1 files changed, 291 insertions, 0 deletions
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
new file mode 100644
index 000000000..f2b4abbca
--- /dev/null
+++ b/include/linux/migrate.h
@@ -0,0 +1,291 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_MIGRATE_H
+#define _LINUX_MIGRATE_H
+
+#include <linux/mm.h>
+#include <linux/mempolicy.h>
+#include <linux/migrate_mode.h>
+#include <linux/hugetlb.h>
+
+typedef struct page *new_page_t(struct page *page, unsigned long private);
+typedef void free_page_t(struct page *page, unsigned long private);
+
+/*
+ * Return values from addresss_space_operations.migratepage():
+ * - negative errno on page migration failure;
+ * - zero on page migration success;
+ */
+#define MIGRATEPAGE_SUCCESS		0
+
+enum migrate_reason {
+	MR_COMPACTION,
+	MR_MEMORY_FAILURE,
+	MR_MEMORY_HOTPLUG,
+	MR_SYSCALL,		/* also applies to cpusets */
+	MR_MEMPOLICY_MBIND,
+	MR_NUMA_MISPLACED,
+	MR_CONTIG_RANGE,
+	MR_TYPES
+};
+
+/* In mm/debug.c; also keep sync with include/trace/events/migrate.h */
+extern char *migrate_reason_names[MR_TYPES];
+
+static inline struct page *new_page_nodemask(struct page *page,
+				int preferred_nid, nodemask_t *nodemask)
+{
+	gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL;
+	unsigned int order = 0;
+	struct page *new_page = NULL;
+
+	if (PageHuge(page))
+		return alloc_huge_page_nodemask(page_hstate(compound_head(page)),
+				preferred_nid, nodemask);
+
+	if (PageTransHuge(page)) {
+		gfp_mask |= GFP_TRANSHUGE;
+		order = HPAGE_PMD_ORDER;
+	}
+
+	if (PageHighMem(page) || (zone_idx(page_zone(page)) == ZONE_MOVABLE))
+		gfp_mask |= __GFP_HIGHMEM;
+
+	new_page = __alloc_pages_nodemask(gfp_mask, order,
+				preferred_nid, nodemask);
+
+	if (new_page && PageTransHuge(new_page))
+		prep_transhuge_page(new_page);
+
+	return new_page;
+}
+
+#ifdef CONFIG_MIGRATION
+
+extern void putback_movable_pages(struct list_head *l);
+extern int migrate_page(struct address_space *mapping,
+			struct page *newpage, struct page *page,
+			enum migrate_mode mode);
+extern int migrate_pages(struct list_head *l, new_page_t new, free_page_t free,
+		unsigned long private, enum migrate_mode mode, int reason);
+extern int isolate_movable_page(struct page *page, isolate_mode_t mode);
+extern void putback_movable_page(struct page *page);
+
+extern int migrate_prep(void);
+extern int migrate_prep_local(void);
+extern void migrate_page_states(struct page *newpage, struct page *page);
+extern void migrate_page_copy(struct page *newpage, struct page *page);
+extern int migrate_huge_page_move_mapping(struct address_space *mapping,
+				  struct page *newpage, struct page *page);
+extern int migrate_page_move_mapping(struct address_space *mapping,
+		struct page *newpage, struct page *page,
+		struct buffer_head *head, enum migrate_mode mode,
+		int extra_count);
+#else
+
+static inline void putback_movable_pages(struct list_head *l) {}
+static inline int migrate_pages(struct list_head *l, new_page_t new,
+		free_page_t free, unsigned long private, enum migrate_mode mode,
+		int reason)
+	{ return -ENOSYS; }
+static inline int isolate_movable_page(struct page *page, isolate_mode_t mode)
+	{ return -EBUSY; }
+
+static inline int migrate_prep(void) { return -ENOSYS; }
+static inline int migrate_prep_local(void) { return -ENOSYS; }
+
+static inline void migrate_page_states(struct page *newpage, struct page *page)
+{
+}
+
+static inline void migrate_page_copy(struct page *newpage,
+				     struct page *page) {}
+
+static inline int migrate_huge_page_move_mapping(struct address_space *mapping,
+				  struct page *newpage, struct page *page)
+{
+	return -ENOSYS;
+}
+
+#endif /* CONFIG_MIGRATION */
+
+#ifdef CONFIG_COMPACTION
+extern int PageMovable(struct page *page);
+extern void __SetPageMovable(struct page *page, struct address_space *mapping);
+extern void __ClearPageMovable(struct page *page);
+#else
+static inline int PageMovable(struct page *page) { return 0; };
+static inline void __SetPageMovable(struct page *page,
+				struct address_space *mapping)
+{
+}
+static inline void __ClearPageMovable(struct page *page)
+{
+}
+#endif
+
+#ifdef CONFIG_NUMA_BALANCING
+extern bool pmd_trans_migrating(pmd_t pmd);
+extern int migrate_misplaced_page(struct page *page,
+				  struct vm_area_struct *vma, int node);
+#else
+static inline bool pmd_trans_migrating(pmd_t pmd)
+{
+	return false;
+}
+static inline int migrate_misplaced_page(struct page *page,
+					 struct vm_area_struct *vma, int node)
+{
+	return -EAGAIN; /* can't migrate now */
+}
+#endif /* CONFIG_NUMA_BALANCING */
+
+#if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
+extern int migrate_misplaced_transhuge_page(struct mm_struct *mm,
+			struct vm_area_struct *vma,
+			pmd_t *pmd, pmd_t entry,
+			unsigned long address,
+			struct page *page, int node);
+#else
+static inline int migrate_misplaced_transhuge_page(struct mm_struct *mm,
+			struct vm_area_struct *vma,
+			pmd_t *pmd, pmd_t entry,
+			unsigned long address,
+			struct page *page, int node)
+{
+	return -EAGAIN;
+}
+#endif /* CONFIG_NUMA_BALANCING && CONFIG_TRANSPARENT_HUGEPAGE*/
+
+
+#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_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)
+{
+	if (!(mpfn & MIGRATE_PFN_VALID))
+		return NULL;
+	return pfn_to_page(mpfn >> MIGRATE_PFN_SHIFT);
+}
+
+static inline unsigned long migrate_pfn(unsigned long pfn)
+{
+	return (pfn << MIGRATE_PFN_SHIFT) | MIGRATE_PFN_VALID;
+}
+
+/*
+ * struct migrate_vma_ops - migrate operation callback
+ *
+ * @alloc_and_copy: alloc destination memory and copy source memory to it
+ * @finalize_and_map: allow caller to map the successfully migrated pages
+ *
+ *
+ * The alloc_and_copy() callback happens once all source pages have been locked,
+ * unmapped and checked (checked whether pinned or not). All pages that can be
+ * migrated will have an entry in the src array set with the pfn value of the
+ * page and with the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set (other
+ * flags might be set but should be ignored by the callback).
+ *
+ * The alloc_and_copy() callback can 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
+ * callback must update each corresponding entry in the dst array with the pfn
+ * value of the destination page and with the MIGRATE_PFN_VALID and
+ * MIGRATE_PFN_LOCKED flags set (destination pages must have their struct pages
+ * locked, via lock_page()).
+ *
+ * At this point the alloc_and_copy() callback is done and returns.
+ *
+ * Note that the callback 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 (ie the MIGRATE_PFN_DEVICE flag is also
+ * set in the src array entry). If the device driver cannot migrate a device
+ * page back to system memory, then it must set the corresponding dst array
+ * entry to MIGRATE_PFN_ERROR. This will trigger a SIGBUS if CPU tries to
+ * access any of the virtual addresses originally backed by this page. Because
+ * a SIGBUS is such a severe result for the userspace process, the device
+ * driver should avoid setting MIGRATE_PFN_ERROR unless it is really in an
+ * unrecoverable state.
+ *
+ * For empty entry 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 device driver to allocate device memory for those unback virtual
+ * address. For this the device driver simply have to allocate device memory
+ * and properly set the destination entry like for regular migration. Note that
+ * this can still fails and thus inside the device driver must check if the
+ * migration was successful for those entry inside the finalize_and_map()
+ * callback just like for regular migration.
+ *
+ * THE alloc_and_copy() CALLBACK MUST NOT CHANGE ANY OF THE SRC ARRAY ENTRIES
+ * OR BAD THINGS WILL HAPPEN !
+ *
+ *
+ * The finalize_and_map() callback happens after struct page migration from
+ * source to destination (destination struct pages are the struct pages for the
+ * memory allocated by the alloc_and_copy() callback).  Migration can fail, and
+ * thus the finalize_and_map() allows the driver to 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 from within the finalize_and_map()
+ * callback because both destination and source page are still locked, and the
+ * mmap_sem is held in read mode (hence no one can unmap the range being
+ * migrated).
+ *
+ * Once callback is done cleaning up things and updating its page table (if it
+ * chose to do so, this is not an obligation) then it returns. At this point,
+ * the HMM core will finish up the final steps, and the migration is complete.
+ *
+ * THE finalize_and_map() CALLBACK MUST NOT CHANGE ANY OF THE SRC OR DST ARRAY
+ * ENTRIES OR BAD THINGS WILL HAPPEN !
+ */
+struct migrate_vma_ops {
+	void (*alloc_and_copy)(struct vm_area_struct *vma,
+			       const unsigned long *src,
+			       unsigned long *dst,
+			       unsigned long start,
+			       unsigned long end,
+			       void *private);
+	void (*finalize_and_map)(struct vm_area_struct *vma,
+				 const unsigned long *src,
+				 const unsigned long *dst,
+				 unsigned long start,
+				 unsigned long end,
+				 void *private);
+};
+
+#if defined(CONFIG_MIGRATE_VMA_HELPER)
+int migrate_vma(const struct migrate_vma_ops *ops,
+		struct vm_area_struct *vma,
+		unsigned long start,
+		unsigned long end,
+		unsigned long *src,
+		unsigned long *dst,
+		void *private);
+#else
+static inline int migrate_vma(const struct migrate_vma_ops *ops,
+			      struct vm_area_struct *vma,
+			      unsigned long start,
+			      unsigned long end,
+			      unsigned long *src,
+			      unsigned long *dst,
+			      void *private)
+{
+	return -EINVAL;
+}
+#endif /* IS_ENABLED(CONFIG_MIGRATE_VMA_HELPER) */
+
+#endif /* CONFIG_MIGRATION */
+
+#endif /* _LINUX_MIGRATE_H */