Re: scary ext2 filesystem question

Mirian Crzig Lennox (mirian@xensei.com)
25 Dec 1998 19:10:28 -0500

Kurt Garloff <K.Garloff@ping.de> writes:
> On Fri, Dec 25, 1998 at 11:42:57AM -0500, Mirian Crzig Lennox wrote:
> > _Practical File System Design_, Dominic Giampaolo, p. 36
>
> Nonsense!
> The ext2fs uses write cacheing, like any powerful filesystem does.
> This cannot confuse any program. Any program that reads data from the disk
> goes through the page cache, so it get's the recent data, whether it was
> written to disk yet, or not yet. It is guaranteed to be written to disk
> sometime, thats what bdflush/update and kswapd are for. Un unmounting the fs
> all buffers are flushed, even if you managed to kill your bdflush before.

That's exactly what I was thinking.

Obviously, if [any] computer system crashes, bad things can happen.
That was not my point of confusion; rather, I was bewildered because
the author seemed to be implying that these kinds of problems could
occur *even during normal filesystem operation*. I couldn't figure
out how that could be, unless it was due to some kind of bug in the
caching code, not a flaw in the design of the filesystem.

> I noted the name of the author in my ignore list ... obviuosly he did not
> understand anything!

I'm inclined to agree, especially since elsewhere he refers to ext2 as
"the fast and unsafe grandchild" of FFS.

-- 
Mirian Crzig Lennox                                Systems Anarchist
          "There's a New World Order coming every minute.
                      Make mine extra cheese."


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