Hi Alasdair, Mike,
On 11/16/2009 10:54 PM +0900, Alasdair G Kergon wrote:
> On Sun, Nov 15, 2009 at 11:38:29PM -0800, Mike Anderson wrote:
>> Add element to multipath structure for indication of suspended state.
>
> Is there a way to avoid this?
> It seems redundant for a target to need to track whether or not
> it is suspended. Core dm should be capable of that.
>
> dm_suspend has:
> dm_table_postsuspend_targets(map);
>
> set_bit(DMF_SUSPENDED, &md->flags);
>
> Can we reorder those two?
For multipath and dm-core, yes.
I'm not sure whether other targets care about the ordering.
But from semantics point of view, is it confusing if dm_suspended()
returns true but a target is doing something in postsuspend()?
If we take the approach instead of this patch, the patch-set is like:
1/4: http://patchwork.kernel.org/patch/61588/
2/4: http://patchwork.kernel.org/patch/61589/
3/4: http://patchwork.kernel.org/patch/61594/
4/4: http://patchwork.kernel.org/patch/61595/
Please review.
> What about dm_resume?
> clear_bit(DMF_SUSPENDED, &md->flags);
> Can that move a little higher up the function?
> - preresume, clear DMF_SUSPENDED, resume perhaps?
I think we shouldn't move the clear_bit in resume.
It doesn't make sense to clear the flag before I/Os start flowing.
If targets want to do any preparation before I/Os flowing through,
it can do in the resume() callback.
Thanks,
Kiyoshi Ueda
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