linux-ext4 - Re: [PATCH 1/1] jbd2: fix incorrect unlock on j_list

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Date:	Wed, 18 Mar 2015 11:43:21 +0100 (CET)
From:	Lukáš Czerner <lczerner@...hat.com>
To:	Taesoo Kim <tsgatesv@...il.com>
cc:	tytso@....edu, linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org, taesoo@...ech.edu,
	changwoo@...ech.edu, sanidhya@...ech.edu, blee@...ech.edu,
	csong84@...ech.edu
Subject: Re: [PATCH 1/1] jbd2: fix incorrect unlock on j_list_lock

On Tue, 17 Mar 2015, Taesoo Kim wrote:

> Date: Tue, 17 Mar 2015 22:08:38 -0400
> From: Taesoo Kim <tsgatesv@...il.com>
> To: tytso@....edu, linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
> Cc: taesoo@...ech.edu, changwoo@...ech.edu, sanidhya@...ech.edu,
>     blee@...ech.edu, csong84@...ech.edu, Taesoo Kim <tsgatesv@...il.com>
> Subject: [PATCH 1/1] jbd2: fix incorrect unlock on j_list_lock
> 
> When 'jh->b_transaction == transaction' (asserted by below)
> 
>   J_ASSERT_JH(jh, (jh->b_transaction == transaction || ...
> 
> 'journal->j_list_lock' will be incorrectly unlocked, since
> the the lock is aquired only at the end of if / else-if
> statements (missing the else case).

The patch looks good, thanks.

Reviewed-by: Lukas Czerner <lczerner@...hat.com>

Btw, were you able to reproduce the problem, or have you seen the
problem in the wild ? Or did you just spot it in the code ?

Thanks!
-Lukas

> 
> Signed-off-by: Taesoo Kim <tsgatesv@...il.com>
> ---
>  fs/jbd2/transaction.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
> index 5f09370..edb7f59 100644
> --- a/fs/jbd2/transaction.c
> +++ b/fs/jbd2/transaction.c
> @@ -1091,6 +1091,7 @@ int jbd2_journal_get_create_access(handle_t *handle, struct buffer_head *bh)
>  		JBUFFER_TRACE(jh, "file as BJ_Reserved");
>  		spin_lock(&journal->j_list_lock);
>  		__jbd2_journal_file_buffer(jh, transaction, BJ_Reserved);
> +		spin_unlock(&journal->j_list_lock);
>  	} else if (jh->b_transaction == journal->j_committing_transaction) {
>  		/* first access by this transaction */
>  		jh->b_modified = 0;
> @@ -1098,8 +1099,8 @@ int jbd2_journal_get_create_access(handle_t *handle, struct buffer_head *bh)
>  		JBUFFER_TRACE(jh, "set next transaction");
>  		spin_lock(&journal->j_list_lock);
>  		jh->b_next_transaction = transaction;
> +		spin_unlock(&journal->j_list_lock);
>  	}
> -	spin_unlock(&journal->j_list_lock);
>  	jbd_unlock_bh_state(bh);
> 
>  	/*
> --
> 2.3.3
> 
> --
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