[dm-devel] [PATCH 6/6] dm-snapshot: use bufio prefetch

[Mikulas Patocka]

On Tue, 14 Jan 2014, Mike Snitzer wrote:

> On Tue, Jan 14 2014 at  3:43pm -0500,
> Mikulas Patocka <mpatocka at redhat.com> wrote:
> 
> > 
> > 
> > On Tue, 14 Jan 2014, Mike Snitzer wrote:
> > 
> > > On Mon, Jan 13 2014 at  7:14pm -0500,
> > > Mikulas Patocka <mpatocka at redhat.com> wrote:
> > > 
> > > > +	dm_bufio_set_minimum_buffers(client, DM_PREFETCH_CHUNKS + 1);
> > > > +
> > > 
> > > Why the +1?  I'd prefer that be managed in dm-bufio rather than relying
> > > on all callers to know to add +1.
> > > 
> > > Can you supply a followup patch that cleans this up in bufio and remove
> > > the +1 in the above dm_bufio_set_minimum_buffers call?
> > 
> > If DM_PREFETCH_CHUNKS is 12, we need 13 buffers in dm-bufio (one for the 
> > current buffer that is being read and 12 read ahead buffers).
> > 
> > It is correct to have +1 in snapshot code, not in dm-bufio code.
> 
> OK, thanks for clarifying.
> 
> I've folded the dm bufio changes needed for the respective dm snapshot
> changes -- so there are now 4 patches instead of your otiginal 6.
> I added a comment for "1 + DM_PREFETCH_CHUNKS" above the
> dm_bufio_set_minimum_buffers call and tweaked the headers a little.
> 
> I also staged your non-modular kobject release patch (tweaked the header
> on that a little bit too).
> 
> Please see the 5 topmost commits here:
> http://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/log/?h=for-next

OK. The patches look good.

Mikulas