linux-kernel - Re: [PATCH] f2fs: use round_up()/DIV_ROUND

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Date:   Mon, 30 Mar 2020 11:42:30 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, chao@...nel.org
Subject: Re: [PATCH] f2fs: use round_up()/DIV_ROUND_UP()

On 03/30, Chao Yu wrote:
> .i_cluster_size should be power of 2, so we can use round_up() instead
> of roundup() to enhance the calculation.
> 
> In addition, use DIV_ROUND_UP to clean up codes.
> 
> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> ---
>  fs/f2fs/data.c | 16 ++++++----------
>  fs/f2fs/file.c | 17 +++++------------
>  2 files changed, 11 insertions(+), 22 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 0a829a89f596..8257d5e7aa3b 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1969,8 +1969,6 @@ static int f2fs_read_single_page(struct inode *inode, struct page *page,
>  					bool is_readahead)
>  {
>  	struct bio *bio = *bio_ret;
> -	const unsigned blkbits = inode->i_blkbits;
> -	const unsigned blocksize = 1 << blkbits;
>  	sector_t block_in_file;
>  	sector_t last_block;
>  	sector_t last_block_in_file;
> @@ -1979,8 +1977,8 @@ static int f2fs_read_single_page(struct inode *inode, struct page *page,
>  
>  	block_in_file = (sector_t)page_index(page);
>  	last_block = block_in_file + nr_pages;
> -	last_block_in_file = (f2fs_readpage_limit(inode) + blocksize - 1) >>
> -							blkbits;
> +	last_block_in_file = DIV_ROUND_UP(f2fs_readpage_limit(inode),
> +								PAGE_SIZE);

What if PAGE_SIZE is bigger than 4KB?

>  	if (last_block > last_block_in_file)
>  		last_block = last_block_in_file;
>  
> @@ -2062,7 +2060,7 @@ static int f2fs_read_single_page(struct inode *inode, struct page *page,
>  	 */
>  	f2fs_wait_on_block_writeback(inode, block_nr);
>  
> -	if (bio_add_page(bio, page, blocksize, 0) < blocksize)
> +	if (bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_SIZE)
>  		goto submit_and_realloc;
>  
>  	inc_page_count(F2FS_I_SB(inode), F2FS_RD_DATA);
> @@ -2091,16 +2089,14 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
>  	struct bio *bio = *bio_ret;
>  	unsigned int start_idx = cc->cluster_idx << cc->log_cluster_size;
>  	sector_t last_block_in_file;
> -	const unsigned blkbits = inode->i_blkbits;
> -	const unsigned blocksize = 1 << blkbits;
>  	struct decompress_io_ctx *dic = NULL;
>  	int i;
>  	int ret = 0;
>  
>  	f2fs_bug_on(sbi, f2fs_cluster_is_empty(cc));
>  
> -	last_block_in_file = (f2fs_readpage_limit(inode) +
> -					blocksize - 1) >> blkbits;
> +	last_block_in_file = DIV_ROUND_UP(f2fs_readpage_limit(inode),
> +								PAGE_SIZE);
>  
>  	/* get rid of pages beyond EOF */
>  	for (i = 0; i < cc->cluster_size; i++) {
> @@ -2197,7 +2193,7 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
>  
>  		f2fs_wait_on_block_writeback(inode, blkaddr);
>  
> -		if (bio_add_page(bio, page, blocksize, 0) < blocksize)
> +		if (bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_SIZE)
>  			goto submit_and_realloc;
>  
>  		inc_page_count(sbi, F2FS_RD_DATA);
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index c2d38a1c4972..0f8be076620c 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -736,16 +736,9 @@ int f2fs_truncate_blocks(struct inode *inode, u64 from, bool lock)
>  	 * for compressed file, only support cluster size
>  	 * aligned truncation.
>  	 */
> -	if (f2fs_compressed_file(inode)) {
> -		size_t cluster_shift = PAGE_SHIFT +
> -					F2FS_I(inode)->i_log_cluster_size;
> -		size_t cluster_mask = (1 << cluster_shift) - 1;
> -
> -		free_from = from >> cluster_shift;
> -		if (from & cluster_mask)
> -			free_from++;
> -		free_from <<= cluster_shift;
> -	}
> +	if (f2fs_compressed_file(inode))
> +		free_from = round_up(from,
> +				F2FS_I(inode)->i_cluster_size << PAGE_SHIFT);
>  #endif
>  
>  	err = f2fs_do_truncate_blocks(inode, free_from, lock);
> @@ -3537,7 +3530,7 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)
>  
>  		end_offset = ADDRS_PER_PAGE(dn.node_page, inode);
>  		count = min(end_offset - dn.ofs_in_node, last_idx - page_idx);
> -		count = roundup(count, F2FS_I(inode)->i_cluster_size);
> +		count = round_up(count, F2FS_I(inode)->i_cluster_size);
>  
>  		ret = release_compress_blocks(&dn, count);
>  
> @@ -3689,7 +3682,7 @@ static int f2fs_reserve_compress_blocks(struct file *filp, unsigned long arg)
>  
>  		end_offset = ADDRS_PER_PAGE(dn.node_page, inode);
>  		count = min(end_offset - dn.ofs_in_node, last_idx - page_idx);
> -		count = roundup(count, F2FS_I(inode)->i_cluster_size);
> +		count = round_up(count, F2FS_I(inode)->i_cluster_size);
>  
>  		ret = reserve_compress_blocks(&dn, count);
>  
> -- 
> 2.18.0.rc1