[Devel] [PATCH rh7 1/5] cbt: factor out alloc_page

[Dmitry Monakhov]

Maxim Patlasov <mpatlasov at virtuozzo.com> writes:

> The patch moves the logic of allocating new page for cbt->map[idx] to
> a separate function. It will be used in further patches.
ACK
>
> Signed-off-by: Maxim Patlasov <mpatlasov at virtuozzo.com>
> ---
>  block/blk-cbt.c |   98 +++++++++++++++++++++++++++++++++++--------------------
>  1 file changed, 62 insertions(+), 36 deletions(-)
>
> diff --git a/block/blk-cbt.c b/block/blk-cbt.c
> index b66f513..08cefd8 100644
> --- a/block/blk-cbt.c
> +++ b/block/blk-cbt.c
> @@ -76,6 +76,61 @@ static void set_bits(void *bm, int cur, int len, bool is_set)
>  	}
>  }
>  
> +/*
> + * Return values:
> + * 0 if OK,
> + * -EAGAIN if cbt was updated,
> + * -EBADF if cbt is dead,
> + * -ENOMEM if alloc_page failed.
> + */
> +static int cbt_page_alloc(struct cbt_info  **cbt_pp, unsigned long idx,
> +			  int in_rcu)
> +{
> +	struct cbt_info	 *cbt = *cbt_pp;
> +	struct page *page;
> +
> +	/* Page not allocated yet. Synchronization required */
> +	spin_lock_irq(&cbt->lock);
> +	if (likely(!test_bit(CBT_DEAD, &cbt->flags))) {
> +		cbt->count++;
> +	} else {
> +		struct cbt_info *new = rcu_dereference(cbt->queue->cbt);
> +
> +		spin_unlock_irq(&cbt->lock);
> +		/* was cbt updated ? */
> +		if (new != cbt) {
> +			*cbt_pp = new;
> +			return -EAGAIN;
> +		} else {
> +			return -EBADF;
> +		}
> +	}
> +	spin_unlock_irq(&cbt->lock);
> +	if (in_rcu)
> +		rcu_read_unlock();
> +	page = alloc_page(GFP_NOIO|__GFP_ZERO);
> +	if (in_rcu)
> +		rcu_read_lock();
> +	spin_lock_irq(&cbt->lock);
> +	if (unlikely(!cbt->count-- && test_bit(CBT_DEAD, &cbt->flags))) {
> +		spin_unlock_irq(&cbt->lock);
> +		call_rcu(&cbt->rcu, &cbt_release_callback);
> +		if (page)
> +			__free_page(page);
> +		return -EBADF;
> +	}
> +	if (unlikely(!page)) {
> +		set_bit(CBT_ERROR, &cbt->flags);
> +		spin_unlock_irq(&cbt->lock);
> +		return -ENOMEM;
> +	}
> +	cbt->map[idx] = page;
> +	page = NULL;
> +	spin_unlock_irq(&cbt->lock);
> +
> +	return 0;
> +}
> +
>  static int __blk_cbt_set(struct cbt_info  *cbt, blkcnt_t block,
>  			  blkcnt_t count, bool in_rcu, bool set)
>  {
> @@ -95,6 +150,7 @@ static int __blk_cbt_set(struct cbt_info  *cbt, blkcnt_t block,
>  		unsigned long off = block & (BITS_PER_PAGE -1);
>  		unsigned long len = min_t(unsigned long, BITS_PER_PAGE - off,
>  					  count);
> +		int ret;
>  
>  		page = cbt->map[idx];
>  		if (page) {
> @@ -112,44 +168,14 @@ static int __blk_cbt_set(struct cbt_info  *cbt, blkcnt_t block,
>  				continue;
>  			}
>  		}
> -		/* Page not allocated yet. Synchronization required */
> -		spin_lock_irq(&cbt->lock);
> -		if (likely(!test_bit(CBT_DEAD, &cbt->flags))) {
> -			cbt->count++;
> -		} else {
> -			struct cbt_info *new = rcu_dereference(cbt->queue->cbt);
>  
> -			spin_unlock_irq(&cbt->lock);
> -			/* was cbt updated ? */
> -			if (new != cbt) {
> -				cbt = new;
> -				continue;
> -			} else {
> -				break;
> -			}
> -		}
> -		spin_unlock_irq(&cbt->lock);
> -		if (in_rcu)
> -			rcu_read_unlock();
> -		page = alloc_page(GFP_NOIO|__GFP_ZERO);
> -		if (in_rcu)
> -			rcu_read_lock();
> -		spin_lock_irq(&cbt->lock);
> -		if (unlikely(!cbt->count-- && test_bit(CBT_DEAD, &cbt->flags))) {
> -			spin_unlock_irq(&cbt->lock);
> -			call_rcu(&cbt->rcu, &cbt_release_callback);
> -			if (page)
> -				__free_page(page);
> +		ret = cbt_page_alloc(&cbt, idx, in_rcu);
> +		if (ret == -EAGAIN) /* new cbt */
> +			continue;
> +		else if (ret == -EBADF) /* dead cbt */
>  			break;
> -		}
> -		if (unlikely(!page)) {
> -			set_bit(CBT_ERROR, &cbt->flags);
> -			spin_unlock_irq(&cbt->lock);
> -			return -ENOMEM;
> -		}
> -		cbt->map[idx] = page;
> -		page = NULL;
> -		spin_unlock_irq(&cbt->lock);
> +		else if (ret)
> +			return ret;
>  	}
>  	return 0;
>  }
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