shmem: Convert find_swap_entry to XArray

This is a 1:1 conversion.  The major part of this patch is converting
the test framework from userspace to kernel space and mirroring the
algorithm now used in find_swap_entry().

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

1 files changed, 10 insertions, 17 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index ce91569426f3..a305529d6b89 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1100,34 +1100,27 @@ static void shmem_evict_inode(struct inode *inode)
         clear_inode(inode);
 }
 
-static unsigned long find_swap_entry(struct radix_tree_root *root, void *item)
+static unsigned long find_swap_entry(struct xarray *xa, void *item)
 {
-        struct radix_tree_iter iter;
-        void __rcu **slot;
-        unsigned long found = -1;
+        XA_STATE(xas, xa, 0);
         unsigned int checked = 0;
+        void *entry;
 
         rcu_read_lock();
-        radix_tree_for_each_slot(slot, root, &iter, 0) {
-                void *entry = radix_tree_deref_slot(slot);
-
-                if (radix_tree_deref_retry(entry)) {
-                        slot = radix_tree_iter_retry(&iter);
+        xas_for_each(&xas, entry, ULONG_MAX) {
+                if (xas_retry(&xas, entry))
                         continue;
-                }
-                if (entry == item) {
-                        found = iter.index;
+                if (entry == item)
                         break;
-                }
                 checked++;
-                if ((checked % 4096) != 0)
+                if ((checked % XA_CHECK_SCHED) != 0)
                         continue;
-                slot = radix_tree_iter_resume(slot, &iter);
+                xas_pause(&xas);
                 cond_resched_rcu();
         }
-
         rcu_read_unlock();
-        return found;
+
+        return entry ? xas.xa_index : -1;
 }
 
 /*