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Date:   Wed, 26 May 2021 18:40:03 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <chao@kernel.org>
Cc:     Chao Yu <yuchao0@huawei.com>,
        linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] f2fs: swap: remove dead codes
Message-ID: <YK74cyGYzWZCmZue@google.com>
References: <20210526062927.52629-1-yuchao0@huawei.com>
 <YK5NXdyjgB6EFY5Q@google.com>
 <e4c1df88-f1f4-99e0-6f83-fa0f3110d737@kernel.org>
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On 05/26, Chao Yu wrote:
> On 2021/5/26 21:30, Jaegeuk Kim wrote:
> > 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?
> 
> Well, if so, at that time, it would be better to refactor
> check_swap_activate_fast() implementation based on f2fs_map_block() rather
> than refactoring check_swap_activate() implementation based on low efficient
> bmap()?

Let's first check whether we support large page. Have you quickly tested it?
If we support it now and current flow is just inefficient, I'd say keeping but
refactoring it later.

> 
> Thanks,
> 
> > 
> > > 
> > > 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