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

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Date:	Mon, 7 Apr 2014 15:02:04 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Tanya Brokhman <tlinder@...eaurora.org>
Cc:	Artem Bityutskiy <dedekind1@...il.com>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC/PATCH] mtd: ubi: Free peb's synchronously for fastmap

On Tue, Apr 1, 2014 at 10:01 AM, Tanya Brokhman <tlinder@...eaurora.org> 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@...eaurora.org>
>
> 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.

> +                       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?

-- 
Thanks,
//richard
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