Messages in this thread | | | Date | Thu, 4 Sep 2003 13:10:52 -0700 | From | Andrew Morton <> | Subject | Re: precise characterization of ext3 atomicity |
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Daniel Phillips <phillips@arcor.de> wrote: > > On Thursday 04 September 2003 17:55, Andrew Morton wrote: > > Hans Reiser <reiser@namesys.com> wrote: > > > Is it correct to say of ext3 that it guarantees and only guarantees > > > atomicity of writes that do not cross page boundaries? > > > > Yes. > > Is that just happenstance, or does Posix or similar mandate it?
Happenstance.
It's semi-trivial to do this in ext3. You'd open the file with O_ATOMIC and a write() would either be completely atomic or would return -EFOO without having written anything.
The thing which prevents this is the ranking order between journal_start() and lock_page().
It's not trivial but also not too hard to change things so that journal_start() can rank outside lock_page() - this would also offer some CPU savings.
Can't say that I'm terribly motivated about the feature though.
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