Re: [PATCH 6/6] migrate: Make migration handlers simpler and more flexible

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Feb 03, 2025 at 11:20:03AM +0100, Stefano Brivio wrote:
> On Mon,  3 Feb 2025 20:26:15 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > +/* Stages for version 1 */
> > +static const struct migrate_stage stages_v1[] = {
> > +	{
> > +		.name = "flow pre",
> > +		.source = flow_migrate_source_pre,
> > +		.target = NULL,
> > +	},
> > +	DATA_STAGE(flow_first_free),
> > +	DATA_STAGE(flowtab),
> > +	DATA_STAGE(flow_hashtab),
> > +	DATA_STAGE(g_hash_secret),
> 
> ...so this one for g_hash_secret (which is the abomination I wanted
> to drop) would eventually turn into a function?

Yes.

> It looks neat, I'm just not sure if we'll really have "data stages"
> after I change the approach to only transfer the data we need as you
> suggested.

I agree, that may well be the case, but we can just drop the macro and
helepr functions then.

> Is that part of your pending queue by the way, or should I go ahead with
> it?

Is which part of my pending queue?  g_hash_secret as a function?  No,
I've thought of it, but I haven't written it yet.

> 
> > [...]
> >
> >  /**
> > - * struct migrate_data - Data sections for given source version
> > - * @v:			Source version this applies to, host order
> > - * @sections:		Array of data sections, NULL-terminated
> > + * migrate_cb_t - Callback function to implement one migration stage
> >   */
> > -struct migrate_data {
> > -	uint32_t v;
> > -	struct iovec *sections;
> > -};
> > +typedef int (*migrate_cb_t)(struct ctx *c, struct migrate_meta *m,
> > +			    const struct migrate_stage *stage, int fd);
> 
> typedef is really annoying, we already have a flow_sidx which kind of
> made sense, but this has really no advantage over something like:

Eh, I guess.  I find the extra . or -> a little annoying, but we can
do this if you'd prefer.

> struct migrate_handler {
> 	int (*fn)(struct ctx *c, struct migrate_meta *m);
> };
> 

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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