[Ocfs2-devel] [PATCH v1 1/5] ocfs2: partly revert da5e7c87827e8 for mounting crash issue

[Heming Zhao via Ocfs2-devel <ocfs2-devel@oss.oracle.com>]

After commit da5e7c87827e8 ("ocfs2: cleanup journal init and shutdown"),
journal init later than before, it makes NULL pointer access in free
routine.

Crash flow:

ocfs2_fill_super
 + ocfs2_mount_volume
 |  + ocfs2_dlm_init //fail & return, osb->journal is NULL.
 |  + ...
 |  + ocfs2_check_volume //no chance to init osb->journal
 |
 + ...
 + ocfs2_dismount_volume
    ocfs2_release_system_inodes
      ...
       evict
        ...
         ocfs2_clear_inode
          ocfs2_checkpoint_inode
           ocfs2_ci_fully_checkpointed
            time_after(journal->j_trans_id, ci->ci_last_trans)
             + journal is empty, crash!

For fixing, there are three solutions:

1> Revert commit da5e7c87827e8

For avoiding kernel crash, this make sense for us. We only concerned
whether there has any non-system inode access before dlm init. The
answer is NO. And all journal replay/recovery handling happen after
dlm & journal init done. So this method is not graceful but workable.

2> Add osb->journal check in free inode routine (eg ocfs2_clear_inode)

The fix code is special for mounting phase, but it will continue
working after mounting stage. In another word, this method adds useless
code in normal inode free flow.

3> Do directly free inode in mounting phase

This method is brutal/complex and may introduce unsafe code, currently
maintainer didn't like.

At last, we chose method <1> and partly reverted commit da5e7c87827e8.
We reverted journal init code, and kept cleanup code flow.

Fixes: da5e7c87827e8 ("ocfs2: cleanup journal init and shutdown")
Signed-off-by: Heming Zhao <heming.zhao@suse.com>
---
 fs/ocfs2/inode.c   |  4 ++--
 fs/ocfs2/journal.c | 21 +--------------------
 fs/ocfs2/super.c   | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 36 insertions(+), 22 deletions(-)

diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index 5739dc301569..bb116c39b581 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -125,6 +125,7 @@ struct inode *ocfs2_iget(struct ocfs2_super *osb, u64 blkno, unsigned flags,
 	struct inode *inode = NULL;
 	struct super_block *sb = osb->sb;
 	struct ocfs2_find_inode_args args;
+	journal_t *journal = osb->journal->j_journal;
 
 	trace_ocfs2_iget_begin((unsigned long long)blkno, flags,
 			       sysfile_type);
@@ -171,11 +172,10 @@ struct inode *ocfs2_iget(struct ocfs2_super *osb, u64 blkno, unsigned flags,
 	 * part of the transaction - the inode could have been reclaimed and
 	 * now it is reread from disk.
 	 */
-	if (osb->journal) {
+	if (journal) {
 		transaction_t *transaction;
 		tid_t tid;
 		struct ocfs2_inode_info *oi = OCFS2_I(inode);
-		journal_t *journal = osb->journal->j_journal;
 
 		read_lock(&journal->j_state_lock);
 		if (journal->j_running_transaction)
diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c
index 1887a2708709..afb85de3bb60 100644
--- a/fs/ocfs2/journal.c
+++ b/fs/ocfs2/journal.c
@@ -815,30 +815,11 @@ int ocfs2_journal_init(struct ocfs2_super *osb, int *dirty)
 	int status = -1;
 	struct inode *inode = NULL; /* the journal inode */
 	journal_t *j_journal = NULL;
-	struct ocfs2_journal *journal = NULL;
+	struct ocfs2_journal *journal = osb->journal;
 	struct ocfs2_dinode *di = NULL;
 	struct buffer_head *bh = NULL;
 	int inode_lock = 0;
 
-	/* initialize our journal structure */
-	journal = kzalloc(sizeof(struct ocfs2_journal), GFP_KERNEL);
-	if (!journal) {
-		mlog(ML_ERROR, "unable to alloc journal\n");
-		status = -ENOMEM;
-		goto done;
-	}
-	osb->journal = journal;
-	journal->j_osb = osb;
-
-	atomic_set(&journal->j_num_trans, 0);
-	init_rwsem(&journal->j_trans_barrier);
-	init_waitqueue_head(&journal->j_checkpointed);
-	spin_lock_init(&journal->j_lock);
-	journal->j_trans_id = 1UL;
-	INIT_LIST_HEAD(&journal->j_la_cleanups);
-	INIT_WORK(&journal->j_recovery_work, ocfs2_complete_recovery);
-	journal->j_state = OCFS2_JOURNAL_FREE;
-
 	/* already have the inode for our journal */
 	inode = ocfs2_get_system_file_inode(osb, JOURNAL_SYSTEM_INODE,
 					    osb->slot_num);
diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index 477cdf94122e..5f63a2333e52 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -2015,6 +2015,7 @@ static int ocfs2_initialize_super(struct super_block *sb,
 	int i, cbits, bbits;
 	struct ocfs2_dinode *di = (struct ocfs2_dinode *)bh->b_data;
 	struct inode *inode = NULL;
+	struct ocfs2_journal *journal;
 	struct ocfs2_super *osb;
 	u64 total_blocks;
 
@@ -2195,6 +2196,32 @@ static int ocfs2_initialize_super(struct super_block *sb,
 
 	get_random_bytes(&osb->s_next_generation, sizeof(u32));
 
+	/* FIXME
+	 * This should be done in ocfs2_journal_init(), but unknown
+	 * ordering issues will cause the filesystem to crash.
+	 * If anyone wants to figure out what part of the code
+	 * refers to osb->journal before ocfs2_journal_init() is run,
+	 * be my guest.
+	 */
+	/* initialize our journal structure */
+	journal = kzalloc(sizeof(struct ocfs2_journal), GFP_KERNEL);
+	if (!journal) {
+		mlog(ML_ERROR, "unable to alloc journal\n");
+		status = -ENOMEM;
+		goto bail;
+	}
+	osb->journal = journal;
+	journal->j_osb = osb;
+
+	atomic_set(&journal->j_num_trans, 0);
+	init_rwsem(&journal->j_trans_barrier);
+	init_waitqueue_head(&journal->j_checkpointed);
+	spin_lock_init(&journal->j_lock);
+	journal->j_trans_id = 1UL;
+	INIT_LIST_HEAD(&journal->j_la_cleanups);
+	INIT_WORK(&journal->j_recovery_work, ocfs2_complete_recovery);
+	journal->j_state = OCFS2_JOURNAL_FREE;
+
 	INIT_WORK(&osb->dquot_drop_work, ocfs2_drop_dquot_refs);
 	init_llist_head(&osb->dquot_drop_list);
 
@@ -2483,6 +2510,12 @@ static void ocfs2_delete_osb(struct ocfs2_super *osb)
 
 	kfree(osb->osb_orphan_wipes);
 	kfree(osb->slot_recovery_generations);
+	/* FIXME
+	 * This belongs in journal shutdown, but because we have to
+	 * allocate osb->journal at the middle of ocfs2_initialize_super(),
+	 * we free it here.
+	 */
+	kfree(osb->journal);
 	kfree(osb->local_alloc_copy);
 	kfree(osb->uuid_str);
 	kfree(osb->vol_label);
-- 
2.35.1


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