Re: [RFC/PATCH] mtd: ubi: Free peb's synchronously for fastmap

[Tanya Brokhman]

On 4/7/2014 4:02 PM, Richard Weinberger wrote:
> On Tue, Apr 1, 2014 at 10:01 AM, Tanya Brokhman <tlinder@xxxxxxxxxxxxxx> wrote:
> > At first mount it's possible that there are not enough free PEBs since
> > there are PEB's pending to be erased. In such scenario, fm_pool (which is
> > the pool from which user required PEBs are allocated) will be empty.
> > Try fixing the above described situation by synchronously performing
> > pending erase work, thus produce another free PEB.
> >
> > Signed-off-by: Tatyana Brokhman <tlinder@xxxxxxxxxxxxxx>
> >
> > diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
> > index 457ead3..9a36f78 100644
> > --- a/drivers/mtd/ubi/wl.c
> > +++ b/drivers/mtd/ubi/wl.c
> > @@ -595,10 +595,29 @@ static void refill_wl_pool(struct ubi_device *ubi)
> >   static void refill_wl_user_pool(struct ubi_device *ubi)
> >   {
> >          struct ubi_fm_pool *pool = &ubi->fm_pool;
> > +       int err;
> >
> >          return_unused_pool_pebs(ubi, pool);
> >
> >          for (pool->size = 0; pool->size < pool->max_size; pool->size++) {
> > +retry:
> > +               if (!ubi->free.rb_node ||
> > +                  (ubi->free_count - ubi->beb_rsvd_pebs < 1)) {
> > +                       /*
> > +                        * There are no available PEBs. Try to free
> > +                        * PEB by means of synchronous execution of
> > +                        * pending works.
> > +                        */
> > +                       if (ubi->works_count == 0)
> > +                               break;
> > +                       spin_unlock(&ubi->wl_lock);
> > +                       err = do_work(ubi);
> > +                       spin_lock(&ubi->wl_lock);
>
> This is basically what produce_free_peb() does.

Right. I didn't use t just because of the termination condition. 
produce_free_peb stops if there is 1 free peb. I need more then 1

> > +                       if (err < 0)
> > +                               break;
> > +                       goto retry;
> > +               }
> > +
> >                  pool->pebs[pool->size] = __wl_get_peb(ubi);
>
> __wl_get_peb() already calls produce_free_peb() when we run out of free PEBs.
>
> Does your patch really fix a problem you encounter or did you find the
> issue by reviewing
> the code?

Yes. We encountered this issue, as described in the commit message. This 
is the fix. Verified and working for us.

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