Re: Reading from file in module fails

[root <libor@conet.cz>]

On Mon, May 03, 2004 at 01:48:59PM +0200, Erik Mouw wrote:
> On Mon, May 03, 2004 at 01:43:16PM +0200, Libor Vanek wrote:
> > > (BTW, if you need to copy files from kernel, it's usually a sign of bad
> > > design)
> > It's not bad design - what I'm doing is writing snapshots for VFS as
> > my diploma thesis. And I need to create copy of file before it's
> > changed (copy-on-write). There is no other way how to do it in
> > kernel-space (and user-space solutions like using LUFS are really
> > slow)
> Have a look at the cowlinks (copy-on-write links) thread from last
> month, it might do the trick.

Hmmm, that seems to have several serious disadvantages:
- it's not filesystem/user-space SW independent (requires modifying them - as far as I understand how it's done)
- needs to "touch" all existing files/dirs (maybe I'm wrong but from very first look it seems to me that I need to setup "cow" flag on each file/dir I want to "cow") - my approach should be "atomic" even when I need to setup snapshot on directory containing 100s thousands of files/dirs (and that's an average server I'm thinking of!)

Nevertheless - thanks for a tip.

Libor