mm: convert migrate_pages() to work on folios

Almost all of the callers & implementors of migrate_pages() were already
converted to use folios.  compaction_alloc() & compaction_free() are
trivial to convert a part of this patch and not worth splitting out.

Link: https://lkml.kernel.org/r/20230513001101.276972-1-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/mm/page_migration.rst

@@ -73,14 +73,13 @@ In kernel use of migrate_pages()
    It also prevents the swapper or other scans from encountering
    the page.
 
-2. We need to have a function of type new_page_t that can be
+2. We need to have a function of type new_folio_t that can be
    passed to migrate_pages(). This function should figure out
-   how to allocate the correct new page given the old page.
+   how to allocate the correct new folio given the old folio.
 
 3. The migrate_pages() function is called which attempts
    to do the migration. It will call the function to allocate
-   the new page for each page that is considered for
-   moving.
+   the new folio for each folio that is considered for moving.
 
 How migrate_pages() works
 =========================

Documentation/translations/zh_CN/mm/page_migration.rst

@@ -55,7 +55,7 @@ mbind()设置一个新的内存策略。一个进程的页面也可以通过sys_
    消失。它还可以防止交换器或其他扫描器遇到该页。
 
 
-2. 我们需要有一个new_page_t类型的函数，可以传递给migrate_pages()。这个函数应该计算
+2. 我们需要有一个new_folio_t类型的函数，可以传递给migrate_pages()。这个函数应该计算
    出如何在给定的旧页面中分配正确的新页面。
 
 3. migrate_pages()函数被调用，它试图进行迁移。它将调用该函数为每个被考虑迁移的页面分

include/linux/migrate.h

@@ -7,8 +7,8 @@
 #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);
+typedef struct folio *new_folio_t(struct folio *folio, unsigned long private);
+typedef void free_folio_t(struct folio *folio, unsigned long private);
 
 struct migration_target_control;
 
@@ -67,10 +67,10 @@ int migrate_folio_extra(struct address_space *mapping, struct folio *dst,
 		struct folio *src, enum migrate_mode mode, int extra_count);
 int migrate_folio(struct address_space *mapping, struct folio *dst,
 		struct folio *src, enum migrate_mode mode);
-int migrate_pages(struct list_head *l, new_page_t new, free_page_t free,
+int migrate_pages(struct list_head *l, new_folio_t new, free_folio_t free,
 		  unsigned long private, enum migrate_mode mode, int reason,
 		  unsigned int *ret_succeeded);
-struct page *alloc_migration_target(struct page *page, unsigned long private);
+struct folio *alloc_migration_target(struct folio *src, unsigned long private);
 bool isolate_movable_page(struct page *page, isolate_mode_t mode);
 
 int migrate_huge_page_move_mapping(struct address_space *mapping,
@@ -85,11 +85,11 @@ int folio_migrate_mapping(struct address_space *mapping,
 #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, unsigned int *ret_succeeded)
+static inline int migrate_pages(struct list_head *l, new_folio_t new,
+		free_folio_t free, unsigned long private,
+		enum migrate_mode mode, int reason, unsigned int *ret_succeeded)
 	{ return -ENOSYS; }
-static inline struct page *alloc_migration_target(struct page *page,
+static inline struct folio *alloc_migration_target(struct folio *src,
 		unsigned long private)
 	{ return NULL; }
 static inline bool isolate_movable_page(struct page *page, isolate_mode_t mode)

mm/compaction.c

@@ -1685,11 +1685,10 @@ static void isolate_freepages(struct compact_control *cc)
  * This is a migrate-callback that "allocates" freepages by taking pages
  * from the isolated freelists in the block we are migrating to.
  */
-static struct page *compaction_alloc(struct page *migratepage,
-					unsigned long data)
+static struct folio *compaction_alloc(struct folio *src, unsigned long data)
 {
 	struct compact_control *cc = (struct compact_control *)data;
-	struct page *freepage;
+	struct folio *dst;
 
 	if (list_empty(&cc->freepages)) {
 		isolate_freepages(cc);
@@ -1698,11 +1697,11 @@ static struct page *compaction_alloc(struct page *migratepage,
 			return NULL;
 	}
 
-	freepage = list_entry(cc->freepages.next, struct page, lru);
-	list_del(&freepage->lru);
+	dst = list_entry(cc->freepages.next, struct folio, lru);
+	list_del(&dst->lru);
 	cc->nr_freepages--;
 
-	return freepage;
+	return dst;
 }
 
 /*
@@ -1710,11 +1709,11 @@ static struct page *compaction_alloc(struct page *migratepage,
  * freelist.  All pages on the freelist are from the same zone, so there is no
  * special handling needed for NUMA.
  */
-static void compaction_free(struct page *page, unsigned long data)
+static void compaction_free(struct folio *dst, unsigned long data)
 {
 	struct compact_control *cc = (struct compact_control *)data;
 
-	list_add(&page->lru, &cc->freepages);
+	list_add(&dst->lru, &cc->freepages);
 	cc->nr_freepages++;
 }
 

mm/mempolicy.c

@@ -1195,24 +1195,22 @@ int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
  * list of pages handed to migrate_pages()--which is how we get here--
  * is in virtual address order.
  */
-static struct page *new_page(struct page *page, unsigned long start)
+static struct folio *new_folio(struct folio *src, unsigned long start)
 {
-	struct folio *dst, *src = page_folio(page);
 	struct vm_area_struct *vma;
 	unsigned long address;
 	VMA_ITERATOR(vmi, current->mm, start);
 	gfp_t gfp = GFP_HIGHUSER_MOVABLE | __GFP_RETRY_MAYFAIL;
 
 	for_each_vma(vmi, vma) {
-		address = page_address_in_vma(page, vma);
+		address = page_address_in_vma(&src->page, vma);
 		if (address != -EFAULT)
 			break;
 	}
 
 	if (folio_test_hugetlb(src)) {
-		dst = alloc_hugetlb_folio_vma(folio_hstate(src),
+		return alloc_hugetlb_folio_vma(folio_hstate(src),
 				vma, address);
-		return &dst->page;
 	}
 
 	if (folio_test_large(src))
@@ -1221,9 +1219,8 @@ static struct page *new_page(struct page *page, unsigned long start)
 	/*
 	 * if !vma, vma_alloc_folio() will use task or system default policy
 	 */
-	dst = vma_alloc_folio(gfp, folio_order(src), vma, address,
+	return vma_alloc_folio(gfp, folio_order(src), vma, address,
 			folio_test_large(src));
-	return &dst->page;
 }
 #else
 
@@ -1239,7 +1236,7 @@ int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
 	return -ENOSYS;
 }
 
-static struct page *new_page(struct page *page, unsigned long start)
+static struct folio *new_folio(struct folio *src, unsigned long start)
 {
 	return NULL;
 }
@@ -1334,7 +1331,7 @@ static long do_mbind(unsigned long start, unsigned long len,
 
 		if (!list_empty(&pagelist)) {
 			WARN_ON_ONCE(flags & MPOL_MF_LAZY);
-			nr_failed = migrate_pages(&pagelist, new_page, NULL,
+			nr_failed = migrate_pages(&pagelist, new_folio, NULL,
 				start, MIGRATE_SYNC, MR_MEMPOLICY_MBIND, NULL);
 			if (nr_failed)
 				putback_movable_pages(&pagelist);

mm/vmscan.c

@@ -1621,9 +1621,10 @@ static void folio_check_dirty_writeback(struct folio *folio,
 		mapping->a_ops->is_dirty_writeback(folio, dirty, writeback);
 }
 
-static struct page *alloc_demote_page(struct page *page, unsigned long private)
+static struct folio *alloc_demote_folio(struct folio *src,
+		unsigned long private)
 {
-	struct page *target_page;
+	struct folio *dst;
 	nodemask_t *allowed_mask;
 	struct migration_target_control *mtc;
 
@@ -1641,14 +1642,14 @@ static struct page *alloc_demote_page(struct page *page, unsigned long private)
 	 */
 	mtc->nmask = NULL;
 	mtc->gfp_mask |= __GFP_THISNODE;
-	target_page = alloc_migration_target(page, (unsigned long)mtc);
-	if (target_page)
-		return target_page;
+	dst = alloc_migration_target(src, (unsigned long)mtc);
+	if (dst)
+		return dst;
 
 	mtc->gfp_mask &= ~__GFP_THISNODE;
 	mtc->nmask = allowed_mask;
 
-	return alloc_migration_target(page, (unsigned long)mtc);
+	return alloc_migration_target(src, (unsigned long)mtc);
 }
 
 /*
@@ -1683,7 +1684,7 @@ static unsigned int demote_folio_list(struct list_head *demote_folios,
 	node_get_allowed_targets(pgdat, &allowed_mask);
 
 	/* Demotion ignores all cpuset and mempolicy settings */
-	migrate_pages(demote_folios, alloc_demote_page, NULL,
+	migrate_pages(demote_folios, alloc_demote_folio, NULL,
 		      (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION,
 		      &nr_succeeded);