Re: [f2fs-dev] [PATCH v2] f2fs: compress: avoid duplicate counting of valid blocks when read compressed file

[Chao Yu <chao@kernel.org>]

On 2021/8/11 16:40, 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/compress.c |  1 +
>   fs/f2fs/data.c     | 21 ++++++++++++++++-----
>   fs/f2fs/f2fs.h     |  1 +
>   3 files changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> index 7dbfd6965b97..71768f15752a 100644
> --- a/fs/f2fs/compress.c
> +++ b/fs/f2fs/compress.c
> @@ -152,6 +152,7 @@ void f2fs_destroy_compress_ctx(struct compress_ctx *cc, bool reuse)
>   	cc->rpages = NULL;
>   	cc->nr_rpages = 0;
>   	cc->nr_cpages = 0;
> +	cc->nc_cluster_idx = NULL_CLUSTER;
>   	if (!reuse)
>   		cc->cluster_idx = NULL_CLUSTER;
>   }
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index df5e8d8c654e..3ee1a88d8400 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -2294,6 +2294,7 @@ static int f2fs_mpage_readpages(struct inode *inode,
>   		.log_cluster_size = F2FS_I(inode)->i_log_cluster_size,
>   		.cluster_size = F2FS_I(inode)->i_cluster_size,
>   		.cluster_idx = NULL_CLUSTER,
> +		.nc_cluster_idx = NULL_CLUSTER,
>   		.rpages = NULL,
>   		.cpages = NULL,
>   		.nr_rpages = 0,

pgoff_t nc_cluster_idx = NULL_CLUSTER;

> @@ -2331,12 +2332,22 @@ static int f2fs_mpage_readpages(struct inode *inode,
>   				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 (cc.nc_cluster_idx != NULL_CLUSTER &&
> +					cc.nc_cluster_idx == page->index >> cc.log_cluster_size) {

				 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) {
> +					cc.nc_cluster_idx = page->index >> cc.log_cluster_size;

					nc_cluster_idx =
						page->index >> cc.log_cluster_size;

> +					goto read_single_page;
> +				}
>   
> +				cc.nc_cluster_idx = NULL_CLUSTER;
> +			}
>   			ret = f2fs_init_compress_ctx(&cc);
>   			if (ret)
>   				goto set_error_page;
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index e97b4d8c5efc..e9b6890a3f19 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1471,6 +1471,7 @@ struct compress_data {
>   struct compress_ctx {
>   	struct inode *inode;		/* inode the context belong to */
>   	pgoff_t cluster_idx;		/* cluster index number */
> +	pgoff_t nc_cluster_idx;		/* cluster index number for non-compressed cluster use*/

We only use this field in read flow, please add a local variable to record
last cluster index number of non-compressed cluster.

Thanks,

>   	unsigned int cluster_size;	/* page count in cluster */
>   	unsigned int log_cluster_size;	/* log of cluster size */
>   	struct page **rpages;		/* pages store raw data in cluster */
> 


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