Re: removing an ext2fs file forces disk activity

[Thomas Bushnell, BSG]

nisse@lysator.liu.se (Niels Möller) writes:

> Is it not good enough to maintain the order of the writes, updating
> diskblocks in the same order as the corresponding write by the client?

Yes, that's enough.  But you cannot skip any writes.

> One problem is that if the filesystem modifies block A, then block B,
> and then block A again, then you may need to keep this ordering, and
> not merge it as one write to A and one to B. Is the touch-rm-loop of
> this kind? Then I guess the simple ordering breaks down.

In general, such loops cannot be broken without knowing what exactly
is going on.  Usually, it's safe to break them, because usually there
is no real connection between the writes.

I have a more concrete idea about how to change diskfs into an
"ordered writes" instead of a "synchronous writes" model.  If someone
prods me, I can explain it.