ext4: Handle nested ext4_journal_start/stop calls without a journal

This patch fixes a problem with handling nested calls to
ext4_journal_start/ext4_journal_stop, when there is no journal present.

Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
index 139fb8cb87e4..a2865980342f 100644
--- a/fs/ext4/ext4_jbd2.h
+++ b/fs/ext4/ext4_jbd2.h
@@ -161,11 +161,13 @@ int __ext4_handle_dirty_metadata(const char *where, handle_t *handle,
 handle_t *ext4_journal_start_sb(struct super_block *sb, int nblocks);
 int __ext4_journal_stop(const char *where, handle_t *handle);
 
-#define EXT4_NOJOURNAL_HANDLE   ((handle_t *) 0x1)
+#define EXT4_NOJOURNAL_MAX_REF_COUNT ((unsigned long) 4096)
 
+/* Note:  Do not use this for NULL handles.  This is only to determine if
+ * a properly allocated handle is using a journal or not. */
 static inline int ext4_handle_valid(handle_t *handle)
 {
-        if (handle == EXT4_NOJOURNAL_HANDLE)
+        if ((unsigned long)handle < EXT4_NOJOURNAL_MAX_REF_COUNT)
                 return 0;
         return 1;
 }