Re: [PATCH 6/8] erofs: get rid of fe->backmost for cache decompression

[Yue Hu <zbestahu@gmail.com>]

On Thu, 17 Aug 2023 16:28:11 +0800
Gao Xiang <hsiangkao@linux.alibaba.com> wrote:

> EROFS_MAP_FULL_MAPPED is more accurate to decide if caching the last
> incomplete pcluster for later read or not.
> 
> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
> ---
>  fs/erofs/zdata.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index 4009283944ca..c28945532a02 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -528,8 +528,6 @@ struct z_erofs_decompress_frontend {
>  	z_erofs_next_pcluster_t owned_head;
>  	enum z_erofs_pclustermode mode;
>  
> -	/* used for applying cache strategy on the fly */
> -	bool backmost;
>  	erofs_off_t headoffset;
>  
>  	/* a pointer used to pick up inplace I/O pages */
> @@ -538,7 +536,7 @@ struct z_erofs_decompress_frontend {
>  
>  #define DECOMPRESS_FRONTEND_INIT(__i) { \
>  	.inode = __i, .owned_head = Z_EROFS_PCLUSTER_TAIL, \
> -	.mode = Z_EROFS_PCLUSTER_FOLLOWED, .backmost = true }
> +	.mode = Z_EROFS_PCLUSTER_FOLLOWED }
>  
>  static bool z_erofs_should_alloc_cache(struct z_erofs_decompress_frontend *fe)
>  {
> @@ -547,7 +545,7 @@ static bool z_erofs_should_alloc_cache(struct z_erofs_decompress_frontend *fe)
>  	if (cachestrategy <= EROFS_ZIP_CACHE_DISABLED)
>  		return false;
>  
> -	if (fe->backmost)
> +	if (!(fe->map.m_flags & EROFS_MAP_FULL_MAPPED))

So, i understand (map.m_flags & EROFS_MAP_FULL_MAPPED) should be false if allocate cache is needed
(fe->backmost is true)?

>  		return true;
>  
>  	if (cachestrategy >= EROFS_ZIP_CACHE_READAROUND &&
> @@ -939,7 +937,6 @@ static void z_erofs_pcluster_end(struct z_erofs_decompress_frontend *fe)
>  		erofs_workgroup_put(&pcl->obj);
>  
>  	fe->pcl = NULL;
> -	fe->backmost = false;
>  }
>  
>  static int z_erofs_read_fragment(struct super_block *sb, struct page *page,