/* * Memory Migration functionality - linux/mm/migration.c * * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter * * Page migration was first developed in the context of the memory hotplug * project. The main authors of the migration code are: * * IWAMOTO Toshihiro <iwamoto@valinux.co.jp> * Hirokazu Takahashi <taka@valinux.co.jp> * Dave Hansen <haveblue@us.ibm.com> * Christoph Lameter */ #include <linux/migrate.h>#include <linux/export.h>#include <linux/swap.h>#include <linux/swapops.h>#include <linux/pagemap.h>#include <linux/buffer_head.h>#include <linux/mm_inline.h>#include <linux/nsproxy.h>#include <linux/pagevec.h>#include <linux/ksm.h>#include <linux/rmap.h>#include <linux/topology.h>#include <linux/cpu.h>#include <linux/cpuset.h>#include <linux/writeback.h>#include <linux/mempolicy.h>#include <linux/vmalloc.h>#include <linux/security.h>#include <linux/memcontrol.h>#include <linux/syscalls.h>#include <linux/hugetlb.h>#include <linux/hugetlb_cgroup.h>#include <linux/gfp.h>#include <linux/balloon_compaction.h>#include <linux/mmu_notifier.h> #include <asm/tlbflush.h> #define CREATE_TRACE_POINTS#include <trace/events/migrate.h> #include "internal.h" /* * migrate_prep() needs to be called before we start compiling a list of pages * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is * undesirable, use migrate_prep_local() */int migrate_prep(void){	/*	 * Clear the LRU lists so pages can be isolated.	 * Note that pages may be moved off the LRU after we have	 * drained them. Those pages will fail to migrate like other	 * pages that may be busy.	 */	lru_add_drain_all(); 	return 0;} /* Do the necessary work of migrate_prep but not if it involves other CPUs */int migrate_prep_local(void){	lru_add_drain(); 	return 0;} /* * Add isolated pages on the list back to the LRU under page lock * to avoid leaking evictable pages back onto unevictable list. */void putback_lru_pages(struct list_head *l){	struct page *page;	struct page *page2; 	list_for_each_entry_safe(page, page2, l, lru) {		list_del(&page->lru);		dec_zone_page_state(page, NR_ISOLATED_ANON +				page_is_file_cache(page));			putback_lru_page(page);	}} /* * Put previously isolated pages back onto the appropriate lists * from where they were once taken off for compaction/migration. * * This function shall be used instead of putback_lru_pages(), * whenever the isolated pageset has been built by isolate_migratepages_range() */void putback_movable_pages(struct list_head *l){	struct page *page;	struct page *page2; 	list_for_each_entry_safe(page, page2, l, lru) {		if (unlikely(PageHuge(page))) {			putback_active_hugepage(page);			continue;		}		list_del(&page->lru);		dec_zone_page_state(page, NR_ISOLATED_ANON +				page_is_file_cache(page));		if (unlikely(isolated_balloon_page(page)))			balloon_page_putback(page);		else			putback_lru_page(page);	}} /* * Restore a potential migration pte to a working pte entry */static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,				 unsigned long addr, void *old){	struct mm_struct *mm = vma->vm_mm;	swp_entry_t entry; 	pmd_t *pmd;	pte_t *ptep, pte; 	spinlock_t *ptl; 	if (unlikely(PageHuge(new))) {		ptep = huge_pte_offset(mm, addr);		if (!ptep)			goto out;		ptl = huge_pte_lockptr(hstate_vma(vma), mm, ptep);	} else {		pmd = mm_find_pmd(mm, addr);		if (!pmd)			goto out;		if (pmd_trans_huge(*pmd))			goto out; 		ptep = pte_offset_map(pmd, addr); 		/*		 * Peek to check is_swap_pte() before taking ptlock?  No, we		 * can race mremap's move_ptes(), which skips anon_vma lock.		 */ 		ptl = pte_lockptr(mm, pmd);	}  	spin_lock(ptl);	pte = *ptep;	if (!is_swap_pte(pte))		goto unlock; 	entry = pte_to_swp_entry(pte); 	if (!is_migration_entry(entry) ||	    migration_entry_to_page(entry) != old)		goto unlock; 	get_page(new);	pte = pte_mkold(mk_pte(new, vma->vm_page_prot));	if (pte_swp_soft_dirty(*ptep))		pte = pte_mksoft_dirty(pte);	if (is_write_migration_entry(entry))		pte = pte_mkwrite(pte);#ifdef CONFIG_HUGETLB_PAGE	if (PageHuge(new)) {		pte = pte_mkhuge(pte);		pte = arch_make_huge_pte(pte, vma, new, 0);	}#endif	flush_dcache_page(new);	set_pte_at(mm, addr, ptep, pte); 	if (PageHuge(new)) {		if (PageAnon(new))			hugepage_add_anon_rmap(new, vma, addr);		else			page_dup_rmap(new);	} else if (PageAnon(new))		page_add_anon_rmap(new, vma, addr);	else		page_add_file_rmap(new); 	/* No need to invalidate - it was non-present before */	update_mmu_cache(vma, addr, ptep);unlock:	pte_unmap_unlock(ptep, ptl);out:	return SWAP_AGAIN;} /* * Get rid of all migration entries and replace them by * references to the indicated page. */static void remove_migration_ptes(struct page *old, struct page *new){	rmap_walk(new, remove_migration_pte, old);} /* * Something used the pte of a page under migration. We need to * get to the page and wait until migration is finished. * When we return from this function the fault will be retried. */static void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,				spinlock_t *ptl){	pte_t pte;	swp_entry_t entry;	struct page *page; 	spin_lock(ptl);	pte = *ptep;	if (!is_swap_pte(pte))		goto out; 	entry = pte_to_swp_entry(pte);	if (!is_migration_entry(entry))		goto out; 	page = migration_entry_to_page(entry); 	/*	 * Once radix-tree replacement of page migration started, page_count	 * *must* be zero. And, we don't want to call wait_on_page_locked()	 * against a page without get_page().	 * So, we use get_page_unless_zero(), here. Even failed, page fault	 * will occur again.	 */	if (!get_page_unless_zero(page))		goto out;	pte_unmap_unlock(ptep, ptl);	wait_on_page_locked(page);	put_page(page);	return;out:	pte_unmap_unlock(ptep, ptl);} void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,				unsigned long address){	spinlock_t *ptl = pte_lockptr(mm, pmd);	pte_t *ptep = pte_offset_map(pmd, address);	__migration_entry_wait(mm, ptep, ptl);} void migration_entry_wait_huge(struct vm_area_struct *vma,		struct mm_struct *mm, pte_t *pte){	spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);	__migration_entry_wait(mm, pte, ptl);} #ifdef CONFIG_BLOCK/* Returns true if all buffers are successfully locked */static bool buffer_migrate_lock_buffers(struct buffer_head *head,							enum migrate_mode mode){	struct buffer_head *bh = head; 	/* Simple case, sync compaction */	if (mode != MIGRATE_ASYNC) {		do {			get_bh(bh);			lock_buffer(bh);			bh = bh->b_this_page; 		} while (bh != head); 		return true;	} 	/* async case, we cannot block on lock_buffer so use trylock_buffer */	do {		get_bh(bh);		if (!trylock_buffer(bh)) {			/*			 * We failed to lock the buffer and cannot stall in			 * async migration. Release the taken locks			 */			struct buffer_head *failed_bh = bh;			put_bh(failed_bh);			bh = head;			while (bh != failed_bh) {				unlock_buffer(bh);				put_bh(bh);				bh = bh->b_this_page;			}			return false;		} 		bh = bh->b_this_page;	} while (bh != head);	return true;}#elsestatic inline bool buffer_migrate_lock_buffers(struct buffer_head *head,							enum migrate_mode mode){	return true;}#endif /* CONFIG_BLOCK */ /* * Replace the page in the mapping. * * The number of remaining references must be: * 1 for anonymous pages without a mapping * 2 for pages with a mapping * 3 for pages with a mapping and PagePrivate/PagePrivate2 set. */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){	int expected_count = 1 + extra_count;	void **pslot; 	if (!mapping) {		/* Anonymous page without mapping */		if (page_count(page) != expected_count)			return -EAGAIN;		return MIGRATEPAGE_SUCCESS;	} 	spin_lock_irq(&mapping->tree_lock); 	pslot = radix_tree_lookup_slot(&mapping->page_tree, 					page_index(page)); 	expected_count += 1 + page_has_private(page);	if (page_count(page) != expected_count ||		radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {		spin_unlock_irq(&mapping->tree_lock);		return -EAGAIN;	} 	if (!page_freeze_refs(page, expected_count)) {		spin_unlock_irq(&mapping->tree_lock);		return -EAGAIN;	} 	/*	 * In the async migration case of moving a page with buffers, lock the	 * buffers using trylock before the mapping is moved. If the mapping	 * was moved, we later failed to lock the buffers and could not move	 * the mapping back due to an elevated page count, we would have to	 * block waiting on other references to be dropped.	 */	if (mode == MIGRATE_ASYNC && head &&			!buffer_migrate_lock_buffers(head, mode)) {		page_unfreeze_refs(page, expected_count);		spin_unlock_irq(&mapping->tree_lock);		return -EAGAIN;	} 	/*	 * Now we know that no one else is looking at the page.	 */	get_page(newpage);	/* add cache reference */	if (PageSwapCache(page)) {		SetPageSwapCache(newpage);		set_page_private(newpage, page_private(page));	} 	radix_tree_replace_slot(pslot, newpage); 	/*	 * Drop cache reference from old page by unfreezing	 * to one less reference.	 * We know this isn't the last reference.	 */	page_unfreeze_refs(page, expected_count - 1); 	/*	 * If moved to a different zone then also account	 * the page for that zone. Other VM counters will be	 * taken care of when we establish references to the	 * new page and drop references to the old page.	 *	 * Note that anonymous pages are accounted for	 * via NR_FILE_PAGES and NR_ANON_PAGES if they	 * are mapped to swap space.	 */	__dec_zone_page_state(page, NR_FILE_PAGES);	__inc_zone_page_state(newpage, NR_FILE_PAGES);	if (!PageSwapCache(page) && PageSwapBacked(page)) {		__dec_zone_page_state(page, NR_SHMEM);		__inc_zone_page_state(newpage, NR_SHMEM);	}	spin_unlock_irq(&mapping->tree_lock); 	return MIGRATEPAGE_SUCCESS;} /* * The expected number of remaining references is the same as that * of migrate_page_move_mapping(). */int migrate_huge_page_move_mapping(struct address_space *mapping,				   struct page *newpage, struct page *page){	int expected_count;	void **pslot; 	if (!mapping) {		if (page_count(page) != 1)			return -EAGAIN;		return MIGRATEPAGE_SUCCESS;	} 	spin_lock_irq(&mapping->tree_lock); 	pslot = radix_tree_lookup_slot(&mapping->page_tree,					page_index(page)); 	expected_count = 2 + page_has_private(page);	if (page_count(page) != expected_count ||		radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {		spin_unlock_irq(&mapping->tree_lock);		return -EAGAIN;	} 	if (!page_freeze_refs(page, expected_count)) {		spin_unlock_irq(&mapping->tree_lock);		return -EAGAIN;	} 	get_page(newpage); 	radix_tree_replace_slot(pslot, newpage); 	page_unfreeze_refs(page, expected_count - 1); 	spin_unlock_irq(&mapping->tree_lock);	return MIGRATEPAGE_SUCCESS;} /* * Gigantic pages are so large that we do not guarantee that page++ pointer * arithmetic will work across the entire page.  We need something more * specialized. */static void __copy_gigantic_page(struct page *dst, struct page *src,				int nr_pages){	int i;	struct page *dst_base = dst;	struct page *src_base = src; 	for (i = 0; i < nr_pages; ) {		cond_resched();		copy_highpage(dst, src); 		i++;		dst = mem_map_next(dst, dst_base, i);		src = mem_map_next(src, src_base, i);	}} static void copy_huge_page(struct page *dst, struct page *src){	int i;	int nr_pages; 	if (PageHuge(src)) {		/* hugetlbfs page */		struct hstate *h = page_hstate(src);		nr_pages = pages_per_huge_page(h); 		if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {			__copy_gigantic_page(dst, src, nr_pages);			return;		}	} else {		/* thp page */		BUG_ON(!PageTransHuge(src));		nr_pages = hpage_nr_pages(src);	} 	for (i = 0; i < nr_pages; i++) {		cond_resched();		copy_highpage(dst + i, src + i);	}} /* * Copy the page to its new location */void migrate_page_copy(struct page *newpage, struct page *page){	int cpupid; 

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