[PATCH] Direct Migration V9: Avoid writeback / page_migrate() method

Migrate a page with buffers without requiring writeback

This introduces a new address space operation migratepage() that may be used
by a filesystem to implement its own version of page migration.

A version is provided that migrates buffers attached to pages.  Some
filesystems (ext2, ext3, xfs) are modified to utilize this feature.

The swapper address space operation are modified so that a regular
migrate_page() will occur for anonymous pages without writeback (migrate_pages
forces every anonymous page to have a swap entry).

Signed-off-by: Mike Kravetz <kravetz@us.ibm.com>
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 13 insertions, 0 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 84bb449b9b01..e059da947007 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -363,6 +363,8 @@ struct address_space_operations {
                         loff_t offset, unsigned long nr_segs);
         struct page* (*get_xip_page)(struct address_space *, sector_t,
                         int);
+        /* migrate the contents of a page to the specified target */
+        int (*migratepage) (struct page *, struct page *);
 };
 
 struct backing_dev_info;
@@ -1719,6 +1721,12 @@ extern void simple_release_fs(struct vfsmount **mount, int *count);
 
 extern ssize_t simple_read_from_buffer(void __user *, size_t, loff_t *, const void *, size_t);
 
+#ifdef CONFIG_MIGRATION
+extern int buffer_migrate_page(struct page *, struct page *);
+#else
+#define buffer_migrate_page NULL
+#endif
+
 extern int inode_change_ok(struct inode *, struct iattr *);
 extern int __must_check inode_setattr(struct inode *, struct iattr *);
 
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 229b6d04b4b6..f3e17d5963c3 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -193,13 +193,18 @@ extern int isolate_lru_page(struct page *p);
 extern int putback_lru_pages(struct list_head *l);
 extern int migrate_page(struct page *, struct page *);
 extern void migrate_page_copy(struct page *, struct page *);
+extern int migrate_page_remove_references(struct page *, struct page *, int);
 extern int migrate_pages(struct list_head *l, struct list_head *t,
                 struct list_head *moved, struct list_head *failed);
+extern int fail_migrate_page(struct page *, struct page *);
 #else
 static inline int isolate_lru_page(struct page *p) { return -ENOSYS; }
 static inline int putback_lru_pages(struct list_head *l) { return 0; }
 static inline int migrate_pages(struct list_head *l, struct list_head *t,
         struct list_head *moved, struct list_head *failed) { return -ENOSYS; }
+/* Possible settings for the migrate_page() method in address_operations */
+#define migrate_page NULL
+#define fail_migrate_page NULL
 #endif
 
 #ifdef CONFIG_MMU