linux-kernel - Re: [PATCH v6 20/22] erofs: implement fscache-based data read for data blobs

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Date:   Mon, 28 Mar 2022 17:50:52 +0800
From:   Gao Xiang <hsiangkao@...ux.alibaba.com>
To:     Jeffle Xu <jefflexu@...ux.alibaba.com>
Cc:     dhowells@...hat.com, linux-cachefs@...hat.com, xiang@...nel.org,
        chao@...nel.org, linux-erofs@...ts.ozlabs.org,
        torvalds@...ux-foundation.org, gregkh@...uxfoundation.org,
        willy@...radead.org, linux-fsdevel@...r.kernel.org,
        joseph.qi@...ux.alibaba.com, bo.liu@...ux.alibaba.com,
        tao.peng@...ux.alibaba.com, gerry@...ux.alibaba.com,
        eguan@...ux.alibaba.com, linux-kernel@...r.kernel.org,
        luodaowen.backend@...edance.com, tianzichen@...ishou.com,
        fannaihao@...du.com
Subject: Re: [PATCH v6 20/22] erofs: implement fscache-based data read for
 data blobs

On Fri, Mar 25, 2022 at 08:22:21PM +0800, Jeffle Xu wrote:
> Implements the data plane of reading data from data blob file over
> fscache.
> 
> Signed-off-by: Jeffle Xu <jefflexu@...ux.alibaba.com>
> ---
>  fs/erofs/data.c     |  3 +++
>  fs/erofs/fscache.c  | 15 +++++++++++++--
>  fs/erofs/internal.h |  1 +
>  3 files changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/erofs/data.c b/fs/erofs/data.c
> index b4571bea93d5..b9a05de3c3b2 100644
> --- a/fs/erofs/data.c
> +++ b/fs/erofs/data.c
> @@ -206,6 +206,7 @@ int erofs_map_dev(struct super_block *sb, struct erofs_map_dev *map)
>  	map->m_bdev = sb->s_bdev;
>  	map->m_daxdev = EROFS_SB(sb)->dax_dev;
>  	map->m_dax_part_off = EROFS_SB(sb)->dax_part_off;
> +	map->m_fscache = EROFS_SB(sb)->bootstrap;
>  
>  	if (map->m_deviceid) {
>  		down_read(&devs->rwsem);
> @@ -217,6 +218,7 @@ int erofs_map_dev(struct super_block *sb, struct erofs_map_dev *map)
>  		map->m_bdev = dif->bdev;
>  		map->m_daxdev = dif->dax_dev;
>  		map->m_dax_part_off = dif->dax_part_off;
> +		map->m_fscache = dif->blob;
>  		up_read(&devs->rwsem);
>  	} else if (devs->extra_devices) {
>  		down_read(&devs->rwsem);
> @@ -234,6 +236,7 @@ int erofs_map_dev(struct super_block *sb, struct erofs_map_dev *map)
>  				map->m_bdev = dif->bdev;
>  				map->m_daxdev = dif->dax_dev;
>  				map->m_dax_part_off = dif->dax_part_off;
> +				map->m_fscache = dif->blob;
>  				break;
>  			}
>  		}
> diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
> index d75958470645..cbb39657615e 100644
> --- a/fs/erofs/fscache.c
> +++ b/fs/erofs/fscache.c
> @@ -63,9 +63,20 @@ static int erofs_fscache_readpage_blob(struct file *data, struct page *page)
>  static inline int erofs_fscache_get_map(struct erofs_map_blocks *map,
>  					struct super_block *sb)
>  {

So erofs_fscache_get_map seems really unneeded...
erofs_map_dev can be used directly so we can avoid this patch.

Thanks,
Gao Xiang

> -	struct erofs_sb_info *sbi = EROFS_SB(sb);
> +	struct erofs_map_dev mdev;
> +	int ret;
> +
> +	mdev = (struct erofs_map_dev) {
> +		.m_deviceid = map->m_deviceid,
> +		.m_pa = map->m_pa,
> +	};
> +
> +	ret = erofs_map_dev(sb, &mdev);
> +	if (ret)
> +		return ret;
>  
> -	map->m_fscache	= sbi->bootstrap;
> +	map->m_fscache	= mdev.m_fscache;
> +	map->m_pa	= mdev.m_pa;
>  	return 0;
>  }
>  
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index 94a118caf580..cea08f12a2c3 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -487,6 +487,7 @@ struct erofs_map_dev {
>  	struct block_device *m_bdev;
>  	struct dax_device *m_daxdev;
>  	u64 m_dax_part_off;
> +	struct erofs_fscache *m_fscache;
>  
>  	erofs_off_t m_pa;
>  	unsigned int m_deviceid;
> -- 
> 2.27.0