From 4cbaa4d55c37e1e0687fd575febccae02ec6d5e8 Mon Sep 17 00:00:00 2001
From: roy <roywfhuang@gmail.com>
Date: Sun, 4 Aug 2024 22:01:03 +0800
Subject: [PATCH] Fix cache leak in umount simplefs

1. When the cache be destoryed, we should call rcu_barrier() to prevent
call_rcu() still works and this also prevent the cache be reused.

2. After simplefs_destroy_inode_cache() function, we need rcu_barrier()
to make sure all memory have be freed.
---
 fs.c    | 4 ++++
 super.c | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/fs.c b/fs.c
index da7e187..7bd6ac3 100644
--- a/fs.c
+++ b/fs.c
@@ -58,6 +58,8 @@ static int __init simplefs_init(void)
 
 err_inode:
     simplefs_destroy_inode_cache();
+    /* Only after rcu_barrier() is the memory guaranteed to be freed. */
+    rcu_barrier();
 err:
     return ret;
 }
@@ -69,6 +71,8 @@ static void __exit simplefs_exit(void)
         pr_err("Failed to unregister file system\n");
 
     simplefs_destroy_inode_cache();
+    /* Only after rcu_barrier() is the memory guaranteed to be freed. */
+    rcu_barrier();
 
     pr_info("module unloaded\n");
 }
diff --git a/super.c b/super.c
index e966ec9..cad118c 100644
--- a/super.c
+++ b/super.c
@@ -32,6 +32,9 @@ int simplefs_init_inode_cache(void)
 /* De-allocate the inode cache */
 void simplefs_destroy_inode_cache(void)
 {
+    /* wait for call_rcu() and prevent the free cache be used */
+    rcu_barrier();
+
     kmem_cache_destroy(simplefs_inode_cache);
 }