mm: zswap: simplify zswap_invalidate()

The branching is awkward and duplicates code. The comment about
writeback is also misleading: yes, the entry might have been written
back. Or it might have never been stored in zswap to begin with due to
a rejection - zswap_invalidate() is called on all exiting swap entries.

Link: https://lkml.kernel.org/r/20240130014208.565554-10-hannes@cmpxchg.orgSigned-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/zswap.c

@@ -1739,15 +1739,10 @@ void zswap_invalidate(int type, pgoff_t offset)
 	struct zswap_tree *tree = swap_zswap_tree(swp_entry(type, offset));
 	struct zswap_entry *entry;
 
-	/* find */
 	spin_lock(&tree->lock);
 	entry = zswap_rb_search(&tree->rbroot, offset);
-	if (!entry) {
-		/* entry was written back */
-		spin_unlock(&tree->lock);
-		return;
-	}
-	zswap_invalidate_entry(tree, entry);
+	if (entry)
+		zswap_invalidate_entry(tree, entry);
 	spin_unlock(&tree->lock);
 }