linux-ext4 - Re: ext4: Forbid journal_async

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Message-ID: <20141126012002.GA28130@thunk.org>
Date:	Tue, 25 Nov 2014 20:20:02 -0500
From:	Theodore Ts'o <tytso@....edu>
To:	Jan Kara <jack@...e.cz>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: ext4: Forbid journal_async_commit in data=ordered mode

On Tue, Nov 25, 2014 at 04:56:15PM +0100, Jan Kara wrote:
> Option journal_async_commit breaks gurantees of data=ordered mode as it
> sends only a single cache flush after writing a transaction commit
> block. Thus even though the transaction including the commit block is
> fully stored on persistent storage, file data may still linger in drives
> caches and will be lost on power failure. Since all checksums match on
> journal recovery, we replay the transaction thus possibly exposing stale
> user data.
> 
> To fix this data exposure issue, remove the possibility to use
> journal_async_commit in data=ordered mode.
> 
> Signed-off-by: Jan Kara <jack@...e.cz>

Applied, thanks.

						- Ted
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