Re: [PATCH] [RFC] UBI: Implement Fastmap support

[Richard Weinberger]

On 24.05.2012 11:56, Shmulik Ladkani wrote:
> Hi Artem,
>
> On Thu, 24 May 2012 11:17:52 +0300 Artem Bityutskiy<dedekind1@xxxxxxxxx>  wrote:
> > On Tue, 2012-05-22 at 18:55 +0200, Richard Weinberger wrote:
> > > > > +    e = find_early_wl_entry(&ubi->free, max_pnum);
> > > >
> > > > This picks the eb with the lowest pnum within 'ubi->free'.
> > > >
> > > > When called with INT_MAX (for the FM_DATA), why do you need to pick
> > > a
> > > > free eb with the minimal pnum? The FM_DATA EBs may reside everywhere
> > > (as
> > > > the FM_SB holds their location).
> > > > So why not pick the eb with a medium EC value (as done for standard
> > > > get_peb calls)? That might be better wear-leveling wise.
> > >
> > > Fair point.
> > > I'll fix that.
> > > Artem, any comments on that?
> >
> > The 'find_early_wl_entry()' function is used (currently) only at early
> > stages. At these stages the we do not have the PEBs sorted by EC. We
> > have just a list. This function should not be use after the WL subsystem
> > is initialized.
>
> 'find_early_wl_entry' is only called from 'ubi_wl_get_fm_peb'.

Correct.

> 'ubi_wl_get_fm_peb' is called twice from within 'ubi_update_fastmap':
> First call, to get the FM_SB, with 'max_pnum' set as UBI_FM_MAX_START.
> Second, to get FM_DATA pebs, with 'max_pnum' as -1, do indicate "no
> matter the location, give me pebs from the free pool".

Correct. Maybe I should rename find_early_wl_entry() to 
find_wl_entry_for_fastmap() or something like that...

> 'ubi_update_fastmap' is called from 'ubi_volume_notify' and from
> 'ubi_wl_get_peb' - at both points, I assume ubi->free rbtree is properly
> populated. Am I mistaken?

Also correct.

Thanks,
//richard

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