Re: [f2fs-dev] [PATCH v4] f2fs: compress: avoid duplicate counting of valid blocks when read compressed file

[Chao Yu <chao@kernel.org>]

On 2021/8/12 11:18, Fengnan Chang wrote:
> Since cluster is basic unit of compression, one cluster is compressed or
> not, so we can calculate valid blocks only for first page in cluster,
> the other pages just skip.
> 
> Signed-off-by: Fengnan Chang <changfengnan@vivo.com>
> ---
>   fs/f2fs/data.c | 24 +++++++++++++++++++-----
>   1 file changed, 19 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index df5e8d8c654e..fc0115a61082 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -2299,6 +2299,7 @@ static int f2fs_mpage_readpages(struct inode *inode,
>   		.nr_rpages = 0,
>   		.nr_cpages = 0,
>   	};
> +	pgoff_t nc_cluster_idx = NULL_CLUSTER;
>   #endif
>   	unsigned nr_pages = rac ? readahead_count(rac) : 1;
>   	unsigned max_nr_pages = nr_pages;
> @@ -2328,15 +2329,27 @@ static int f2fs_mpage_readpages(struct inode *inode,
>   							&last_block_in_bio,
>   							rac != NULL, false);
>   				f2fs_destroy_compress_ctx(&cc, false);
> +				nc_cluster_idx = NULL_CLUSTER;

Can we get rid of this?

>   				if (ret)
>   					goto set_error_page;
>   			}
> -			ret = f2fs_is_compressed_cluster(inode, page->index);
> -			if (ret < 0)
> -				goto set_error_page;
> -			else if (!ret)
> -				goto read_single_page;
> +			if (cc.cluster_idx == NULL_CLUSTER) {
> +				if (nc_cluster_idx ==
> +					page->index >> cc.log_cluster_size) {
> +					goto read_single_page;
> +				}
> +
> +				ret = f2fs_is_compressed_cluster(inode, page->index);
> +				if (ret < 0)
> +					goto set_error_page;
> +				else if (!ret) {
> +					nc_cluster_idx =
> +						page->index >> cc.log_cluster_size;
> +					goto read_single_page;
> +				}
>   
> +				nc_cluster_idx = NULL_CLUSTER;
> +			}
>   			ret = f2fs_init_compress_ctx(&cc);
>   			if (ret)
>   				goto set_error_page;
> @@ -2373,6 +2386,7 @@ static int f2fs_mpage_readpages(struct inode *inode,
>   							&last_block_in_bio,
>   							rac != NULL, false);
>   				f2fs_destroy_compress_ctx(&cc, false);
> +				nc_cluster_idx = NULL_CLUSTER;

Ditto,

Thanks,

>   			}
>   		}
>   #endif
> 


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