"If you accept that it makes sense to allocate on rename commits for
overwrites of *existing* files, it follows that it makes sense to commit
on *all* renames."

Renaming a new file over an existing one carries the risk of destroying
*old* data.  If I create a new file and don't rename it to anything,
it's possible I will lose *the new file only*, on any filesystem (unless
I fsync()).  This is universally considered an acceptable risk: losing
up to a couple of minutes' work (but nothing earlier) in the event of a
system crash.  This is the exact risk carried by renaming a file to a
name that doesn't exist -- unless you gratuitously delete the old file
first, which is completely pointless on Unix and obviously destroys any
hope of atomicity (if the system crashes/app dies/etc. between delete
and rename).

"Only files for which atomicty matters are renamed that way -- which are
precisely the files that would get the commit-on-rename treatment in
other circumstances."

Virtually all users of this atomicity technique appear to rename over
the existing file, which is why almost all problems disappeared when
users applied Ted's patches.  Gaim only did otherwise as a flawed
attempt to work around a quirk of the Windows API, in a way that wasn't
atomic anyway, and that can be expected to be fixed in Gaim.

-- 
Ext4 data loss
https://bugs.launchpad.net/bugs/317781
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