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>

3 files changed, 17 insertions, 2 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--;
diff --git a/fs/logfs/readwrite.c b/fs/logfs/readwrite.c
index e3ab5e5a904c..c8ea8664699c 100644
--- a/fs/logfs/readwrite.c
+++ b/fs/logfs/readwrite.c
@@ -2189,7 +2189,6 @@ void logfs_evict_inode(struct inode *inode)
                 return;
         }
 
-        BUG_ON(inode->i_ino < LOGFS_RESERVED_INOS);
         page = inode_to_page(inode);
         BUG_ON(!page); /* FIXME: Use emergency page */
         logfs_put_write_page(page);
diff --git a/fs/logfs/segment.c b/fs/logfs/segment.c
index e28d090c98d6..038da0991794 100644
--- a/fs/logfs/segment.c
+++ b/fs/logfs/segment.c
@@ -886,7 +886,7 @@ static struct logfs_area *alloc_area(struct super_block *sb)
 
 static void map_invalidatepage(struct page *page, unsigned long l)
 {
-        BUG();
+        return;
 }
 
 static int map_releasepage(struct page *page, gfp_t g)