From 5afbafc6872e31a9244efbc9deacc648bc132870 Mon Sep 17 00:00:00 2001
From: roy <roywfhuang@gmail.com>
Date: Sun, 19 May 2024 20:42:07 +0800
Subject: [PATCH 1/2] Fix sb_read cache not be freed

---
 dir.c   | 6 ++++--
 inode.c | 4 ++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/dir.c b/dir.c
index 3c665ef..b9d4e24 100644
--- a/dir.c
+++ b/dir.c
@@ -60,9 +60,11 @@ static int simplefs_iterate(struct file *dir, struct dir_context *ctx)
                 goto release_bh;
             }
             dblock = (struct simplefs_dir_block *) bh2->b_data;
-            if (dblock->files[0].inode == 0)
+            if (dblock->files[0].inode == 0) {
+                brelse(bh2);
+                bh2 = NULL;
                 break;
-
+            }
             /* Iterate every file in one block */
             for (; fi < SIMPLEFS_FILES_PER_BLOCK; fi++) {
                 f = &dblock->files[fi];
diff --git a/inode.c b/inode.c
index 7cb19c7..ce7b585 100644
--- a/inode.c
+++ b/inode.c
@@ -749,8 +749,8 @@ static int simplefs_rename(struct inode *old_dir,
                     break;
                 }
             }
-            if (new_pos < 0)
-                brelse(bh2);
+
+            brelse(bh2);
         }
     }
 

From cc21eeeab47ec0438eecf5a6c5b8816c810ef943 Mon Sep 17 00:00:00 2001
From: roy <roywfhuang@gmail.com>
Date: Sun, 4 Aug 2024 22:01:03 +0800
Subject: [PATCH 2/2] 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 1a7a303..36f0c56 100644
--- a/super.c
+++ b/super.c
@@ -37,6 +37,9 @@ 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);
 }