linux-ext4 - Re: [PATCH] Fix commit block write in JBD

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Date:	Sat, 26 Jan 2008 22:02:07 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Jan Kara <jack@...e.cz>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] Fix commit block write in JBD

> On Wed, 23 Jan 2008 20:09:43 +0100 Jan Kara <jack@...e.cz> wrote:
> 
> Commit block is expected to have several copies of the header. Fix the
> bug Andrew has spotted ages ago.
> 

"ages" indeed.

> 
> diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
> index 610264b..a69b240 100644
> --- a/fs/jbd/commit.c
> +++ b/fs/jbd/commit.c
> @@ -116,9 +116,8 @@ static int journal_write_commit_record(journal_t *journal,
>  
>  	bh = jh2bh(descriptor);
>  
> -	/* AKPM: buglet - add `i' to tmp! */
>  	for (i = 0; i < bh->b_size; i += 512) {
> -		journal_header_t *tmp = (journal_header_t*)bh->b_data;
> +		journal_header_t *tmp = (journal_header_t*)(bh->b_data+i);
>  		tmp->h_magic = cpu_to_be32(JFS_MAGIC_NUMBER);
>  		tmp->h_blocktype = cpu_to_be32(JFS_COMMIT_BLOCK);
>  		tmp->h_sequence = cpu_to_be32(commit_transaction->t_tid);

But I don't think we can _use_ this feature now.  Because there are
100000000000 disks out there which didn't implement it.

So why not just remove the loop and do a single write?
-
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