft_dirty(swp_pte);
- if (pte_uffd_wp(pte))
- swp_pte = pte_swp_mkuffd_wp(swp_pte);
- } else {
- if (pte_swp_soft_dirty(pte))
- swp_pte = pte_swp_mksoft_dirty(swp_pte);
- if (pte_swp_uffd_wp(pte))
- swp_pte = pte_swp_mkuffd_wp(swp_pte);
- }
- set_pte_at(mm, addr, ptep, swp_pte);
-
- /*
- * This is like regular unmap: we remove the rmap and
- * drop page refcount. Page won't be freed, as we took
- * a reference just above.
- */
- page_remove_rmap(page, false);
- put_page(page);
-
- if (pte_present(pte))
- unmapped++;
- } else {
- put_page(page);
- mpfn = 0;
- }
-
-next:
- migrate->dst[migrate->npages] = 0;
- migrate->src[migrate->npages++] = mpfn;
- }
- arch_leave_lazy_mmu_mode();
- pte_unmap_unlock(ptep - 1, ptl);
-
- /* Only flush the TLB if we actually modified any entries */
- if (unmapped)
- flush_tlb_range(walk->vma, start, end);
-
- return 0;
-}
-
-static const struct mm_walk_ops migrate_vma_walk_ops = {
- .pmd_entry = migrate_vma_collect_pmd,
- .pte_hole = migrate_vma_collect_hole,
-};
-
-/*
- * migrate_vma_collect() - collect pages over a range of virtual addresses
- * @migrate: migrate struct containing all migration information
- *
- * This will walk the CPU page table. For each virtual address backed by a
- * valid page, it updates the src array and takes a reference on the page, in
- * order to pin the page until we lock it and unmap it.
- */
-static void migrate_vma_collect(struct migrate_vma *migrate)
-{
- struct mmu_notifier_range range;
-
- /*
- * Note that the pgmap_owner is passed to the mmu notifier callback so
- * that the registered device driver can skip invalidating device
- * private page mappings that won't be migrated.
- */
- mmu_notifier_range_init_owner(&range, MMU_NOTIFY_MIGRATE, 0,
- migrate->vma, migrate->vma->vm_mm, migrate->start, migrate->end,
- migrate->pgmap_owner);
- mmu_notifier_invalidate_range_start(&range);
-
- walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end,
- &migrate_vma_walk_ops, migrate);
-
- mmu_notifier_invalidate_range_end(&range);
- migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
-}
-
-/*
- * migrate_vma_check_page() - check if page is pinned or not
- * @page: struct page to check
- *
- * Pinned pages cannot be migrated. This is the same test as in
- * folio_migrate_mapping(), except that here we allow migration of a
- * ZONE_DEVICE page.
- */
-static bool migrate_vma_check_page(struct page *page)
-{
- /*
- * One extra ref because caller holds an extra reference, either from
- * isolate_lru_page() for a regular page, or migrate_vma_collect() for
- * a device page.
- */
- int extra = 1;
-
- /*
- * FIXME support THP (transparent huge page), it is bit more complex to
- * check them than regular pages, because they can be mapped with a pmd
- * or with a pte (split pte mapping).
- */
- if (PageCompound(page))
- return false;
-
- /* Page from ZONE_DEVICE have one extra reference */
- if (is_zone_device_page(page))
- extra++;
-
- /* For file back page */
- if (page_mapping(page))
- extra += 1 + page_has_private(page);
-
- if ((page_count(page) - extra) > page_mapcount(page))
- return false;
-
- return true;
-}
-
-/*
- * migrate_vma_unmap() - replace page mapping with special migration pte entry
- * @migrate: migrate struct containing all migration information
- *
- * Isolate pages from the LRU and replace mappings (CPU page table pte) with a
- * special migration pte entry and check if it has been pinned. Pinned pages are
- * restored because we cannot migrate them.
- *
- * This is the last step before we call the device driver callback to allocate
- * destination memory and copy contents of original page over to new page.
- */
-static void migrate_vma_unmap(struct migrate_vma *migrate)
-{
- const unsigned long npages = migrate->npages;
- unsigned long i, restore = 0;
- bool allow_drain = true;
-
- lru_add_drain();
-
- for (i = 0; i < npages; i++) {
- struct page *page = migrate_pfn_to_page(migrate->src[i]);
-
- if (!page)
- continue;
-
- /* 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)) {
- migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
- migrate->cpages--;
- restore++;
- continue;
- }
-
- /* Drop the reference we took in collect */
- put_page(page);
- }
-
- if (page_mapped(page))
- try_to_migrate(page, 0);
-
- if (page_mapped(page) || !migrate_vma_check_page(page)) {
- if (!is_zone_device_page(page)) {
- get_page(page);
- putback_lru_page(page);
- }
-
- migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
- migrate->cpages--;
- restore++;
- continue;
- }
- }
-
- for (i = 0; i < npages && restore; i++) {
- struct page *page = migrate_pfn_to_page(migrate->src[i]);
-
- if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
- continue;
-
- remove_migration_ptes(page, page, false);
-
- migrate->src[i] = 0;
- unlock_page(page);
- put_page(page);
- restore--;
- }
-}
-
-/**
- * migrate_vma_setup() - prepare to migrate a range of memory
- * @args: contains the vma, start, and pfns arrays for the migration
- *
- * Returns: negative errno on failures, 0 when 0 or more pages were migrated
- * without an error.
- *
- * Prepare to migrate a range of memory virtual address range by collecting all
- * the pages backing each virtual address in the range, saving them inside the
- * src array. Then lock those pages and unmap them. Once the pages are locked
- * and unmapped, check whether each page is pinned or not. Pages that aren't
- * pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the
- * corresponding src array entry. Then restores any pages that are pinned, by
- * remapping and unlocking those pages.
- *
- * The caller should then allocate destination memory and copy source memory to
- * it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE
- * flag set). Once these are allocated and copied, the caller must update each
- * corresponding entry in the dst array with the pfn value of the destination
- * page and with MIGRATE_PFN_VALID. Destination pages must be locked via
- * lock_page().
- *
- * Note that the caller does not have to migrate all the pages that are marked
- * with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from
- * device memory to system memory. If the caller cannot migrate a device page
- * back to system memory, then it must return VM_FAULT_SIGBUS, which has severe
- * consequences for the userspace process, so it must be avoided if at all
- * possible.
- *
- * For empty entries inside CPU page table (pte_none() or pmd_none() is true) we
- * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus
- * allowing the caller to allocate device memory for those unbacked virtual
- * addresses. For this the caller simply has to allocate device memory and
- * properly set the destination entry like for regular migration. Note that
- * this can still fail, and thus inside the device driver you must check if the
- * migration was successful for those entries after calling migrate_vma_pages(),
- * just like for regular migration.
- *
- * After that, the callers must call migrate_vma_pages() to go over each entry
- * in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
- * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
- * then migrate_vma_pages() to migrate struct page information from the source
- * struct page to the destination struct page. If it fails to migrate the
- * struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the
- * src array.
- *
- * At this point all successfully migrated pages have an entry in the src
- * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
- * array entry with MIGRATE_PFN_VALID flag set.
- *
- * Once migrate_vma_pages() returns the caller may inspect which pages were
- * successfully migrated, and which were not. Successfully migrated pages will
- * have the MIGRATE_PFN_MIGRATE flag set for their src array entry.
- *
- * It is safe to update device page table after migrate_vma_pages() because
- * both destination and source page are still locked, and the mmap_lock is held
- * in read mode (hence no one can unmap the range being migrated).
- *
- * Once the caller is done cleaning up things and updating its page table (if it
- * chose to do so, this is not an obligation) it finally calls
- * migrate_vma_finalize() to update the CPU page table to point to new pages
- * for successfully migrated pages or otherwise restore the CPU page table to
- * point to the original source pages.
- */
-int migrate_vma_setup(struct migrate_vma *args)
-{
- long nr_pages = (args->end - args->start) >> PAGE_SHIFT;
-
- args->start &= PAGE_MASK;
- args->end &= PAGE_MASK;
- if (!args->vma || is_vm_hugetlb_page(args->vma) ||
- (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma))
- return -EINVAL;
- if (nr_pages <= 0)
- return -EINVAL;
- if (args->start < args->vma->vm_start ||
- args->start >= args->vma->vm_end)
- return -EINVAL;
- if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end)
- return -EINVAL;
- if (!args->src || !args->dst)
- return -EINVAL;
-
- memset(args->src, 0, sizeof(*args->src) * nr_pages);
- args->cpages = 0;
- args->npages = 0;
-
- migrate_vma_collect(args);
-
- if (args->cpages)
- migrate_vma_unmap(args);
-
- /*
- * At this point pages are locked and unmapped, and thus they have
- * stable content and can safely be copied to destination memory that
- * is allocated by the drivers.
- */
- return 0;
-
-}
-EXPORT_SYMBOL(migrate_vma_setup);
-
-/*
- * This code closely matches the code in:
- * __handle_mm_fault()
- * handle_pte_fault()
- * do_anonymous_page()
- * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE
- * private page.
- */
-static void migrate_vma_insert_page(struct migrate_vma *migrate,
- unsigned long addr,
- struct page *page,
- unsigned long *src)
-{
- struct vm_area_struct *vma = migrate->vma;
- struct mm_struct *mm = vma->vm_mm;
- bool flush = false;
- spinlock_t *ptl;
- pte_t entry;
- pgd_t *pgdp;
- p4d_t *p4dp;
- pud_t *pudp;
- pmd_t *pmdp;
- pte_t *ptep;
-
- /* Only allow populating anonymous memory */
- if (!vma_is_anonymous(vma))
- goto abort;
-
- pgdp = pgd_offset(mm, addr);
- p4dp = p4d_alloc(mm, pgdp, addr);
- if (!p4dp)
- goto abort;
- pudp = pud_alloc(mm, p4dp, addr);
- if (!pudp)
- goto abort;
- pmdp = pmd_alloc(mm, pudp, addr);
- if (!pmdp)
- goto abort;
-
- if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
- goto abort;
-
- /*
- * Use pte_alloc() instead of pte_alloc_map(). We can't run
- * pte_offset_map() on pmds where a huge pmd might be created
- * from a different thread.
- *
- * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when
- * parallel threads are excluded by other means.
- *
- * Here we only have mmap_read_lock(mm).
- */
- if (pte_alloc(mm, pmdp))
- goto abort;
-
- /* See the comment in pte_alloc_one_map() */
- if (unlikely(pmd_trans_unstable(pmdp)))
- goto abort;
-
- if (unlikely(anon_vma_prepare(vma)))
- goto abort;
- if (mem_cgroup_charge(page_folio(page), vma->vm_mm, GFP_KERNEL))
- goto abort;
-
- /*
- * The memory barrier inside __SetPageUptodate makes sure that
- * preceding stores to the page contents become visible before
- * the set_pte_at() write.
- */
- __SetPageUptodate(page);
-
- if (is_device_private_page(page)) {
- swp_entry_t swp_entry;
-
- if (vma->vm_flags & VM_WRITE)
- swp_entry = make_writable_device_private_entry(
- page_to_pfn(page));
- else
- swp_entry = make_readable_device_private_entry(
- page_to_pfn(page));
- entry = swp_entry_to_pte(swp_entry);
- } else {
- /*
- * For now we only support migrating to un-addressable device
- * memory.
- */
- if (is_zone_device_page(page)) {
- pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
- goto abort;
- }
- entry = mk_pte(page, vma->vm_page_prot);
- if (vma->vm_flags & VM_WRITE)
- entry = pte_mkwrite(pte_mkdirty(entry));
- }
-
- ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
-
- if (check_stable_address_space(mm))
- goto unlock_abort;
-
- if (pte_present(*ptep)) {
- unsigned long pfn = pte_pfn(*ptep);
-
- if (!is_zero_pfn(pfn))
- goto unlock_abort;
- flush = true;
- } else if (!pte_none(*ptep))
- goto unlock_abort;
-
- /*
- * Check for userfaultfd but do not deliver the fault. Instead,
- * just back off.
- */
- if (userfaultfd_missing(vma))
- goto unlock_abort;
-
- inc_mm_counter(mm, MM_ANONPAGES);
- page_add_new_anon_rmap(page, vma, addr, false);
- if (!is_zone_device_page(page))
- lru_cache_add_inactive_or_unevictable(page, vma);
- get_page(page);
-
- if (flush) {
- flush_cache_page(vma, addr, pte_pfn(*ptep));
- ptep_clear_flush_notify(vma, addr, ptep);
- set_pte_at_notify(mm, addr, ptep, entry);
- update_mmu_cache(vma, addr, ptep);
- } else {
- /* No need to invalidate - it was non-present before */
- set_pte_at(mm, addr, ptep, entry);
- update_mmu_cache(vma, addr, ptep);
- }
-
- pte_unmap_unlock(ptep, ptl);
- *src = MIGRATE_PFN_MIGRATE;
- return;
-
-unlock_abort:
- pte_unmap_unlock(ptep, ptl);
-abort:
- *src &= ~MIGRATE_PFN_MIGRATE;
-}
-
-/**
- * migrate_vma_pages() - migrate meta-data from src page to dst page
- * @migrate: migrate struct containing all migration information
- *
- * This migrates struct page meta-data from source struct page to destination
- * struct page. This effectively finishes the migration from source page to the
- * destination page.
- */
-void migrate_vma_pages(struct migrate_vma *migrate)
-{
- const unsigned long npages = migrate->npages;
- const unsigned long start = migrate->start;
- struct mmu_notifier_range range;
- unsigned long addr, i;
- bool notified = false;
-
- for (i = 0, addr = start; i < npages; addr += PAGE_SIZE, i++) {
- struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
- struct page *page = migrate_pfn_to_page(migrate->src[i]);
- struct address_space *mapping;
- int r;
-
- if (!newpage) {
- migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
- continue;
- }
-
- if (!page) {
- if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE))
- continue;
- if (!notified) {
- notified = true;
-
- mmu_notifier_range_init_owner(&range,
- MMU_NOTIFY_MIGRATE, 0, migrate->vma,
- migrate->vma->vm_mm, addr, migrate->end,
- migrate->pgmap_owner);
- mmu_notifier_invalidate_range_start(&range);
- }
- migrate_vma_insert_page(migrate, addr, newpage,
- &migrate->src[i]);
- continue;
- }
-
- mapping = page_mapping(page);
-
- 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 if (is_zone_device_page(newpage)) {
- /*
- * 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;
- }
-
- /*
- * No need to double call mmu_notifier->invalidate_range() callback as
- * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
- * did already call it.
- */
- if (notified)
- mmu_notifier_invalidate_range_only_end(&range);
-}
-EXPORT_SYMBOL(migrate_vma_pages);
-
-/**
- * migrate_vma_finalize() - restore CPU page table entry
- * @migrate: migrate struct containing all migration information
- *
- * This replaces the special migration pte entry with either a mapping to the
- * new page if migration was successful for that page, or to the original page
- * otherwise.
- *
- * This also unlocks the pages and puts them back on the lru, or drops the extra
- * refcount, for device pages.
- */
-void migrate_vma_finalize(struct migrate_vma *migrate)
-{
- const unsigned long npages = migrate->npages;
- unsigned long i;
-
- for (i = 0; i < npages; i++) {
- struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
- struct page *page = migrate_pfn_to_page(migrate->src[i]);
-
- if (!page) {
- if (newpage) {
- unlock_page(newpage);
- put_page(newpage);
- }
- continue;
- }
-
- if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE) || !newpage) {
- if (newpage) {
- unlock_page(newpage);
- put_page(newpage);
- }
- newpage = page;
- }
-
- remove_migration_ptes(page, newpage, false);
- unlock_page(page);
-
- 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);
- }
- }
-}
-EXPORT_SYMBOL(migrate_vma_finalize);
-#endif /* CONFIG_DEVICE_PRIVATE */
-
/*
* node_demotion[] example:
*
diff --git a/mm/migrate_device.c b/mm/migrate_device.c
new file mode 100644
index 00000000000000..749e0bab8e4779
--- /dev/null
+++ b/mm/migrate_device.c
@@ -0,0 +1,765 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Device Memory Migration functionality.
+ *
+ * Originally written by Jérôme Glisse.
+ */
+#include <linux/export.h>
+#include <linux/memremap.h>
+#include <linux/migrate.h>
+#include <linux/mm_inline.h>
+#include <linux/mmu_notifier.h>
+#include <linux/oom.h>
+#include <linux/pagewalk.h>
+#include <linux/rmap.h>
+#include <linux/swapops.h>
+#include "internal.h"
+
+static int migrate_vma_collect_skip(unsigned long start,
+ unsigned long end,
+ struct mm_walk *walk)
+{
+ struct migrate_vma *migrate = walk->private;
+ unsigned long addr;
+
+ for (addr = start; addr < end; addr += PAGE_SIZE) {
+ migrate->dst[migrate->npages] = 0;
+ migrate->src[migrate->npages++] = 0;
+ }
+
+ return 0;
+}
+
+static int migrate_vma_collect_hole(unsigned long start,
+ unsigned long end,
+ __always_unused int depth,
+ struct mm_walk *walk)
+{
+ struct migrate_vma *migrate = walk->private;
+ unsigned long addr;
+
+ /* Only allow populating anonymous memory. */
+ if (!vma_is_anonymous(walk->vma))
+ return migrate_vma_collect_skip(start, end, walk);
+
+ for (addr = start; addr < end; addr += PAGE_SIZE) {
+ migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
+ migrate->dst[migrate->npages] = 0;
+ migrate->npages++;
+ migrate->cpages++;
+ }
+
+ return 0;
+}
+
+static int migrate_vma_collect_pmd(pmd_t *pmdp,
+ unsigned long start,
+ unsigned long end,
+ struct mm_walk *walk)
+{
+ struct migrate_vma *migrate = walk->private;
+ struct vm_area_struct *vma = walk->vma;
+ struct mm_struct *mm = vma->vm_mm;
+ unsigned long addr = start, unmapped = 0;
+ spinlock_t *ptl;
+ pte_t *ptep;
+
+again:
+ if (pmd_none(*pmdp))
+ return migrate_vma_collect_hole(start, end, -1, walk);
+
+ if (pmd_trans_huge(*pmdp)) {
+ struct page *page;
+
+ ptl = pmd_lock(mm, pmdp);
+ if (unlikely(!pmd_trans_huge(*pmdp))) {
+ spin_unlock(ptl);
+ goto again;
+ }
+
+ page = pmd_page(*pmdp);
+ if (is_huge_zero_page(page)) {
+ spin_unlock(ptl);
+ split_huge_pmd(vma, pmdp, addr);
+ if (pmd_trans_unstable(pmdp))
+ return migrate_vma_collect_skip(start, end,
+ walk);
+ } else {
+ int ret;
+
+ get_page(page);
+ spin_unlock(ptl);
+ if (unlikely(!trylock_page(page)))
+ return migrate_vma_collect_skip(start, end,
+ walk);
+ ret = split_huge_page(page);
+ unlock_page(page);
+ put_page(page);
+ if (ret)
+ return migrate_vma_collect_skip(start, end,
+ walk);
+ if (pmd_none(*pmdp))
+ return migrate_vma_collect_hole(start, end, -1,
+ walk);
+ }
+ }
+
+ if (unlikely(pmd_bad(*pmdp)))
+ return migrate_vma_collect_skip(start, end, walk);
+
+ ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
+ arch_enter_lazy_mmu_mode();
+
+ for (; addr < end; addr += PAGE_SIZE, ptep++) {
+ unsigned long mpfn = 0, pfn;
+ struct page *page;
+ swp_entry_t entry;
+ pte_t pte;
+
+ pte = *ptep;
+
+ if (pte_none(pte)) {
+ if (vma_is_anonymous(vma)) {
+ mpfn = MIGRATE_PFN_MIGRATE;
+ migrate->cpages++;
+ }
+ goto next;
+ }
+
+ if (!pte_present(pte)) {
+ /*
+ * 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 = pfn_swap_entry_to_page(entry);
+ if (!(migrate->flags &
+ MIGRATE_VMA_SELECT_DEVICE_PRIVATE) ||
+ page->pgmap->owner != migrate->pgmap_owner)
+ goto next;
+
+ mpfn = migrate_pfn(page_to_pfn(page)) |
+ MIGRATE_PFN_MIGRATE;
+ if (is_writable_device_private_entry(entry))
+ mpfn |= MIGRATE_PFN_WRITE;
+ } else {
+ if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
+ goto next;
+ pfn = pte_pfn(pte);
+ if (is_zero_pfn(pfn)) {
+ mpfn = MIGRATE_PFN_MIGRATE;
+ migrate->cpages++;
+ goto next;
+ }
+ 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 */
+ if (!page || !page->mapping || PageTransCompound(page)) {
+ mpfn = 0;
+ goto next;
+ }
+
+ /*
+ * By getting a reference on the page we pin it and that blocks
+ * any kind of migration. Side effect is that it "freezes" the
+ * pte.
+ *
+ * We drop this reference after isolating the page from the lru
+ * for non device page (device page are not on the lru and thus
+ * can't be dropped from it).
+ */
+ get_page(page);
+
+ /*
+ * Optimize for the common case where page is only mapped once
+ * in one process. If we can lock the page, then we can safely
+ * set up a special migration page table entry now.
+ */
+ if (trylock_page(page)) {
+ pte_t swp_pte;
+
+ migrate->cpages++;
+ ptep_get_and_clear(mm, addr, ptep);
+
+ /* Setup special migration page table entry */
+ if (mpfn & MIGRATE_PFN_WRITE)
+ entry = make_writable_migration_entry(
+ page_to_pfn(page));
+ else
+ entry = make_readable_migration_entry(
+ page_to_pfn(page));
+ swp_pte = swp_entry_to_pte(entry);
+ if (pte_present(pte)) {
+ if (pte_soft_dirty(pte))
+ swp_pte = pte_swp_mksoft_dirty(swp_pte);
+ if (pte_uffd_wp(pte))
+ swp_pte = pte_swp_mkuffd_wp(swp_pte);
+ } else {
+ if (pte_swp_soft_dirty(pte))
+ swp_pte = pte_swp_mksoft_dirty(swp_pte);
+ if (pte_swp_uffd_wp(pte))
+ swp_pte = pte_swp_mkuffd_wp(swp_pte);
+ }
+ set_pte_at(mm, addr, ptep, swp_pte);
+
+ /*
+ * This is like regular unmap: we remove the rmap and
+ * drop page refcount. Page won't be freed, as we took
+ * a reference just above.
+ */
+ page_remove_rmap(page, false);
+ put_page(page);
+
+ if (pte_present(pte))
+ unmapped++;
+ } else {
+ put_page(page);
+ mpfn = 0;
+ }
+
+next:
+ migrate->dst[migrate->npages] = 0;
+ migrate->src[migrate->npages++] = mpfn;
+ }
+ arch_leave_lazy_mmu_mode();
+ pte_unmap_unlock(ptep - 1, ptl);
+
+ /* Only flush the TLB if we actually modified any entries */
+ if (unmapped)
+ flush_tlb_range(walk->vma, start, end);
+
+ return 0;
+}
+
+static const struct mm_walk_ops migrate_vma_walk_ops = {
+ .pmd_entry = migrate_vma_collect_pmd,
+ .pte_hole = migrate_vma_collect_hole,
+};
+
+/*
+ * migrate_vma_collect() - collect pages over a range of virtual addresses
+ * @migrate: migrate struct containing all migration information
+ *
+ * This will walk the CPU page table. For each virtual address backed by a
+ * valid page, it updates the src array and takes a reference on the page, in
+ * order to pin the page until we lock it and unmap it.
+ */
+static void migrate_vma_collect(struct migrate_vma *migrate)
+{
+ struct mmu_notifier_range range;
+
+ /*
+ * Note that the pgmap_owner is passed to the mmu notifier callback so
+ * that the registered device driver can skip invalidating device
+ * private page mappings that won't be migrated.
+ */
+ mmu_notifier_range_init_owner(&range, MMU_NOTIFY_MIGRATE, 0,
+ migrate->vma, migrate->vma->vm_mm, migrate->start, migrate->end,
+ migrate->pgmap_owner);
+ mmu_notifier_invalidate_range_start(&range);
+
+ walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end,
+ &migrate_vma_walk_ops, migrate);
+
+ mmu_notifier_invalidate_range_end(&range);
+ migrate->end = migrate->start + (migrate->npages << PAGE_SHIFT);
+}
+
+/*
+ * migrate_vma_check_page() - check if page is pinned or not
+ * @page: struct page to check
+ *
+ * Pinned pages cannot be migrated. This is the same test as in
+ * folio_migrate_mapping(), except that here we allow migration of a
+ * ZONE_DEVICE page.
+ */
+static bool migrate_vma_check_page(struct page *page)
+{
+ /*
+ * One extra ref because caller holds an extra reference, either from
+ * isolate_lru_page() for a regular page, or migrate_vma_collect() for
+ * a device page.
+ */
+ int extra = 1;
+
+ /*
+ * FIXME support THP (transparent huge page), it is bit more complex to
+ * check them than regular pages, because they can be mapped with a pmd
+ * or with a pte (split pte mapping).
+ */
+ if (PageCompound(page))
+ return false;
+
+ /* Page from ZONE_DEVICE have one extra reference */
+ if (is_zone_device_page(page))
+ extra++;
+
+ /* For file back page */
+ if (page_mapping(page))
+ extra += 1 + page_has_private(page);
+
+ if ((page_count(page) - extra) > page_mapcount(page))
+ return false;
+
+ return true;
+}
+
+/*
+ * migrate_vma_unmap() - replace page mapping with special migration pte entry
+ * @migrate: migrate struct containing all migration information
+ *
+ * Isolate pages from the LRU and replace mappings (CPU page table pte) with a
+ * special migration pte entry and check if it has been pinned. Pinned pages are
+ * restored because we cannot migrate them.
+ *
+ * This is the last step before we call the device driver callback to allocate
+ * destination memory and copy contents of original page over to new page.
+ */
+static void migrate_vma_unmap(struct migrate_vma *migrate)
+{
+ const unsigned long npages = migrate->npages;
+ unsigned long i, restore = 0;
+ bool allow_drain = true;
+
+ lru_add_drain();
+
+ for (i = 0; i < npages; i++) {
+ struct page *page = migrate_pfn_to_page(migrate->src[i]);
+
+ if (!page)
+ continue;
+
+ /* 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)) {
+ migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
+ migrate->cpages--;
+ restore++;
+ continue;
+ }
+
+ /* Drop the reference we took in collect */
+ put_page(page);
+ }
+
+ if (page_mapped(page))
+ try_to_migrate(page, 0);
+
+ if (page_mapped(page) || !migrate_vma_check_page(page)) {
+ if (!is_zone_device_page(page)) {
+ get_page(page);
+ putback_lru_page(page);
+ }
+
+ migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
+ migrate->cpages--;
+ restore++;
+ continue;
+ }
+ }
+
+ for (i = 0; i < npages && restore; i++) {
+ struct page *page = migrate_pfn_to_page(migrate->src[i]);
+
+ if (!page || (migrate->src[i] & MIGRATE_PFN_MIGRATE))
+ continue;
+
+ remove_migration_ptes(page, page, false);
+
+ migrate->src[i] = 0;
+ unlock_page(page);
+ put_page(page);
+ restore--;
+ }
+}
+
+/**
+ * migrate_vma_setup() - prepare to migrate a range of memory
+ * @args: contains the vma, start, and pfns arrays for the migration
+ *
+ * Returns: negative errno on failures, 0 when 0 or more pages were migrated
+ * without an error.
+ *
+ * Prepare to migrate a range of memory virtual address range by collecting all
+ * the pages backing each virtual address in the range, saving them inside the
+ * src array. Then lock those pages and unmap them. Once the pages are locked
+ * and unmapped, check whether each page is pinned or not. Pages that aren't
+ * pinned have the MIGRATE_PFN_MIGRATE flag set (by this function) in the
+ * corresponding src array entry. Then restores any pages that are pinned, by
+ * remapping and unlocking those pages.
+ *
+ * The caller should then allocate destination memory and copy source memory to
+ * it for all those entries (ie with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE
+ * flag set). Once these are allocated and copied, the caller must update each
+ * corresponding entry in the dst array with the pfn value of the destination
+ * page and with MIGRATE_PFN_VALID. Destination pages must be locked via
+ * lock_page().
+ *
+ * Note that the caller does not have to migrate all the pages that are marked
+ * with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration from
+ * device memory to system memory. If the caller cannot migrate a device page
+ * back to system memory, then it must return VM_FAULT_SIGBUS, which has severe
+ * consequences for the userspace process, so it must be avoided if at all
+ * possible.
+ *
+ * For empty entries inside CPU page table (pte_none() or pmd_none() is true) we
+ * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus
+ * allowing the caller to allocate device memory for those unbacked virtual
+ * addresses. For this the caller simply has to allocate device memory and
+ * properly set the destination entry like for regular migration. Note that
+ * this can still fail, and thus inside the device driver you must check if the
+ * migration was successful for those entries after calling migrate_vma_pages(),
+ * just like for regular migration.
+ *
+ * After that, the callers must call migrate_vma_pages() to go over each entry
+ * in the src array that has the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag
+ * set. If the corresponding entry in dst array has MIGRATE_PFN_VALID flag set,
+ * then migrate_vma_pages() to migrate struct page information from the source
+ * struct page to the destination struct page. If it fails to migrate the
+ * struct page information, then it clears the MIGRATE_PFN_MIGRATE flag in the
+ * src array.
+ *
+ * At this point all successfully migrated pages have an entry in the src
+ * array with MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set and the dst
+ * array entry with MIGRATE_PFN_VALID flag set.
+ *
+ * Once migrate_vma_pages() returns the caller may inspect which pages were
+ * successfully migrated, and which were not. Successfully migrated pages will
+ * have the MIGRATE_PFN_MIGRATE flag set for their src array entry.
+ *
+ * It is safe to update device page table after migrate_vma_pages() because
+ * both destination and source page are still locked, and the mmap_lock is held
+ * in read mode (hence no one can unmap the range being migrated).
+ *
+ * Once the caller is done cleaning up things and updating its page table (if it
+ * chose to do so, this is not an obligation) it finally calls
+ * migrate_vma_finalize() to update the CPU page table to point to new pages
+ * for successfully migrated pages or otherwise restore the CPU page table to
+ * point to the original source pages.
+ */
+int migrate_vma_setup(struct migrate_vma *args)
+{
+ long nr_pages = (args->end - args->start) >> PAGE_SHIFT;
+
+ args->start &= PAGE_MASK;
+ args->end &= PAGE_MASK;
+ if (!args->vma || is_vm_hugetlb_page(args->vma) ||
+ (args->vma->vm_flags & VM_SPECIAL) || vma_is_dax(args->vma))
+ return -EINVAL;
+ if (nr_pages <= 0)
+ return -EINVAL;
+ if (args->start < args->vma->vm_start ||
+ args->start >= args->vma->vm_end)
+ return -EINVAL;
+ if (args->end <= args->vma->vm_start || args->end > args->vma->vm_end)
+ return -EINVAL;
+ if (!args->src || !args->dst)
+ return -EINVAL;
+
+ memset(args->src, 0, sizeof(*args->src) * nr_pages);
+ args->cpages = 0;
+ args->npages = 0;
+
+ migrate_vma_collect(args);
+
+ if (args->cpages)
+ migrate_vma_unmap(args);
+
+ /*
+ * At this point pages are locked and unmapped, and thus they have
+ * stable content and can safely be copied to destination memory that
+ * is allocated by the drivers.
+ */
+ return 0;
+
+}
+EXPORT_SYMBOL(migrate_vma_setup);
+
+/*
+ * This code closely matches the code in:
+ * __handle_mm_fault()
+ * handle_pte_fault()
+ * do_anonymous_page()
+ * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE
+ * private page.
+ */
+static void migrate_vma_insert_page(struct migrate_vma *migrate,
+ unsigned long addr,
+ struct page *page,
+ unsigned long *src)
+{
+ struct vm_area_struct *vma = migrate->vma;
+ struct mm_struct *mm = vma->vm_mm;
+ bool flush = false;
+ spinlock_t *ptl;
+ pte_t entry;
+ pgd_t *pgdp;
+ p4d_t *p4dp;
+ pud_t *pudp;
+ pmd_t *pmdp;
+ pte_t *ptep;
+
+ /* Only allow populating anonymous memory */
+ if (!vma_is_anonymous(vma))
+ goto abort;
+
+ pgdp = pgd_offset(mm, addr);
+ p4dp = p4d_alloc(mm, pgdp, addr);
+ if (!p4dp)
+ goto abort;
+ pudp = pud_alloc(mm, p4dp, addr);
+ if (!pudp)
+ goto abort;
+ pmdp = pmd_alloc(mm, pudp, addr);
+ if (!pmdp)
+ goto abort;
+
+ if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
+ goto abort;
+
+ /*
+ * Use pte_alloc() instead of pte_alloc_map(). We can't run
+ * pte_offset_map() on pmds where a huge pmd might be created
+ * from a different thread.
+ *
+ * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when
+ * parallel threads are excluded by other means.
+ *
+ * Here we only have mmap_read_lock(mm).
+ */
+ if (pte_alloc(mm, pmdp))
+ goto abort;
+
+ /* See the comment in pte_alloc_one_map() */
+ if (unlikely(pmd_trans_unstable(pmdp)))
+ goto abort;
+
+ if (unlikely(anon_vma_prepare(vma)))
+ goto abort;
+ if (mem_cgroup_charge(page_folio(page), vma->vm_mm, GFP_KERNEL))
+ goto abort;
+
+ /*
+ * The memory barrier inside __SetPageUptodate makes sure that
+ * preceding stores to the page contents become visible before
+ * the set_pte_at() write.
+ */
+ __SetPageUptodate(page);
+
+ if (is_device_private_page(page)) {
+ swp_entry_t swp_entry;
+
+ if (vma->vm_flags & VM_WRITE)
+ swp_entry = make_writable_device_private_entry(
+ page_to_pfn(page));
+ else
+ swp_entry = make_readable_device_private_entry(
+ page_to_pfn(page));
+ entry = swp_entry_to_pte(swp_entry);
+ } else {
+ /*
+ * For now we only support migrating to un-addressable device
+ * memory.
+ */
+ if (is_zone_device_page(page)) {
+ pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
+ goto abort;
+ }
+ entry = mk_pte(page, vma->vm_page_prot);
+ if (vma->vm_flags & VM_WRITE)
+ entry = pte_mkwrite(pte_mkdirty(entry));
+ }
+
+ ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
+
+ if (check_stable_address_space(mm))
+ goto unlock_abort;
+
+ if (pte_present(*ptep)) {
+ unsigned long pfn = pte_pfn(*ptep);
+
+ if (!is_zero_pfn(pfn))
+ goto unlock_abort;
+ flush = true;
+ } else if (!pte_none(*ptep))
+ goto unlock_abort;
+
+ /*
+ * Check for userfaultfd but do not deliver the fault. Instead,
+ * just back off.
+ */
+ if (userfaultfd_missing(vma))
+ goto unlock_abort;
+
+ inc_mm_counter(mm, MM_ANONPAGES);
+ page_add_new_anon_rmap(page, vma, addr, false);
+ if (!is_zone_device_page(page))
+ lru_cache_add_inactive_or_unevictable(page, vma);
+ get_page(page);
+
+ if (flush) {
+ flush_cache_page(vma, addr, pte_pfn(*ptep));
+ ptep_clear_flush_notify(vma, addr, ptep);
+ set_pte_at_notify(mm, addr, ptep, entry);
+ update_mmu_cache(vma, addr, ptep);
+ } else {
+ /* No need to invalidate - it was non-present before */
+ set_pte_at(mm, addr, ptep, entry);
+ update_mmu_cache(vma, addr, ptep);
+ }
+
+ pte_unmap_unlock(ptep, ptl);
+ *src = MIGRATE_PFN_MIGRATE;
+ return;
+
+unlock_abort:
+ pte_unmap_unlock(ptep, ptl);
+abort:
+ *src &= ~MIGRATE_PFN_MIGRATE;
+}
+
+/**
+ * migrate_vma_pages() - migrate meta-data from src page to dst page
+ * @migrate: migrate struct containing all migration information
+ *
+ * This migrates struct page meta-data from source struct page to destination
+ * struct page. This effectively finishes the migration from source page to the
+ * destination page.
+ */
+void migrate_vma_pages(struct migrate_vma *migrate)
+{
+ const unsigned long npages = migrate->npages;
+ const unsigned long start = migrate->start;
+ struct mmu_notifier_range range;
+ unsigned long addr, i;
+ bool notified = false;
+
+ for (i = 0, addr = start; i < npages; addr += PAGE_SIZE, i++) {
+ struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
+ struct page *page = migrate_pfn_to_page(migrate->src[i]);
+ struct address_space *mapping;
+ int r;
+
+ if (!newpage) {
+ migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
+ continue;
+ }
+
+ if (!page) {
+ if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE))
+ continue;
+ if (!notified) {
+ notified = true;
+
+ mmu_notifier_range_init_owner(&range,
+ MMU_NOTIFY_MIGRATE, 0, migrate->vma,
+ migrate->vma->vm_mm, addr, migrate->end,
+ migrate->pgmap_owner);
+ mmu_notifier_invalidate_range_start(&range);
+ }
+ migrate_vma_insert_page(migrate, addr, newpage,
+ &migrate->src[i]);
+ continue;
+ }
+
+ mapping = page_mapping(page);
+
+ 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 if (is_zone_device_page(newpage)) {
+ /*
+ * 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;
+ }
+
+ /*
+ * No need to double call mmu_notifier->invalidate_range() callback as
+ * the above ptep_clear_flush_notify() inside migrate_vma_insert_page()
+ * did already call it.
+ */
+ if (notified)
+ mmu_notifier_invalidate_range_only_end(&range);
+}
+EXPORT_SYMBOL(migrate_vma_pages);
+
+/**
+ * migrate_vma_finalize() - restore CPU page table entry
+ * @migrate: migrate struct containing all migration information
+ *
+ * This replaces the special migration pte entry with either a mapping to the
+ * new page if migration was successful for that page, or to the original page
+ * otherwise.
+ *
+ * This also unlocks the pages and puts them back on the lru, or drops the extra
+ * refcount, for device pages.
+ */
+void migrate_vma_finalize(struct migrate_vma *migrate)
+{
+ const unsigned long npages = migrate->npages;
+ unsigned long i;
+
+ for (i = 0; i < npages; i++) {
+ struct page *newpage = migrate_pfn_to_page(migrate->dst[i]);
+ struct page *page = migrate_pfn_to_page(migrate->src[i]);
+
+ if (!page) {
+ if (newpage) {
+ unlock_page(newpage);
+ put_page(newpage);
+ }
+ continue;
+ }
+
+ if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE) || !newpage) {
+ if (newpage) {
+ unlock_page(newpage);
+ put_page(newpage);
+ }
+ newpage = page;
+ }
+
+ remove_migration_ptes(page, newpage, false);
+ unlock_page(page);
+
+ 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);
+ }
+ }
+}
+EXPORT_SYMBOL(migrate_vma_finalize);
--
2.30.2