linux-kernel - Re: [PATCH] ext3: wait on all pending commits in ext3_sync

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Message-Id: <20081103142706.92e3a2ae.akpm@linux-foundation.org>
Date:	Mon, 3 Nov 2008 14:27:06 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Theodore Tso <tytso@....edu>
Cc:	ajones@...erbed.com, sandeen@...hat.com,
	linux-ext4@...r.kernel.org, sct@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ext3: wait on all pending commits in ext3_sync_fs

On Mon, 3 Nov 2008 17:01:44 -0500
Theodore Tso <tytso@....edu> wrote:

>  static int ext4_sync_fs(struct super_block *sb, int wait)
>  {
> -	tid_t target;
> +	int ret;
>  
>  	trace_mark(ext4_sync_fs, "dev %s wait %d", sb->s_id, wait);
> -	sb->s_dirt = 0;
> -	if (jbd2_journal_start_commit(EXT4_SB(sb)->s_journal, &target)) {
> -		if (wait)
> -			jbd2_log_wait_commit(EXT4_SB(sb)->s_journal, target);
> -	}
> -	return 0;
> +	if (wait)
> +		ret = ext4_force_commit(sb);
> +	else
> +		ret = jbd2_journal_start_commit(EXT4_SB(sb)->s_journal, NULL);
> +	if (!ret)
> +		sb->s_dirt = 0;
> +	return ret;
>  }

It should clear s_dirt before doing the "i/o", methinks?

The usual pattern is

	foo->dirty = 0;
	do_io_on(foo);

because


	do_io_on(foo);
					modify(foo);
					foo->dirty = 1;
	foo->dirty = 0;

is racy.
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