ocfs2: fix umount hang while shutting down truncate log

Revert commit 75f82eaa502c ("ocfs2: fix NULL pointer dereference when
dismount and ocfs2rec simultaneously") because it may cause a umount
hang while shutting down the truncate log.

fix NULL pointer dereference when dismount and ocfs2rec simultaneously

The situation is as followes:
ocfs2_dismout_volume
-> ocfs2_recovery_exit
  -> free osb->recovery_map
-> ocfs2_truncate_shutdown
  -> lock global bitmap inode
    -> ocfs2_wait_for_recovery
	  -> check whether osb->recovery_map->rm_used is zero

Because osb->recovery_map is already freed, rm_used can be any other
values, so it may yield umount hang.

To prevent NULL pointer dereference while getting sys_root_inode, we use
a osb_tl_disable flag to disable schedule osb_truncate_log_wq after
truncate log shutdown.

Signed-off-by: joyce.xue <xuejiufei@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 6 insertions, 1 deletions

diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
index b4deb5f750d9..9d8fcf2f3b94 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -6046,7 +6046,8 @@ static void ocfs2_truncate_log_worker(struct work_struct *work)
 void ocfs2_schedule_truncate_log_flush(struct ocfs2_super *osb,
                                        int cancel)
 {
-        if (osb->osb_tl_inode) {
+        if (osb->osb_tl_inode &&
+                        atomic_read(&osb->osb_tl_disable) == 0) {
                 /* We want to push off log flushes while truncates are
                  * still running. */
                 if (cancel)
@@ -6223,6 +6224,8 @@ void ocfs2_truncate_log_shutdown(struct ocfs2_super *osb)
         int status;
         struct inode *tl_inode = osb->osb_tl_inode;
 
+        atomic_set(&osb->osb_tl_disable, 1);
+
         if (tl_inode) {
                 cancel_delayed_work(&osb->osb_truncate_log_wq);
                 flush_workqueue(ocfs2_wq);
@@ -6254,6 +6257,7 @@ int ocfs2_truncate_log_init(struct ocfs2_super *osb)
          * until we're sure all is well. */
         INIT_DELAYED_WORK(&osb->osb_truncate_log_wq,
                           ocfs2_truncate_log_worker);
+        atomic_set(&osb->osb_tl_disable, 0);
         osb->osb_tl_bh    = tl_bh;
         osb->osb_tl_inode = tl_inode;
 
diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index 8d64a97a9d5e..bbec539230fd 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -422,6 +422,7 @@ struct ocfs2_super
         struct inode                    *osb_tl_inode;
         struct buffer_head              *osb_tl_bh;
         struct delayed_work             osb_truncate_log_wq;
+        atomic_t                        osb_tl_disable;
         /*
          * How many clusters in our truncate log.
          * It must be protected by osb_tl_inode->i_mutex.