memfd: Convert memfd_tag_pins to XArray

Switch to a batch-processing model like memfd_wait_for_pins() and
use the xa_state previously set up by memfd_wait_for_pins().

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>

diff --git a/mm/memfd.c b/mm/memfd.c
index cf0ddd5fc859901aa38078722051a8293667fc50..97264c79d2cd3007d5d1e30def6a05e9bb95132d 100644 (file)
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -28,37 +28,29 @@
 #define MEMFD_TAG_PINNED        PAGECACHE_TAG_TOWRITE
 #define LAST_SCAN               4       /* about 150ms max */
 
-static void memfd_tag_pins(struct address_space *mapping)
+static void memfd_tag_pins(struct xa_state *xas)
 {
-       struct radix_tree_iter iter;
-       void __rcu **slot;
-       pgoff_t start;
        struct page *page;
+       unsigned int tagged = 0;
 
        lru_add_drain();
-       start = 0;
-       rcu_read_lock();
-
-       radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) {
-               page = radix_tree_deref_slot(slot);
-               if (!page || radix_tree_exception(page)) {
-                       if (radix_tree_deref_retry(page)) {
-                               slot = radix_tree_iter_retry(&iter);
-                               continue;
-                       }
-               } else if (page_count(page) - page_mapcount(page) > 1) {
-                       xa_lock_irq(&mapping->i_pages);
-                       radix_tree_tag_set(&mapping->i_pages, iter.index,
-                                          MEMFD_TAG_PINNED);
-                       xa_unlock_irq(&mapping->i_pages);
-               }
 
-               if (need_resched()) {
-                       slot = radix_tree_iter_resume(slot, &iter);
-                       cond_resched_rcu();
-               }
+       xas_lock_irq(xas);
+       xas_for_each(xas, page, ULONG_MAX) {
+               if (xa_is_value(page))
+                       continue;
+               if (page_count(page) - page_mapcount(page) > 1)
+                       xas_set_mark(xas, MEMFD_TAG_PINNED);
+
+               if (++tagged % XA_CHECK_SCHED)
+                       continue;
+
+               xas_pause(xas);
+               xas_unlock_irq(xas);
+               cond_resched();
+               xas_lock_irq(xas);
        }
-       rcu_read_unlock();
+       xas_unlock_irq(xas);
 }
 
 /*
@@ -76,7 +68,7 @@ static int memfd_wait_for_pins(struct address_space *mapping)
        struct page *page;
        int error, scan;
 
-       memfd_tag_pins(mapping);
+       memfd_tag_pins(&xas);
 
        error = 0;
        for (scan = 0; scan <= LAST_SCAN; scan++) {