ized way when under high pressure.
+ * Return: true if any cluster is discarded.
+ */
+static bool swap_sync_discard(void)
+{
+	bool ret = false;
+	int nid = numa_node_id();
+	struct swap_info_struct *si, *next;
+
+	spin_lock(&swap_avail_lock);
+	plist_for_each_entry_safe(si, next, &swap_avail_heads[nid], avail_lists[nid]) {
+		spin_unlock(&swap_avail_lock);
+		if (get_swap_device_info(si)) {
+			if (si->flags & SWP_PAGE_DISCARD)
+				ret = swap_do_scheduled_discard(si);
+			put_swap_device(si);
+		}
+		if (ret)
+			return true;
+		spin_lock(&swap_avail_lock);
+	}
+	spin_unlock(&swap_avail_lock);
+
+	return false;
+}
+
 /**
  * folio_alloc_swap - allocate swap space for a folio
  * @folio: folio we want to move to swap
@@ -1432,11 +1452,17 @@ int folio_alloc_swap(struct folio *folio, gfp_t gfp)
 		}
 	}
 
+again:
 	local_lock(&percpu_swap_cluster.lock);
 	if (!swap_alloc_fast(&entry, order))
 		swap_alloc_slow(&entry, order);
 	local_unlock(&percpu_swap_cluster.lock);
 
+	if (unlikely(!order && !entry.val)) {
+		if (swap_sync_discard())
+			goto again;
+	}
+
 	/* Need to call this even if allocation failed, for MEMCG_SWAP_FAIL. */
 	if (mem_cgroup_try_charge_swap(folio, entry))
 		goto out_free;

-- 
2.51.0[PATCH v2 1/5] mm, swap: do not perform synchronous discard during allocationKairui Song <ryncsn@gmail.com> undefinedlinux-mm@kvack.org undefined undefined undefined undefined undefined undefined undefined undefined undefined undefined undefined undefined undefined undefined undefined„1ƒÂ2