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Date:	Sat, 29 Jun 2013 19:46:48 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Younger Liu <younger.liu@...wei.com>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	jbacik@...ionio.com, Jan Kara <jack@...e.cz>
Subject: Re: [PATCH] jbd2: invalidate handle if jbd2_journal_restart() fails

On Tue, Jun 25, 2013 at 05:42:10PM +0800, Younger Liu wrote:
> If jbd2__journal_restart fails, handle->h_transaction may be NULL.
> So we should check handle->h_transaction before 
> "journal = transaction->t_journal", Right?

Good point, yes.  Here's a new version of the patch which I have in my tree.

     	    	  	       	       	      - Ted

>From fd8d369f9ad921eb6dc5c56e87e4c6d6106bad56 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso@....edu>
Date: Sun, 23 Jun 2013 12:59:01 -0400
Subject: [PATCH] jbd2: invalidate handle if jbd2_journal_restart() fails

If jbd2_journal_restart() fails the handle will have been disconnected
from the current transaction.  In this situation, the handle must not
be used for for any jbd2 function other than jbd2_journal_stop().
Enforce this with by treating a handle which has a NULL transaction
pointer as an aborted handle, and issue a kernel warning if
jbd2_journal_extent(), jbd2_journal_get_write_access(),
jbd2_journal_dirty_metadata(), etc. is called with an invalid handle.

This commit also fixes a bug where jbd2_journal_stop() would trip over
a kernel jbd2 assertion check when trying to free an invalid handle.

Also move the responsibility of setting current->journal_info to
start_this_handle(), simplifying the three users of this function.

Signed-off-by: "Theodore Ts'o" <tytso@....edu>
Reported-by: Younger Liu <younger.liu@...wei.com>
Cc: Jan Kara <jack@...e.cz>
---
 fs/jbd2/transaction.c | 74 ++++++++++++++++++++++++++++++---------------------
 include/linux/jbd2.h  |  2 +-
 2 files changed, 44 insertions(+), 32 deletions(-)

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 383b0fb..7aa9a32 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -368,6 +368,7 @@ repeat:
 		  atomic_read(&transaction->t_outstanding_credits),
 		  jbd2_log_space_left(journal));
 	read_unlock(&journal->j_state_lock);
+	current->journal_info = handle;
 
 	lock_map_acquire(&handle->h_lockdep_map);
 	jbd2_journal_free_transaction(new_transaction);
@@ -442,14 +443,11 @@ handle_t *jbd2__journal_start(journal_t *journal, int nblocks, int rsv_blocks,
 		handle->h_rsv_handle = rsv_handle;
 	}
 
-	current->journal_info = handle;
-
 	err = start_this_handle(journal, handle, gfp_mask);
 	if (err < 0) {
 		if (handle->h_rsv_handle)
 			jbd2_free_handle(handle->h_rsv_handle);
 		jbd2_free_handle(handle);
-		current->journal_info = NULL;
 		return ERR_PTR(err);
 	}
 	handle->h_type = type;
@@ -511,16 +509,13 @@ int jbd2_journal_start_reserved(handle_t *handle, unsigned int type,
 	}
 
 	handle->h_journal = NULL;
-	current->journal_info = handle;
 	/*
 	 * GFP_NOFS is here because callers are likely from writeback or
 	 * similarly constrained call sites
 	 */
 	ret = start_this_handle(journal, handle, GFP_NOFS);
-	if (ret < 0) {
-		current->journal_info = NULL;
+	if (ret < 0)
 		jbd2_journal_free_reserved(handle);
-	}
 	handle->h_type = type;
 	handle->h_line_no = line_no;
 	return ret;
@@ -550,20 +545,21 @@ EXPORT_SYMBOL(jbd2_journal_start_reserved);
 int jbd2_journal_extend(handle_t *handle, int nblocks)
 {
 	transaction_t *transaction = handle->h_transaction;
-	journal_t *journal = transaction->t_journal;
+	journal_t *journal;
 	int result;
 	int wanted;
 
-	result = -EIO;
+	WARN_ON(!transaction);
 	if (is_handle_aborted(handle))
-		goto out;
+		return -EROFS;
+	journal = transaction->t_journal;
 
 	result = 1;
 
 	read_lock(&journal->j_state_lock);
 
 	/* Don't extend a locked-down transaction! */
-	if (handle->h_transaction->t_state != T_RUNNING) {
+	if (transaction->t_state != T_RUNNING) {
 		jbd_debug(3, "denied handle %p %d blocks: "
 			  "transaction not running\n", handle, nblocks);
 		goto error_out;
@@ -589,7 +585,7 @@ int jbd2_journal_extend(handle_t *handle, int nblocks)
 	}
 
 	trace_jbd2_handle_extend(journal->j_fs_dev->bd_dev,
-				 handle->h_transaction->t_tid,
+				 transaction->t_tid,
 				 handle->h_type, handle->h_line_no,
 				 handle->h_buffer_credits,
 				 nblocks);
@@ -603,7 +599,6 @@ unlock:
 	spin_unlock(&transaction->t_handle_lock);
 error_out:
 	read_unlock(&journal->j_state_lock);
-out:
 	return result;
 }
 
@@ -626,14 +621,16 @@ out:
 int jbd2__journal_restart(handle_t *handle, int nblocks, gfp_t gfp_mask)
 {
 	transaction_t *transaction = handle->h_transaction;
-	journal_t *journal = transaction->t_journal;
+	journal_t *journal;
 	tid_t		tid;
 	int		need_to_start, ret;
 
+	WARN_ON(!transaction);
 	/* If we've had an abort of any type, don't even think about
 	 * actually doing the restart! */
 	if (is_handle_aborted(handle))
 		return 0;
+	journal = transaction->t_journal;
 
 	/*
 	 * First unlink the handle from its current transaction, and start the
@@ -654,6 +651,8 @@ int jbd2__journal_restart(handle_t *handle, int nblocks, gfp_t gfp_mask)
 		wake_up(&journal->j_wait_updates);
 	tid = transaction->t_tid;
 	spin_unlock(&transaction->t_handle_lock);
+	handle->h_transaction = NULL;
+	current->journal_info = NULL;
 
 	jbd_debug(2, "restarting handle %p\n", handle);
 	need_to_start = !tid_geq(journal->j_commit_request, tid);
@@ -783,17 +782,16 @@ do_get_write_access(handle_t *handle, struct journal_head *jh,
 			int force_copy)
 {
 	struct buffer_head *bh;
-	transaction_t *transaction;
+	transaction_t *transaction = handle->h_transaction;
 	journal_t *journal;
 	int error;
 	char *frozen_buffer = NULL;
 	int need_copy = 0;
 	unsigned long start_lock, time_lock;
 
+	WARN_ON(!transaction);
 	if (is_handle_aborted(handle))
 		return -EROFS;
-
-	transaction = handle->h_transaction;
 	journal = transaction->t_journal;
 
 	jbd_debug(5, "journal_head %p, force_copy %d\n", jh, force_copy);
@@ -1052,14 +1050,16 @@ int jbd2_journal_get_write_access(handle_t *handle, struct buffer_head *bh)
 int jbd2_journal_get_create_access(handle_t *handle, struct buffer_head *bh)
 {
 	transaction_t *transaction = handle->h_transaction;
-	journal_t *journal = transaction->t_journal;
+	journal_t *journal;
 	struct journal_head *jh = jbd2_journal_add_journal_head(bh);
 	int err;
 
 	jbd_debug(5, "journal_head %p\n", jh);
+	WARN_ON(!transaction);
 	err = -EROFS;
 	if (is_handle_aborted(handle))
 		goto out;
+	journal = transaction->t_journal;
 	err = 0;
 
 	JBUFFER_TRACE(jh, "entry");
@@ -1265,12 +1265,14 @@ void jbd2_buffer_abort_trigger(struct journal_head *jh,
 int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
 {
 	transaction_t *transaction = handle->h_transaction;
-	journal_t *journal = transaction->t_journal;
+	journal_t *journal;
 	struct journal_head *jh;
 	int ret = 0;
 
+	WARN_ON(!transaction);
 	if (is_handle_aborted(handle))
-		goto out;
+		return -EROFS;
+	journal = transaction->t_journal;
 	jh = jbd2_journal_grab_journal_head(bh);
 	if (!jh) {
 		ret = -EUCLEAN;
@@ -1364,7 +1366,7 @@ int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
 
 	JBUFFER_TRACE(jh, "file as BJ_Metadata");
 	spin_lock(&journal->j_list_lock);
-	__jbd2_journal_file_buffer(jh, handle->h_transaction, BJ_Metadata);
+	__jbd2_journal_file_buffer(jh, transaction, BJ_Metadata);
 	spin_unlock(&journal->j_list_lock);
 out_unlock_bh:
 	jbd_unlock_bh_state(bh);
@@ -1395,12 +1397,17 @@ out:
 int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh)
 {
 	transaction_t *transaction = handle->h_transaction;
-	journal_t *journal = transaction->t_journal;
+	journal_t *journal;
 	struct journal_head *jh;
 	int drop_reserve = 0;
 	int err = 0;
 	int was_modified = 0;
 
+	WARN_ON(!transaction);
+	if (is_handle_aborted(handle))
+		return -EROFS;
+	journal = transaction->t_journal;
+
 	BUFFER_TRACE(bh, "entry");
 
 	jbd_lock_bh_state(bh);
@@ -1427,7 +1434,7 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh)
 	 */
 	jh->b_modified = 0;
 
-	if (jh->b_transaction == handle->h_transaction) {
+	if (jh->b_transaction == transaction) {
 		J_ASSERT_JH(jh, !jh->b_frozen_data);
 
 		/* If we are forgetting a buffer which is already part
@@ -1522,19 +1529,21 @@ drop:
 int jbd2_journal_stop(handle_t *handle)
 {
 	transaction_t *transaction = handle->h_transaction;
-	journal_t *journal = transaction->t_journal;
-	int err, wait_for_commit = 0;
+	journal_t *journal;
+	int err = 0, wait_for_commit = 0;
 	tid_t tid;
 	pid_t pid;
 
+	if (!transaction)
+		goto free_and_exit;
+	journal = transaction->t_journal;
+
 	J_ASSERT(journal_current_handle() == handle);
 
 	if (is_handle_aborted(handle))
 		err = -EIO;
-	else {
+	else
 		J_ASSERT(atomic_read(&transaction->t_updates) > 0);
-		err = 0;
-	}
 
 	if (--handle->h_ref > 0) {
 		jbd_debug(4, "h_ref %d -> %d\n", handle->h_ref + 1,
@@ -1544,7 +1553,7 @@ int jbd2_journal_stop(handle_t *handle)
 
 	jbd_debug(4, "Handle %p going down\n", handle);
 	trace_jbd2_handle_stats(journal->j_fs_dev->bd_dev,
-				handle->h_transaction->t_tid,
+				transaction->t_tid,
 				handle->h_type, handle->h_line_no,
 				jiffies - handle->h_start_jiffies,
 				handle->h_sync, handle->h_requested_credits,
@@ -1657,6 +1666,7 @@ int jbd2_journal_stop(handle_t *handle)
 
 	if (handle->h_rsv_handle)
 		jbd2_journal_free_reserved(handle->h_rsv_handle);
+free_and_exit:
 	jbd2_free_handle(handle);
 	return err;
 }
@@ -2362,10 +2372,12 @@ void jbd2_journal_refile_buffer(journal_t *journal, struct journal_head *jh)
 int jbd2_journal_file_inode(handle_t *handle, struct jbd2_inode *jinode)
 {
 	transaction_t *transaction = handle->h_transaction;
-	journal_t *journal = transaction->t_journal;
+	journal_t *journal;
 
+	WARN_ON(!transaction);
 	if (is_handle_aborted(handle))
-		return -EIO;
+		return -EROFS;
+	journal = transaction->t_journal;
 
 	jbd_debug(4, "Adding inode %lu, tid:%d\n", jinode->i_vfs_inode->i_ino,
 			transaction->t_tid);
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 0302f3f..d5b50a1 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1266,7 +1266,7 @@ static inline int is_journal_aborted(journal_t *journal)
 
 static inline int is_handle_aborted(handle_t *handle)
 {
-	if (handle->h_aborted)
+	if (handle->h_aborted || !handle->h_transaction)
 		return 1;
 	return is_journal_aborted(handle->h_transaction->t_journal);
 }
-- 
1.7.12.rc0.22.gcdd159b

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