linux-kernel - Re: [PATCH 6/6] UBI: Fastmap: Make ubi_refill

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Message-ID: <5481F1A1.50609@codeaurora.org>
Date:	Fri, 05 Dec 2014 19:55:45 +0200
From:	Tanya Brokhman <tlinder@...eaurora.org>
To:	Richard Weinberger <richard@....at>, dedekind1@...il.com
CC:	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] UBI: Fastmap: Make ubi_refill_pools() fair

Hi Richard,

On 11/24/2014 3:20 PM, Richard Weinberger wrote:
> Currently ubi_refill_pools() first fills the first and then
> the second one.
> If only very few free PEBs are available the second pool can get
> zero PEBs.
> Change ubi_refill_pools() to distribute free PEBs fair between
> all pools.
>
> Signed-off-by: Richard Weinberger <richard@....at>
> ---
>   drivers/mtd/ubi/wl.c | 77 +++++++++++++++++++++++++++-------------------------
>   1 file changed, 40 insertions(+), 37 deletions(-)
>
> diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
> index f028b68..c2822f7 100644
> --- a/drivers/mtd/ubi/wl.c
> +++ b/drivers/mtd/ubi/wl.c
> @@ -583,59 +583,62 @@ static void return_unused_pool_pebs(struct ubi_device *ubi,
>   }
>
>   /**
> - * refill_wl_pool - refills all the fastmap pool used by the
> - * WL sub-system.
> + * ubi_refill_pools - refills all fastmap PEB pools.
>    * @ubi: UBI device description object
>    */
> -static void refill_wl_pool(struct ubi_device *ubi)
> +void ubi_refill_pools(struct ubi_device *ubi)
>   {
> +	struct ubi_fm_pool *wl_pool = &ubi->fm_wl_pool;
> +	struct ubi_fm_pool *pool = &ubi->fm_pool;
>   	struct ubi_wl_entry *e;
> -	struct ubi_fm_pool *pool = &ubi->fm_wl_pool;
> +	int enough;
>
> +	spin_lock(&ubi->wl_lock);
> +
> +	return_unused_pool_pebs(ubi, wl_pool);
>   	return_unused_pool_pebs(ubi, pool);
>
> -	for (pool->size = 0; pool->size < pool->max_size; pool->size++) {
> -		if (!ubi->free.rb_node ||
> -		   (ubi->free_count - ubi->beb_rsvd_pebs < 5))
> -			break;
> +	wl_pool->size = 0;
> +	pool->size = 0;
>
> -		e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);
> -		self_check_in_wl_tree(ubi, e, &ubi->free);
> -		rb_erase(&e->u.rb, &ubi->free);
> -		ubi->free_count--;
> +	for (;;) {

You loop for max(pool->max_size, wl_pool->max_size) itterations. IMO, 
the code will be more clear if you use for(i=0; i<max(pool->max_size, 
wl_pool->max_size); i++) instead of "int enough".
This is just coding style preference of course. I personally don't like 
for(;;) that much.... Just a suggestion. :)

> +		enough = 0;
> +		if (pool->size < pool->max_size) {
> +			if (!ubi->free.rb_node ||
> +			   (ubi->free_count - ubi->beb_rsvd_pebs < 5))
> +				break;
>
> -		pool->pebs[pool->size] = e->pnum;
> -	}
> -	pool->used = 0;
> -}
> +			e = wl_get_wle(ubi);
> +			if (!e)
> +				break;
>
> -/**
> - * refill_wl_user_pool - refills all the fastmap pool used by ubi_wl_get_peb.
> - * @ubi: UBI device description object
> - */
> -static void refill_wl_user_pool(struct ubi_device *ubi)
> -{
> -	struct ubi_fm_pool *pool = &ubi->fm_pool;
> +			pool->pebs[pool->size] = e->pnum;
> +			pool->size++;
> +		} else
> +			enough++;
>
> -	return_unused_pool_pebs(ubi, pool);
> +		if (wl_pool->size < wl_pool->max_size) {
> +			if (!ubi->free.rb_node ||
> +			   (ubi->free_count - ubi->beb_rsvd_pebs < 5))
> +				break;
>
> -	for (pool->size = 0; pool->size < pool->max_size; pool->size++) {
> -		pool->pebs[pool->size] = __wl_get_peb(ubi);
> -		if (pool->pebs[pool->size] < 0)
> +			e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);
> +			self_check_in_wl_tree(ubi, e, &ubi->free);
> +			rb_erase(&e->u.rb, &ubi->free);
> +			ubi->free_count--;

why don't you use wl_get_peb() here?

Other then that - I agree with the patch. So if you want to keep it as 
is, I'll add Reviewed-by.

> +
> +			wl_pool->pebs[wl_pool->size] = e->pnum;
> +			wl_pool->size++;
> +		} else
> +			enough++;
> +
> +		if (enough == 2)
>   			break;
>   	}
> +
> +	wl_pool->used = 0;
>   	pool->used = 0;
> -}
>
> -/**
> - * ubi_refill_pools - refills all fastmap PEB pools.
> - * @ubi: UBI device description object
> - */
> -void ubi_refill_pools(struct ubi_device *ubi)
> -{
> -	spin_lock(&ubi->wl_lock);
> -	refill_wl_pool(ubi);
> -	refill_wl_user_pool(ubi);
>   	spin_unlock(&ubi->wl_lock);
>   }
>
>


Thanks,
Tanya Brokhman
-- 
Qualcomm Israel, on behalf of Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
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