logfs: destroy the reserved inodes while unmounting

We were assuming that the evict_inode() would never be called on
reserved inodes. However, (after the commit 8e22c1a4e logfs: get rid
of magical inodes) while unmounting the file system, in put_super, we
call iput() on all of the reserved inodes.

The following simple test used to cause a kernel panic on LogFS:

1. Mount a LogFS file system on /mnt

2. Create a file
   $ touch /mnt/a

3. Try to unmount the FS
   $ umount /mnt

The simple fix would be to drop the assumption and properly destroy
the reserved inodes.

Signed-off-by: Prasad Joshi <prasadjoshi.linux@gmail.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/fs/logfs/inode.c b/fs/logfs/inode.c
index a422f42238b2..df093d9e4da1 100644
--- a/fs/logfs/inode.c
+++ b/fs/logfs/inode.c
@@ -156,10 +156,26 @@ static void __logfs_destroy_inode(struct inode *inode)
         call_rcu(&inode->i_rcu, logfs_i_callback);
 }
 
+static void __logfs_destroy_meta_inode(struct inode *inode)
+{
+        struct logfs_inode *li = logfs_inode(inode);
+        BUG_ON(li->li_block);
+        call_rcu(&inode->i_rcu, logfs_i_callback);
+}
+
 static void logfs_destroy_inode(struct inode *inode)
 {
         struct logfs_inode *li = logfs_inode(inode);
 
+        if (inode->i_ino < LOGFS_RESERVED_INOS) {
+                /*
+                 * The reserved inodes are never destroyed unless we are in
+                 * unmont path.
+                 */
+                __logfs_destroy_meta_inode(inode);
+                return;
+        }
+
         BUG_ON(list_empty(&li->li_freeing_list));
         spin_lock(&logfs_inode_lock);
         li->li_refcount--;