mm: Convert page migration to XArray

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

diff --git a/mm/migrate.c b/mm/migrate.c
index d6a2e89b086a43d77f155f6b525fc15326d9c035..b3cde3fd094a711f4b70e9961b570b32bc82dc11 100644 (file)
--- 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;
 }