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



On Tue, Jan 14 2014 at  3:43pm -0500,
Mikulas Patocka <mpatocka redhat com> wrote:

> 
> 
> On Tue, 14 Jan 2014, Mike Snitzer wrote:
> 
> > On Mon, Jan 13 2014 at  7:14pm -0500,
> > Mikulas Patocka <mpatocka 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


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