mm/shmem.c: clean up comment of shmem_swapin_folio

shmem_swapin_folio has changed to use folio but comment still mentions
page.  Update the relevant comment accordingly as suggested by Naoya.

Link: https://lkml.kernel.org/r/20220530115841.4348-1-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Suggested-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/shmem.c

@@ -1706,10 +1706,10 @@ static void shmem_set_folio_swapin_error(struct inode *inode, pgoff_t index,
 }
 
 /*
- * Swap in the page pointed to by *pagep.
- * Caller has to make sure that *pagep contains a valid swapped page.
- * Returns 0 and the page in pagep if success. On failure, returns the
- * error code and NULL in *pagep.
+ * Swap in the folio pointed to by *foliop.
+ * Caller has to make sure that *foliop contains a valid swapped folio.
+ * Returns 0 and the folio in foliop if success. On failure, returns the
+ * error code and NULL in *foliop.
  */
 static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
 			     struct folio **foliop, enum sgp_type sgp,
@@ -1749,7 +1749,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
 	}
 	folio = page_folio(page);
 
-	/* We have to do this with page locked to prevent races */
+	/* We have to do this with folio locked to prevent races */
 	folio_lock(folio);
 	if (!folio_test_swapcache(folio) ||
 	    folio_swap_entry(folio).val != swap.val ||