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Date:	Mon, 24 Jun 2013 11:53:59 +0200
From:	Jan Kara <jack@...e.cz>
To:	Theodore Ts'o <tytso@....edu>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	jbacik@...ionio.com, younger.liu@...wei.com,
	Jan Kara <jack@...e.cz>
Subject: Re: [PATCH] jbd2: invalidate handle if jbd2_journal_restart() fails

On Sun 23-06-13 13:44:28, Ted Tso wrote:
> 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>
  The patch looks good to me. So you can add:
Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/jbd2/transaction.c | 27 ++++++++++++++++-----------
>  include/linux/jbd2.h  |  2 +-
>  2 files changed, 17 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
> index 7391456..8ac8306 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;
> @@ -555,6 +550,7 @@ int jbd2_journal_extend(handle_t *handle, int nblocks)
>  	int wanted;
>  
>  	result = -EIO;
> +	WARN_ON(!handle->h_transaction);
>  	if (is_handle_aborted(handle))
>  		goto out;
>  
> @@ -630,6 +626,7 @@ int jbd2__journal_restart(handle_t *handle, int nblocks, gfp_t gfp_mask)
>  	tid_t		tid;
>  	int		need_to_start, ret;
>  
> +	WARN_ON(!handle->h_transaction);
>  	/* If we've had an abort of any type, don't even think about
>  	 * actually doing the restart! */
>  	if (is_handle_aborted(handle))
> @@ -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);
> @@ -790,6 +789,7 @@ do_get_write_access(handle_t *handle, struct journal_head *jh,
>  	int need_copy = 0;
>  	unsigned long start_lock, time_lock;
>  
> +	WARN_ON(!handle->h_transaction);
>  	if (is_handle_aborted(handle))
>  		return -EROFS;
>  
> @@ -1057,6 +1057,7 @@ int jbd2_journal_get_create_access(handle_t *handle, struct buffer_head *bh)
>  	int err;
>  
>  	jbd_debug(5, "journal_head %p\n", jh);
> +	WARN_ON(!handle->h_transaction);
>  	err = -EROFS;
>  	if (is_handle_aborted(handle))
>  		goto out;
> @@ -1269,6 +1270,7 @@ int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
>  	struct journal_head *jh;
>  	int ret = 0;
>  
> +	WARN_ON(!handle->h_transaction);
>  	if (is_handle_aborted(handle))
>  		goto out;
>  	jh = jbd2_journal_grab_journal_head(bh);
> @@ -1523,18 +1525,19 @@ 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;
> +	int err = 0, wait_for_commit = 0;
>  	tid_t tid;
>  	pid_t pid;
>  
> +	if (!handle->h_transaction)
> +		goto free_and_exit;
> +
>  	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,
> @@ -1657,6 +1660,7 @@ 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;
>  }
> @@ -2364,6 +2368,7 @@ int jbd2_journal_file_inode(handle_t *handle, struct jbd2_inode *jinode)
>  	transaction_t *transaction = handle->h_transaction;
>  	journal_t *journal = transaction->t_journal;
>  
> +	WARN_ON(!handle->h_transaction);
>  	if (is_handle_aborted(handle))
>  		return -EIO;
>  
> diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
> index 5f3c094..1891112 100644
> --- a/include/linux/jbd2.h
> +++ b/include/linux/jbd2.h
> @@ -1295,7 +1295,7 @@ 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
> 
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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