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Date:   Wed, 16 Sep 2020 22:33:04 +0800
From:   Gao Xiang <hsiangkao@redhat.com>
To:     Chao Yu <chao@kernel.org>
Cc:     linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org,
        Chao Yu <yuchao0@huawei.com>
Subject: Re: [PATCH] erofs: remove unneeded parameter
Message-ID: <20200916143304.GA23176@xiangao.remote.csb>
References: <20200916140604.3799-1-chao@kernel.org>
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Hi Chao,

On Wed, Sep 16, 2020 at 10:06:04PM +0800, Chao Yu wrote:
> From: Chao Yu <yuchao0@huawei.com>
> 
> In below call path, no page will be cached into @pagepool list
> or grabbed from @pagepool list:
> - z_erofs_readpage
>  - z_erofs_do_read_page
>   - preload_compressed_pages
>   - erofs_allocpage
> 
> Let's get rid of this unneeded parameter.

That would be unneeded after .readahead() is introduced recently
(so add_to_page_cache_lru() is also moved to mm code), so I agree
with you on it.

> 
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> ---
>  fs/erofs/utils.c |  2 +-
>  fs/erofs/zdata.c | 14 ++++++--------
>  2 files changed, 7 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/erofs/utils.c b/fs/erofs/utils.c
> index de9986d2f82f..7a6e5456b0b8 100644
> --- a/fs/erofs/utils.c
> +++ b/fs/erofs/utils.c
> @@ -11,7 +11,7 @@ struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp)
>  {
>  	struct page *page;
>  
> -	if (!list_empty(pool)) {
> +	if (pool && !list_empty(pool)) {
>  		page = lru_to_page(pool);
>  		DBG_BUGON(page_ref_count(page) != 1);
>  		list_del(&page->lru);
> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index 6c939def00f9..f218f58f4159 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -153,8 +153,7 @@ static DEFINE_MUTEX(z_pagemap_global_lock);
>  
>  static void preload_compressed_pages(struct z_erofs_collector *clt,
>  				     struct address_space *mc,
> -				     enum z_erofs_cache_alloctype type,
> -				     struct list_head *pagepool)
> +				     enum z_erofs_cache_alloctype type)
>  {
>  	const struct z_erofs_pcluster *pcl = clt->pcl;
>  	const unsigned int clusterpages = BIT(pcl->clusterbits);
> @@ -562,8 +561,7 @@ static bool should_alloc_managed_pages(struct z_erofs_decompress_frontend *fe,
>  }
>  
>  static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
> -				struct page *page,
> -				struct list_head *pagepool)
> +				struct page *page)
>  {
>  	struct inode *const inode = fe->inode;
>  	struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
> @@ -621,7 +619,7 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
>  		cache_strategy = DONTALLOC;
>  
>  	preload_compressed_pages(clt, MNGD_MAPPING(sbi),
> -				 cache_strategy, pagepool);
> +				 cache_strategy);
>  
>  hitted:
>  	/*
> @@ -653,7 +651,7 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
>  	/* should allocate an additional staging page for pagevec */
>  	if (err == -EAGAIN) {
>  		struct page *const newpage =
> -			erofs_allocpage(pagepool, GFP_NOFS | __GFP_NOFAIL);
> +			erofs_allocpage(NULL, GFP_NOFS | __GFP_NOFAIL);

Could we use allocpage instead, so erofs_allocpage modification is unneeded as well :)

Thanks,
Gao Xiang