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Date:   Wed, 26 May 2021 06:30:05 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <yuchao0@huawei.com>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, chao@kernel.org
Subject: Re: [PATCH 1/2] f2fs: swap: remove dead codes
Message-ID: <YK5NXdyjgB6EFY5Q@google.com>
References: <20210526062927.52629-1-yuchao0@huawei.com>
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On 05/26, Chao Yu wrote:
> After commit af4b6b8edf6a ("f2fs: introduce check_swap_activate_fast()"),
> we will never run into original logic of check_swap_activate() before
> f2fs supports non 4k-sized page, so let's delete those dead codes.

Why not keeping this for large page support in future maybe?

> 
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> ---
>  fs/f2fs/data.c | 171 +------------------------------------------------
>  1 file changed, 3 insertions(+), 168 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 3058c7e28b11..9c23fde93b76 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -3830,67 +3830,7 @@ int f2fs_migrate_page(struct address_space *mapping,
>  #endif
>  
>  #ifdef CONFIG_SWAP
> -static int f2fs_is_file_aligned(struct inode *inode)
> -{
> -	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> -	block_t main_blkaddr = SM_I(sbi)->main_blkaddr;
> -	block_t cur_lblock;
> -	block_t last_lblock;
> -	block_t pblock;
> -	unsigned long nr_pblocks;
> -	unsigned int blocks_per_sec = BLKS_PER_SEC(sbi);
> -	unsigned int not_aligned = 0;
> -	int ret = 0;
> -
> -	cur_lblock = 0;
> -	last_lblock = bytes_to_blks(inode, i_size_read(inode));
> -
> -	while (cur_lblock < last_lblock) {
> -		struct f2fs_map_blocks map;
> -
> -		memset(&map, 0, sizeof(map));
> -		map.m_lblk = cur_lblock;
> -		map.m_len = last_lblock - cur_lblock;
> -		map.m_next_pgofs = NULL;
> -		map.m_next_extent = NULL;
> -		map.m_seg_type = NO_CHECK_TYPE;
> -		map.m_may_create = false;
> -
> -		ret = f2fs_map_blocks(inode, &map, 0, F2FS_GET_BLOCK_FIEMAP);
> -		if (ret)
> -			goto out;
> -
> -		/* hole */
> -		if (!(map.m_flags & F2FS_MAP_FLAGS)) {
> -			f2fs_err(sbi, "Swapfile has holes\n");
> -			ret = -ENOENT;
> -			goto out;
> -		}
> -
> -		pblock = map.m_pblk;
> -		nr_pblocks = map.m_len;
> -
> -		if ((pblock - main_blkaddr) & (blocks_per_sec - 1) ||
> -			nr_pblocks & (blocks_per_sec - 1)) {
> -			if (f2fs_is_pinned_file(inode)) {
> -				f2fs_err(sbi, "Swapfile does not align to section");
> -				ret = -EINVAL;
> -				goto out;
> -			}
> -			not_aligned++;
> -		}
> -
> -		cur_lblock += nr_pblocks;
> -	}
> -	if (not_aligned)
> -		f2fs_warn(sbi, "Swapfile (%u) is not align to section: \n"
> -			"\t1) creat(), 2) ioctl(F2FS_IOC_SET_PIN_FILE), 3) fallocate()",
> -			not_aligned);
> -out:
> -	return ret;
> -}
> -
> -static int check_swap_activate_fast(struct swap_info_struct *sis,
> +static int check_swap_activate(struct swap_info_struct *sis,
>  				struct file *swap_file, sector_t *span)
>  {
>  	struct address_space *mapping = swap_file->f_mapping;
> @@ -3907,6 +3847,8 @@ static int check_swap_activate_fast(struct swap_info_struct *sis,
>  	unsigned int not_aligned = 0;
>  	int ret = 0;
>  
> +	f2fs_bug_on(sbi, PAGE_SIZE != F2FS_BLKSIZE);
> +
>  	/*
>  	 * Map all the blocks into the extent list.  This code doesn't try
>  	 * to be very smart.
> @@ -3986,113 +3928,6 @@ static int check_swap_activate_fast(struct swap_info_struct *sis,
>  	return ret;
>  }
>  
> -/* Copied from generic_swapfile_activate() to check any holes */
> -static int check_swap_activate(struct swap_info_struct *sis,
> -				struct file *swap_file, sector_t *span)
> -{
> -	struct address_space *mapping = swap_file->f_mapping;
> -	struct inode *inode = mapping->host;
> -	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> -	unsigned blocks_per_page;
> -	unsigned long page_no;
> -	sector_t probe_block;
> -	sector_t last_block;
> -	sector_t lowest_block = -1;
> -	sector_t highest_block = 0;
> -	int nr_extents = 0;
> -	int ret = 0;
> -
> -	if (PAGE_SIZE == F2FS_BLKSIZE)
> -		return check_swap_activate_fast(sis, swap_file, span);
> -
> -	ret = f2fs_is_file_aligned(inode);
> -	if (ret)
> -		goto out;
> -
> -	blocks_per_page = bytes_to_blks(inode, PAGE_SIZE);
> -
> -	/*
> -	 * Map all the blocks into the extent list.  This code doesn't try
> -	 * to be very smart.
> -	 */
> -	probe_block = 0;
> -	page_no = 0;
> -	last_block = bytes_to_blks(inode, i_size_read(inode));
> -	while ((probe_block + blocks_per_page) <= last_block &&
> -			page_no < sis->max) {
> -		unsigned block_in_page;
> -		sector_t first_block;
> -		sector_t block = 0;
> -
> -		cond_resched();
> -
> -		block = probe_block;
> -		ret = bmap(inode, &block);
> -		if (ret)
> -			goto out;
> -		if (!block)
> -			goto bad_bmap;
> -		first_block = block;
> -
> -		/*
> -		 * It must be PAGE_SIZE aligned on-disk
> -		 */
> -		if (first_block & (blocks_per_page - 1)) {
> -			probe_block++;
> -			goto reprobe;
> -		}
> -
> -		for (block_in_page = 1; block_in_page < blocks_per_page;
> -					block_in_page++) {
> -
> -			block = probe_block + block_in_page;
> -			ret = bmap(inode, &block);
> -			if (ret)
> -				goto out;
> -			if (!block)
> -				goto bad_bmap;
> -
> -			if (block != first_block + block_in_page) {
> -				/* Discontiguity */
> -				probe_block++;
> -				goto reprobe;
> -			}
> -		}
> -
> -		first_block >>= (PAGE_SHIFT - inode->i_blkbits);
> -		if (page_no) {	/* exclude the header page */
> -			if (first_block < lowest_block)
> -				lowest_block = first_block;
> -			if (first_block > highest_block)
> -				highest_block = first_block;
> -		}
> -
> -		/*
> -		 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
> -		 */
> -		ret = add_swap_extent(sis, page_no, 1, first_block);
> -		if (ret < 0)
> -			goto out;
> -		nr_extents += ret;
> -		page_no++;
> -		probe_block += blocks_per_page;
> -reprobe:
> -		continue;
> -	}
> -	ret = nr_extents;
> -	*span = 1 + highest_block - lowest_block;
> -	if (page_no == 0)
> -		page_no = 1;	/* force Empty message */
> -	sis->max = page_no;
> -	sis->pages = page_no - 1;
> -	sis->highest_bit = page_no - 1;
> -out:
> -	return ret;
> -bad_bmap:
> -	f2fs_err(sbi, "Swapfile has holes\n");
> -	return -EINVAL;
> -}
> -
>  static int f2fs_swap_activate(struct swap_info_struct *sis, struct file *file,
>  				sector_t *span)
>  {
> -- 
> 2.29.2