mm/filemap: Convert mapping_get_entry to return a folio

The pagecache only contains folios, so indicate that this is definitely
not a tail page.  Shrinks mapping_get_entry() by 56 bytes, but grows
pagecache_get_page() by 21 bytes as gcc makes slightly different hot/cold
code decisions.  A net reduction of 35 bytes of text.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>

diff --git a/mm/filemap.c b/mm/filemap.c
index 3902e7e..5c99fd9 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1810,49 +1810,42 @@ EXPORT_SYMBOL(page_cache_prev_miss);
  * @mapping: the address_space to search
  * @index: The page cache index.
  *
- * Looks up the page cache slot at @mapping & @index.  If there is a
- * page cache page, the head page is returned with an increased refcount.
+ * Looks up the page cache entry at @mapping & @index.  If it is a folio,
+ * it is returned with an increased refcount.  If it is a shadow entry
+ * of a previously evicted folio, or a swap entry from shmem/tmpfs,
+ * it is returned without further action.
  *
- * If the slot holds a shadow entry of a previously evicted page, or a
- * swap entry from shmem/tmpfs, it is returned.
- *
- * Return: The head page or shadow entry, %NULL if nothing is found.
+ * Return: The folio, swap or shadow entry, %NULL if nothing is found.
  */
-static struct page *mapping_get_entry(struct address_space *mapping,
-               pgoff_t index)
+static void *mapping_get_entry(struct address_space *mapping, pgoff_t index)
 {
        XA_STATE(xas, &mapping->i_pages, index);
-       struct page *page;
+       struct folio *folio;
 
        rcu_read_lock();
 repeat:
        xas_reset(&xas);
-       page = xas_load(&xas);
-       if (xas_retry(&xas, page))
+       folio = xas_load(&xas);
+       if (xas_retry(&xas, folio))
                goto repeat;
        /*
         * A shadow entry of a recently evicted page, or a swap entry from
         * shmem/tmpfs.  Return it without attempting to raise page count.
         */
-       if (!page || xa_is_value(page))
+       if (!folio || xa_is_value(folio))
                goto out;
 
-       if (!page_cache_get_speculative(page))
+       if (!folio_try_get_rcu(folio))
                goto repeat;
 
-       /*
-        * Has the page moved or been split?
-        * This is part of the lockless pagecache protocol. See
-        * include/linux/pagemap.h for details.
-        */
-       if (unlikely(page != xas_reload(&xas))) {
-               put_page(page);
+       if (unlikely(folio != xas_reload(&xas))) {
+               folio_put(folio);
                goto repeat;
        }
 out:
        rcu_read_unlock();
 
-       return page;
+       return folio;
 }
 
 /**