[PATCH v2 00/19] Convert aops->migratepage to aops->migrate_folio

[PATCH v2 00/19] Convert aops->migratepage to aops->migrate_folio

[Matthew Wilcox (Oracle)]

We're getting to the last aops that take a struct page.  The only
remaining ones are ->writepage, ->write_begin, ->write_end and
->error_remove_page.

Changes from v1:
 - Remove ->isolate_page from secretmem
 - Split the movable_operations from address_space_operations
 - Drop the conversions of balloon, zsmalloc and z3fold
 - Fix the build errors with hugetlbfs
 - Fix the kerneldoc errors
 - Fix the ;; typo

Matthew Wilcox (Oracle) (19):
  secretmem: Remove isolate_page
  mm: Convert all PageMovable users to movable_operations
  fs: Add aops->migrate_folio
  mm/migrate: Convert fallback_migrate_page() to
    fallback_migrate_folio()
  mm/migrate: Convert writeout() to take a folio
  mm/migrate: Convert buffer_migrate_page() to buffer_migrate_folio()
  mm/migrate: Convert expected_page_refs() to folio_expected_refs()
  btrfs: Convert btree_migratepage to migrate_folio
  nfs: Convert to migrate_folio
  mm/migrate: Convert migrate_page() to migrate_folio()
  mm/migrate: Add filemap_migrate_folio()
  btrfs: Convert btrfs_migratepage to migrate_folio
  ubifs: Convert to filemap_migrate_folio()
  f2fs: Convert to filemap_migrate_folio()
  aio: Convert to migrate_folio
  hugetlb: Convert to migrate_folio
  secretmem: Convert to migrate_folio
  fs: Remove aops->migratepage()
  mm/folio-compat: Remove migration compatibility functions

 Documentation/filesystems/locking.rst       |   5 +-
 Documentation/filesystems/vfs.rst           |  13 +-
 Documentation/vm/page_migration.rst         |  33 +--
 arch/powerpc/platforms/pseries/cmm.c        |  60 +----
 block/fops.c                                |   2 +-
 drivers/gpu/drm/i915/gem/i915_gem_userptr.c |   4 +-
 drivers/misc/vmw_balloon.c                  |  61 +----
 drivers/virtio/virtio_balloon.c             |  47 +---
 fs/aio.c                                    |  36 +--
 fs/btrfs/disk-io.c                          |  22 +-
 fs/btrfs/inode.c                            |  26 +--
 fs/ext2/inode.c                             |   4 +-
 fs/ext4/inode.c                             |   4 +-
 fs/f2fs/checkpoint.c                        |   4 +-
 fs/f2fs/data.c                              |  40 +---
 fs/f2fs/f2fs.h                              |   4 -
 fs/f2fs/node.c                              |   4 +-
 fs/gfs2/aops.c                              |   2 +-
 fs/hugetlbfs/inode.c                        |  23 +-
 fs/iomap/buffered-io.c                      |  25 --
 fs/nfs/file.c                               |   4 +-
 fs/nfs/internal.h                           |   6 +-
 fs/nfs/write.c                              |  16 +-
 fs/ntfs/aops.c                              |   6 +-
 fs/ocfs2/aops.c                             |   2 +-
 fs/ubifs/file.c                             |  29 +--
 fs/xfs/xfs_aops.c                           |   2 +-
 fs/zonefs/super.c                           |   2 +-
 include/linux/balloon_compaction.h          |   6 +-
 include/linux/buffer_head.h                 |  10 +
 include/linux/fs.h                          |  20 +-
 include/linux/iomap.h                       |   6 -
 include/linux/migrate.h                     |  48 ++--
 include/linux/page-flags.h                  |   2 +-
 include/linux/pagemap.h                     |   6 +
 include/uapi/linux/magic.h                  |   4 -
 mm/balloon_compaction.c                     |  10 +-
 mm/compaction.c                             |  34 ++-
 mm/folio-compat.c                           |  22 --
 mm/ksm.c                                    |   2 +-
 mm/migrate.c                                | 238 ++++++++++++--------
 mm/migrate_device.c                         |   3 +-
 mm/secretmem.c                              |  13 +-
 mm/shmem.c                                  |   2 +-
 mm/swap_state.c                             |   2 +-
 mm/util.c                                   |   4 +-
 mm/z3fold.c                                 |  82 +------
 mm/zsmalloc.c                               | 102 ++-------
 48 files changed, 367 insertions(+), 735 deletions(-)

-- 
2.35.1


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http://lists.infradead.org/mailman/listinfo/linux-mtd/

[PATCH v2 01/19] secretmem: Remove isolate_page

[Matthew Wilcox (Oracle)]

The isolate_page operation is never called for filesystems, only
for device drivers which call SetPageMovable.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/secretmem.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/mm/secretmem.c b/mm/secretmem.c
index 206ed6b40c1d..1c7f1775b56e 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -133,11 +133,6 @@ static const struct file_operations secretmem_fops = {
 	.mmap		= secretmem_mmap,
 };
 
-static bool secretmem_isolate_page(struct page *page, isolate_mode_t mode)
-{
-	return false;
-}
-
 static int secretmem_migratepage(struct address_space *mapping,
 				 struct page *newpage, struct page *page,
 				 enum migrate_mode mode)
@@ -155,7 +150,6 @@ const struct address_space_operations secretmem_aops = {
 	.dirty_folio	= noop_dirty_folio,
 	.free_folio	= secretmem_free_folio,
 	.migratepage	= secretmem_migratepage,
-	.isolate_page	= secretmem_isolate_page,
 };
 
 static int secretmem_setattr(struct user_namespace *mnt_userns,
-- 
2.35.1


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http://lists.infradead.org/mailman/listinfo/linux-mtd/

[PATCH v2 02/19] mm: Convert all PageMovable users to movable_operations

[Matthew Wilcox (Oracle)]

These drivers are rather uncomfortably hammered into the
address_space_operations hole.  They aren't filesystems and don't behave
like filesystems.  They just need their own movable_operations structure,
which we can point to directly from page->mapping.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 arch/powerpc/platforms/pseries/cmm.c |  60 +---------------
 drivers/misc/vmw_balloon.c           |  61 +---------------
 drivers/virtio/virtio_balloon.c      |  47 +-----------
 include/linux/balloon_compaction.h   |   6 +-
 include/linux/fs.h                   |   2 -
 include/linux/migrate.h              |  26 +++++--
 include/linux/page-flags.h           |   2 +-
 include/uapi/linux/magic.h           |   4 --
 mm/balloon_compaction.c              |  10 ++-
 mm/compaction.c                      |  29 ++++----
 mm/migrate.c                         |  24 +++----
 mm/util.c                            |   4 +-
 mm/z3fold.c                          |  82 +++------------------
 mm/zsmalloc.c                        | 102 ++++++---------------------
 14 files changed, 94 insertions(+), 365 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/cmm.c b/arch/powerpc/platforms/pseries/cmm.c
index 15ed8206c463..5f4037c1d7fe 100644
--- a/arch/powerpc/platforms/pseries/cmm.c
+++ b/arch/powerpc/platforms/pseries/cmm.c
@@ -19,9 +19,6 @@
 #include <linux/stringify.h>
 #include <linux/swap.h>
 #include <linux/device.h>
-#include <linux/mount.h>
-#include <linux/pseudo_fs.h>
-#include <linux/magic.h>
 #include <linux/balloon_compaction.h>
 #include <asm/firmware.h>
 #include <asm/hvcall.h>
@@ -500,19 +497,6 @@ static struct notifier_block cmm_mem_nb = {
 };
 
 #ifdef CONFIG_BALLOON_COMPACTION
-static struct vfsmount *balloon_mnt;
-
-static int cmm_init_fs_context(struct fs_context *fc)
-{
-	return init_pseudo(fc, PPC_CMM_MAGIC) ? 0 : -ENOMEM;
-}
-
-static struct file_system_type balloon_fs = {
-	.name = "ppc-cmm",
-	.init_fs_context = cmm_init_fs_context,
-	.kill_sb = kill_anon_super,
-};
-
 static int cmm_migratepage(struct balloon_dev_info *b_dev_info,
 			   struct page *newpage, struct page *page,
 			   enum migrate_mode mode)
@@ -564,47 +548,13 @@ static int cmm_migratepage(struct balloon_dev_info *b_dev_info,
 	return MIGRATEPAGE_SUCCESS;
 }
 
-static int cmm_balloon_compaction_init(void)
+static void cmm_balloon_compaction_init(void)
 {
-	int rc;
-
 	balloon_devinfo_init(&b_dev_info);
 	b_dev_info.migratepage = cmm_migratepage;
-
-	balloon_mnt = kern_mount(&balloon_fs);
-	if (IS_ERR(balloon_mnt)) {
-		rc = PTR_ERR(balloon_mnt);
-		balloon_mnt = NULL;
-		return rc;
-	}
-
-	b_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
-	if (IS_ERR(b_dev_info.inode)) {
-		rc = PTR_ERR(b_dev_info.inode);
-		b_dev_info.inode = NULL;
-		kern_unmount(balloon_mnt);
-		balloon_mnt = NULL;
-		return rc;
-	}
-
-	b_dev_info.inode->i_mapping->a_ops = &balloon_aops;
-	return 0;
-}
-static void cmm_balloon_compaction_deinit(void)
-{
-	if (b_dev_info.inode)
-		iput(b_dev_info.inode);
-	b_dev_info.inode = NULL;
-	kern_unmount(balloon_mnt);
-	balloon_mnt = NULL;
 }
 #else /* CONFIG_BALLOON_COMPACTION */
-static int cmm_balloon_compaction_init(void)
-{
-	return 0;
-}
-
-static void cmm_balloon_compaction_deinit(void)
+static void cmm_balloon_compaction_init(void)
 {
 }
 #endif /* CONFIG_BALLOON_COMPACTION */
@@ -622,9 +572,7 @@ static int cmm_init(void)
 	if (!firmware_has_feature(FW_FEATURE_CMO) && !simulate)
 		return -EOPNOTSUPP;
 
-	rc = cmm_balloon_compaction_init();
-	if (rc)
-		return rc;
+	cmm_balloon_compaction_init();
 
 	rc = register_oom_notifier(&cmm_oom_nb);
 	if (rc < 0)
@@ -658,7 +606,6 @@ static int cmm_init(void)
 out_oom_notifier:
 	unregister_oom_notifier(&cmm_oom_nb);
 out_balloon_compaction:
-	cmm_balloon_compaction_deinit();
 	return rc;
 }
 
@@ -677,7 +624,6 @@ static void cmm_exit(void)
 	unregister_memory_notifier(&cmm_mem_nb);
 	cmm_free_pages(atomic_long_read(&loaned_pages));
 	cmm_unregister_sysfs(&cmm_dev);
-	cmm_balloon_compaction_deinit();
 }
 
 /**
diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
index 086ce77d9074..85dd6aa33df6 100644
--- a/drivers/misc/vmw_balloon.c
+++ b/drivers/misc/vmw_balloon.c
@@ -29,8 +29,6 @@
 #include <linux/rwsem.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
-#include <linux/mount.h>
-#include <linux/pseudo_fs.h>
 #include <linux/balloon_compaction.h>
 #include <linux/vmw_vmci_defs.h>
 #include <linux/vmw_vmci_api.h>
@@ -1730,20 +1728,6 @@ static inline void vmballoon_debugfs_exit(struct vmballoon *b)
 
 
 #ifdef CONFIG_BALLOON_COMPACTION
-
-static int vmballoon_init_fs_context(struct fs_context *fc)
-{
-	return init_pseudo(fc, BALLOON_VMW_MAGIC) ? 0 : -ENOMEM;
-}
-
-static struct file_system_type vmballoon_fs = {
-	.name           	= "balloon-vmware",
-	.init_fs_context	= vmballoon_init_fs_context,
-	.kill_sb        	= kill_anon_super,
-};
-
-static struct vfsmount *vmballoon_mnt;
-
 /**
  * vmballoon_migratepage() - migrates a balloon page.
  * @b_dev_info: balloon device information descriptor.
@@ -1862,21 +1846,6 @@ static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info,
 	return ret;
 }
 
-/**
- * vmballoon_compaction_deinit() - removes compaction related data.
- *
- * @b: pointer to the balloon.
- */
-static void vmballoon_compaction_deinit(struct vmballoon *b)
-{
-	if (!IS_ERR(b->b_dev_info.inode))
-		iput(b->b_dev_info.inode);
-
-	b->b_dev_info.inode = NULL;
-	kern_unmount(vmballoon_mnt);
-	vmballoon_mnt = NULL;
-}
-
 /**
  * vmballoon_compaction_init() - initialized compaction for the balloon.
  *
@@ -1888,33 +1857,15 @@ static void vmballoon_compaction_deinit(struct vmballoon *b)
  *
  * Return: zero on success or error code on failure.
  */
-static __init int vmballoon_compaction_init(struct vmballoon *b)
+static __init void vmballoon_compaction_init(struct vmballoon *b)
 {
-	vmballoon_mnt = kern_mount(&vmballoon_fs);
-	if (IS_ERR(vmballoon_mnt))
-		return PTR_ERR(vmballoon_mnt);
-
 	b->b_dev_info.migratepage = vmballoon_migratepage;
-	b->b_dev_info.inode = alloc_anon_inode(vmballoon_mnt->mnt_sb);
-
-	if (IS_ERR(b->b_dev_info.inode))
-		return PTR_ERR(b->b_dev_info.inode);
-
-	b->b_dev_info.inode->i_mapping->a_ops = &balloon_aops;
-	return 0;
 }
 
 #else /* CONFIG_BALLOON_COMPACTION */
-
-static void vmballoon_compaction_deinit(struct vmballoon *b)
-{
-}
-
-static int vmballoon_compaction_init(struct vmballoon *b)
+static inline void vmballoon_compaction_init(struct vmballoon *b)
 {
-	return 0;
 }
-
 #endif /* CONFIG_BALLOON_COMPACTION */
 
 static int __init vmballoon_init(void)
@@ -1939,9 +1890,7 @@ static int __init vmballoon_init(void)
 	 * balloon_devinfo_init() .
 	 */
 	balloon_devinfo_init(&balloon.b_dev_info);
-	error = vmballoon_compaction_init(&balloon);
-	if (error)
-		goto fail;
+	vmballoon_compaction_init(&balloon);
 
 	INIT_LIST_HEAD(&balloon.huge_pages);
 	spin_lock_init(&balloon.comm_lock);
@@ -1958,7 +1907,6 @@ static int __init vmballoon_init(void)
 	return 0;
 fail:
 	vmballoon_unregister_shrinker(&balloon);
-	vmballoon_compaction_deinit(&balloon);
 	return error;
 }
 
@@ -1985,8 +1933,5 @@ static void __exit vmballoon_exit(void)
 	 */
 	vmballoon_send_start(&balloon, 0);
 	vmballoon_pop(&balloon);
-
-	/* Only once we popped the balloon, compaction can be deinit */
-	vmballoon_compaction_deinit(&balloon);
 }
 module_exit(vmballoon_exit);
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index b9737da6c4dd..bd360b91e9d3 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -17,9 +17,6 @@
 #include <linux/oom.h>
 #include <linux/wait.h>
 #include <linux/mm.h>
-#include <linux/mount.h>
-#include <linux/magic.h>
-#include <linux/pseudo_fs.h>
 #include <linux/page_reporting.h>
 
 /*
@@ -42,10 +39,6 @@
 	(1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT))
 #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
 
-#ifdef CONFIG_BALLOON_COMPACTION
-static struct vfsmount *balloon_mnt;
-#endif
-
 enum virtio_balloon_vq {
 	VIRTIO_BALLOON_VQ_INFLATE,
 	VIRTIO_BALLOON_VQ_DEFLATE,
@@ -805,18 +798,6 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 
 	return MIGRATEPAGE_SUCCESS;
 }
-
-static int balloon_init_fs_context(struct fs_context *fc)
-{
-	return init_pseudo(fc, BALLOON_KVM_MAGIC) ? 0 : -ENOMEM;
-}
-
-static struct file_system_type balloon_fs = {
-	.name           = "balloon-kvm",
-	.init_fs_context = balloon_init_fs_context,
-	.kill_sb        = kill_anon_super,
-};
-
 #endif /* CONFIG_BALLOON_COMPACTION */
 
 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
@@ -909,19 +890,7 @@ static int virtballoon_probe(struct virtio_device *vdev)
 		goto out_free_vb;
 
 #ifdef CONFIG_BALLOON_COMPACTION
-	balloon_mnt = kern_mount(&balloon_fs);
-	if (IS_ERR(balloon_mnt)) {
-		err = PTR_ERR(balloon_mnt);
-		goto out_del_vqs;
-	}
-
 	vb->vb_dev_info.migratepage = virtballoon_migratepage;
-	vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
-	if (IS_ERR(vb->vb_dev_info.inode)) {
-		err = PTR_ERR(vb->vb_dev_info.inode);
-		goto out_kern_unmount;
-	}
-	vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
 #endif
 	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
 		/*
@@ -930,13 +899,13 @@ static int virtballoon_probe(struct virtio_device *vdev)
 		 */
 		if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
 			err = -ENOSPC;
-			goto out_iput;
+			goto out_del_vqs;
 		}
 		vb->balloon_wq = alloc_workqueue("balloon-wq",
 					WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
 		if (!vb->balloon_wq) {
 			err = -ENOMEM;
-			goto out_iput;
+			goto out_del_vqs;
 		}
 		INIT_WORK(&vb->report_free_page_work, report_free_page_func);
 		vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
@@ -1030,13 +999,7 @@ static int virtballoon_probe(struct virtio_device *vdev)
 out_del_balloon_wq:
 	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
 		destroy_workqueue(vb->balloon_wq);
-out_iput:
-#ifdef CONFIG_BALLOON_COMPACTION
-	iput(vb->vb_dev_info.inode);
-out_kern_unmount:
-	kern_unmount(balloon_mnt);
 out_del_vqs:
-#endif
 	vdev->config->del_vqs(vdev);
 out_free_vb:
 	kfree(vb);
@@ -1083,12 +1046,6 @@ static void virtballoon_remove(struct virtio_device *vdev)
 	}
 
 	remove_common(vb);
-#ifdef CONFIG_BALLOON_COMPACTION
-	if (vb->vb_dev_info.inode)
-		iput(vb->vb_dev_info.inode);
-
-	kern_unmount(balloon_mnt);
-#endif
 	kfree(vb);
 }
 
diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h
index edb7f6d41faa..5ca2d5699620 100644
--- a/include/linux/balloon_compaction.h
+++ b/include/linux/balloon_compaction.h
@@ -57,7 +57,6 @@ struct balloon_dev_info {
 	struct list_head pages;		/* Pages enqueued & handled to Host */
 	int (*migratepage)(struct balloon_dev_info *, struct page *newpage,
 			struct page *page, enum migrate_mode mode);
-	struct inode *inode;
 };
 
 extern struct page *balloon_page_alloc(void);
@@ -75,11 +74,10 @@ static inline void balloon_devinfo_init(struct balloon_dev_info *balloon)
 	spin_lock_init(&balloon->pages_lock);
 	INIT_LIST_HEAD(&balloon->pages);
 	balloon->migratepage = NULL;
-	balloon->inode = NULL;
 }
 
 #ifdef CONFIG_BALLOON_COMPACTION
-extern const struct address_space_operations balloon_aops;
+extern const struct movable_operations balloon_mops;
 
 /*
  * balloon_page_insert - insert a page into the balloon's page list and make
@@ -94,7 +92,7 @@ static inline void balloon_page_insert(struct balloon_dev_info *balloon,
 				       struct page *page)
 {
 	__SetPageOffline(page);
-	__SetPageMovable(page, balloon->inode->i_mapping);
+	__SetPageMovable(page, &balloon_mops);
 	set_page_private(page, (unsigned long)balloon);
 	list_add(&page->lru, &balloon->pages);
 }
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9ad5e3520fae..5d8ee3155ca2 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -367,8 +367,6 @@ struct address_space_operations {
 	 */
 	int (*migratepage) (struct address_space *,
 			struct page *, struct page *, enum migrate_mode);
-	bool (*isolate_page)(struct page *, isolate_mode_t);
-	void (*putback_page)(struct page *);
 	int (*launder_folio)(struct folio *);
 	bool (*is_partially_uptodate) (struct folio *, size_t from,
 			size_t count);
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 069a89e847f3..48aa4be04108 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -19,6 +19,13 @@ struct migration_target_control;
  */
 #define MIGRATEPAGE_SUCCESS		0
 
+struct movable_operations {
+	bool (*isolate_page)(struct page *, isolate_mode_t);
+	int (*migrate_page)(struct page *dst, struct page *src,
+			enum migrate_mode);
+	void (*putback_page)(struct page *);
+};
+
 /* Defined in mm/debug.c: */
 extern const char *migrate_reason_names[MR_TYPES];
 
@@ -91,13 +98,13 @@ static inline int next_demotion_node(int node)
 #endif
 
 #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);
+bool PageMovable(struct page *page);
+void __SetPageMovable(struct page *page, const struct movable_operations *ops);
+void __ClearPageMovable(struct page *page);
 #else
-static inline int PageMovable(struct page *page) { return 0; }
+static inline bool PageMovable(struct page *page) { return false; }
 static inline void __SetPageMovable(struct page *page,
-				struct address_space *mapping)
+		const struct movable_operations *ops)
 {
 }
 static inline void __ClearPageMovable(struct page *page)
@@ -110,6 +117,15 @@ static inline bool folio_test_movable(struct folio *folio)
 	return PageMovable(&folio->page);
 }
 
+static inline
+const struct movable_operations *page_movable_ops(struct page *page)
+{
+	VM_BUG_ON(!__PageMovable(page));
+
+	return (const struct movable_operations *)
+		((unsigned long)page->mapping - PAGE_MAPPING_MOVABLE);
+}
+
 #ifdef CONFIG_NUMA_BALANCING
 extern int migrate_misplaced_page(struct page *page,
 				  struct vm_area_struct *vma, int node);
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index e66f7aa3191d..3f5490f6f038 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -639,7 +639,7 @@ __PAGEFLAG(Reported, reported, PF_NO_COMPOUND)
  * structure which KSM associates with that merged page.  See ksm.h.
  *
  * PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is used for non-lru movable
- * page and then page->mapping points a struct address_space.
+ * page and then page->mapping points to a struct movable_operations.
  *
  * Please note that, confusingly, "page_mapping" refers to the inode
  * address_space which maps the page from disk; whereas "page_mapped"
diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
index f724129c0425..6325d1d0e90f 100644
--- a/include/uapi/linux/magic.h
+++ b/include/uapi/linux/magic.h
@@ -98,12 +98,8 @@
 
 /* Since UDF 2.01 is ISO 13346 based... */
 #define UDF_SUPER_MAGIC		0x15013346
-#define BALLOON_KVM_MAGIC	0x13661366
-#define ZSMALLOC_MAGIC		0x58295829
 #define DMA_BUF_MAGIC		0x444d4142	/* "DMAB" */
 #define DEVMEM_MAGIC		0x454d444d	/* "DMEM" */
-#define Z3FOLD_MAGIC		0x33
-#define PPC_CMM_MAGIC		0xc7571590
 #define SECRETMEM_MAGIC		0x5345434d	/* "SECM" */
 
 #endif /* __LINUX_MAGIC_H__ */
diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
index 4b8eab4b3f45..22c96fed70b5 100644
--- a/mm/balloon_compaction.c
+++ b/mm/balloon_compaction.c
@@ -228,10 +228,8 @@ static void balloon_page_putback(struct page *page)
 	spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
 }
 
-
 /* move_to_new_page() counterpart for a ballooned page */
-static int balloon_page_migrate(struct address_space *mapping,
-		struct page *newpage, struct page *page,
+static int balloon_page_migrate(struct page *newpage, struct page *page,
 		enum migrate_mode mode)
 {
 	struct balloon_dev_info *balloon = balloon_page_device(page);
@@ -250,11 +248,11 @@ static int balloon_page_migrate(struct address_space *mapping,
 	return balloon->migratepage(balloon, newpage, page, mode);
 }
 
-const struct address_space_operations balloon_aops = {
-	.migratepage = balloon_page_migrate,
+const struct movable_operations balloon_mops = {
+	.migrate_page = balloon_page_migrate,
 	.isolate_page = balloon_page_isolate,
 	.putback_page = balloon_page_putback,
 };
-EXPORT_SYMBOL_GPL(balloon_aops);
+EXPORT_SYMBOL_GPL(balloon_mops);
 
 #endif /* CONFIG_BALLOON_COMPACTION */
diff --git a/mm/compaction.c b/mm/compaction.c
index 1f89b969c12b..f23efba1d118 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -110,28 +110,27 @@ static void split_map_pages(struct list_head *list)
 }
 
 #ifdef CONFIG_COMPACTION
-
-int PageMovable(struct page *page)
+bool PageMovable(struct page *page)
 {
-	struct address_space *mapping;
+	const struct movable_operations *mops;
 
 	VM_BUG_ON_PAGE(!PageLocked(page), page);
 	if (!__PageMovable(page))
-		return 0;
+		return false;
 
-	mapping = page_mapping(page);
-	if (mapping && mapping->a_ops && mapping->a_ops->isolate_page)
-		return 1;
+	mops = page_movable_ops(page);
+	if (mops)
+		return true;
 
-	return 0;
+	return false;
 }
 EXPORT_SYMBOL(PageMovable);
 
-void __SetPageMovable(struct page *page, struct address_space *mapping)
+void __SetPageMovable(struct page *page, const struct movable_operations *mops)
 {
 	VM_BUG_ON_PAGE(!PageLocked(page), page);
-	VM_BUG_ON_PAGE((unsigned long)mapping & PAGE_MAPPING_MOVABLE, page);
-	page->mapping = (void *)((unsigned long)mapping | PAGE_MAPPING_MOVABLE);
+	VM_BUG_ON_PAGE((unsigned long)mops & PAGE_MAPPING_MOVABLE, page);
+	page->mapping = (void *)((unsigned long)mops | PAGE_MAPPING_MOVABLE);
 }
 EXPORT_SYMBOL(__SetPageMovable);
 
@@ -139,12 +138,10 @@ void __ClearPageMovable(struct page *page)
 {
 	VM_BUG_ON_PAGE(!PageMovable(page), page);
 	/*
-	 * Clear registered address_space val with keeping PAGE_MAPPING_MOVABLE
-	 * flag so that VM can catch up released page by driver after isolation.
-	 * With it, VM migration doesn't try to put it back.
+	 * This page still has the type of a movable page, but it's
+	 * actually not movable any more.
 	 */
-	page->mapping = (void *)((unsigned long)page->mapping &
-				PAGE_MAPPING_MOVABLE);
+	page->mapping = (void *)PAGE_MAPPING_MOVABLE;
 }
 EXPORT_SYMBOL(__ClearPageMovable);
 
diff --git a/mm/migrate.c b/mm/migrate.c
index e51588e95f57..3ce6fee87efa 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -59,7 +59,7 @@
 
 int isolate_movable_page(struct page *page, isolate_mode_t mode)
 {
-	struct address_space *mapping;
+	const struct movable_operations *mops;
 
 	/*
 	 * Avoid burning cycles with pages that are yet under __free_pages(),
@@ -97,10 +97,10 @@ int isolate_movable_page(struct page *page, isolate_mode_t mode)
 	if (!PageMovable(page) || PageIsolated(page))
 		goto out_no_isolated;
 
-	mapping = page_mapping(page);
-	VM_BUG_ON_PAGE(!mapping, page);
+	mops = page_movable_ops(page);
+	VM_BUG_ON_PAGE(!mops, page);
 
-	if (!mapping->a_ops->isolate_page(page, mode))
+	if (!mops->isolate_page(page, mode))
 		goto out_no_isolated;
 
 	/* Driver shouldn't use PG_isolated bit of page->flags */
@@ -120,10 +120,9 @@ int isolate_movable_page(struct page *page, isolate_mode_t mode)
 
 static void putback_movable_page(struct page *page)
 {
-	struct address_space *mapping;
+	const struct movable_operations *mops = page_movable_ops(page);
 
-	mapping = page_mapping(page);
-	mapping->a_ops->putback_page(page);
+	mops->putback_page(page);
 	ClearPageIsolated(page);
 }
 
@@ -846,16 +845,15 @@ static int fallback_migrate_page(struct address_space *mapping,
 static int move_to_new_folio(struct folio *dst, struct folio *src,
 				enum migrate_mode mode)
 {
-	struct address_space *mapping;
 	int rc = -EAGAIN;
 	bool is_lru = !__PageMovable(&src->page);
 
 	VM_BUG_ON_FOLIO(!folio_test_locked(src), src);
 	VM_BUG_ON_FOLIO(!folio_test_locked(dst), dst);
 
-	mapping = folio_mapping(src);
-
 	if (likely(is_lru)) {
+		struct address_space *mapping = folio_mapping(src);
+
 		if (!mapping)
 			rc = migrate_page(mapping, &dst->page, &src->page, mode);
 		else if (mapping->a_ops->migratepage)
@@ -872,6 +870,8 @@ static int move_to_new_folio(struct folio *dst, struct folio *src,
 			rc = fallback_migrate_page(mapping, &dst->page,
 							&src->page, mode);
 	} else {
+		const struct movable_operations *mops;
+
 		/*
 		 * In case of non-lru page, it could be released after
 		 * isolation step. In that case, we shouldn't try migration.
@@ -883,8 +883,8 @@ static int move_to_new_folio(struct folio *dst, struct folio *src,
 			goto out;
 		}
 
-		rc = mapping->a_ops->migratepage(mapping, &dst->page,
-						&src->page, mode);
+		mops = page_movable_ops(&src->page);
+		rc = mops->migrate_page(&dst->page, &src->page, mode);
 		WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
 				!folio_test_isolated(src));
 	}
diff --git a/mm/util.c b/mm/util.c
index 0837570c9225..53af0e79d3e4 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -804,10 +804,10 @@ struct address_space *folio_mapping(struct folio *folio)
 		return swap_address_space(folio_swap_entry(folio));
 
 	mapping = folio->mapping;
-	if ((unsigned long)mapping & PAGE_MAPPING_ANON)
+	if ((unsigned long)mapping & PAGE_MAPPING_FLAGS)
 		return NULL;
 
-	return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS);
+	return mapping;
 }
 EXPORT_SYMBOL(folio_mapping);
 
diff --git a/mm/z3fold.c b/mm/z3fold.c
index f41f8b0d9e9a..13b1e9d15056 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -34,15 +34,11 @@
 #include <linux/node.h>
 #include <linux/compaction.h>
 #include <linux/percpu.h>
-#include <linux/mount.h>
-#include <linux/pseudo_fs.h>
-#include <linux/fs.h>
 #include <linux/preempt.h>
 #include <linux/workqueue.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/zpool.h>
-#include <linux/magic.h>
 #include <linux/kmemleak.h>
 
 /*
@@ -149,7 +145,6 @@ struct z3fold_header {
  * @compact_wq:	workqueue for page layout background optimization
  * @release_wq:	workqueue for safe page release
  * @work:	work_struct for safe page release
- * @inode:	inode for z3fold pseudo filesystem
  *
  * This structure is allocated at pool creation time and maintains metadata
  * pertaining to a particular z3fold pool.
@@ -169,7 +164,6 @@ struct z3fold_pool {
 	struct workqueue_struct *compact_wq;
 	struct workqueue_struct *release_wq;
 	struct work_struct work;
-	struct inode *inode;
 };
 
 /*
@@ -334,54 +328,6 @@ static inline void free_handle(unsigned long handle, struct z3fold_header *zhdr)
 	}
 }
 
-static int z3fold_init_fs_context(struct fs_context *fc)
-{
-	return init_pseudo(fc, Z3FOLD_MAGIC) ? 0 : -ENOMEM;
-}
-
-static struct file_system_type z3fold_fs = {
-	.name		= "z3fold",
-	.init_fs_context = z3fold_init_fs_context,
-	.kill_sb	= kill_anon_super,
-};
-
-static struct vfsmount *z3fold_mnt;
-static int __init z3fold_mount(void)
-{
-	int ret = 0;
-
-	z3fold_mnt = kern_mount(&z3fold_fs);
-	if (IS_ERR(z3fold_mnt))
-		ret = PTR_ERR(z3fold_mnt);
-
-	return ret;
-}
-
-static void z3fold_unmount(void)
-{
-	kern_unmount(z3fold_mnt);
-}
-
-static const struct address_space_operations z3fold_aops;
-static int z3fold_register_migration(struct z3fold_pool *pool)
-{
-	pool->inode = alloc_anon_inode(z3fold_mnt->mnt_sb);
-	if (IS_ERR(pool->inode)) {
-		pool->inode = NULL;
-		return 1;
-	}
-
-	pool->inode->i_mapping->private_data = pool;
-	pool->inode->i_mapping->a_ops = &z3fold_aops;
-	return 0;
-}
-
-static void z3fold_unregister_migration(struct z3fold_pool *pool)
-{
-	if (pool->inode)
-		iput(pool->inode);
-}
-
 /* Initializes the z3fold header of a newly allocated z3fold page */
 static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
 					struct z3fold_pool *pool, gfp_t gfp)
@@ -1002,14 +948,10 @@ static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
 	pool->release_wq = create_singlethread_workqueue(pool->name);
 	if (!pool->release_wq)
 		goto out_wq;
-	if (z3fold_register_migration(pool))
-		goto out_rwq;
 	INIT_WORK(&pool->work, free_pages_work);
 	pool->ops = ops;
 	return pool;
 
-out_rwq:
-	destroy_workqueue(pool->release_wq);
 out_wq:
 	destroy_workqueue(pool->compact_wq);
 out_unbuddied:
@@ -1043,11 +985,12 @@ static void z3fold_destroy_pool(struct z3fold_pool *pool)
 
 	destroy_workqueue(pool->compact_wq);
 	destroy_workqueue(pool->release_wq);
-	z3fold_unregister_migration(pool);
 	free_percpu(pool->unbuddied);
 	kfree(pool);
 }
 
+static const struct movable_operations z3fold_mops;
+
 /**
  * z3fold_alloc() - allocates a region of a given size
  * @pool:	z3fold pool from which to allocate
@@ -1117,11 +1060,11 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
 	}
 	if (can_sleep) {
 		lock_page(page);
-		__SetPageMovable(page, pool->inode->i_mapping);
+		__SetPageMovable(page, &z3fold_mops);
 		unlock_page(page);
 	} else {
 		WARN_ON(!trylock_page(page));
-		__SetPageMovable(page, pool->inode->i_mapping);
+		__SetPageMovable(page, &z3fold_mops);
 		unlock_page(page);
 	}
 	z3fold_page_lock(zhdr);
@@ -1554,8 +1497,8 @@ static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
 	return false;
 }
 
-static int z3fold_page_migrate(struct address_space *mapping, struct page *newpage,
-			       struct page *page, enum migrate_mode mode)
+static int z3fold_page_migrate(struct page *newpage, struct page *page,
+		enum migrate_mode mode)
 {
 	struct z3fold_header *zhdr, *new_zhdr;
 	struct z3fold_pool *pool;
@@ -1608,7 +1551,7 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa
 	spin_lock(&pool->lock);
 	list_add(&newpage->lru, &pool->lru);
 	spin_unlock(&pool->lock);
-	__SetPageMovable(newpage, new_mapping);
+	__SetPageMovable(newpage, &z3fold_mops);
 	z3fold_page_unlock(new_zhdr);
 
 	queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
@@ -1642,9 +1585,9 @@ static void z3fold_page_putback(struct page *page)
 	z3fold_page_unlock(zhdr);
 }
 
-static const struct address_space_operations z3fold_aops = {
+static const struct movable_operations z3fold_mops = {
 	.isolate_page = z3fold_page_isolate,
-	.migratepage = z3fold_page_migrate,
+	.migrate_page = z3fold_page_migrate,
 	.putback_page = z3fold_page_putback,
 };
 
@@ -1746,17 +1689,11 @@ MODULE_ALIAS("zpool-z3fold");
 
 static int __init init_z3fold(void)
 {
-	int ret;
-
 	/*
 	 * Make sure the z3fold header is not larger than the page size and
 	 * there has remaining spaces for its buddy.
 	 */
 	BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE - CHUNK_SIZE);
-	ret = z3fold_mount();
-	if (ret)
-		return ret;
-
 	zpool_register_driver(&z3fold_zpool_driver);
 
 	return 0;
@@ -1764,7 +1701,6 @@ static int __init init_z3fold(void)
 
 static void __exit exit_z3fold(void)
 {
-	z3fold_unmount();
 	zpool_unregister_driver(&z3fold_zpool_driver);
 }
 
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 5d5fc04385b8..71d6edcbea48 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -41,7 +41,6 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/sched.h>
-#include <linux/magic.h>
 #include <linux/bitops.h>
 #include <linux/errno.h>
 #include <linux/highmem.h>
@@ -59,8 +58,6 @@
 #include <linux/debugfs.h>
 #include <linux/zsmalloc.h>
 #include <linux/zpool.h>
-#include <linux/mount.h>
-#include <linux/pseudo_fs.h>
 #include <linux/migrate.h>
 #include <linux/wait.h>
 #include <linux/pagemap.h>
@@ -177,10 +174,6 @@ struct zs_size_stat {
 static struct dentry *zs_stat_root;
 #endif
 
-#ifdef CONFIG_COMPACTION
-static struct vfsmount *zsmalloc_mnt;
-#endif
-
 /*
  * We assign a page to ZS_ALMOST_EMPTY fullness group when:
  *	n <= N / f, where
@@ -252,7 +245,6 @@ struct zs_pool {
 	struct dentry *stat_dentry;
 #endif
 #ifdef CONFIG_COMPACTION
-	struct inode *inode;
 	struct work_struct free_work;
 #endif
 	/* protect page/zspage migration */
@@ -271,6 +263,7 @@ struct zspage {
 	unsigned int freeobj;
 	struct page *first_page;
 	struct list_head list; /* fullness list */
+	struct zs_pool *pool;
 #ifdef CONFIG_COMPACTION
 	rwlock_t lock;
 #endif
@@ -295,8 +288,6 @@ static bool ZsHugePage(struct zspage *zspage)
 }
 
 #ifdef CONFIG_COMPACTION
-static int zs_register_migration(struct zs_pool *pool);
-static void zs_unregister_migration(struct zs_pool *pool);
 static void migrate_lock_init(struct zspage *zspage);
 static void migrate_read_lock(struct zspage *zspage);
 static void migrate_read_unlock(struct zspage *zspage);
@@ -307,10 +298,6 @@ static void kick_deferred_free(struct zs_pool *pool);
 static void init_deferred_free(struct zs_pool *pool);
 static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage);
 #else
-static int zsmalloc_mount(void) { return 0; }
-static void zsmalloc_unmount(void) {}
-static int zs_register_migration(struct zs_pool *pool) { return 0; }
-static void zs_unregister_migration(struct zs_pool *pool) {}
 static void migrate_lock_init(struct zspage *zspage) {}
 static void migrate_read_lock(struct zspage *zspage) {}
 static void migrate_read_unlock(struct zspage *zspage) {}
@@ -1083,6 +1070,7 @@ static struct zspage *alloc_zspage(struct zs_pool *pool,
 
 	create_page_chain(class, zspage, pages);
 	init_zspage(class, zspage);
+	zspage->pool = pool;
 
 	return zspage;
 }
@@ -1754,33 +1742,6 @@ static void lock_zspage(struct zspage *zspage)
 	migrate_read_unlock(zspage);
 }
 
-static int zs_init_fs_context(struct fs_context *fc)
-{
-	return init_pseudo(fc, ZSMALLOC_MAGIC) ? 0 : -ENOMEM;
-}
-
-static struct file_system_type zsmalloc_fs = {
-	.name		= "zsmalloc",
-	.init_fs_context = zs_init_fs_context,
-	.kill_sb	= kill_anon_super,
-};
-
-static int zsmalloc_mount(void)
-{
-	int ret = 0;
-
-	zsmalloc_mnt = kern_mount(&zsmalloc_fs);
-	if (IS_ERR(zsmalloc_mnt))
-		ret = PTR_ERR(zsmalloc_mnt);
-
-	return ret;
-}
-
-static void zsmalloc_unmount(void)
-{
-	kern_unmount(zsmalloc_mnt);
-}
-
 static void migrate_lock_init(struct zspage *zspage)
 {
 	rwlock_init(&zspage->lock);
@@ -1823,6 +1784,8 @@ static void dec_zspage_isolation(struct zspage *zspage)
 	zspage->isolated--;
 }
 
+static const struct movable_operations zsmalloc_mops;
+
 static void replace_sub_page(struct size_class *class, struct zspage *zspage,
 				struct page *newpage, struct page *oldpage)
 {
@@ -1843,7 +1806,7 @@ static void replace_sub_page(struct size_class *class, struct zspage *zspage,
 	set_first_obj_offset(newpage, get_first_obj_offset(oldpage));
 	if (unlikely(ZsHugePage(zspage)))
 		newpage->index = oldpage->index;
-	__SetPageMovable(newpage, page_mapping(oldpage));
+	__SetPageMovable(newpage, &zsmalloc_mops);
 }
 
 static bool zs_page_isolate(struct page *page, isolate_mode_t mode)
@@ -1865,8 +1828,8 @@ static bool zs_page_isolate(struct page *page, isolate_mode_t mode)
 	return true;
 }
 
-static int zs_page_migrate(struct address_space *mapping, struct page *newpage,
-		struct page *page, enum migrate_mode mode)
+static int zs_page_migrate(struct page *newpage, struct page *page,
+		enum migrate_mode mode)
 {
 	struct zs_pool *pool;
 	struct size_class *class;
@@ -1889,14 +1852,15 @@ static int zs_page_migrate(struct address_space *mapping, struct page *newpage,
 	VM_BUG_ON_PAGE(!PageMovable(page), page);
 	VM_BUG_ON_PAGE(!PageIsolated(page), page);
 
-	pool = mapping->private_data;
+	/* The page is locked, so this pointer must remain valid */
+	zspage = get_zspage(page);
+	pool = zspage->pool;
 
 	/*
 	 * The pool migrate_lock protects the race between zpage migration
 	 * and zs_free.
 	 */
 	write_lock(&pool->migrate_lock);
-	zspage = get_zspage(page);
 	class = zspage_class(pool, zspage);
 
 	/*
@@ -1964,31 +1928,12 @@ static void zs_page_putback(struct page *page)
 	migrate_write_unlock(zspage);
 }
 
-static const struct address_space_operations zsmalloc_aops = {
+static const struct movable_operations zsmalloc_mops = {
 	.isolate_page = zs_page_isolate,
-	.migratepage = zs_page_migrate,
+	.migrate_page = zs_page_migrate,
 	.putback_page = zs_page_putback,
 };
 
-static int zs_register_migration(struct zs_pool *pool)
-{
-	pool->inode = alloc_anon_inode(zsmalloc_mnt->mnt_sb);
-	if (IS_ERR(pool->inode)) {
-		pool->inode = NULL;
-		return 1;
-	}
-
-	pool->inode->i_mapping->private_data = pool;
-	pool->inode->i_mapping->a_ops = &zsmalloc_aops;
-	return 0;
-}
-
-static void zs_unregister_migration(struct zs_pool *pool)
-{
-	flush_work(&pool->free_work);
-	iput(pool->inode);
-}
-
 /*
  * Caller should hold page_lock of all pages in the zspage
  * In here, we cannot use zspage meta data.
@@ -2032,6 +1977,11 @@ static void kick_deferred_free(struct zs_pool *pool)
 	schedule_work(&pool->free_work);
 }
 
+static void zs_flush_migration(struct zs_pool *pool)
+{
+	flush_work(&pool->free_work);
+}
+
 static void init_deferred_free(struct zs_pool *pool)
 {
 	INIT_WORK(&pool->free_work, async_free_zspage);
@@ -2043,10 +1993,12 @@ static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage)
 
 	do {
 		WARN_ON(!trylock_page(page));
-		__SetPageMovable(page, pool->inode->i_mapping);
+		__SetPageMovable(page, &zsmalloc_mops);
 		unlock_page(page);
 	} while ((page = get_next_page(page)) != NULL);
 }
+#else
+static inline void zs_flush_migration(struct zs_pool *pool) { }
 #endif
 
 /*
@@ -2324,9 +2276,6 @@ struct zs_pool *zs_create_pool(const char *name)
 	/* debug only, don't abort if it fails */
 	zs_pool_stat_create(pool, name);
 
-	if (zs_register_migration(pool))
-		goto err;
-
 	/*
 	 * Not critical since shrinker is only used to trigger internal
 	 * defragmentation of the pool which is pretty optional thing.  If
@@ -2348,7 +2297,7 @@ void zs_destroy_pool(struct zs_pool *pool)
 	int i;
 
 	zs_unregister_shrinker(pool);
-	zs_unregister_migration(pool);
+	zs_flush_migration(pool);
 	zs_pool_stat_destroy(pool);
 
 	for (i = 0; i < ZS_SIZE_CLASSES; i++) {
@@ -2380,14 +2329,10 @@ static int __init zs_init(void)
 {
 	int ret;
 
-	ret = zsmalloc_mount();
-	if (ret)
-		goto out;
-
 	ret = cpuhp_setup_state(CPUHP_MM_ZS_PREPARE, "mm/zsmalloc:prepare",
 				zs_cpu_prepare, zs_cpu_dead);
 	if (ret)
-		goto hp_setup_fail;
+		goto out;
 
 #ifdef CONFIG_ZPOOL
 	zpool_register_driver(&zs_zpool_driver);
@@ -2397,8 +2342,6 @@ static int __init zs_init(void)
 
 	return 0;
 
-hp_setup_fail:
-	zsmalloc_unmount();
 out:
 	return ret;
 }
@@ -2408,7 +2351,6 @@ static void __exit zs_exit(void)
 #ifdef CONFIG_ZPOOL
 	zpool_unregister_driver(&zs_zpool_driver);
 #endif
-	zsmalloc_unmount();
 	cpuhp_remove_state(CPUHP_MM_ZS_PREPARE);
 
 	zs_stat_exit();
-- 
2.35.1


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[PATCH v2 03/19] fs: Add aops->migrate_folio

[Matthew Wilcox (Oracle)]

Provide a folio-based replacement for aops->migratepage.  Update the
documentation to document migrate_folio instead of migratepage.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 Documentation/filesystems/locking.rst |  5 ++--
 Documentation/filesystems/vfs.rst     | 13 ++++++-----
 Documentation/vm/page_migration.rst   | 33 ++++++++++++++-------------
 include/linux/fs.h                    |  4 +++-
 mm/compaction.c                       |  4 +++-
 mm/migrate.c                          | 11 +++++----
 6 files changed, 40 insertions(+), 30 deletions(-)

diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst
index c0fe711f14d3..3d28b23676bd 100644
--- a/Documentation/filesystems/locking.rst
+++ b/Documentation/filesystems/locking.rst
@@ -253,7 +253,8 @@ prototypes::
 	void (*free_folio)(struct folio *);
 	int (*direct_IO)(struct kiocb *, struct iov_iter *iter);
 	bool (*isolate_page) (struct page *, isolate_mode_t);
-	int (*migratepage)(struct address_space *, struct page *, struct page *);
+	int (*migrate_folio)(struct address_space *, struct folio *dst,
+			struct folio *src, enum migrate_mode);
 	void (*putback_page) (struct page *);
 	int (*launder_folio)(struct folio *);
 	bool (*is_partially_uptodate)(struct folio *, size_t from, size_t count);
@@ -281,7 +282,7 @@ release_folio:		yes
 free_folio:		yes
 direct_IO:
 isolate_page:		yes
-migratepage:		yes (both)
+migrate_folio:		yes (both)
 putback_page:		yes
 launder_folio:		yes
 is_partially_uptodate:	yes
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
index a08c652467d7..3ae1b039b03f 100644
--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -740,7 +740,8 @@ cache in your filesystem.  The following members are defined:
 		/* isolate a page for migration */
 		bool (*isolate_page) (struct page *, isolate_mode_t);
 		/* migrate the contents of a page to the specified target */
-		int (*migratepage) (struct page *, struct page *);
+		int (*migrate_folio)(struct mapping *, struct folio *dst,
+				struct folio *src, enum migrate_mode);
 		/* put migration-failed page back to right list */
 		void (*putback_page) (struct page *);
 		int (*launder_folio) (struct folio *);
@@ -935,12 +936,12 @@ cache in your filesystem.  The following members are defined:
 	is successfully isolated, VM marks the page as PG_isolated via
 	__SetPageIsolated.
 
-``migrate_page``
+``migrate_folio``
 	This is used to compact the physical memory usage.  If the VM
-	wants to relocate a page (maybe off a memory card that is
-	signalling imminent failure) it will pass a new page and an old
-	page to this function.  migrate_page should transfer any private
-	data across and update any references that it has to the page.
+	wants to relocate a folio (maybe from a memory device that is
+	signalling imminent failure) it will pass a new folio and an old
+	folio to this function.  migrate_folio should transfer any private
+	data across and update any references that it has to the folio.
 
 ``putback_page``
 	Called by the VM when isolated page's migration fails.
diff --git a/Documentation/vm/page_migration.rst b/Documentation/vm/page_migration.rst
index 8c5cb8147e55..e0f73ddfabb1 100644
--- a/Documentation/vm/page_migration.rst
+++ b/Documentation/vm/page_migration.rst
@@ -181,22 +181,23 @@ which are function pointers of struct address_space_operations.
    Once page is successfully isolated, VM uses page.lru fields so driver
    shouldn't expect to preserve values in those fields.
 
-2. ``int (*migratepage) (struct address_space *mapping,``
-|	``struct page *newpage, struct page *oldpage, enum migrate_mode);``
-
-   After isolation, VM calls migratepage() of driver with the isolated page.
-   The function of migratepage() is to move the contents of the old page to the
-   new page
-   and set up fields of struct page newpage. Keep in mind that you should
-   indicate to the VM the oldpage is no longer movable via __ClearPageMovable()
-   under page_lock if you migrated the oldpage successfully and returned
-   MIGRATEPAGE_SUCCESS. If driver cannot migrate the page at the moment, driver
-   can return -EAGAIN. On -EAGAIN, VM will retry page migration in a short time
-   because VM interprets -EAGAIN as "temporary migration failure". On returning
-   any error except -EAGAIN, VM will give up the page migration without
-   retrying.
-
-   Driver shouldn't touch the page.lru field while in the migratepage() function.
+2. ``int (*migrate_folio) (struct address_space *mapping,``
+|	``struct folio *dst, struct folio *src, enum migrate_mode);``
+
+   After isolation, VM calls the driver's migrate_folio() with the
+   isolated folio.  The purpose of migrate_folio() is to move the contents
+   of the source folio to the destination folio and set up the fields
+   of destination folio.  Keep in mind that you should indicate to the
+   VM the source folio is no longer movable via __ClearPageMovable()
+   under folio if you migrated the source successfully and returned
+   MIGRATEPAGE_SUCCESS.  If driver cannot migrate the folio at the
+   moment, driver can return -EAGAIN. On -EAGAIN, VM will retry folio
+   migration in a short time because VM interprets -EAGAIN as "temporary
+   migration failure".  On returning any error except -EAGAIN, VM will
+   give up the folio migration without retrying.
+
+   Driver shouldn't touch the folio.lru field while in the migrate_folio()
+   function.
 
 3. ``void (*putback_page)(struct page *);``
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 5d8ee3155ca2..47431cf8fbb3 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -362,9 +362,11 @@ struct address_space_operations {
 	void (*free_folio)(struct folio *folio);
 	ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter);
 	/*
-	 * migrate the contents of a page to the specified target. If
+	 * migrate the contents of a folio to the specified target. If
 	 * migrate_mode is MIGRATE_ASYNC, it must not block.
 	 */
+	int (*migrate_folio)(struct address_space *, struct folio *dst,
+			struct folio *src, enum migrate_mode);
 	int (*migratepage) (struct address_space *,
 			struct page *, struct page *, enum migrate_mode);
 	int (*launder_folio)(struct folio *);
diff --git a/mm/compaction.c b/mm/compaction.c
index f23efba1d118..458f49f9ab09 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1042,7 +1042,9 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 				goto isolate_fail_put;
 
 			mapping = page_mapping(page);
-			migrate_dirty = !mapping || mapping->a_ops->migratepage;
+			migrate_dirty = !mapping ||
+					mapping->a_ops->migrate_folio ||
+					mapping->a_ops->migratepage;
 			unlock_page(page);
 			if (!migrate_dirty)
 				goto isolate_fail_put;
diff --git a/mm/migrate.c b/mm/migrate.c
index 3ce6fee87efa..e064b998ead0 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -856,14 +856,17 @@ static int move_to_new_folio(struct folio *dst, struct folio *src,
 
 		if (!mapping)
 			rc = migrate_page(mapping, &dst->page, &src->page, mode);
-		else if (mapping->a_ops->migratepage)
+		else if (mapping->a_ops->migrate_folio)
 			/*
-			 * Most pages have a mapping and most filesystems
-			 * provide a migratepage callback. Anonymous pages
+			 * Most folios have a mapping and most filesystems
+			 * provide a migrate_folio callback. Anonymous folios
 			 * are part of swap space which also has its own
-			 * migratepage callback. This is the most common path
+			 * migrate_folio callback. This is the most common path
 			 * for page migration.
 			 */
+			rc = mapping->a_ops->migrate_folio(mapping, dst, src,
+								mode);
+		else if (mapping->a_ops->migratepage)
 			rc = mapping->a_ops->migratepage(mapping, &dst->page,
 							&src->page, mode);
 		else
-- 
2.35.1


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[PATCH v2 04/19] mm/migrate: Convert fallback_migrate_page() to fallback_migrate_folio()

[Matthew Wilcox (Oracle)]

Use a folio throughout.  migrate_page() will be converted to
migrate_folio() later.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 mm/migrate.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index e064b998ead0..1878de817a01 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -805,11 +805,11 @@ static int writeout(struct address_space *mapping, struct page *page)
 /*
  * Default handling if a filesystem does not provide a migration function.
  */
-static int fallback_migrate_page(struct address_space *mapping,
-	struct page *newpage, struct page *page, enum migrate_mode mode)
+static int fallback_migrate_folio(struct address_space *mapping,
+		struct folio *dst, struct folio *src, enum migrate_mode mode)
 {
-	if (PageDirty(page)) {
-		/* Only writeback pages in full synchronous migration */
+	if (folio_test_dirty(src)) {
+		/* Only writeback folios in full synchronous migration */
 		switch (mode) {
 		case MIGRATE_SYNC:
 		case MIGRATE_SYNC_NO_COPY:
@@ -817,18 +817,18 @@ static int fallback_migrate_page(struct address_space *mapping,
 		default:
 			return -EBUSY;
 		}
-		return writeout(mapping, page);
+		return writeout(mapping, &src->page);
 	}
 
 	/*
 	 * Buffers may be managed in a filesystem specific way.
 	 * We must have no buffers or drop them.
 	 */
-	if (page_has_private(page) &&
-	    !try_to_release_page(page, GFP_KERNEL))
+	if (folio_test_private(src) &&
+	    !filemap_release_folio(src, GFP_KERNEL))
 		return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
 
-	return migrate_page(mapping, newpage, page, mode);
+	return migrate_page(mapping, &dst->page, &src->page, mode);
 }
 
 /*
@@ -870,8 +870,7 @@ static int move_to_new_folio(struct folio *dst, struct folio *src,
 			rc = mapping->a_ops->migratepage(mapping, &dst->page,
 							&src->page, mode);
 		else
-			rc = fallback_migrate_page(mapping, &dst->page,
-							&src->page, mode);
+			rc = fallback_migrate_folio(mapping, dst, src, mode);
 	} else {
 		const struct movable_operations *mops;
 
-- 
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[PATCH v2 05/19] mm/migrate: Convert writeout() to take a folio

[Matthew Wilcox (Oracle)]

Use a folio throughout this function.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 mm/migrate.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 1878de817a01..6b6fec26f4d0 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -761,11 +761,10 @@ int buffer_migrate_page_norefs(struct address_space *mapping,
 #endif
 
 /*
- * Writeback a page to clean the dirty state
+ * Writeback a folio to clean the dirty state
  */
-static int writeout(struct address_space *mapping, struct page *page)
+static int writeout(struct address_space *mapping, struct folio *folio)
 {
-	struct folio *folio = page_folio(page);
 	struct writeback_control wbc = {
 		.sync_mode = WB_SYNC_NONE,
 		.nr_to_write = 1,
@@ -779,25 +778,25 @@ static int writeout(struct address_space *mapping, struct page *page)
 		/* No write method for the address space */
 		return -EINVAL;
 
-	if (!clear_page_dirty_for_io(page))
+	if (!folio_clear_dirty_for_io(folio))
 		/* Someone else already triggered a write */
 		return -EAGAIN;
 
 	/*
-	 * A dirty page may imply that the underlying filesystem has
-	 * the page on some queue. So the page must be clean for
-	 * migration. Writeout may mean we loose the lock and the
-	 * page state is no longer what we checked for earlier.
+	 * A dirty folio may imply that the underlying filesystem has
+	 * the folio on some queue. So the folio must be clean for
+	 * migration. Writeout may mean we lose the lock and the
+	 * folio state is no longer what we checked for earlier.
 	 * At this point we know that the migration attempt cannot
 	 * be successful.
 	 */
 	remove_migration_ptes(folio, folio, false);
 
-	rc = mapping->a_ops->writepage(page, &wbc);
+	rc = mapping->a_ops->writepage(&folio->page, &wbc);
 
 	if (rc != AOP_WRITEPAGE_ACTIVATE)
 		/* unlocked. Relock */
-		lock_page(page);
+		folio_lock(folio);
 
 	return (rc < 0) ? -EIO : -EAGAIN;
 }
@@ -817,7 +816,7 @@ static int fallback_migrate_folio(struct address_space *mapping,
 		default:
 			return -EBUSY;
 		}
-		return writeout(mapping, &src->page);
+		return writeout(mapping, src);
 	}
 
 	/*
-- 
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[PATCH v2 06/19] mm/migrate: Convert buffer_migrate_page() to buffer_migrate_folio()

[Matthew Wilcox (Oracle)]

Use a folio throughout __buffer_migrate_folio(), add kernel-doc for
buffer_migrate_folio() and buffer_migrate_folio_norefs(), move their
declarations to buffer.h and switch all filesystems that have wired
them up.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 block/fops.c                |  2 +-
 fs/ext2/inode.c             |  4 +-
 fs/ext4/inode.c             |  4 +-
 fs/ntfs/aops.c              |  6 +--
 fs/ocfs2/aops.c             |  2 +-
 include/linux/buffer_head.h | 10 +++++
 include/linux/fs.h          | 12 ------
 mm/migrate.c                | 76 ++++++++++++++++++++++---------------
 8 files changed, 65 insertions(+), 51 deletions(-)

diff --git a/block/fops.c b/block/fops.c
index d6b3276a6c68..743fc46d0aad 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -417,7 +417,7 @@ const struct address_space_operations def_blk_aops = {
 	.write_end	= blkdev_write_end,
 	.writepages	= blkdev_writepages,
 	.direct_IO	= blkdev_direct_IO,
-	.migratepage	= buffer_migrate_page_norefs,
+	.migrate_folio	= buffer_migrate_folio_norefs,
 	.is_dirty_writeback = buffer_check_dirty_writeback,
 };
 
diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 360ce3604a2d..84570c6265aa 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -973,7 +973,7 @@ const struct address_space_operations ext2_aops = {
 	.bmap			= ext2_bmap,
 	.direct_IO		= ext2_direct_IO,
 	.writepages		= ext2_writepages,
-	.migratepage		= buffer_migrate_page,
+	.migrate_folio		= buffer_migrate_folio,
 	.is_partially_uptodate	= block_is_partially_uptodate,
 	.error_remove_page	= generic_error_remove_page,
 };
@@ -989,7 +989,7 @@ const struct address_space_operations ext2_nobh_aops = {
 	.bmap			= ext2_bmap,
 	.direct_IO		= ext2_direct_IO,
 	.writepages		= ext2_writepages,
-	.migratepage		= buffer_migrate_page,
+	.migrate_folio		= buffer_migrate_folio,
 	.error_remove_page	= generic_error_remove_page,
 };
 
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1aaea53e67b5..53877ffe3c41 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3633,7 +3633,7 @@ static const struct address_space_operations ext4_aops = {
 	.invalidate_folio	= ext4_invalidate_folio,
 	.release_folio		= ext4_release_folio,
 	.direct_IO		= noop_direct_IO,
-	.migratepage		= buffer_migrate_page,
+	.migrate_folio		= buffer_migrate_folio,
 	.is_partially_uptodate  = block_is_partially_uptodate,
 	.error_remove_page	= generic_error_remove_page,
 	.swap_activate		= ext4_iomap_swap_activate,
@@ -3668,7 +3668,7 @@ static const struct address_space_operations ext4_da_aops = {
 	.invalidate_folio	= ext4_invalidate_folio,
 	.release_folio		= ext4_release_folio,
 	.direct_IO		= noop_direct_IO,
-	.migratepage		= buffer_migrate_page,
+	.migrate_folio		= buffer_migrate_folio,
 	.is_partially_uptodate  = block_is_partially_uptodate,
 	.error_remove_page	= generic_error_remove_page,
 	.swap_activate		= ext4_iomap_swap_activate,
diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index 9e3964ea2ea0..5f4fb6ca6f2e 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -1659,7 +1659,7 @@ const struct address_space_operations ntfs_normal_aops = {
 	.dirty_folio	= block_dirty_folio,
 #endif /* NTFS_RW */
 	.bmap		= ntfs_bmap,
-	.migratepage	= buffer_migrate_page,
+	.migrate_folio	= buffer_migrate_folio,
 	.is_partially_uptodate = block_is_partially_uptodate,
 	.error_remove_page = generic_error_remove_page,
 };
@@ -1673,7 +1673,7 @@ const struct address_space_operations ntfs_compressed_aops = {
 	.writepage	= ntfs_writepage,
 	.dirty_folio	= block_dirty_folio,
 #endif /* NTFS_RW */
-	.migratepage	= buffer_migrate_page,
+	.migrate_folio	= buffer_migrate_folio,
 	.is_partially_uptodate = block_is_partially_uptodate,
 	.error_remove_page = generic_error_remove_page,
 };
@@ -1688,7 +1688,7 @@ const struct address_space_operations ntfs_mst_aops = {
 	.writepage	= ntfs_writepage,	/* Write dirty page to disk. */
 	.dirty_folio	= filemap_dirty_folio,
 #endif /* NTFS_RW */
-	.migratepage	= buffer_migrate_page,
+	.migrate_folio	= buffer_migrate_folio,
 	.is_partially_uptodate	= block_is_partially_uptodate,
 	.error_remove_page = generic_error_remove_page,
 };
diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 767df51f8657..1d489003f99d 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -2462,7 +2462,7 @@ const struct address_space_operations ocfs2_aops = {
 	.direct_IO		= ocfs2_direct_IO,
 	.invalidate_folio	= block_invalidate_folio,
 	.release_folio		= ocfs2_release_folio,
-	.migratepage		= buffer_migrate_page,
+	.migrate_folio		= buffer_migrate_folio,
 	.is_partially_uptodate	= block_is_partially_uptodate,
 	.error_remove_page	= generic_error_remove_page,
 };
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index c9d1463bb20f..b0366c89d6a4 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -267,6 +267,16 @@ int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);
 int nobh_writepage(struct page *page, get_block_t *get_block,
                         struct writeback_control *wbc);
 
+#ifdef CONFIG_MIGRATION
+extern int buffer_migrate_folio(struct address_space *,
+		struct folio *dst, struct folio *src, enum migrate_mode);
+extern int buffer_migrate_folio_norefs(struct address_space *,
+		struct folio *dst, struct folio *src, enum migrate_mode);
+#else
+#define buffer_migrate_folio NULL
+#define buffer_migrate_folio_norefs NULL
+#endif
+
 void buffer_init(void);
 
 /*
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 47431cf8fbb3..9e6b17da4e11 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3215,18 +3215,6 @@ extern int generic_check_addressable(unsigned, u64);
 
 extern void generic_set_encrypted_ci_d_ops(struct dentry *dentry);
 
-#ifdef CONFIG_MIGRATION
-extern int buffer_migrate_page(struct address_space *,
-				struct page *, struct page *,
-				enum migrate_mode);
-extern int buffer_migrate_page_norefs(struct address_space *,
-				struct page *, struct page *,
-				enum migrate_mode);
-#else
-#define buffer_migrate_page NULL
-#define buffer_migrate_page_norefs NULL
-#endif
-
 int may_setattr(struct user_namespace *mnt_userns, struct inode *inode,
 		unsigned int ia_valid);
 int setattr_prepare(struct user_namespace *, struct dentry *, struct iattr *);
diff --git a/mm/migrate.c b/mm/migrate.c
index 6b6fec26f4d0..2975f0c4d7cf 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -656,23 +656,23 @@ static bool buffer_migrate_lock_buffers(struct buffer_head *head,
 	return true;
 }
 
-static int __buffer_migrate_page(struct address_space *mapping,
-		struct page *newpage, struct page *page, enum migrate_mode mode,
+static int __buffer_migrate_folio(struct address_space *mapping,
+		struct folio *dst, struct folio *src, enum migrate_mode mode,
 		bool check_refs)
 {
 	struct buffer_head *bh, *head;
 	int rc;
 	int expected_count;
 
-	if (!page_has_buffers(page))
-		return migrate_page(mapping, newpage, page, mode);
+	head = folio_buffers(src);
+	if (!head)
+		return migrate_page(mapping, &dst->page, &src->page, mode);
 
 	/* Check whether page does not have extra refs before we do more work */
-	expected_count = expected_page_refs(mapping, page);
-	if (page_count(page) != expected_count)
+	expected_count = expected_page_refs(mapping, &src->page);
+	if (folio_ref_count(src) != expected_count)
 		return -EAGAIN;
 
-	head = page_buffers(page);
 	if (!buffer_migrate_lock_buffers(head, mode))
 		return -EAGAIN;
 
@@ -703,23 +703,22 @@ static int __buffer_migrate_page(struct address_space *mapping,
 		}
 	}
 
-	rc = migrate_page_move_mapping(mapping, newpage, page, 0);
+	rc = folio_migrate_mapping(mapping, dst, src, 0);
 	if (rc != MIGRATEPAGE_SUCCESS)
 		goto unlock_buffers;
 
-	attach_page_private(newpage, detach_page_private(page));
+	folio_attach_private(dst, folio_detach_private(src));
 
 	bh = head;
 	do {
-		set_bh_page(bh, newpage, bh_offset(bh));
+		set_bh_page(bh, &dst->page, bh_offset(bh));
 		bh = bh->b_this_page;
-
 	} while (bh != head);
 
 	if (mode != MIGRATE_SYNC_NO_COPY)
-		migrate_page_copy(newpage, page);
+		folio_migrate_copy(dst, src);
 	else
-		migrate_page_states(newpage, page);
+		folio_migrate_flags(dst, src);
 
 	rc = MIGRATEPAGE_SUCCESS;
 unlock_buffers:
@@ -729,34 +728,51 @@ static int __buffer_migrate_page(struct address_space *mapping,
 	do {
 		unlock_buffer(bh);
 		bh = bh->b_this_page;
-
 	} while (bh != head);
 
 	return rc;
 }
 
-/*
- * Migration function for pages with buffers. This function can only be used
- * if the underlying filesystem guarantees that no other references to "page"
- * exist. For example attached buffer heads are accessed only under page lock.
+/**
+ * buffer_migrate_folio() - Migration function for folios with buffers.
+ * @mapping: The address space containing @src.
+ * @dst: The folio to migrate to.
+ * @src: The folio to migrate from.
+ * @mode: How to migrate the folio.
+ *
+ * This function can only be used if the underlying filesystem guarantees
+ * that no other references to @src exist. For example attached buffer
+ * heads are accessed only under the folio lock.  If your filesystem cannot
+ * provide this guarantee, buffer_migrate_folio_norefs() may be more
+ * appropriate.
+ *
+ * Return: 0 on success or a negative errno on failure.
  */
-int buffer_migrate_page(struct address_space *mapping,
-		struct page *newpage, struct page *page, enum migrate_mode mode)
+int buffer_migrate_folio(struct address_space *mapping,
+		struct folio *dst, struct folio *src, enum migrate_mode mode)
 {
-	return __buffer_migrate_page(mapping, newpage, page, mode, false);
+	return __buffer_migrate_folio(mapping, dst, src, mode, false);
 }
-EXPORT_SYMBOL(buffer_migrate_page);
+EXPORT_SYMBOL(buffer_migrate_folio);
 
-/*
- * Same as above except that this variant is more careful and checks that there
- * are also no buffer head references. This function is the right one for
- * mappings where buffer heads are directly looked up and referenced (such as
- * block device mappings).
+/**
+ * buffer_migrate_folio_norefs() - Migration function for folios with buffers.
+ * @mapping: The address space containing @src.
+ * @dst: The folio to migrate to.
+ * @src: The folio to migrate from.
+ * @mode: How to migrate the folio.
+ *
+ * Like buffer_migrate_folio() except that this variant is more careful
+ * and checks that there are also no buffer head references. This function
+ * is the right one for mappings where buffer heads are directly looked
+ * up and referenced (such as block device mappings).
+ *
+ * Return: 0 on success or a negative errno on failure.
  */
-int buffer_migrate_page_norefs(struct address_space *mapping,
-		struct page *newpage, struct page *page, enum migrate_mode mode)
+int buffer_migrate_folio_norefs(struct address_space *mapping,
+		struct folio *dst, struct folio *src, enum migrate_mode mode)
 {
-	return __buffer_migrate_page(mapping, newpage, page, mode, true);
+	return __buffer_migrate_folio(mapping, dst, src, mode, true);
 }
 #endif
 
-- 
2.35.1


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[PATCH v2 07/19] mm/migrate: Convert expected_page_refs() to folio_expected_refs()

[Matthew Wilcox (Oracle)]

Now that both callers have a folio, convert this function to
take a folio & rename it.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 mm/migrate.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 2975f0c4d7cf..2e2f41572066 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -336,13 +336,18 @@ void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
 }
 #endif
 
-static int expected_page_refs(struct address_space *mapping, struct page *page)
+static int folio_expected_refs(struct address_space *mapping,
+		struct folio *folio)
 {
-	int expected_count = 1;
+	int refs = 1;
+	if (!mapping)
+		return refs;
 
-	if (mapping)
-		expected_count += compound_nr(page) + page_has_private(page);
-	return expected_count;
+	refs += folio_nr_pages(folio);
+	if (folio_get_private(folio))
+		refs++;
+
+	return refs;
 }
 
 /*
@@ -359,7 +364,7 @@ int folio_migrate_mapping(struct address_space *mapping,
 	XA_STATE(xas, &mapping->i_pages, folio_index(folio));
 	struct zone *oldzone, *newzone;
 	int dirty;
-	int expected_count = expected_page_refs(mapping, &folio->page) + extra_count;
+	int expected_count = folio_expected_refs(mapping, folio) + extra_count;
 	long nr = folio_nr_pages(folio);
 
 	if (!mapping) {
@@ -669,7 +674,7 @@ static int __buffer_migrate_folio(struct address_space *mapping,
 		return migrate_page(mapping, &dst->page, &src->page, mode);
 
 	/* Check whether page does not have extra refs before we do more work */
-	expected_count = expected_page_refs(mapping, &src->page);
+	expected_count = folio_expected_refs(mapping, src);
 	if (folio_ref_count(src) != expected_count)
 		return -EAGAIN;
 
-- 
2.35.1


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[PATCH v2 08/19] btrfs: Convert btree_migratepage to migrate_folio

[Matthew Wilcox (Oracle)]

Use a folio throughout this function.  migrate_page() will be converted
later.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/btrfs/disk-io.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 12b11e645c14..9ceb73f683af 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -952,28 +952,28 @@ void btrfs_submit_metadata_bio(struct inode *inode, struct bio *bio, int mirror_
 }
 
 #ifdef CONFIG_MIGRATION
-static int btree_migratepage(struct address_space *mapping,
-			struct page *newpage, struct page *page,
-			enum migrate_mode mode)
+static int btree_migrate_folio(struct address_space *mapping,
+		struct folio *dst, struct folio *src, enum migrate_mode mode)
 {
 	/*
 	 * we can't safely write a btree page from here,
 	 * we haven't done the locking hook
 	 */
-	if (PageDirty(page))
+	if (folio_test_dirty(src))
 		return -EAGAIN;
 	/*
 	 * Buffers may be managed in a filesystem specific way.
 	 * We must have no buffers or drop them.
 	 */
-	if (page_has_private(page) &&
-	    !try_to_release_page(page, GFP_KERNEL))
+	if (folio_get_private(src) &&
+	    !filemap_release_folio(src, GFP_KERNEL))
 		return -EAGAIN;
-	return migrate_page(mapping, newpage, page, mode);
+	return migrate_page(mapping, &dst->page, &src->page, mode);
 }
+#else
+#define btree_migrate_folio NULL
 #endif
 
-
 static int btree_writepages(struct address_space *mapping,
 			    struct writeback_control *wbc)
 {
@@ -1073,10 +1073,8 @@ static const struct address_space_operations btree_aops = {
 	.writepages	= btree_writepages,
 	.release_folio	= btree_release_folio,
 	.invalidate_folio = btree_invalidate_folio,
-#ifdef CONFIG_MIGRATION
-	.migratepage	= btree_migratepage,
-#endif
-	.dirty_folio = btree_dirty_folio,
+	.migrate_folio	= btree_migrate_folio,
+	.dirty_folio	= btree_dirty_folio,
 };
 
 struct extent_buffer *btrfs_find_create_tree_block(
-- 
2.35.1


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[PATCH v2 09/19] nfs: Convert to migrate_folio

[Matthew Wilcox (Oracle)]

Use a folio throughout this function.  migrate_page() will be converted
later.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/nfs/file.c     |  4 +---
 fs/nfs/internal.h |  6 ++++--
 fs/nfs/write.c    | 16 ++++++++--------
 3 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 2d72b1b7ed74..549baed76351 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -533,9 +533,7 @@ const struct address_space_operations nfs_file_aops = {
 	.write_end = nfs_write_end,
 	.invalidate_folio = nfs_invalidate_folio,
 	.release_folio = nfs_release_folio,
-#ifdef CONFIG_MIGRATION
-	.migratepage = nfs_migrate_page,
-#endif
+	.migrate_folio = nfs_migrate_folio,
 	.launder_folio = nfs_launder_folio,
 	.is_dirty_writeback = nfs_check_dirty_writeback,
 	.error_remove_page = generic_error_remove_page,
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 8f8cd6e2d4db..437ebe544aaf 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -578,8 +578,10 @@ void nfs_clear_pnfs_ds_commit_verifiers(struct pnfs_ds_commit_info *cinfo)
 #endif
 
 #ifdef CONFIG_MIGRATION
-extern int nfs_migrate_page(struct address_space *,
-		struct page *, struct page *, enum migrate_mode);
+int nfs_migrate_folio(struct address_space *, struct folio *dst,
+		struct folio *src, enum migrate_mode);
+#else
+#define nfs_migrate_folio NULL
 #endif
 
 static inline int
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 1c706465d090..649b9e633459 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -2119,27 +2119,27 @@ int nfs_wb_page(struct inode *inode, struct page *page)
 }
 
 #ifdef CONFIG_MIGRATION
-int nfs_migrate_page(struct address_space *mapping, struct page *newpage,
-		struct page *page, enum migrate_mode mode)
+int nfs_migrate_folio(struct address_space *mapping, struct folio *dst,
+		struct folio *src, enum migrate_mode mode)
 {
 	/*
-	 * If PagePrivate is set, then the page is currently associated with
+	 * If the private flag is set, the folio is currently associated with
 	 * an in-progress read or write request. Don't try to migrate it.
 	 *
 	 * FIXME: we could do this in principle, but we'll need a way to ensure
 	 *        that we can safely release the inode reference while holding
-	 *        the page lock.
+	 *        the folio lock.
 	 */
-	if (PagePrivate(page))
+	if (folio_test_private(src))
 		return -EBUSY;
 
-	if (PageFsCache(page)) {
+	if (folio_test_fscache(src)) {
 		if (mode == MIGRATE_ASYNC)
 			return -EBUSY;
-		wait_on_page_fscache(page);
+		folio_wait_fscache(src);
 	}
 
-	return migrate_page(mapping, newpage, page, mode);
+	return migrate_page(mapping, &dst->page, &src->page, mode);
 }
 #endif
 
-- 
2.35.1


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[PATCH v2 10/19] mm/migrate: Convert migrate_page() to migrate_folio()

[Matthew Wilcox (Oracle)]

Convert all callers to pass a folio.  Most have the folio
already available.  Switch all users from aops->migratepage to
aops->migrate_folio.  Also turn the documentation into kerneldoc.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 drivers/gpu/drm/i915/gem/i915_gem_userptr.c |  4 +--
 fs/btrfs/disk-io.c                          |  2 +-
 fs/nfs/write.c                              |  2 +-
 include/linux/migrate.h                     |  5 ++-
 mm/migrate.c                                | 37 +++++++++++----------
 mm/migrate_device.c                         |  3 +-
 mm/shmem.c                                  |  2 +-
 mm/swap_state.c                             |  2 +-
 8 files changed, 30 insertions(+), 27 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
index 094f06b4ce33..8423df021b71 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
@@ -216,8 +216,8 @@ i915_gem_userptr_put_pages(struct drm_i915_gem_object *obj,
 			 * However...!
 			 *
 			 * The mmu-notifier can be invalidated for a
-			 * migrate_page, that is alreadying holding the lock
-			 * on the page. Such a try_to_unmap() will result
+			 * migrate_folio, that is alreadying holding the lock
+			 * on the folio. Such a try_to_unmap() will result
 			 * in us calling put_pages() and so recursively try
 			 * to lock the page. We avoid that deadlock with
 			 * a trylock_page() and in exchange we risk missing
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 9ceb73f683af..8e5f1fa1e972 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -968,7 +968,7 @@ static int btree_migrate_folio(struct address_space *mapping,
 	if (folio_get_private(src) &&
 	    !filemap_release_folio(src, GFP_KERNEL))
 		return -EAGAIN;
-	return migrate_page(mapping, &dst->page, &src->page, mode);
+	return migrate_folio(mapping, dst, src, mode);
 }
 #else
 #define btree_migrate_folio NULL
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 649b9e633459..69569696dde0 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -2139,7 +2139,7 @@ int nfs_migrate_folio(struct address_space *mapping, struct folio *dst,
 		folio_wait_fscache(src);
 	}
 
-	return migrate_page(mapping, &dst->page, &src->page, mode);
+	return migrate_folio(mapping, dst, src, mode);
 }
 #endif
 
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 48aa4be04108..82f00ad69a54 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -32,9 +32,8 @@ extern const char *migrate_reason_names[MR_TYPES];
 #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);
+int migrate_folio(struct address_space *mapping, struct folio *dst,
+		struct folio *src, 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,
 		unsigned int *ret_succeeded);
diff --git a/mm/migrate.c b/mm/migrate.c
index 2e2f41572066..785e32d0cf1b 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -593,34 +593,37 @@ EXPORT_SYMBOL(folio_migrate_copy);
  *                    Migration functions
  ***********************************************************/
 
-/*
- * Common logic to directly migrate a single LRU page suitable for
- * pages that do not use PagePrivate/PagePrivate2.
+/**
+ * migrate_folio() - Simple folio migration.
+ * @mapping: The address_space containing the folio.
+ * @dst: The folio to migrate the data to.
+ * @src: The folio containing the current data.
+ * @mode: How to migrate the page.
  *
- * Pages are locked upon entry and exit.
+ * Common logic to directly migrate a single LRU folio suitable for
+ * folios that do not use PagePrivate/PagePrivate2.
+ *
+ * Folios are locked upon entry and exit.
  */
-int migrate_page(struct address_space *mapping,
-		struct page *newpage, struct page *page,
-		enum migrate_mode mode)
+int migrate_folio(struct address_space *mapping, struct folio *dst,
+		struct folio *src, enum migrate_mode mode)
 {
-	struct folio *newfolio = page_folio(newpage);
-	struct folio *folio = page_folio(page);
 	int rc;
 
-	BUG_ON(folio_test_writeback(folio));	/* Writeback must be complete */
+	BUG_ON(folio_test_writeback(src));	/* Writeback must be complete */
 
-	rc = folio_migrate_mapping(mapping, newfolio, folio, 0);
+	rc = folio_migrate_mapping(mapping, dst, src, 0);
 
 	if (rc != MIGRATEPAGE_SUCCESS)
 		return rc;
 
 	if (mode != MIGRATE_SYNC_NO_COPY)
-		folio_migrate_copy(newfolio, folio);
+		folio_migrate_copy(dst, src);
 	else
-		folio_migrate_flags(newfolio, folio);
+		folio_migrate_flags(dst, src);
 	return MIGRATEPAGE_SUCCESS;
 }
-EXPORT_SYMBOL(migrate_page);
+EXPORT_SYMBOL(migrate_folio);
 
 #ifdef CONFIG_BLOCK
 /* Returns true if all buffers are successfully locked */
@@ -671,7 +674,7 @@ static int __buffer_migrate_folio(struct address_space *mapping,
 
 	head = folio_buffers(src);
 	if (!head)
-		return migrate_page(mapping, &dst->page, &src->page, mode);
+		return migrate_folio(mapping, dst, src, mode);
 
 	/* Check whether page does not have extra refs before we do more work */
 	expected_count = folio_expected_refs(mapping, src);
@@ -848,7 +851,7 @@ static int fallback_migrate_folio(struct address_space *mapping,
 	    !filemap_release_folio(src, GFP_KERNEL))
 		return mode == MIGRATE_SYNC ? -EAGAIN : -EBUSY;
 
-	return migrate_page(mapping, &dst->page, &src->page, mode);
+	return migrate_folio(mapping, dst, src, mode);
 }
 
 /*
@@ -875,7 +878,7 @@ static int move_to_new_folio(struct folio *dst, struct folio *src,
 		struct address_space *mapping = folio_mapping(src);
 
 		if (!mapping)
-			rc = migrate_page(mapping, &dst->page, &src->page, mode);
+			rc = migrate_folio(mapping, dst, src, mode);
 		else if (mapping->a_ops->migrate_folio)
 			/*
 			 * Most folios have a mapping and most filesystems
diff --git a/mm/migrate_device.c b/mm/migrate_device.c
index 5052093d0262..5dd97c39ca6a 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -718,7 +718,8 @@ void migrate_vma_pages(struct migrate_vma *migrate)
 			continue;
 		}
 
-		r = migrate_page(mapping, newpage, page, MIGRATE_SYNC_NO_COPY);
+		r = migrate_folio(mapping, page_folio(newpage),
+				page_folio(page), MIGRATE_SYNC_NO_COPY);
 		if (r != MIGRATEPAGE_SUCCESS)
 			migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
 	}
diff --git a/mm/shmem.c b/mm/shmem.c
index 313ae7df59d8..e37ff6a1a6d0 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3801,7 +3801,7 @@ const struct address_space_operations shmem_aops = {
 	.write_end	= shmem_write_end,
 #endif
 #ifdef CONFIG_MIGRATION
-	.migratepage	= migrate_page,
+	.migrate_folio	= migrate_folio,
 #endif
 	.error_remove_page = shmem_error_remove_page,
 };
diff --git a/mm/swap_state.c b/mm/swap_state.c
index f5b6f5638908..0a2021fc55ad 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -33,7 +33,7 @@ static const struct address_space_operations swap_aops = {
 	.writepage	= swap_writepage,
 	.dirty_folio	= noop_dirty_folio,
 #ifdef CONFIG_MIGRATION
-	.migratepage	= migrate_page,
+	.migrate_folio	= migrate_folio,
 #endif
 };
 
-- 
2.35.1


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[PATCH v2 11/19] mm/migrate: Add filemap_migrate_folio()

[Matthew Wilcox (Oracle)]

There is nothing iomap-specific about iomap_migratepage(), and it fits
a pattern used by several other filesystems, so move it to mm/migrate.c,
convert it to be filemap_migrate_folio() and convert the iomap filesystems
to use it.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/gfs2/aops.c          |  2 +-
 fs/iomap/buffered-io.c  | 25 -------------------------
 fs/xfs/xfs_aops.c       |  2 +-
 fs/zonefs/super.c       |  2 +-
 include/linux/iomap.h   |  6 ------
 include/linux/pagemap.h |  6 ++++++
 mm/migrate.c            | 20 ++++++++++++++++++++
 7 files changed, 29 insertions(+), 34 deletions(-)

diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
index 106e90a36583..57ff883d432c 100644
--- a/fs/gfs2/aops.c
+++ b/fs/gfs2/aops.c
@@ -774,7 +774,7 @@ static const struct address_space_operations gfs2_aops = {
 	.invalidate_folio = iomap_invalidate_folio,
 	.bmap = gfs2_bmap,
 	.direct_IO = noop_direct_IO,
-	.migratepage = iomap_migrate_page,
+	.migrate_folio = filemap_migrate_folio,
 	.is_partially_uptodate = iomap_is_partially_uptodate,
 	.error_remove_page = generic_error_remove_page,
 };
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 66278a14bfa7..5a91aa1db945 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -489,31 +489,6 @@ void iomap_invalidate_folio(struct folio *folio, size_t offset, size_t len)
 }
 EXPORT_SYMBOL_GPL(iomap_invalidate_folio);
 
-#ifdef CONFIG_MIGRATION
-int
-iomap_migrate_page(struct address_space *mapping, struct page *newpage,
-		struct page *page, enum migrate_mode mode)
-{
-	struct folio *folio = page_folio(page);
-	struct folio *newfolio = page_folio(newpage);
-	int ret;
-
-	ret = folio_migrate_mapping(mapping, newfolio, folio, 0);
-	if (ret != MIGRATEPAGE_SUCCESS)
-		return ret;
-
-	if (folio_test_private(folio))
-		folio_attach_private(newfolio, folio_detach_private(folio));
-
-	if (mode != MIGRATE_SYNC_NO_COPY)
-		folio_migrate_copy(newfolio, folio);
-	else
-		folio_migrate_flags(newfolio, folio);
-	return MIGRATEPAGE_SUCCESS;
-}
-EXPORT_SYMBOL_GPL(iomap_migrate_page);
-#endif /* CONFIG_MIGRATION */
-
 static void
 iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
 {
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 8ec38b25187b..5d1a995b15f8 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -570,7 +570,7 @@ const struct address_space_operations xfs_address_space_operations = {
 	.invalidate_folio	= iomap_invalidate_folio,
 	.bmap			= xfs_vm_bmap,
 	.direct_IO		= noop_direct_IO,
-	.migratepage		= iomap_migrate_page,
+	.migrate_folio		= filemap_migrate_folio,
 	.is_partially_uptodate  = iomap_is_partially_uptodate,
 	.error_remove_page	= generic_error_remove_page,
 	.swap_activate		= xfs_iomap_swapfile_activate,
diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
index bcb21aea990a..d4c3f28f34ee 100644
--- a/fs/zonefs/super.c
+++ b/fs/zonefs/super.c
@@ -237,7 +237,7 @@ static const struct address_space_operations zonefs_file_aops = {
 	.dirty_folio		= filemap_dirty_folio,
 	.release_folio		= iomap_release_folio,
 	.invalidate_folio	= iomap_invalidate_folio,
-	.migratepage		= iomap_migrate_page,
+	.migrate_folio		= filemap_migrate_folio,
 	.is_partially_uptodate	= iomap_is_partially_uptodate,
 	.error_remove_page	= generic_error_remove_page,
 	.direct_IO		= noop_direct_IO,
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index e552097c67e0..758a1125e72f 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -231,12 +231,6 @@ void iomap_readahead(struct readahead_control *, const struct iomap_ops *ops);
 bool iomap_is_partially_uptodate(struct folio *, size_t from, size_t count);
 bool iomap_release_folio(struct folio *folio, gfp_t gfp_flags);
 void iomap_invalidate_folio(struct folio *folio, size_t offset, size_t len);
-#ifdef CONFIG_MIGRATION
-int iomap_migrate_page(struct address_space *mapping, struct page *newpage,
-		struct page *page, enum migrate_mode mode);
-#else
-#define iomap_migrate_page NULL
-#endif
 int iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
 		const struct iomap_ops *ops);
 int iomap_zero_range(struct inode *inode, loff_t pos, loff_t len,
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 1caccb9f99aa..2a67c0ad7348 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -1078,6 +1078,12 @@ static inline int __must_check write_one_page(struct page *page)
 int __set_page_dirty_nobuffers(struct page *page);
 bool noop_dirty_folio(struct address_space *mapping, struct folio *folio);
 
+#ifdef CONFIG_MIGRATION
+int filemap_migrate_folio(struct address_space *mapping, struct folio *dst,
+		struct folio *src, enum migrate_mode mode);
+#else
+#define filemap_migrate_folio NULL
+#endif
 void page_endio(struct page *page, bool is_write, int err);
 
 void folio_end_private_2(struct folio *folio);
diff --git a/mm/migrate.c b/mm/migrate.c
index 785e32d0cf1b..4d8115ca93bb 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -784,6 +784,26 @@ int buffer_migrate_folio_norefs(struct address_space *mapping,
 }
 #endif
 
+int filemap_migrate_folio(struct address_space *mapping,
+		struct folio *dst, struct folio *src, enum migrate_mode mode)
+{
+	int ret;
+
+	ret = folio_migrate_mapping(mapping, dst, src, 0);
+	if (ret != MIGRATEPAGE_SUCCESS)
+		return ret;
+
+	if (folio_get_private(src))
+		folio_attach_private(dst, folio_detach_private(src));
+
+	if (mode != MIGRATE_SYNC_NO_COPY)
+		folio_migrate_copy(dst, src);
+	else
+		folio_migrate_flags(dst, src);
+	return MIGRATEPAGE_SUCCESS;
+}
+EXPORT_SYMBOL_GPL(filemap_migrate_folio);
+
 /*
  * Writeback a folio to clean the dirty state
  */
-- 
2.35.1


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[PATCH v2 12/19] btrfs: Convert btrfs_migratepage to migrate_folio

[Matthew Wilcox (Oracle)]

Use filemap_migrate_folio() to do the bulk of the work, and then copy
the ordered flag across if needed.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/btrfs/inode.c | 26 +++++++++-----------------
 1 file changed, 9 insertions(+), 17 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 81737eff92f3..5f41d869c648 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8255,30 +8255,24 @@ static bool btrfs_release_folio(struct folio *folio, gfp_t gfp_flags)
 }
 
 #ifdef CONFIG_MIGRATION
-static int btrfs_migratepage(struct address_space *mapping,
-			     struct page *newpage, struct page *page,
+static int btrfs_migrate_folio(struct address_space *mapping,
+			     struct folio *dst, struct folio *src,
 			     enum migrate_mode mode)
 {
-	int ret;
+	int ret = filemap_migrate_folio(mapping, dst, src, mode);
 
-	ret = migrate_page_move_mapping(mapping, newpage, page, 0);
 	if (ret != MIGRATEPAGE_SUCCESS)
 		return ret;
 
-	if (page_has_private(page))
-		attach_page_private(newpage, detach_page_private(page));
-
-	if (PageOrdered(page)) {
-		ClearPageOrdered(page);
-		SetPageOrdered(newpage);
+	if (folio_test_ordered(src)) {
+		folio_clear_ordered(src);
+		folio_set_ordered(dst);
 	}
 
-	if (mode != MIGRATE_SYNC_NO_COPY)
-		migrate_page_copy(newpage, page);
-	else
-		migrate_page_states(newpage, page);
 	return MIGRATEPAGE_SUCCESS;
 }
+#else
+#define btrfs_migrate_folio NULL
 #endif
 
 static void btrfs_invalidate_folio(struct folio *folio, size_t offset,
@@ -11422,9 +11416,7 @@ static const struct address_space_operations btrfs_aops = {
 	.direct_IO	= noop_direct_IO,
 	.invalidate_folio = btrfs_invalidate_folio,
 	.release_folio	= btrfs_release_folio,
-#ifdef CONFIG_MIGRATION
-	.migratepage	= btrfs_migratepage,
-#endif
+	.migrate_folio	= btrfs_migrate_folio,
 	.dirty_folio	= filemap_dirty_folio,
 	.error_remove_page = generic_error_remove_page,
 	.swap_activate	= btrfs_swap_activate,
-- 
2.35.1


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[PATCH v2 13/19] ubifs: Convert to filemap_migrate_folio()

[Matthew Wilcox (Oracle)]

filemap_migrate_folio() is a little more general than ubifs really needs,
but it's better to share the code.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 fs/ubifs/file.c | 29 ++---------------------------
 1 file changed, 2 insertions(+), 27 deletions(-)

diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index 04ced154960f..f2353dd676ef 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -1461,29 +1461,6 @@ static bool ubifs_dirty_folio(struct address_space *mapping,
 	return ret;
 }
 
-#ifdef CONFIG_MIGRATION
-static int ubifs_migrate_page(struct address_space *mapping,
-		struct page *newpage, struct page *page, enum migrate_mode mode)
-{
-	int rc;
-
-	rc = migrate_page_move_mapping(mapping, newpage, page, 0);
-	if (rc != MIGRATEPAGE_SUCCESS)
-		return rc;
-
-	if (PagePrivate(page)) {
-		detach_page_private(page);
-		attach_page_private(newpage, (void *)1);
-	}
-
-	if (mode != MIGRATE_SYNC_NO_COPY)
-		migrate_page_copy(newpage, page);
-	else
-		migrate_page_states(newpage, page);
-	return MIGRATEPAGE_SUCCESS;
-}
-#endif
-
 static bool ubifs_release_folio(struct folio *folio, gfp_t unused_gfp_flags)
 {
 	struct inode *inode = folio->mapping->host;
@@ -1649,10 +1626,8 @@ const struct address_space_operations ubifs_file_address_operations = {
 	.write_end      = ubifs_write_end,
 	.invalidate_folio = ubifs_invalidate_folio,
 	.dirty_folio	= ubifs_dirty_folio,
-#ifdef CONFIG_MIGRATION
-	.migratepage	= ubifs_migrate_page,
-#endif
-	.release_folio    = ubifs_release_folio,
+	.migrate_folio	= filemap_migrate_folio,
+	.release_folio	= ubifs_release_folio,
 };
 
 const struct inode_operations ubifs_file_inode_operations = {
-- 
2.35.1


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[PATCH v2 14/19] f2fs: Convert to filemap_migrate_folio()

[Matthew Wilcox (Oracle)]

filemap_migrate_folio() fits f2fs's needs perfectly.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 fs/f2fs/checkpoint.c |  4 +---
 fs/f2fs/data.c       | 40 +---------------------------------------
 fs/f2fs/f2fs.h       |  4 ----
 fs/f2fs/node.c       |  4 +---
 4 files changed, 3 insertions(+), 49 deletions(-)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 6d8b2bf14de0..8259e0fa97e1 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -463,9 +463,7 @@ const struct address_space_operations f2fs_meta_aops = {
 	.dirty_folio	= f2fs_dirty_meta_folio,
 	.invalidate_folio = f2fs_invalidate_folio,
 	.release_folio	= f2fs_release_folio,
-#ifdef CONFIG_MIGRATION
-	.migratepage    = f2fs_migrate_page,
-#endif
+	.migrate_folio	= filemap_migrate_folio,
 };
 
 static void __add_ino_entry(struct f2fs_sb_info *sbi, nid_t ino,
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 7fcbcf979737..318a3f91ad74 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3751,42 +3751,6 @@ static sector_t f2fs_bmap(struct address_space *mapping, sector_t block)
 	return blknr;
 }
 
-#ifdef CONFIG_MIGRATION
-#include <linux/migrate.h>
-
-int f2fs_migrate_page(struct address_space *mapping,
-		struct page *newpage, struct page *page, enum migrate_mode mode)
-{
-	int rc, extra_count = 0;
-
-	BUG_ON(PageWriteback(page));
-
-	rc = migrate_page_move_mapping(mapping, newpage,
-				page, extra_count);
-	if (rc != MIGRATEPAGE_SUCCESS)
-		return rc;
-
-	/* guarantee to start from no stale private field */
-	set_page_private(newpage, 0);
-	if (PagePrivate(page)) {
-		set_page_private(newpage, page_private(page));
-		SetPagePrivate(newpage);
-		get_page(newpage);
-
-		set_page_private(page, 0);
-		ClearPagePrivate(page);
-		put_page(page);
-	}
-
-	if (mode != MIGRATE_SYNC_NO_COPY)
-		migrate_page_copy(newpage, page);
-	else
-		migrate_page_states(newpage, page);
-
-	return MIGRATEPAGE_SUCCESS;
-}
-#endif
-
 #ifdef CONFIG_SWAP
 static int f2fs_migrate_blocks(struct inode *inode, block_t start_blk,
 							unsigned int blkcnt)
@@ -4018,15 +3982,13 @@ const struct address_space_operations f2fs_dblock_aops = {
 	.write_begin	= f2fs_write_begin,
 	.write_end	= f2fs_write_end,
 	.dirty_folio	= f2fs_dirty_data_folio,
+	.migrate_folio	= filemap_migrate_folio,
 	.invalidate_folio = f2fs_invalidate_folio,
 	.release_folio	= f2fs_release_folio,
 	.direct_IO	= noop_direct_IO,
 	.bmap		= f2fs_bmap,
 	.swap_activate  = f2fs_swap_activate,
 	.swap_deactivate = f2fs_swap_deactivate,
-#ifdef CONFIG_MIGRATION
-	.migratepage    = f2fs_migrate_page,
-#endif
 };
 
 void f2fs_clear_page_cache_dirty_tag(struct page *page)
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index d9bbecd008d2..f258a1b6faed 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -3764,10 +3764,6 @@ int f2fs_write_single_data_page(struct page *page, int *submitted,
 void f2fs_write_failed(struct inode *inode, loff_t to);
 void f2fs_invalidate_folio(struct folio *folio, size_t offset, size_t length);
 bool f2fs_release_folio(struct folio *folio, gfp_t wait);
-#ifdef CONFIG_MIGRATION
-int f2fs_migrate_page(struct address_space *mapping, struct page *newpage,
-			struct page *page, enum migrate_mode mode);
-#endif
 bool f2fs_overwrite_io(struct inode *inode, loff_t pos, size_t len);
 void f2fs_clear_page_cache_dirty_tag(struct page *page);
 int f2fs_init_post_read_processing(void);
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 836c79a20afc..ed1cbfb0345f 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -2163,9 +2163,7 @@ const struct address_space_operations f2fs_node_aops = {
 	.dirty_folio	= f2fs_dirty_node_folio,
 	.invalidate_folio = f2fs_invalidate_folio,
 	.release_folio	= f2fs_release_folio,
-#ifdef CONFIG_MIGRATION
-	.migratepage	= f2fs_migrate_page,
-#endif
+	.migrate_folio	= filemap_migrate_folio,
 };
 
 static struct free_nid *__lookup_free_nid_list(struct f2fs_nm_info *nm_i,
-- 
2.35.1


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[PATCH v2 15/19] aio: Convert to migrate_folio

[Matthew Wilcox (Oracle)]

Use a folio throughout this function.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/aio.c | 36 ++++++++++++++++++------------------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 3c249b938632..a1911e86859c 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -400,8 +400,8 @@ static const struct file_operations aio_ring_fops = {
 };
 
 #if IS_ENABLED(CONFIG_MIGRATION)
-static int aio_migratepage(struct address_space *mapping, struct page *new,
-			struct page *old, enum migrate_mode mode)
+static int aio_migrate_folio(struct address_space *mapping, struct folio *dst,
+			struct folio *src, enum migrate_mode mode)
 {
 	struct kioctx *ctx;
 	unsigned long flags;
@@ -435,10 +435,10 @@ static int aio_migratepage(struct address_space *mapping, struct page *new,
 		goto out;
 	}
 
-	idx = old->index;
+	idx = src->index;
 	if (idx < (pgoff_t)ctx->nr_pages) {
-		/* Make sure the old page hasn't already been changed */
-		if (ctx->ring_pages[idx] != old)
+		/* Make sure the old folio hasn't already been changed */
+		if (ctx->ring_pages[idx] != &src->page)
 			rc = -EAGAIN;
 	} else
 		rc = -EINVAL;
@@ -447,27 +447,27 @@ static int aio_migratepage(struct address_space *mapping, struct page *new,
 		goto out_unlock;
 
 	/* Writeback must be complete */
-	BUG_ON(PageWriteback(old));
-	get_page(new);
+	BUG_ON(folio_test_writeback(src));
+	folio_get(dst);
 
-	rc = migrate_page_move_mapping(mapping, new, old, 1);
+	rc = folio_migrate_mapping(mapping, dst, src, 1);
 	if (rc != MIGRATEPAGE_SUCCESS) {
-		put_page(new);
+		folio_put(dst);
 		goto out_unlock;
 	}
 
 	/* Take completion_lock to prevent other writes to the ring buffer
-	 * while the old page is copied to the new.  This prevents new
+	 * while the old folio is copied to the new.  This prevents new
 	 * events from being lost.
 	 */
 	spin_lock_irqsave(&ctx->completion_lock, flags);
-	migrate_page_copy(new, old);
-	BUG_ON(ctx->ring_pages[idx] != old);
-	ctx->ring_pages[idx] = new;
+	folio_migrate_copy(dst, src);
+	BUG_ON(ctx->ring_pages[idx] != &src->page);
+	ctx->ring_pages[idx] = &dst->page;
 	spin_unlock_irqrestore(&ctx->completion_lock, flags);
 
-	/* The old page is no longer accessible. */
-	put_page(old);
+	/* The old folio is no longer accessible. */
+	folio_put(src);
 
 out_unlock:
 	mutex_unlock(&ctx->ring_lock);
@@ -475,13 +475,13 @@ static int aio_migratepage(struct address_space *mapping, struct page *new,
 	spin_unlock(&mapping->private_lock);
 	return rc;
 }
+#else
+#define aio_migrate_folio NULL
 #endif
 
 static const struct address_space_operations aio_ctx_aops = {
 	.dirty_folio	= noop_dirty_folio,
-#if IS_ENABLED(CONFIG_MIGRATION)
-	.migratepage	= aio_migratepage,
-#endif
+	.migrate_folio	= aio_migrate_folio,
 };
 
 static int aio_setup_ring(struct kioctx *ctx, unsigned int nr_events)
-- 
2.35.1


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[PATCH v2 16/19] hugetlb: Convert to migrate_folio

[Matthew Wilcox (Oracle)]

This involves converting migrate_huge_page_move_mapping().  We also need a
folio variant of hugetlb_set_page_subpool(), but that's for a later patch.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 fs/hugetlbfs/inode.c    | 23 ++++++++++++++---------
 include/linux/migrate.h |  6 +++---
 mm/migrate.c            | 18 +++++++++---------
 3 files changed, 26 insertions(+), 21 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 14d33f725e05..eca1d0fabd7e 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -954,28 +954,33 @@ static int hugetlbfs_symlink(struct user_namespace *mnt_userns,
 	return error;
 }
 
-static int hugetlbfs_migrate_page(struct address_space *mapping,
-				struct page *newpage, struct page *page,
+#ifdef CONFIG_MIGRATION
+static int hugetlbfs_migrate_folio(struct address_space *mapping,
+				struct folio *dst, struct folio *src,
 				enum migrate_mode mode)
 {
 	int rc;
 
-	rc = migrate_huge_page_move_mapping(mapping, newpage, page);
+	rc = migrate_huge_page_move_mapping(mapping, dst, src);
 	if (rc != MIGRATEPAGE_SUCCESS)
 		return rc;
 
-	if (hugetlb_page_subpool(page)) {
-		hugetlb_set_page_subpool(newpage, hugetlb_page_subpool(page));
-		hugetlb_set_page_subpool(page, NULL);
+	if (hugetlb_page_subpool(&src->page)) {
+		hugetlb_set_page_subpool(&dst->page,
+					hugetlb_page_subpool(&src->page));
+		hugetlb_set_page_subpool(&src->page, NULL);
 	}
 
 	if (mode != MIGRATE_SYNC_NO_COPY)
-		migrate_page_copy(newpage, page);
+		folio_migrate_copy(dst, src);
 	else
-		migrate_page_states(newpage, page);
+		folio_migrate_flags(dst, src);
 
 	return MIGRATEPAGE_SUCCESS;
 }
+#else
+#define hugetlbfs_migrate_folio NULL
+#endif
 
 static int hugetlbfs_error_remove_page(struct address_space *mapping,
 				struct page *page)
@@ -1142,7 +1147,7 @@ static const struct address_space_operations hugetlbfs_aops = {
 	.write_begin	= hugetlbfs_write_begin,
 	.write_end	= hugetlbfs_write_end,
 	.dirty_folio	= noop_dirty_folio,
-	.migratepage    = hugetlbfs_migrate_page,
+	.migrate_folio  = hugetlbfs_migrate_folio,
 	.error_remove_page	= hugetlbfs_error_remove_page,
 };
 
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 82f00ad69a54..59d64a1e6b4b 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -42,8 +42,8 @@ extern int isolate_movable_page(struct page *page, isolate_mode_t mode);
 
 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);
+int migrate_huge_page_move_mapping(struct address_space *mapping,
+		struct folio *dst, struct folio *src);
 extern int migrate_page_move_mapping(struct address_space *mapping,
 		struct page *newpage, struct page *page, int extra_count);
 void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep,
@@ -74,7 +74,7 @@ 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)
+				  struct folio *dst, struct folio *src)
 {
 	return -ENOSYS;
 }
diff --git a/mm/migrate.c b/mm/migrate.c
index 4d8115ca93bb..bed0de86f3ae 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -474,26 +474,26 @@ EXPORT_SYMBOL(folio_migrate_mapping);
  * of folio_migrate_mapping().
  */
 int migrate_huge_page_move_mapping(struct address_space *mapping,
-				   struct page *newpage, struct page *page)
+				   struct folio *dst, struct folio *src)
 {
-	XA_STATE(xas, &mapping->i_pages, page_index(page));
+	XA_STATE(xas, &mapping->i_pages, folio_index(src));
 	int expected_count;
 
 	xas_lock_irq(&xas);
-	expected_count = 2 + page_has_private(page);
-	if (!page_ref_freeze(page, expected_count)) {
+	expected_count = 2 + folio_has_private(src);
+	if (!folio_ref_freeze(src, expected_count)) {
 		xas_unlock_irq(&xas);
 		return -EAGAIN;
 	}
 
-	newpage->index = page->index;
-	newpage->mapping = page->mapping;
+	dst->index = src->index;
+	dst->mapping = src->mapping;
 
-	get_page(newpage);
+	folio_get(dst);
 
-	xas_store(&xas, newpage);
+	xas_store(&xas, dst);
 
-	page_ref_unfreeze(page, expected_count - 1);
+	folio_ref_unfreeze(src, expected_count - 1);
 
 	xas_unlock_irq(&xas);
 
-- 
2.35.1


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[PATCH v2 17/19] secretmem: Convert to migrate_folio

[Matthew Wilcox (Oracle)]

This is little more than changing the types over; there's no real work
being done in this function.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/secretmem.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/secretmem.c b/mm/secretmem.c
index 1c7f1775b56e..658a7486efa9 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -133,9 +133,8 @@ static const struct file_operations secretmem_fops = {
 	.mmap		= secretmem_mmap,
 };
 
-static int secretmem_migratepage(struct address_space *mapping,
-				 struct page *newpage, struct page *page,
-				 enum migrate_mode mode)
+static int secretmem_migrate_folio(struct address_space *mapping,
+		struct folio *dst, struct folio *src, enum migrate_mode mode)
 {
 	return -EBUSY;
 }
@@ -149,7 +148,7 @@ static void secretmem_free_folio(struct folio *folio)
 const struct address_space_operations secretmem_aops = {
 	.dirty_folio	= noop_dirty_folio,
 	.free_folio	= secretmem_free_folio,
-	.migratepage	= secretmem_migratepage,
+	.migrate_folio	= secretmem_migrate_folio,
 };
 
 static int secretmem_setattr(struct user_namespace *mnt_userns,
-- 
2.35.1


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[PATCH v2 18/19] fs: Remove aops->migratepage()

[Matthew Wilcox (Oracle)]

With all users converted to migrate_folio(), remove this operation.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 include/linux/fs.h | 2 --
 mm/compaction.c    | 5 ++---
 mm/migrate.c       | 3 ---
 3 files changed, 2 insertions(+), 8 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9e6b17da4e11..7e06919b8f60 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -367,8 +367,6 @@ struct address_space_operations {
 	 */
 	int (*migrate_folio)(struct address_space *, struct folio *dst,
 			struct folio *src, enum migrate_mode);
-	int (*migratepage) (struct address_space *,
-			struct page *, struct page *, enum migrate_mode);
 	int (*launder_folio)(struct folio *);
 	bool (*is_partially_uptodate) (struct folio *, size_t from,
 			size_t count);
diff --git a/mm/compaction.c b/mm/compaction.c
index 458f49f9ab09..a2c53fcf933e 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1031,7 +1031,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 
 			/*
 			 * Only pages without mappings or that have a
-			 * ->migratepage callback are possible to migrate
+			 * ->migrate_folio callback are possible to migrate
 			 * without blocking. However, we can be racing with
 			 * truncation so it's necessary to lock the page
 			 * to stabilise the mapping as truncation holds
@@ -1043,8 +1043,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 
 			mapping = page_mapping(page);
 			migrate_dirty = !mapping ||
-					mapping->a_ops->migrate_folio ||
-					mapping->a_ops->migratepage;
+					mapping->a_ops->migrate_folio;
 			unlock_page(page);
 			if (!migrate_dirty)
 				goto isolate_fail_put;
diff --git a/mm/migrate.c b/mm/migrate.c
index bed0de86f3ae..767e41800d15 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -909,9 +909,6 @@ static int move_to_new_folio(struct folio *dst, struct folio *src,
 			 */
 			rc = mapping->a_ops->migrate_folio(mapping, dst, src,
 								mode);
-		else if (mapping->a_ops->migratepage)
-			rc = mapping->a_ops->migratepage(mapping, &dst->page,
-							&src->page, mode);
 		else
 			rc = fallback_migrate_folio(mapping, dst, src, mode);
 	} else {
-- 
2.35.1


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[PATCH v2 19/19] mm/folio-compat: Remove migration compatibility functions

[Matthew Wilcox (Oracle)]

migrate_page_move_mapping(), migrate_page_copy() and migrate_page_states()
are all now unused after converting all the filesystems from
aops->migratepage() to aops->migrate_folio().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 include/linux/migrate.h | 11 -----------
 mm/folio-compat.c       | 22 ----------------------
 mm/ksm.c                |  2 +-
 3 files changed, 1 insertion(+), 34 deletions(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 59d64a1e6b4b..3e18c7048506 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -40,12 +40,8 @@ extern int migrate_pages(struct list_head *l, new_page_t new, free_page_t free,
 extern struct page *alloc_migration_target(struct page *page, unsigned long private);
 extern int isolate_movable_page(struct page *page, isolate_mode_t mode);
 
-extern void migrate_page_states(struct page *newpage, struct page *page);
-extern void migrate_page_copy(struct page *newpage, struct page *page);
 int migrate_huge_page_move_mapping(struct address_space *mapping,
 		struct folio *dst, struct folio *src);
-extern int migrate_page_move_mapping(struct address_space *mapping,
-		struct page *newpage, struct page *page, int extra_count);
 void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep,
 				spinlock_t *ptl);
 void folio_migrate_flags(struct folio *newfolio, struct folio *folio);
@@ -66,13 +62,6 @@ static inline struct page *alloc_migration_target(struct page *page,
 static inline int isolate_movable_page(struct page *page, isolate_mode_t mode)
 	{ return -EBUSY; }
 
-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 folio *dst, struct folio *src)
 {
diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index 20bc15b57d93..458618c7302c 100644
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -51,28 +51,6 @@ void mark_page_accessed(struct page *page)
 }
 EXPORT_SYMBOL(mark_page_accessed);
 
-#ifdef CONFIG_MIGRATION
-int migrate_page_move_mapping(struct address_space *mapping,
-		struct page *newpage, struct page *page, int extra_count)
-{
-	return folio_migrate_mapping(mapping, page_folio(newpage),
-					page_folio(page), extra_count);
-}
-EXPORT_SYMBOL(migrate_page_move_mapping);
-
-void migrate_page_states(struct page *newpage, struct page *page)
-{
-	folio_migrate_flags(page_folio(newpage), page_folio(page));
-}
-EXPORT_SYMBOL(migrate_page_states);
-
-void migrate_page_copy(struct page *newpage, struct page *page)
-{
-	folio_migrate_copy(page_folio(newpage), page_folio(page));
-}
-EXPORT_SYMBOL(migrate_page_copy);
-#endif
-
 bool set_page_writeback(struct page *page)
 {
 	return folio_start_writeback(page_folio(page));
diff --git a/mm/ksm.c b/mm/ksm.c
index 54f78c9eecae..e8f8c1a2bb39 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -712,7 +712,7 @@ static struct page *get_ksm_page(struct stable_node *stable_node,
 	 * however, it might mean that the page is under page_ref_freeze().
 	 * The __remove_mapping() case is easy, again the node is now stale;
 	 * the same is in reuse_ksm_page() case; but if page is swapcache
-	 * in migrate_page_move_mapping(), it might still be our page,
+	 * in folio_migrate_mapping(), it might still be our page,
 	 * in which case it's essential to keep the node.
 	 */
 	while (!get_page_unless_zero(page)) {
-- 
2.35.1


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Re: [PATCH v2 11/19] mm/migrate: Add filemap_migrate_folio()

[Darrick J. Wong]

On Wed, Jun 08, 2022 at 04:02:41PM +0100, Matthew Wilcox (Oracle) wrote:
> There is nothing iomap-specific about iomap_migratepage(), and it fits
> a pattern used by several other filesystems, so move it to mm/migrate.c,
> convert it to be filemap_migrate_folio() and convert the iomap filesystems
> to use it.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

LGTM
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/gfs2/aops.c          |  2 +-
>  fs/iomap/buffered-io.c  | 25 -------------------------
>  fs/xfs/xfs_aops.c       |  2 +-
>  fs/zonefs/super.c       |  2 +-
>  include/linux/iomap.h   |  6 ------
>  include/linux/pagemap.h |  6 ++++++
>  mm/migrate.c            | 20 ++++++++++++++++++++
>  7 files changed, 29 insertions(+), 34 deletions(-)
> 
> diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
> index 106e90a36583..57ff883d432c 100644
> --- a/fs/gfs2/aops.c
> +++ b/fs/gfs2/aops.c
> @@ -774,7 +774,7 @@ static const struct address_space_operations gfs2_aops = {
>  	.invalidate_folio = iomap_invalidate_folio,
>  	.bmap = gfs2_bmap,
>  	.direct_IO = noop_direct_IO,
> -	.migratepage = iomap_migrate_page,
> +	.migrate_folio = filemap_migrate_folio,
>  	.is_partially_uptodate = iomap_is_partially_uptodate,
>  	.error_remove_page = generic_error_remove_page,
>  };
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 66278a14bfa7..5a91aa1db945 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -489,31 +489,6 @@ void iomap_invalidate_folio(struct folio *folio, size_t offset, size_t len)
>  }
>  EXPORT_SYMBOL_GPL(iomap_invalidate_folio);
>  
> -#ifdef CONFIG_MIGRATION
> -int
> -iomap_migrate_page(struct address_space *mapping, struct page *newpage,
> -		struct page *page, enum migrate_mode mode)
> -{
> -	struct folio *folio = page_folio(page);
> -	struct folio *newfolio = page_folio(newpage);
> -	int ret;
> -
> -	ret = folio_migrate_mapping(mapping, newfolio, folio, 0);
> -	if (ret != MIGRATEPAGE_SUCCESS)
> -		return ret;
> -
> -	if (folio_test_private(folio))
> -		folio_attach_private(newfolio, folio_detach_private(folio));
> -
> -	if (mode != MIGRATE_SYNC_NO_COPY)
> -		folio_migrate_copy(newfolio, folio);
> -	else
> -		folio_migrate_flags(newfolio, folio);
> -	return MIGRATEPAGE_SUCCESS;
> -}
> -EXPORT_SYMBOL_GPL(iomap_migrate_page);
> -#endif /* CONFIG_MIGRATION */
> -
>  static void
>  iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
>  {
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 8ec38b25187b..5d1a995b15f8 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -570,7 +570,7 @@ const struct address_space_operations xfs_address_space_operations = {
>  	.invalidate_folio	= iomap_invalidate_folio,
>  	.bmap			= xfs_vm_bmap,
>  	.direct_IO		= noop_direct_IO,
> -	.migratepage		= iomap_migrate_page,
> +	.migrate_folio		= filemap_migrate_folio,
>  	.is_partially_uptodate  = iomap_is_partially_uptodate,
>  	.error_remove_page	= generic_error_remove_page,
>  	.swap_activate		= xfs_iomap_swapfile_activate,
> diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
> index bcb21aea990a..d4c3f28f34ee 100644
> --- a/fs/zonefs/super.c
> +++ b/fs/zonefs/super.c
> @@ -237,7 +237,7 @@ static const struct address_space_operations zonefs_file_aops = {
>  	.dirty_folio		= filemap_dirty_folio,
>  	.release_folio		= iomap_release_folio,
>  	.invalidate_folio	= iomap_invalidate_folio,
> -	.migratepage		= iomap_migrate_page,
> +	.migrate_folio		= filemap_migrate_folio,
>  	.is_partially_uptodate	= iomap_is_partially_uptodate,
>  	.error_remove_page	= generic_error_remove_page,
>  	.direct_IO		= noop_direct_IO,
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index e552097c67e0..758a1125e72f 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -231,12 +231,6 @@ void iomap_readahead(struct readahead_control *, const struct iomap_ops *ops);
>  bool iomap_is_partially_uptodate(struct folio *, size_t from, size_t count);
>  bool iomap_release_folio(struct folio *folio, gfp_t gfp_flags);
>  void iomap_invalidate_folio(struct folio *folio, size_t offset, size_t len);
> -#ifdef CONFIG_MIGRATION
> -int iomap_migrate_page(struct address_space *mapping, struct page *newpage,
> -		struct page *page, enum migrate_mode mode);
> -#else
> -#define iomap_migrate_page NULL
> -#endif
>  int iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
>  		const struct iomap_ops *ops);
>  int iomap_zero_range(struct inode *inode, loff_t pos, loff_t len,
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 1caccb9f99aa..2a67c0ad7348 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -1078,6 +1078,12 @@ static inline int __must_check write_one_page(struct page *page)
>  int __set_page_dirty_nobuffers(struct page *page);
>  bool noop_dirty_folio(struct address_space *mapping, struct folio *folio);
>  
> +#ifdef CONFIG_MIGRATION
> +int filemap_migrate_folio(struct address_space *mapping, struct folio *dst,
> +		struct folio *src, enum migrate_mode mode);
> +#else
> +#define filemap_migrate_folio NULL
> +#endif
>  void page_endio(struct page *page, bool is_write, int err);
>  
>  void folio_end_private_2(struct folio *folio);
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 785e32d0cf1b..4d8115ca93bb 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -784,6 +784,26 @@ int buffer_migrate_folio_norefs(struct address_space *mapping,
>  }
>  #endif
>  
> +int filemap_migrate_folio(struct address_space *mapping,
> +		struct folio *dst, struct folio *src, enum migrate_mode mode)
> +{
> +	int ret;
> +
> +	ret = folio_migrate_mapping(mapping, dst, src, 0);
> +	if (ret != MIGRATEPAGE_SUCCESS)
> +		return ret;
> +
> +	if (folio_get_private(src))
> +		folio_attach_private(dst, folio_detach_private(src));
> +
> +	if (mode != MIGRATE_SYNC_NO_COPY)
> +		folio_migrate_copy(dst, src);
> +	else
> +		folio_migrate_flags(dst, src);
> +	return MIGRATEPAGE_SUCCESS;
> +}
> +EXPORT_SYMBOL_GPL(filemap_migrate_folio);
> +
>  /*
>   * Writeback a folio to clean the dirty state
>   */
> -- 
> 2.35.1
> 

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Re: [PATCH v2 16/19] hugetlb: Convert to migrate_folio

[Muchun Song]

On Wed, Jun 08, 2022 at 04:02:46PM +0100, Matthew Wilcox (Oracle) wrote:
> This involves converting migrate_huge_page_move_mapping().  We also need a
> folio variant of hugetlb_set_page_subpool(), but that's for a later patch.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Acked-by: Muchun Song <songmuchun@bytedance.com>

Thanks.

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Re: [PATCH v2 02/19] mm: Convert all PageMovable users to movable_operations

[David Hildenbrand]

On 08.06.22 17:02, Matthew Wilcox (Oracle) wrote:
> These drivers are rather uncomfortably hammered into the
> address_space_operations hole.  They aren't filesystems and don't behave
> like filesystems.  They just need their own movable_operations structure,
> which we can point to directly from page->mapping.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  arch/powerpc/platforms/pseries/cmm.c |  60 +---------------
>  drivers/misc/vmw_balloon.c           |  61 +---------------
>  drivers/virtio/virtio_balloon.c      |  47 +-----------
>  include/linux/balloon_compaction.h   |   6 +-
>  include/linux/fs.h                   |   2 -
>  include/linux/migrate.h              |  26 +++++--
>  include/linux/page-flags.h           |   2 +-
>  include/uapi/linux/magic.h           |   4 --
>  mm/balloon_compaction.c              |  10 ++-
>  mm/compaction.c                      |  29 ++++----
>  mm/migrate.c                         |  24 +++----
>  mm/util.c                            |   4 +-
>  mm/z3fold.c                          |  82 +++------------------
>  mm/zsmalloc.c                        | 102 ++++++---------------------
>  14 files changed, 94 insertions(+), 365 deletions(-)

You probably should have cc'ed the relevant maintainers (including me :P ).

For everything except z3fold.c and zsmalloc.c,

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb


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Re: [PATCH v2 01/19] secretmem: Remove isolate_page

[David Hildenbrand]

On 08.06.22 17:02, Matthew Wilcox (Oracle) wrote:
> The isolate_page operation is never called for filesystems, only
> for device drivers which call SetPageMovable.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  mm/secretmem.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/mm/secretmem.c b/mm/secretmem.c
> index 206ed6b40c1d..1c7f1775b56e 100644
> --- a/mm/secretmem.c
> +++ b/mm/secretmem.c
> @@ -133,11 +133,6 @@ static const struct file_operations secretmem_fops = {
>  	.mmap		= secretmem_mmap,
>  };
>  
> -static bool secretmem_isolate_page(struct page *page, isolate_mode_t mode)
> -{
> -	return false;
> -}
> -
>  static int secretmem_migratepage(struct address_space *mapping,
>  				 struct page *newpage, struct page *page,
>  				 enum migrate_mode mode)
> @@ -155,7 +150,6 @@ const struct address_space_operations secretmem_aops = {
>  	.dirty_folio	= noop_dirty_folio,
>  	.free_folio	= secretmem_free_folio,
>  	.migratepage	= secretmem_migratepage,
> -	.isolate_page	= secretmem_isolate_page,
>  };
>  
>  static int secretmem_setattr(struct user_namespace *mnt_userns,

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb


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Re: [PATCH v2 03/19] fs: Add aops->migrate_folio

[David Hildenbrand]

On 08.06.22 17:02, Matthew Wilcox (Oracle) wrote:
> Provide a folio-based replacement for aops->migratepage.  Update the
> documentation to document migrate_folio instead of migratepage.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> ---
>  Documentation/filesystems/locking.rst |  5 ++--
>  Documentation/filesystems/vfs.rst     | 13 ++++++-----
>  Documentation/vm/page_migration.rst   | 33 ++++++++++++++-------------
>  include/linux/fs.h                    |  4 +++-
>  mm/compaction.c                       |  4 +++-
>  mm/migrate.c                          | 11 +++++----
>  6 files changed, 40 insertions(+), 30 deletions(-)
> 
> diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst
> index c0fe711f14d3..3d28b23676bd 100644
> --- a/Documentation/filesystems/locking.rst
> +++ b/Documentation/filesystems/locking.rst
> @@ -253,7 +253,8 @@ prototypes::
>  	void (*free_folio)(struct folio *);
>  	int (*direct_IO)(struct kiocb *, struct iov_iter *iter);
>  	bool (*isolate_page) (struct page *, isolate_mode_t);
> -	int (*migratepage)(struct address_space *, struct page *, struct page *);
> +	int (*migrate_folio)(struct address_space *, struct folio *dst,
> +			struct folio *src, enum migrate_mode);
>  	void (*putback_page) (struct page *);

isolate_page/putback_page are leftovers from the previous patch, no?

>  	int (*launder_folio)(struct folio *);
>  	bool (*is_partially_uptodate)(struct folio *, size_t from, size_t count);
> @@ -281,7 +282,7 @@ release_folio:		yes
>  free_folio:		yes
>  direct_IO:
>  isolate_page:		yes
> -migratepage:		yes (both)
> +migrate_folio:		yes (both)
>  putback_page:		yes

Dito.

>  launder_folio:		yes
>  is_partially_uptodate:	yes
> diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
> index a08c652467d7..3ae1b039b03f 100644
> --- a/Documentation/filesystems/vfs.rst
> +++ b/Documentation/filesystems/vfs.rst
> @@ -740,7 +740,8 @@ cache in your filesystem.  The following members are defined:
>  		/* isolate a page for migration */
>  		bool (*isolate_page) (struct page *, isolate_mode_t);
>  		/* migrate the contents of a page to the specified target */
> -		int (*migratepage) (struct page *, struct page *);
> +		int (*migrate_folio)(struct mapping *, struct folio *dst,
> +				struct folio *src, enum migrate_mode);
>  		/* put migration-failed page back to right list */
>  		void (*putback_page) (struct page *);

Dito.

>  		int (*launder_folio) (struct folio *);
> @@ -935,12 +936,12 @@ cache in your filesystem.  The following members are defined:
>  	is successfully isolated, VM marks the page as PG_isolated via
>  	__SetPageIsolated.
>  
> -``migrate_page``
> +``migrate_folio``
>  	This is used to compact the physical memory usage.  If the VM
> -	wants to relocate a page (maybe off a memory card that is
> -	signalling imminent failure) it will pass a new page and an old
> -	page to this function.  migrate_page should transfer any private
> -	data across and update any references that it has to the page.
> +	wants to relocate a folio (maybe from a memory device that is
> +	signalling imminent failure) it will pass a new folio and an old
> +	folio to this function.  migrate_folio should transfer any private
> +	data across and update any references that it has to the folio.
>  
>  ``putback_page``
>  	Called by the VM when isolated page's migration fails.

Dito.

> diff --git a/Documentation/vm/page_migration.rst b/Documentation/vm/page_migration.rst
> index 8c5cb8147e55..e0f73ddfabb1 100644
> --- a/Documentation/vm/page_migration.rst
> +++ b/Documentation/vm/page_migration.rst
> @@ -181,22 +181,23 @@ which are function pointers of struct address_space_operations.
>     Once page is successfully isolated, VM uses page.lru fields so driver
>     shouldn't expect to preserve values in those fields.
>  
> -2. ``int (*migratepage) (struct address_space *mapping,``
> -|	``struct page *newpage, struct page *oldpage, enum migrate_mode);``
> -
> -   After isolation, VM calls migratepage() of driver with the isolated page.
> -   The function of migratepage() is to move the contents of the old page to the
> -   new page
> -   and set up fields of struct page newpage. Keep in mind that you should
> -   indicate to the VM the oldpage is no longer movable via __ClearPageMovable()
> -   under page_lock if you migrated the oldpage successfully and returned
> -   MIGRATEPAGE_SUCCESS. If driver cannot migrate the page at the moment, driver
> -   can return -EAGAIN. On -EAGAIN, VM will retry page migration in a short time
> -   because VM interprets -EAGAIN as "temporary migration failure". On returning
> -   any error except -EAGAIN, VM will give up the page migration without
> -   retrying.
> -
> -   Driver shouldn't touch the page.lru field while in the migratepage() function.
> +2. ``int (*migrate_folio) (struct address_space *mapping,``
> +|	``struct folio *dst, struct folio *src, enum migrate_mode);``
> +
> +   After isolation, VM calls the driver's migrate_folio() with the
> +   isolated folio.  The purpose of migrate_folio() is to move the contents
> +   of the source folio to the destination folio and set up the fields
> +   of destination folio.  Keep in mind that you should indicate to the
> +   VM the source folio is no longer movable via __ClearPageMovable()
> +   under folio if you migrated the source successfully and returned
> +   MIGRATEPAGE_SUCCESS.  If driver cannot migrate the folio at the
> +   moment, driver can return -EAGAIN. On -EAGAIN, VM will retry folio
> +   migration in a short time because VM interprets -EAGAIN as "temporary
> +   migration failure".  On returning any error except -EAGAIN, VM will
> +   give up the folio migration without retrying.
> +
> +   Driver shouldn't touch the folio.lru field while in the migrate_folio()
> +   function.
>  
>  3. ``void (*putback_page)(struct page *);``

Hmm, here it's a bit more complicated now, because we essentially have
two paths: LRU+migrate_folio or !LRU+movable_ops
(isolate/migrate/putback page)



-- 
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David / dhildenb


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Re: [PATCH v2 03/19] fs: Add aops->migrate_folio

[Matthew Wilcox]

On Thu, Jun 09, 2022 at 02:50:20PM +0200, David Hildenbrand wrote:
> On 08.06.22 17:02, Matthew Wilcox (Oracle) wrote:
> > diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst
> > index c0fe711f14d3..3d28b23676bd 100644
> > --- a/Documentation/filesystems/locking.rst
> > +++ b/Documentation/filesystems/locking.rst
> > @@ -253,7 +253,8 @@ prototypes::
> >  	void (*free_folio)(struct folio *);
> >  	int (*direct_IO)(struct kiocb *, struct iov_iter *iter);
> >  	bool (*isolate_page) (struct page *, isolate_mode_t);
> > -	int (*migratepage)(struct address_space *, struct page *, struct page *);
> > +	int (*migrate_folio)(struct address_space *, struct folio *dst,
> > +			struct folio *src, enum migrate_mode);
> >  	void (*putback_page) (struct page *);
> 
> isolate_page/putback_page are leftovers from the previous patch, no?

Argh, right, I completely forgot I needed to update the documentation in
that patch.

> > +++ b/Documentation/vm/page_migration.rst
> > @@ -181,22 +181,23 @@ which are function pointers of struct address_space_operations.
> >     Once page is successfully isolated, VM uses page.lru fields so driver
> >     shouldn't expect to preserve values in those fields.
> >  
> > -2. ``int (*migratepage) (struct address_space *mapping,``
> > -|	``struct page *newpage, struct page *oldpage, enum migrate_mode);``
> > -
> > -   After isolation, VM calls migratepage() of driver with the isolated page.
> > -   The function of migratepage() is to move the contents of the old page to the
> > -   new page
> > -   and set up fields of struct page newpage. Keep in mind that you should
> > -   indicate to the VM the oldpage is no longer movable via __ClearPageMovable()
> > -   under page_lock if you migrated the oldpage successfully and returned
> > -   MIGRATEPAGE_SUCCESS. If driver cannot migrate the page at the moment, driver
> > -   can return -EAGAIN. On -EAGAIN, VM will retry page migration in a short time
> > -   because VM interprets -EAGAIN as "temporary migration failure". On returning
> > -   any error except -EAGAIN, VM will give up the page migration without
> > -   retrying.
> > -
> > -   Driver shouldn't touch the page.lru field while in the migratepage() function.
> > +2. ``int (*migrate_folio) (struct address_space *mapping,``
> > +|	``struct folio *dst, struct folio *src, enum migrate_mode);``
> > +
> > +   After isolation, VM calls the driver's migrate_folio() with the
> > +   isolated folio.  The purpose of migrate_folio() is to move the contents
> > +   of the source folio to the destination folio and set up the fields
> > +   of destination folio.  Keep in mind that you should indicate to the
> > +   VM the source folio is no longer movable via __ClearPageMovable()
> > +   under folio if you migrated the source successfully and returned
> > +   MIGRATEPAGE_SUCCESS.  If driver cannot migrate the folio at the
> > +   moment, driver can return -EAGAIN. On -EAGAIN, VM will retry folio
> > +   migration in a short time because VM interprets -EAGAIN as "temporary
> > +   migration failure".  On returning any error except -EAGAIN, VM will
> > +   give up the folio migration without retrying.
> > +
> > +   Driver shouldn't touch the folio.lru field while in the migrate_folio()
> > +   function.
> >  
> >  3. ``void (*putback_page)(struct page *);``
> 
> Hmm, here it's a bit more complicated now, because we essentially have
> two paths: LRU+migrate_folio or !LRU+movable_ops
> (isolate/migrate/putback page)

Oh ... actually, this is just documenting the driver side of things.
I don't really like how it's written.  Here, have some rewritten
documentation (which is now part of the previous patch):

+++ b/Documentation/vm/page_migration.rst
@@ -152,110 +152,15 @@ Steps:
 Non-LRU page migration
 ======================

-Although migration originally aimed for reducing the latency of memory accesses
-for NUMA, compaction also uses migration to create high-order pages.
+Although migration originally aimed for reducing the latency of memory
+accesses for NUMA, compaction also uses migration to create high-order
+pages.  For compaction purposes, it is also useful to be able to move
+non-LRU pages, such as zsmalloc and virtio-balloon pages.

-Current problem of the implementation is that it is designed to migrate only
-*LRU* pages. However, there are potential non-LRU pages which can be migrated
-in drivers, for example, zsmalloc, virtio-balloon pages.
-
-For virtio-balloon pages, some parts of migration code path have been hooked
-up and added virtio-balloon specific functions to intercept migration logics.
-It's too specific to a driver so other drivers who want to make their pages
-movable would have to add their own specific hooks in the migration path.
-
-To overcome the problem, VM supports non-LRU page migration which provides
-generic functions for non-LRU movable pages without driver specific hooks
-in the migration path.
-
-If a driver wants to make its pages movable, it should define three functions
-which are function pointers of struct address_space_operations.
-
-1. ``bool (*isolate_page) (struct page *page, isolate_mode_t mode);``
-
-   What VM expects from isolate_page() function of driver is to return *true*
-   if driver isolates the page successfully. On returning true, VM marks the page
-   as PG_isolated so concurrent isolation in several CPUs skip the page
-   for isolation. If a driver cannot isolate the page, it should return *false*.
-
-   Once page is successfully isolated, VM uses page.lru fields so driver
-   shouldn't expect to preserve values in those fields.
-
-2. ``int (*migratepage) (struct address_space *mapping,``
-|      ``struct page *newpage, struct page *oldpage, enum migrate_mode);``
-
-   After isolation, VM calls migratepage() of driver with the isolated page.
-   The function of migratepage() is to move the contents of the old page to the
-   new page
-   and set up fields of struct page newpage. Keep in mind that you should
-   indicate to the VM the oldpage is no longer movable via __ClearPageMovable()
-   under page_lock if you migrated the oldpage successfully and returned
-   MIGRATEPAGE_SUCCESS. If driver cannot migrate the page at the moment, driver
-   can return -EAGAIN. On -EAGAIN, VM will retry page migration in a short time
-   because VM interprets -EAGAIN as "temporary migration failure". On returning
-   any error except -EAGAIN, VM will give up the page migration without
-   retrying.
-
-   Driver shouldn't touch the page.lru field while in the migratepage() function.
-
-3. ``void (*putback_page)(struct page *);``
-
-   If migration fails on the isolated page, VM should return the isolated page
-   to the driver so VM calls the driver's putback_page() with the isolated page.
-   In this function, the driver should put the isolated page back into its own data
-   structure.
-
-Non-LRU movable page flags
-
-   There are two page flags for supporting non-LRU movable page.
-
-   * PG_movable
-
-     Driver should use the function below to make page movable under page_lock::
-
-       void __SetPageMovable(struct page *page, struct address_space *mapping)
-
-     It needs argument of address_space for registering migration
-     family functions which will be called by VM. Exactly speaking,
-     PG_movable is not a real flag of struct page. Rather, VM
-     reuses the page->mapping's lower bits to represent it::
-
-       #define PAGE_MAPPING_MOVABLE 0x2
-       page->mapping = page->mapping | PAGE_MAPPING_MOVABLE;
-
-     so driver shouldn't access page->mapping directly. Instead, driver should
-     use page_mapping() which masks off the low two bits of page->mapping under
-     page lock so it can get the right struct address_space.
-
-     For testing of non-LRU movable pages, VM supports __PageMovable() function.
-     However, it doesn't guarantee to identify non-LRU movable pages because
-     the page->mapping field is unified with other variables in struct page.
-     If the driver releases the page after isolation by VM, page->mapping
-     doesn't have a stable value although it has PAGE_MAPPING_MOVABLE set
-     (look at __ClearPageMovable). But __PageMovable() is cheap to call whether
-     page is LRU or non-LRU movable once the page has been isolated because LRU
-     pages can never have PAGE_MAPPING_MOVABLE set in page->mapping. It is also
-     good for just peeking to test non-LRU movable pages before more expensive
-     checking with lock_page() in pfn scanning to select a victim.
-
-     For guaranteeing non-LRU movable page, VM provides PageMovable() function.
-     Unlike __PageMovable(), PageMovable() validates page->mapping and
-     mapping->a_ops->isolate_page under lock_page(). The lock_page() prevents
-     sudden destroying of page->mapping.
-
-     Drivers using __SetPageMovable() should clear the flag via
-     __ClearMovablePage() under page_lock() before the releasing the page.
-
-   * PG_isolated
-
-     To prevent concurrent isolation among several CPUs, VM marks isolated page
-     as PG_isolated under lock_page(). So if a CPU encounters PG_isolated
-     non-LRU movable page, it can skip it. Driver doesn't need to manipulate the
-     flag because VM will set/clear it automatically. Keep in mind that if the
-     driver sees a PG_isolated page, it means the page has been isolated by the
-     VM so it shouldn't touch the page.lru field.
-     The PG_isolated flag is aliased with the PG_reclaim flag so drivers
-     shouldn't use PG_isolated for its own purposes.
+If a driver wants to make its pages movable, it should define a struct
+movable_operations.  It then needs to call __SetPageMovable() on each
+page that it may be able to move.  This uses the ``page->mapping`` field,
+so this field is not available for the driver to use for other purposes.

 Monitoring Migration
 =====================
@@ -286,3 +191,5 @@ THP_MIGRATION_FAIL and PGMIGRATE_FAIL to increase.

 Christoph Lameter, May 8, 2006.
 Minchan Kim, Mar 28, 2016.
+
+.. kernel-doc:: include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -19,6 +19,43 @@ struct migration_target_control;
  */
 #define MIGRATEPAGE_SUCCESS            0

+/**
+ * struct movable_operations - Driver page migration
+ * @isolate_page:
+ * The VM calls this function to prepare the page to be moved.  The page
+ * is locked and the driver should not unlock it.  The driver should
+ * return ``true`` if the page is movable and ``false`` if it is not
+ * currently movable.  After this function returns, the VM uses the
+ * page->lru field, so the driver must preserve any information which
+ * is usually stored here.
+ *
+ * @migrate_page:
+ * After isolation, the VM calls this function with the isolated
+ * @src page.  The driver should copy the contents of the
+ * @src page to the @dst page and set up the fields of @dst page.
+ * Both pages are locked.
+ * If page migration is successful, the driver should call
+ * __ClearPageMovable(@src) and return MIGRATEPAGE_SUCCESS.
+ * If the driver cannot migrate the page at the moment, it can return
+ * -EAGAIN.  The VM interprets this as a temporary migration failure and
+ * will retry it later.  Any other error value is a permanent migration
+ * failure and migration will not be retried.
+ * The driver shouldn't touch the @src->lru field while in the
+ * migrate_page() function.  It may write to @dst->lru.
+ *
+ * @putback_page:
+ * If migration fails on the isolated page, the VM informs the driver
+ * that the page is no longer a candidate for migration by calling
+ * this function.  The driver should put the isolated page back into
+ * its own data structure.
+ */
+struct movable_operations {
+       bool (*isolate_page)(struct page *, isolate_mode_t);
+       int (*migrate_page)(struct page *dst, struct page *src,
+                       enum migrate_mode);
+       void (*putback_page)(struct page *);
+};
+
 /* Defined in mm/debug.c: */
 extern const char *migrate_reason_names[MR_TYPES];





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Re: [PATCH v2 08/19] btrfs: Convert btree_migratepage to migrate_folio

[David Sterba]

On Wed, Jun 08, 2022 at 04:02:38PM +0100, Matthew Wilcox (Oracle) wrote:
> Use a folio throughout this function.  migrate_page() will be converted
> later.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Acked-by: David Sterba <dsterba@suse.com>

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Re: [PATCH v2 10/19] mm/migrate: Convert migrate_page() to migrate_folio()

[David Sterba]

On Wed, Jun 08, 2022 at 04:02:40PM +0100, Matthew Wilcox (Oracle) wrote:
> Convert all callers to pass a folio.  Most have the folio
> already available.  Switch all users from aops->migratepage to
> aops->migrate_folio.  Also turn the documentation into kerneldoc.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_userptr.c |  4 +--

For

>  fs/btrfs/disk-io.c                          |  2 +-

Acked-by: David Sterba <dsterba@suse.com>

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Re: [PATCH v2 12/19] btrfs: Convert btrfs_migratepage to migrate_folio

[David Sterba]

On Wed, Jun 08, 2022 at 04:02:42PM +0100, Matthew Wilcox (Oracle) wrote:
> Use filemap_migrate_folio() to do the bulk of the work, and then copy
> the ordered flag across if needed.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Acked-by: David Sterba <dsterba@suse.com>

> +static int btrfs_migrate_folio(struct address_space *mapping,
> +			     struct folio *dst, struct folio *src,
>  			     enum migrate_mode mode)
>  {
> -	int ret;
> +	int ret = filemap_migrate_folio(mapping, dst, src, mode);
>  
> -	ret = migrate_page_move_mapping(mapping, newpage, page, 0);
>  	if (ret != MIGRATEPAGE_SUCCESS)
>  		return ret;
>  
> -	if (page_has_private(page))
> -		attach_page_private(newpage, detach_page_private(page));

If I'm reading it correctly, the private pointer does not need to be set
like that anymore because it's done somewhere during the
filemap_migrate_folio() call.

> -
> -	if (PageOrdered(page)) {
> -		ClearPageOrdered(page);
> -		SetPageOrdered(newpage);
> +	if (folio_test_ordered(src)) {
> +		folio_clear_ordered(src);
> +		folio_set_ordered(dst);
>  	}

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Re: [PATCH v2 12/19] btrfs: Convert btrfs_migratepage to migrate_folio

[Matthew Wilcox]

On Thu, Jun 09, 2022 at 06:33:23PM +0200, David Sterba wrote:
> On Wed, Jun 08, 2022 at 04:02:42PM +0100, Matthew Wilcox (Oracle) wrote:
> > Use filemap_migrate_folio() to do the bulk of the work, and then copy
> > the ordered flag across if needed.
> > 
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> > Reviewed-by: Christoph Hellwig <hch@lst.de>
> 
> Acked-by: David Sterba <dsterba@suse.com>
> 
> > +static int btrfs_migrate_folio(struct address_space *mapping,
> > +			     struct folio *dst, struct folio *src,
> >  			     enum migrate_mode mode)
> >  {
> > -	int ret;
> > +	int ret = filemap_migrate_folio(mapping, dst, src, mode);
> >  
> > -	ret = migrate_page_move_mapping(mapping, newpage, page, 0);
> >  	if (ret != MIGRATEPAGE_SUCCESS)
> >  		return ret;
> >  
> > -	if (page_has_private(page))
> > -		attach_page_private(newpage, detach_page_private(page));
> 
> If I'm reading it correctly, the private pointer does not need to be set
> like that anymore because it's done somewhere during the
> filemap_migrate_folio() call.

That's correct.  Everything except moving the ordered flag across is
done for you, and I'm kind of tempted to modify folio_migrate_flags()
to copy the ordered flag across as well.  Then you could just use
filemap_migrate_folio() directly.

> > -
> > -	if (PageOrdered(page)) {
> > -		ClearPageOrdered(page);
> > -		SetPageOrdered(newpage);
> > +	if (folio_test_ordered(src)) {
> > +		folio_clear_ordered(src);
> > +		folio_set_ordered(dst);
> >  	}

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Re: [PATCH v2 16/19] hugetlb: Convert to migrate_folio

[Mike Kravetz]

On 6/8/22 08:02, Matthew Wilcox (Oracle) wrote:
> This involves converting migrate_huge_page_move_mapping().  We also need a
> folio variant of hugetlb_set_page_subpool(), but that's for a later patch.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  fs/hugetlbfs/inode.c    | 23 ++++++++++++++---------
>  include/linux/migrate.h |  6 +++---
>  mm/migrate.c            | 18 +++++++++---------
>  3 files changed, 26 insertions(+), 21 deletions(-)
> 

Thanks,

> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 14d33f725e05..eca1d0fabd7e 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -954,28 +954,33 @@ static int hugetlbfs_symlink(struct user_namespace *mnt_userns,
>  	return error;
>  }
>  
> -static int hugetlbfs_migrate_page(struct address_space *mapping,
> -				struct page *newpage, struct page *page,
> +#ifdef CONFIG_MIGRATION

and, thanks for adding the #ifdef CONFIG_MIGRATION to save a little space.

Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>

-- 
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Re: [PATCH v2 12/19] btrfs: Convert btrfs_migratepage to migrate_folio

[David Sterba]

On Thu, Jun 09, 2022 at 06:40:28PM +0100, Matthew Wilcox wrote:
> On Thu, Jun 09, 2022 at 06:33:23PM +0200, David Sterba wrote:
> > On Wed, Jun 08, 2022 at 04:02:42PM +0100, Matthew Wilcox (Oracle) wrote:
> > > Use filemap_migrate_folio() to do the bulk of the work, and then copy
> > > the ordered flag across if needed.
> > > 
> > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> > > Reviewed-by: Christoph Hellwig <hch@lst.de>
> > 
> > Acked-by: David Sterba <dsterba@suse.com>
> > 
> > > +static int btrfs_migrate_folio(struct address_space *mapping,
> > > +			     struct folio *dst, struct folio *src,
> > >  			     enum migrate_mode mode)
> > >  {
> > > -	int ret;
> > > +	int ret = filemap_migrate_folio(mapping, dst, src, mode);
> > >  
> > > -	ret = migrate_page_move_mapping(mapping, newpage, page, 0);
> > >  	if (ret != MIGRATEPAGE_SUCCESS)
> > >  		return ret;
> > >  
> > > -	if (page_has_private(page))
> > > -		attach_page_private(newpage, detach_page_private(page));
> > 
> > If I'm reading it correctly, the private pointer does not need to be set
> > like that anymore because it's done somewhere during the
> > filemap_migrate_folio() call.
> 
> That's correct.  Everything except moving the ordered flag across is
> done for you, and I'm kind of tempted to modify folio_migrate_flags()
> to copy the ordered flag across as well.  Then you could just use
> filemap_migrate_folio() directly.

Either way it works for me. If it would mean an unsafe change in folios
or complicate other code I'm fine with the migration callback that
does additional work for btrfs that could be changed later.

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Re: [PATCH v2 03/19] fs: Add aops->migrate_folio

[David Hildenbrand]

On 09.06.22 16:35, Matthew Wilcox wrote:
> On Thu, Jun 09, 2022 at 02:50:20PM +0200, David Hildenbrand wrote:
>> On 08.06.22 17:02, Matthew Wilcox (Oracle) wrote:
>>> diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst
>>> index c0fe711f14d3..3d28b23676bd 100644
>>> --- a/Documentation/filesystems/locking.rst
>>> +++ b/Documentation/filesystems/locking.rst
>>> @@ -253,7 +253,8 @@ prototypes::
>>>  	void (*free_folio)(struct folio *);
>>>  	int (*direct_IO)(struct kiocb *, struct iov_iter *iter);
>>>  	bool (*isolate_page) (struct page *, isolate_mode_t);
>>> -	int (*migratepage)(struct address_space *, struct page *, struct page *);
>>> +	int (*migrate_folio)(struct address_space *, struct folio *dst,
>>> +			struct folio *src, enum migrate_mode);
>>>  	void (*putback_page) (struct page *);
>>
>> isolate_page/putback_page are leftovers from the previous patch, no?
> 
> Argh, right, I completely forgot I needed to update the documentation in
> that patch.
> 
>>> +++ b/Documentation/vm/page_migration.rst
>>> @@ -181,22 +181,23 @@ which are function pointers of struct address_space_operations.
>>>     Once page is successfully isolated, VM uses page.lru fields so driver
>>>     shouldn't expect to preserve values in those fields.
>>>  
>>> -2. ``int (*migratepage) (struct address_space *mapping,``
>>> -|	``struct page *newpage, struct page *oldpage, enum migrate_mode);``
>>> -
>>> -   After isolation, VM calls migratepage() of driver with the isolated page.
>>> -   The function of migratepage() is to move the contents of the old page to the
>>> -   new page
>>> -   and set up fields of struct page newpage. Keep in mind that you should
>>> -   indicate to the VM the oldpage is no longer movable via __ClearPageMovable()
>>> -   under page_lock if you migrated the oldpage successfully and returned
>>> -   MIGRATEPAGE_SUCCESS. If driver cannot migrate the page at the moment, driver
>>> -   can return -EAGAIN. On -EAGAIN, VM will retry page migration in a short time
>>> -   because VM interprets -EAGAIN as "temporary migration failure". On returning
>>> -   any error except -EAGAIN, VM will give up the page migration without
>>> -   retrying.
>>> -
>>> -   Driver shouldn't touch the page.lru field while in the migratepage() function.
>>> +2. ``int (*migrate_folio) (struct address_space *mapping,``
>>> +|	``struct folio *dst, struct folio *src, enum migrate_mode);``
>>> +
>>> +   After isolation, VM calls the driver's migrate_folio() with the
>>> +   isolated folio.  The purpose of migrate_folio() is to move the contents
>>> +   of the source folio to the destination folio and set up the fields
>>> +   of destination folio.  Keep in mind that you should indicate to the
>>> +   VM the source folio is no longer movable via __ClearPageMovable()
>>> +   under folio if you migrated the source successfully and returned
>>> +   MIGRATEPAGE_SUCCESS.  If driver cannot migrate the folio at the
>>> +   moment, driver can return -EAGAIN. On -EAGAIN, VM will retry folio
>>> +   migration in a short time because VM interprets -EAGAIN as "temporary
>>> +   migration failure".  On returning any error except -EAGAIN, VM will
>>> +   give up the folio migration without retrying.
>>> +
>>> +   Driver shouldn't touch the folio.lru field while in the migrate_folio()
>>> +   function.
>>>  
>>>  3. ``void (*putback_page)(struct page *);``
>>
>> Hmm, here it's a bit more complicated now, because we essentially have
>> two paths: LRU+migrate_folio or !LRU+movable_ops
>> (isolate/migrate/putback page)
> 
> Oh ... actually, this is just documenting the driver side of things.
> I don't really like how it's written.  Here, have some rewritten
> documentation (which is now part of the previous patch):
> 

LGTM, thanks.


-- 
Thanks,

David / dhildenb


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Re: [f2fs-dev] [PATCH v2 14/19] f2fs: Convert to filemap_migrate_folio()

[Chao Yu]

On 2022/6/8 23:02, Matthew Wilcox (Oracle) wrote:
> filemap_migrate_folio() fits f2fs's needs perfectly.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Acked-by: Chao Yu <chao@kernel.org>

Thanks,

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Re: [PATCH v2 07/19] mm/migrate: Convert expected_page_refs() to folio_expected_refs()

[Hugh Dickins]

On Wed, 8 Jun 2022, Matthew Wilcox (Oracle) wrote:

> Now that both callers have a folio, convert this function to
> take a folio & rename it.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> ---
>  mm/migrate.c | 19 ++++++++++++-------
>  1 file changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 2975f0c4d7cf..2e2f41572066 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -336,13 +336,18 @@ void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
>  }
>  #endif
>  
> -static int expected_page_refs(struct address_space *mapping, struct page *page)
> +static int folio_expected_refs(struct address_space *mapping,
> +		struct folio *folio)
>  {
> -	int expected_count = 1;
> +	int refs = 1;
> +	if (!mapping)
> +		return refs;
>  
> -	if (mapping)
> -		expected_count += compound_nr(page) + page_has_private(page);
> -	return expected_count;
> +	refs += folio_nr_pages(folio);
> +	if (folio_get_private(folio))
> +		refs++;
> +
> +	return refs;
>  }
>  
>  /*
> @@ -359,7 +364,7 @@ int folio_migrate_mapping(struct address_space *mapping,
>  	XA_STATE(xas, &mapping->i_pages, folio_index(folio));
>  	struct zone *oldzone, *newzone;
>  	int dirty;
> -	int expected_count = expected_page_refs(mapping, &folio->page) + extra_count;
> +	int expected_count = folio_expected_refs(mapping, folio) + extra_count;
>  	long nr = folio_nr_pages(folio);
>  
>  	if (!mapping) {
> @@ -669,7 +674,7 @@ static int __buffer_migrate_folio(struct address_space *mapping,
>  		return migrate_page(mapping, &dst->page, &src->page, mode);
>  
>  	/* Check whether page does not have extra refs before we do more work */
> -	expected_count = expected_page_refs(mapping, &src->page);
> +	expected_count = folio_expected_refs(mapping, src);
>  	if (folio_ref_count(src) != expected_count)
>  		return -EAGAIN;
>  
> -- 
> 2.35.1

This commit (742e89c9e352d38df1a5825fe40c4de73a5d5f7a in pagecache.git
folio/for-next and recent linux-next) is dangerously wrong, at least
for swapcache, and probably for some others.

I say "dangerously" because it tells page migration a swapcache page
is safe for migration when it certainly is not.

The fun that typically ensues is kernel BUG at include/linux/mm.h:750!
put_page_testzero() VM_BUG_ON_PAGE(page_ref_count(page) == 0, page),
if CONFIG_DEBUG_VM=y (bisecting for that is what brought me to this).
But I guess you might get silent data corruption too.

I assumed at first that you'd changed the rules, and were now expecting
any subsystem that puts a non-zero value into folio->private to raise
its refcount - whereas the old convention (originating with buffer heads)
is that setting PG_private says an extra refcount has been taken, please
call try_to_release_page() to lower it, and maybe that will use data in
page->private to do so; but page->private free for the subsystem owning
the page to use as it wishes, no refcount implication.  But that you
had missed updating swapcache.

So I got working okay with the patch below; but before turning it into
a proper patch, noticed that there were still plenty of other places
applying the test for PG_private: so now think that maybe you set out
with intention as above, realized it wouldn't work, but got distracted
before cleaning up some places you'd already changed.  And patch below
now goes in the wrong direction.

Or maybe you didn't intend any change, but the PG_private test just got
missed in a few places.  I don't know, hope you remember, but current
linux-next badly inconsistent.
Over to you, thanks,

Hugh

--- a/mm/migrate.c	2022-07-06 14:24:44.499941975 -0700
+++ b/mm/migrate.c	2022-07-06 15:49:25.000000000 -0700
@@ -351,6 +351,10 @@ unlock:
 }
 #endif
 
+static inline bool folio_counted_private(struct folio *folio)
+{
+	return !folio_test_swapcache(folio) && folio_get_private(folio);
+}
 static int folio_expected_refs(struct address_space *mapping,
 		struct folio *folio)
 {
@@ -359,7 +363,7 @@ static int folio_expected_refs(struct ad
 		return refs;
 
 	refs += folio_nr_pages(folio);
-	if (folio_get_private(folio))
+	if (folio_counted_private(folio))
 		refs++;
 
 	return refs;
--- a/mm/vmscan.c	2022-07-06 14:24:44.531942217 -0700
+++ b/mm/vmscan.c	2022-07-06 15:49:37.000000000 -0700
@@ -2494,6 +2494,10 @@ shrink_inactive_list(unsigned long nr_to
  * The downside is that we have to touch folio->_refcount against each folio.
  * But we had to alter folio->flags anyway.
  */
+static inline bool folio_counted_private(struct folio *folio)
+{
+	return !folio_test_swapcache(folio) && folio_get_private(folio);
+}
 static void shrink_active_list(unsigned long nr_to_scan,
 			       struct lruvec *lruvec,
 			       struct scan_control *sc,
@@ -2538,8 +2542,9 @@ static void shrink_active_list(unsigned
 		}
 
 		if (unlikely(buffer_heads_over_limit)) {
-			if (folio_get_private(folio) && folio_trylock(folio)) {
-				if (folio_get_private(folio))
+			if (folio_counted_private(folio) &&
+			    folio_trylock(folio)) {
+				if (folio_counted_private(folio))
 					filemap_release_folio(folio, 0);
 				folio_unlock(folio);
 			}

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Re: [PATCH v2 07/19] mm/migrate: Convert expected_page_refs() to folio_expected_refs()

[Matthew Wilcox]

On Thu, Jul 07, 2022 at 07:50:17PM -0700, Hugh Dickins wrote:
> On Wed, 8 Jun 2022, Matthew Wilcox (Oracle) wrote:
> 
> > Now that both callers have a folio, convert this function to
> > take a folio & rename it.
> > 
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> > Reviewed-by: Christoph Hellwig <hch@lst.de>
> > ---
> >  mm/migrate.c | 19 ++++++++++++-------
> >  1 file changed, 12 insertions(+), 7 deletions(-)
> > 
> > diff --git a/mm/migrate.c b/mm/migrate.c
> > index 2975f0c4d7cf..2e2f41572066 100644
> > --- a/mm/migrate.c
> > +++ b/mm/migrate.c
> > @@ -336,13 +336,18 @@ void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
> >  }
> >  #endif
> >  
> > -static int expected_page_refs(struct address_space *mapping, struct page *page)
> > +static int folio_expected_refs(struct address_space *mapping,
> > +		struct folio *folio)
> >  {
> > -	int expected_count = 1;
> > +	int refs = 1;
> > +	if (!mapping)
> > +		return refs;
> >  
> > -	if (mapping)
> > -		expected_count += compound_nr(page) + page_has_private(page);
> > -	return expected_count;
> > +	refs += folio_nr_pages(folio);
> > +	if (folio_get_private(folio))
> > +		refs++;
> > +
> > +	return refs;
> >  }
> >  
> >  /*
> > @@ -359,7 +364,7 @@ int folio_migrate_mapping(struct address_space *mapping,
> >  	XA_STATE(xas, &mapping->i_pages, folio_index(folio));
> >  	struct zone *oldzone, *newzone;
> >  	int dirty;
> > -	int expected_count = expected_page_refs(mapping, &folio->page) + extra_count;
> > +	int expected_count = folio_expected_refs(mapping, folio) + extra_count;
> >  	long nr = folio_nr_pages(folio);
> >  
> >  	if (!mapping) {
> > @@ -669,7 +674,7 @@ static int __buffer_migrate_folio(struct address_space *mapping,
> >  		return migrate_page(mapping, &dst->page, &src->page, mode);
> >  
> >  	/* Check whether page does not have extra refs before we do more work */
> > -	expected_count = expected_page_refs(mapping, &src->page);
> > +	expected_count = folio_expected_refs(mapping, src);
> >  	if (folio_ref_count(src) != expected_count)
> >  		return -EAGAIN;
> >  
> > -- 
> > 2.35.1
> 
> This commit (742e89c9e352d38df1a5825fe40c4de73a5d5f7a in pagecache.git
> folio/for-next and recent linux-next) is dangerously wrong, at least
> for swapcache, and probably for some others.
> 
> I say "dangerously" because it tells page migration a swapcache page
> is safe for migration when it certainly is not.
> 
> The fun that typically ensues is kernel BUG at include/linux/mm.h:750!
> put_page_testzero() VM_BUG_ON_PAGE(page_ref_count(page) == 0, page),
> if CONFIG_DEBUG_VM=y (bisecting for that is what brought me to this).
> But I guess you might get silent data corruption too.
> 
> I assumed at first that you'd changed the rules, and were now expecting
> any subsystem that puts a non-zero value into folio->private to raise
> its refcount - whereas the old convention (originating with buffer heads)
> is that setting PG_private says an extra refcount has been taken, please
> call try_to_release_page() to lower it, and maybe that will use data in
> page->private to do so; but page->private free for the subsystem owning
> the page to use as it wishes, no refcount implication.  But that you
> had missed updating swapcache.
> 
> So I got working okay with the patch below; but before turning it into
> a proper patch, noticed that there were still plenty of other places
> applying the test for PG_private: so now think that maybe you set out
> with intention as above, realized it wouldn't work, but got distracted
> before cleaning up some places you'd already changed.  And patch below
> now goes in the wrong direction.
> 
> Or maybe you didn't intend any change, but the PG_private test just got
> missed in a few places.  I don't know, hope you remember, but current
> linux-next badly inconsistent.
> Over to you, thanks,

Ugh.  The problem I'm trying to solve is that we're short on page flags.
We _seemed_ to have correlation between "page->private != NULL" and
"PG_private is set", and so I thought I could make progress towards
removing PG_private.  But the rule you set out above wasn't written down
anywhere that I was able to find it.

I'm about to go to sleep, but I'll think on this some more tomorrow.

> Hugh
> 
> --- a/mm/migrate.c	2022-07-06 14:24:44.499941975 -0700
> +++ b/mm/migrate.c	2022-07-06 15:49:25.000000000 -0700
> @@ -351,6 +351,10 @@ unlock:
>  }
>  #endif
>  
> +static inline bool folio_counted_private(struct folio *folio)
> +{
> +	return !folio_test_swapcache(folio) && folio_get_private(folio);
> +}
>  static int folio_expected_refs(struct address_space *mapping,
>  		struct folio *folio)
>  {
> @@ -359,7 +363,7 @@ static int folio_expected_refs(struct ad
>  		return refs;
>  
>  	refs += folio_nr_pages(folio);
> -	if (folio_get_private(folio))
> +	if (folio_counted_private(folio))
>  		refs++;
>  
>  	return refs;
> --- a/mm/vmscan.c	2022-07-06 14:24:44.531942217 -0700
> +++ b/mm/vmscan.c	2022-07-06 15:49:37.000000000 -0700
> @@ -2494,6 +2494,10 @@ shrink_inactive_list(unsigned long nr_to
>   * The downside is that we have to touch folio->_refcount against each folio.
>   * But we had to alter folio->flags anyway.
>   */
> +static inline bool folio_counted_private(struct folio *folio)
> +{
> +	return !folio_test_swapcache(folio) && folio_get_private(folio);
> +}
>  static void shrink_active_list(unsigned long nr_to_scan,
>  			       struct lruvec *lruvec,
>  			       struct scan_control *sc,
> @@ -2538,8 +2542,9 @@ static void shrink_active_list(unsigned
>  		}
>  
>  		if (unlikely(buffer_heads_over_limit)) {
> -			if (folio_get_private(folio) && folio_trylock(folio)) {
> -				if (folio_get_private(folio))
> +			if (folio_counted_private(folio) &&
> +			    folio_trylock(folio)) {
> +				if (folio_counted_private(folio))
>  					filemap_release_folio(folio, 0);
>  				folio_unlock(folio);
>  			}

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