linux-ext4 - RE: [PATCH 2/2] ocfs2: fix a deadlock when commit trans

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Date:   Thu, 27 Jan 2022 12:46:41 +0000
From:   Gautham Ananthakrishna <gautham.ananthakrishna@...cle.com>
To:     Joseph Qi <joseph.qi@...ux.alibaba.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "tytso@....edu" <tytso@....edu>,
        "adilger.kernel@...ger.ca" <adilger.kernel@...ger.ca>
CC:     "ocfs2-devel@....oracle.com" <ocfs2-devel@....oracle.com>,
        "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
        Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com>
Subject: RE: [PATCH 2/2] ocfs2: fix a deadlock when commit trans

Yes. The patch has resolved the issue.

Thanks,
Gautham.

-----Original Message-----
From: Joseph Qi <joseph.qi@...ux.alibaba.com> 
Sent: Monday, January 24, 2022 8:08 AM
To: Gautham Ananthakrishna <gautham.ananthakrishna@...cle.com>; akpm@...ux-foundation.org; tytso@....edu; adilger.kernel@...ger.ca
Cc: ocfs2-devel@....oracle.com; linux-ext4@...r.kernel.org; Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com>
Subject: Re: [PATCH 2/2] ocfs2: fix a deadlock when commit trans

Sure, will do it in v2.
So could this patch resolve your issue?

Thanks,
Joseph

On 1/23/22 1:31 PM, Gautham Ananthakrishna wrote:
> Hi,
> This deadlock was originally reported by saeed.mirzamohammadi@...cle.com  Could you please add Saeed as the reportedby.
> 
> Thanks,
> Gautham.
> 
> -----Original Message-----
> From: Joseph Qi <joseph.qi@...ux.alibaba.com> 
> Sent: Friday, January 21, 2022 12:42 PM
> To: akpm@...ux-foundation.org; tytso@....edu; adilger.kernel@...ger.ca
> Cc: Gautham Ananthakrishna <gautham.ananthakrishna@...cle.com>; ocfs2-devel@....oracle.com; linux-ext4@...r.kernel.org
> Subject: [PATCH 2/2] ocfs2: fix a deadlock when commit trans
> 
> commit 6f1b228529ae introduces a regression which can deadlock as
> follows:
> 
> Task1:                              Task2:
> jbd2_journal_commit_transaction     ocfs2_test_bg_bit_allocatable
> spin_lock(&jh->b_state_lock)        jbd_lock_bh_journal_head
> __jbd2_journal_remove_checkpoint    spin_lock(&jh->b_state_lock)
> jbd2_journal_put_journal_head
> jbd_lock_bh_journal_head
> 
> Task1 and Task2 lock bh->b_state and jh->b_state_lock in different order, which finally result in a deadlock.
> 
> So use jbd2_journal_[grab|put]_journal_head instead in
> ocfs2_test_bg_bit_allocatable() to fix it.
> 
> Reported-by: Gautham Ananthakrishna <gautham.ananthakrishna@...cle.com>
> Fixes: 6f1b228529ae ("ocfs2: fix race between searching chunks and release journal_head from buffer_head")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Joseph Qi <joseph.qi@...ux.alibaba.com>
> ---
>  fs/ocfs2/suballoc.c | 25 +++++++++++--------------
>  1 file changed, 11 insertions(+), 14 deletions(-)
> 
> diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c index 481017e1dac5..166c8918c825 100644
> --- a/fs/ocfs2/suballoc.c
> +++ b/fs/ocfs2/suballoc.c
> @@ -1251,26 +1251,23 @@ static int ocfs2_test_bg_bit_allocatable(struct buffer_head *bg_bh,  {
>  	struct ocfs2_group_desc *bg = (struct ocfs2_group_desc *) bg_bh->b_data;
>  	struct journal_head *jh;
> -	int ret = 1;
> +	int ret;
>  
>  	if (ocfs2_test_bit(nr, (unsigned long *)bg->bg_bitmap))
>  		return 0;
>  
> -	if (!buffer_jbd(bg_bh))
> +	jh = jbd2_journal_grab_journal_head(bg_bh);
> +	if (!jh)
>  		return 1;
>  
> -	jbd_lock_bh_journal_head(bg_bh);
> -	if (buffer_jbd(bg_bh)) {
> -		jh = bh2jh(bg_bh);
> -		spin_lock(&jh->b_state_lock);
> -		bg = (struct ocfs2_group_desc *) jh->b_committed_data;
> -		if (bg)
> -			ret = !ocfs2_test_bit(nr, (unsigned long *)bg->bg_bitmap);
> -		else
> -			ret = 1;
> -		spin_unlock(&jh->b_state_lock);
> -	}
> -	jbd_unlock_bh_journal_head(bg_bh);
> +	spin_lock(&jh->b_state_lock);
> +	bg = (struct ocfs2_group_desc *) jh->b_committed_data;
> +	if (bg)
> +		ret = !ocfs2_test_bit(nr, (unsigned long *)bg->bg_bitmap);
> +	else
> +		ret = 1;
> +	spin_unlock(&jh->b_state_lock);
> +	jbd2_journal_put_journal_head(jh);
>  
>  	return ret;
>  }
> --
> 2.19.1.6.gb485710b