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

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Date:	Thu, 19 Mar 2015 10:48:45 +0100 (CET)
From:	Lukáš Czerner <lczerner@...hat.com>
To:	Taesoo Kim <taesoo@...ech.edu>
cc:	Taesoo Kim <tsgatesv@...il.com>, tytso@....edu,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
	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 Wed, 18 Mar 2015, Taesoo Kim wrote:

> Date: Wed, 18 Mar 2015 13:39:31 -0400
> From: Taesoo Kim <taesoo@...ech.edu>
> To: Lukáš Czerner <lczerner@...hat.com>
> Cc: Taesoo Kim <tsgatesv@...il.com>, tytso@....edu,
>     linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
>     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
> 
> > The patch looks good, thanks.
> 
> Thank you.
>  
> > 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 ?
> 
> We are developing a static checker to spot inconsistent programming
> patterns; our first goal is to scan over existing filesystems and
> figure out how they are implemented differently (or similarly). We
> will report bugs in sequence as soon as our team confirm (just start
> sending patches to other fs).

And this was found but it ?

But anyway it sounds really interesting, do you have any more
information you can share about the project ? Project website,
description, or source code would be great :)

Thanks!
-Lukas

> 
> Thanks,
> Taesoo
> 
> > 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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> > > 
>