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From: Harald Arnesen <skogtun.harald@gmail.com>
To: david@lang.hm
Cc: Bill Davidsen <davidsen@tmr.com>, linux-kernel@vger.kernel.org
Subject: Re: Linux 2.6.29
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Date: Thu, 02 Apr 2009 00:00:04 +0200
In-Reply-To: <alpine.DEB.1.10.0904011311240.28893@asgard.lang.hm>
	(david@lang.hm's message of "Wed, 1 Apr 2009 13:15:34 -0700 (PDT)")
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david@lang.hm writes:

>> Understood that it's not deliberate just careless. The two behaviors
>> which are reported are (a) updating a record in an existing file and
>> having the entire file content vanish, and (b) finding some one
>> else's old data in my file - a serious security issue. I haven't
>> seen any report of the case where a process unlinks or truncates a
>> file, the disk space gets reused, and then the systems fails before
>> the metadata is updated, leaving the data written by some other
>> process in the file where it can be read - another possible security
>> issue.
>
> ext3 eliminates this security issue by writing the data before the
> metadata. ext4 (and I thing XFS) eliminate this security issue by not
> allocating the blocks until it goes to write the data out. I don't
> know how other filesystems deal with this.

I've been wondering about that during the last days. How abut JFS and
data loss (files containing zeroes after a crash), as compared to ext3,
ext4, ordered and writeback journal modes? Is is safe?
-- 
Hilsen Harald.