page cache; Convert find_get_pages_range_tag to XArray

The 'end' parameter of the xas_for_each iterator avoids a useless
iteration at the end of the range.

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

1 files changed, 26 insertions, 42 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 089b67598100..0df28aa6411c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1789,74 +1789,58 @@ EXPORT_SYMBOL(find_get_pages_contig);
  * @tag.   We update @index to index the next page for the traversal.
  */
 unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
-                        pgoff_t end, int tag, unsigned int nr_pages,
+                        pgoff_t end, xa_mark_t tag, unsigned int nr_pages,
                         struct page **pages)
 {
-        struct radix_tree_iter iter;
-        void **slot;
+        XA_STATE(xas, &mapping->i_pages, *index);
+        struct page *page;
         unsigned ret = 0;
 
         if (unlikely(!nr_pages))
                 return 0;
 
         rcu_read_lock();
-        radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter, *index, tag) {
-                struct page *head, *page;
-
-                if (iter.index > end)
-                        break;
-repeat:
-                page = radix_tree_deref_slot(slot);
-                if (unlikely(!page))
+        xas_for_each_marked(&xas, page, end, tag) {
+                struct page *head;
+                if (xas_retry(&xas, page))
                         continue;
-
-                if (radix_tree_exception(page)) {
-                        if (radix_tree_deref_retry(page)) {
-                                slot = radix_tree_iter_retry(&iter);
-                                continue;
-                        }
-                        /*
-                         * A shadow entry of a recently evicted page.
-                         *
-                         * Those entries should never be tagged, but
-                         * this tree walk is lockless and the tags are
-                         * looked up in bulk, one radix tree node at a
-                         * time, so there is a sizable window for page
-                         * reclaim to evict a page we saw tagged.
-                         *
-                         * Skip over it.
-                         */
+                /*
+                 * Shadow entries should never be tagged, but this iteration
+                 * is lockless so there is a window for page reclaim to evict
+                 * a page we saw tagged.  Skip over it.
+                 */
+                if (xa_is_value(page))
                         continue;
-                }
 
                 head = compound_head(page);
                 if (!page_cache_get_speculative(head))
-                        goto repeat;
+                        goto retry;
 
                 /* The page was split under us? */
-                if (compound_head(page) != head) {
-                        put_page(head);
-                        goto repeat;
-                }
+                if (compound_head(page) != head)
+                        goto put_page;
 
                 /* Has the page moved? */
-                if (unlikely(page != *slot)) {
-                        put_page(head);
-                        goto repeat;
-                }
+                if (unlikely(page != xas_reload(&xas)))
+                        goto put_page;
 
                 pages[ret] = page;
                 if (++ret == nr_pages) {
-                        *index = pages[ret - 1]->index + 1;
+                        *index = page->index + 1;
                         goto out;
                 }
+                continue;
+put_page:
+                put_page(head);
+retry:
+                xas_reset(&xas);
         }
 
         /*
-         * We come here when we got at @end. We take care to not overflow the
+         * We come here when we got to @end. We take care to not overflow the
          * index @index as it confuses some of the callers. This breaks the
-         * iteration when there is page at index -1 but that is already broken
-         * anyway.
+         * iteration when there is a page at index -1 but that is already
+         * broken anyway.
          */
         if (end == (pgoff_t)-1)
                 *index = (pgoff_t)-1;