Re: [Ocfs2-devel] [PATCHC RFC V2 1/1] ocfs2: fix a deadlock when commit trans - Joseph Qi via Ocfs2-devel

From: Joseph Qi via Ocfs2-devel <ocfs2-devel@oss.oracle.com>
To: Gautham Ananthakrishna <gautham.ananthakrishna@oracle.com>,
	ocfs2-devel@oss.oracle.com
Cc: rajesh.sivaramasubramaniom@oracle.com
Subject: Re: [Ocfs2-devel] [PATCHC RFC V2 1/1] ocfs2: fix a deadlock when commit trans
Date: Fri, 21 Jan 2022 09:43:12 +0800	[thread overview]
Message-ID: <5d98ad12-26c7-3aba-a4bc-79cdca5c77df@linux.alibaba.com> (raw)
In-Reply-To: <1642682627-12041-1-git-send-email-gautham.ananthakrishna@oracle.com>

Seems you still sent a patch that couldn't build.
Have you checked my previous comments and tried my suggested way?

Thanks,
Joseph

On 1/20/22 8:43 PM, Gautham Ananthakrishna wrote:
> commit 6f1b228529ae49b0f85ab89bcdb6c365df401558 caused a deadlock
> which was uncovered by our internal tests. The deadlock is as foollows:
> 
> Task 1:
> A1) jbd2_journal_commit_transaction()
> A2)         spin_lock(&jh->b_state_lock);
> A3)         __jbd2_journal_remove_checkpoint()
> A4)                         jbd2_journal_put_journal_head()
> A5)                                         jbd_lock_bh_journal_head()
> 
> Task 2:
> B1) ocfs2_test_bg_bit_allocatable()
> B2)         jbd_lock_bh_journal_head()
> B3)         spin_lock(&jh->b_state_lock);
> 
> A1->A2->A3->A4->B1->B2->B3(blocked)->A5(blocked)
> 
> Now cause process 2 has the jbd lock, it doesn’t let process 1 to continue after A5.
> Process 2 now is waiting for b_state_lock to be released by process 1.
> 
> This patch resolves the deadlock.
> 
> Signed-off-by: Gautham Ananthakrishna <gautham.ananthakrishna@oracle.com>
> ---
>  fs/ocfs2/suballoc.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c
> index 481017e..a618970 100644
> --- a/fs/ocfs2/suballoc.c
> +++ b/fs/ocfs2/suballoc.c
> @@ -1259,9 +1259,8 @@ static int ocfs2_test_bg_bit_allocatable(struct buffer_head *bg_bh,
>  	if (!buffer_jbd(bg_bh))
>  		return 1;
>  
> -	jbd_lock_bh_journal_head(bg_bh);
> -	if (buffer_jbd(bg_bh)) {
> -		jh = bh2jh(bg_bh);
> +	jh = jbd2_journal_grab_journal_head(bg_bh);
> +	if (jh) {
>  		spin_lock(&jh->b_state_lock);
>  		bg = (struct ocfs2_group_desc *) jh->b_committed_data;
>  		if (bg)
> @@ -1269,8 +1268,8 @@ static int ocfs2_test_bg_bit_allocatable(struct buffer_head *bg_bh,
>  		else
>  			ret = 1;
>  		spin_unlock(&jh->b_state_lock);
> +		jbd2_journal_put_journal_head(bg_bh);
>  	}
> -	jbd_unlock_bh_journal_head(bg_bh);
>  
>  	return ret;
>  }

_______________________________________________
Ocfs2-devel mailing list
Ocfs2-devel@oss.oracle.com
https://oss.oracle.com/mailman/listinfo/ocfs2-devel