On Tue, 21 Aug 2001, Lutz Pressler wrote:
> Is the way Exim handles spool files and local delivery safe, especially
> on Linux ext2?
> James Antill seems to think that it's not.
I am not an expert on this stuff. I just have to go by what I read in
the manuals and what people tell me.
> Just in case anyone cares here's what exim does (AFAICS)...
>
> int fd1 = open(f1);
> write(fd1);
> fsync(fd1);
>
> int fd2 = open(tmp);
> write(fd2);
> fsync(fd2);
> rename(tmp, f2); // Good at this point.
>
> So that seems to rely on all dir operations being sync.
I'm afraid I don't have enough knowledge/understanding to follow how or
why that is relying on whatever it is that is worrying people. My
understanding of rename() is that it is atomic, that is, from the point
of view of other processes, either it has happened or it has not. There
is never a halfway state when neither the old file nor the new exists.
If there really is a problem, please can somebody explain it to me in
more detail?
--
Philip Hazel University of Cambridge Computing Service,
ph10@??? Cambridge, England. Phone: +44 1223 334714.
