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

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Date:   Mon, 30 Mar 2020 20:55:37 -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 03/31, Chao Yu wrote:
> On 2020/3/31 2:42, Jaegeuk Kim wrote:
> > 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?
> 
> We don't support 8kb+ sized-page, right?

That's only assumption below. I don't think we can just replace block with PAGE
in every places.

> 
> static int __init init_f2fs_fs(void)
> {
> 	int err;
> 
> 	if (PAGE_SIZE != F2FS_BLKSIZE) {
> 		printk("F2FS not supported on PAGE_SIZE(%lu) != %d\n",
> 				PAGE_SIZE, F2FS_BLKSIZE);
> 		return -EINVAL;
> 	}
> 
> Thanks,
> 
> > 
> >>  	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
> > .
> >