mm: Convert page migration to XArray

Signed-off-by: Matthew Wilcox <willy@infradead.org>

1 files changed, 18 insertions, 30 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index d6a2e89b086a..b3cde3fd094a 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -323,7 +323,7 @@ void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
         page = migration_entry_to_page(entry);
 
         /*
-         * Once radix-tree replacement of page migration started, page_count
+         * Once page cache replacement of page migration started, page_count
          * *must* be zero. And, we don't want to call wait_on_page_locked()
          * against a page without get_page().
          * So, we use get_page_unless_zero(), here. Even failed, page fault
@@ -438,10 +438,10 @@ int migrate_page_move_mapping(struct address_space *mapping,
                 struct buffer_head *head, enum migrate_mode mode,
                 int extra_count)
 {
+        XA_STATE(xas, &mapping->i_pages, page_index(page));
         struct zone *oldzone, *newzone;
         int dirty;
         int expected_count = 1 + extra_count;
-        void **pslot;
 
         /*
          * Device public or private pages have an extra refcount as they are
@@ -467,21 +467,16 @@ int migrate_page_move_mapping(struct address_space *mapping,
         oldzone = page_zone(page);
         newzone = page_zone(newpage);
 
-        xa_lock_irq(&mapping->i_pages);
-
-        pslot = radix_tree_lookup_slot(&mapping->i_pages,
-                                        page_index(page));
+        xas_lock_irq(&xas);
 
         expected_count += hpage_nr_pages(page) + page_has_private(page);
-        if (page_count(page) != expected_count ||
-                radix_tree_deref_slot_protected(pslot,
-                                        &mapping->i_pages.xa_lock) != page) {
-                xa_unlock_irq(&mapping->i_pages);
+        if (page_count(page) != expected_count || xas_load(&xas) != page) {
+                xas_unlock_irq(&xas);
                 return -EAGAIN;
         }
 
         if (!page_ref_freeze(page, expected_count)) {
-                xa_unlock_irq(&mapping->i_pages);
+                xas_unlock_irq(&xas);
                 return -EAGAIN;
         }
 
@@ -495,7 +490,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
         if (mode == MIGRATE_ASYNC && head &&
                         !buffer_migrate_lock_buffers(head, mode)) {
                 page_ref_unfreeze(page, expected_count);
-                xa_unlock_irq(&mapping->i_pages);
+                xas_unlock_irq(&xas);
                 return -EAGAIN;
         }
 
@@ -523,16 +518,13 @@ int migrate_page_move_mapping(struct address_space *mapping,
                 SetPageDirty(newpage);
         }
 
-        radix_tree_replace_slot(&mapping->i_pages, pslot, newpage);
+        xas_store(&xas, newpage);
         if (PageTransHuge(page)) {
                 int i;
-                int index = page_index(page);
 
                 for (i = 1; i < HPAGE_PMD_NR; i++) {
-                        pslot = radix_tree_lookup_slot(&mapping->i_pages,
-                                                       index + i);
-                        radix_tree_replace_slot(&mapping->i_pages, pslot,
-                                                newpage + i);
+                        xas_next(&xas);
+                        xas_store(&xas, newpage + i);
                 }
         }
 
@@ -543,7 +535,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
          */
         page_ref_unfreeze(page, expected_count - hpage_nr_pages(page));
 
-        xa_unlock(&mapping->i_pages);
+        xas_unlock(&xas);
         /* Leave irq disabled to prevent preemption while updating stats */
 
         /*
@@ -583,22 +575,18 @@ EXPORT_SYMBOL(migrate_page_move_mapping);
 int migrate_huge_page_move_mapping(struct address_space *mapping,
                                    struct page *newpage, struct page *page)
 {
+        XA_STATE(xas, &mapping->i_pages, page_index(page));
         int expected_count;
-        void **pslot;
-
-        xa_lock_irq(&mapping->i_pages);
-
-        pslot = radix_tree_lookup_slot(&mapping->i_pages, page_index(page));
 
+        xas_lock_irq(&xas);
         expected_count = 2 + page_has_private(page);
-        if (page_count(page) != expected_count ||
-                radix_tree_deref_slot_protected(pslot, &mapping->i_pages.xa_lock) != page) {
-                xa_unlock_irq(&mapping->i_pages);
+        if (page_count(page) != expected_count || xas_load(&xas) != page) {
+                xas_unlock_irq(&xas);
                 return -EAGAIN;
         }
 
         if (!page_ref_freeze(page, expected_count)) {
-                xa_unlock_irq(&mapping->i_pages);
+                xas_unlock_irq(&xas);
                 return -EAGAIN;
         }
 
@@ -607,11 +595,11 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
 
         get_page(newpage);
 
-        radix_tree_replace_slot(&mapping->i_pages, pslot, newpage);
+        xas_store(&xas, newpage);
 
         page_ref_unfreeze(page, expected_count - 1);
 
-        xa_unlock_irq(&mapping->i_pages);
+        xas_unlock_irq(&xas);
 
         return MIGRATEPAGE_SUCCESS;
 }