[Devel] [PATCH rh7 3/5] cbt: make __blk_cbt_set() smarter

[Dmitry Monakhov]

Maxim Patlasov <mpatlasov at virtuozzo.com> writes:

> The patch adds two new args to __blk_cbt_set: pages_missed and idx_first.
> Both are pointers. No logic changed, so far as everybody passes NULL/NULL.
> The next patch will pass non-trivial values.
>
> The idea is to mark slots in cbt->map[idx] that need allocation with
> special flag, save their number in *pages_missed and the first index of
> such a slot in *idx_first. This will be used by next patch.
>
> Signed-off-by: Maxim Patlasov <mpatlasov at virtuozzo.com>
ACK
> ---
>  block/blk-cbt.c |   26 ++++++++++++++++++--------
>  1 file changed, 18 insertions(+), 8 deletions(-)
>
> diff --git a/block/blk-cbt.c b/block/blk-cbt.c
> index ee225a4..f83eb96 100644
> --- a/block/blk-cbt.c
> +++ b/block/blk-cbt.c
> @@ -136,7 +136,9 @@ static int cbt_page_alloc(struct cbt_info  **cbt_pp, unsigned long idx,
>  }
>  
>  static int __blk_cbt_set(struct cbt_info  *cbt, blkcnt_t block,
> -			  blkcnt_t count, bool in_rcu, bool set)
> +			 blkcnt_t count, bool in_rcu, bool set,
> +			 unsigned long *pages_missed,
> +			 unsigned long *idx_first)
>  {
>  	struct page *page;
>  
> @@ -164,7 +166,15 @@ static int __blk_cbt_set(struct cbt_info  *cbt, blkcnt_t block,
>  			count -= len;
>  			block += len;
>  			continue;
> -		} else {
> +		} else if (pages_missed) {
> +			(*pages_missed)++;
> +			if (!*idx_first)
> +				*idx_first = idx;
> +			cbt->map[idx] = CBT_PAGE_MISSED;
> +			count -= len;
> +			block += len;
> +			continue;
> +		}  else {
>  			if (!set) {
>  				/* Nothing to do */
>  				count -= len;
> @@ -181,7 +191,7 @@ static int __blk_cbt_set(struct cbt_info  *cbt, blkcnt_t block,
>  		else if (ret)
>  			return ret;
>  	}
> -	return 0;
> +	return (pages_missed && *pages_missed) ? -EAGAIN : 0;
>  }
>  
>  static void blk_cbt_add(struct request_queue *q, blkcnt_t start, blkcnt_t len)
> @@ -203,7 +213,7 @@ static void blk_cbt_add(struct request_queue *q, blkcnt_t start, blkcnt_t len)
>  	start >>= cbt->block_bits;
>  	len = end - start;
>  	if (unlikely(test_bit(CBT_NOCACHE, &cbt->flags))) {
> -		__blk_cbt_set(cbt, start, len, 1, 1);
> +		__blk_cbt_set(cbt, start, len, 1, 1, NULL, NULL);
>  		goto out_rcu;
>  	}
>  	ex = this_cpu_ptr(cbt->cache);
> @@ -216,7 +226,7 @@ static void blk_cbt_add(struct request_queue *q, blkcnt_t start, blkcnt_t len)
>  	ex->len = len;
>  
>  	if (likely(old.len))
> -		__blk_cbt_set(cbt, old.start, old.len, 1, 1);
> +		__blk_cbt_set(cbt, old.start, old.len, 1, 1, NULL, NULL);
>  out_rcu:
>  	rcu_read_unlock();
>  }
> @@ -401,7 +411,7 @@ static inline void __cbt_flush_cpu_cache(void *ptr)
>  	struct cbt_extent *ex = this_cpu_ptr(cbt->cache);
>  
>  	if (ex->len) {
> -		__blk_cbt_set(cbt, ex->start, ex->len, 0, 1);
> +		__blk_cbt_set(cbt, ex->start, ex->len, 0, 1, NULL, NULL);
>  		ex->start += ex->len;
>  		ex->len = 0;
>  	}
> @@ -522,7 +532,7 @@ static int cbt_ioc_get(struct block_device *bdev, struct blk_user_cbt_info __use
>  			break;
>  		}
>  		if (ci.ci_flags & CI_FLAG_ONCE)
> -			__blk_cbt_set(cbt, ex.start, ex.len, 0, 0);
> +			__blk_cbt_set(cbt, ex.start, ex.len, 0, 0, NULL, NULL);
>  		cur_u_ex++;
>  		ci.ci_mapped_extents++;
>  		block = ex.start + ex.len;
> @@ -592,7 +602,7 @@ static int cbt_ioc_set(struct block_device *bdev, struct blk_user_cbt_info __use
>  			ret = -EINVAL;
>  			break;
>  		}
> -		ret = __blk_cbt_set(cbt, ex.start, ex.len, 0, set);
> +		ret = __blk_cbt_set(cbt, ex.start, ex.len, 0, set, NULL, NULL);
>  		if (ret)
>  			break;
>  		cur_u_ex++;
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