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

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Message-ID: <2b5ec2a6-218a-a291-a6fc-d87cd40be4db@huawei.com>
Date:   Tue, 31 Mar 2020 08:48:49 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
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 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?

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
> .
>