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wc atomic rename safety on non-ext3 file systems

From: Chris Frost <frost_at_cs.ucla.edu>
Date: 2007-03-05 07:06:00 CET

In examining subversion's wc code I have noticed that it atomically creates
files, including the data, using a create foo_tmp, write foo_tmp, and finally
rename foo_tmp to foo. This is a pretty cool technique.

However, is it true that this only works (that is, guarantees the data will
precede rename to disk) for file systems with journal orderings like ext3's
ordered journal? (Where data is written prior to related journaled metadata.)
Popular systems that do not ensure this property include *BSD UFS
(soft updates do not impose such an ordering rule afaik) and WinNT NTFS
(metadata may precede data).

Chris Frost  |  <http://www.frostnet.net/chris/>
PGP: <http://www.frostnet.net/chris/about/pgp_key.txt>
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Received on Mon Mar 5 07:06:23 2007

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