From: Eric Sandeen <sandeen@redhat.com>
Subject: Re: [PATCH] ext3: Avoid false EIO errors
Date: Mon, 30 Mar 2009 08:53:42 -0500
Message-ID: <49D0CEE6.2060409@redhat.com>
References: <1238091711-23464-1-git-send-email-jack@suse.cz> <20090327180806.GB2810@skywalker> <20090327202421.GB31071@duck.suse.cz> <20090330082532.GA15488@skywalker>
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Cc: Jan Kara <jack@suse.cz>, linux-ext4@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
In-Reply-To: <20090330082532.GA15488@skywalker>
Sender: linux-ext4-owner@vger.kernel.org

Aneesh Kumar K.V wrote:

> We do a vmtruncate if we failed to allocate blocks in
> ext3_write_begin. That is done after the closing the current
> transaction. If we crash in between (ie, after committing the
> transaction allocating blocks and before committing the transaction that
> is doing truncate) we would only have  some data blocks leaking. But
> that would be better than user seeing zero's in the file ?. Also if we
> happen to add the inode to the orphan list and crash, the recovery would
> truncate it properly. So by doing a vmtruncate I guess the window would be
> small and we are already doing that in ext3_write_begin.

I don't agree that leaking data blocks is better than exposing zeros...
the former is a security flaw, the latter a (significant) annoyance.

-Eric