Re: [f2fs-dev] [PATCH 3/3] f2fs: check if swapfile is section-alligned

[Chao Yu]

Hi Jianan,

On 2021/2/27 20:02, Huang Jianan via Linux-f2fs-devel wrote:
> If the swapfile isn't created by pin and fallocate, it cann't be

Typo:

can't

> guaranteed section-aligned, so it may be selected by f2fs gc. When
> gc_pin_file_threshold is reached, the address of swapfile may change,
> but won't be synchroniz to swap_extent, so swap will write to wrong

synchronized

> address, which will cause data corruption.
>
> Signed-off-by: Huang Jianan <huangjianan@xxxxxxxx>
> Signed-off-by: Guo Weichao <guoweichao@xxxxxxxx>
> ---
>   fs/f2fs/data.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 63 insertions(+)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 4dbc1cafc55d..3e523d6e4643 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -3781,11 +3781,63 @@ int f2fs_migrate_page(struct address_space *mapping,
>   #endif
>   
>   #ifdef CONFIG_SWAP
> +static int f2fs_check_file_aligned(struct inode *inode)

f2fs_check_file_alignment() or f2fs_is_file_aligned()?

> +{
> +	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 len;
> +	unsigned long nr_pblocks;
> +	unsigned int blocks_per_sec = sbi->blocks_per_seg * sbi->segs_per_sec;

unsigned int blocks_per_sec = BLKS_PER_SEC(sbi);

> +	int ret;
> +
> +	cur_lblock = 0;
> +	last_lblock = bytes_to_blks(inode, i_size_read(inode));
> +	len = i_size_read(inode);
> +
> +	while (cur_lblock < last_lblock) {
> +		struct f2fs_map_blocks map;
> +		pgoff_t next_pgofs;
> +
> +		memset(&map, 0, sizeof(map));
> +		map.m_lblk = cur_lblock;
> +		map.m_len = bytes_to_blks(inode, len) - cur_lblock;

map.m_len = last_lblock - cur_lblock;

> +		map.m_next_pgofs = &next_pgofs;

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);
> +

Unneeded blank line.

> +		if (ret)
> +			goto err_out;
> +
> +		/* hole */
> +		if (!(map.m_flags & F2FS_MAP_FLAGS))

ret = -ENOENT;

> +			goto err_out;
> +
> +		pblock = map.m_pblk;
> +		nr_pblocks = map.m_len;
> +
> +		if ((pblock - main_blkaddr) & (blocks_per_sec - 1) ||
> +			nr_pblocks & (blocks_per_sec - 1))

ret = -EINVAL;

> +			goto err_out;
> +
> +		cur_lblock += nr_pblocks;
> +	}
> +
> +	return 0;
> +err_out:
> +	pr_err("swapon: swapfile isn't section-aligned\n");

We should show above message only after we fail in check condition:

	if ((pblock - main_blkaddr) & (blocks_per_sec - 1) ||
		nr_pblocks & (blocks_per_sec - 1)) {
		f2fs_err(sbi, "Swapfile does not align to section");
		goto err_out;
	}

And please use f2fs_{err,warn,info..} macro rather than pr_{err,warn,info..}.

Could you please fix above related issues in check_swap_activate_fast() as well.

> +	return -EINVAL;

return ret;

> +}
> +
>   static int check_swap_activate_fast(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);
>   	sector_t cur_lblock;
>   	sector_t last_lblock;
>   	sector_t pblock;
> @@ -3793,6 +3845,7 @@ static int check_swap_activate_fast(struct swap_info_struct *sis,
>   	sector_t highest_pblock = 0;
>   	int nr_extents = 0;
>   	unsigned long nr_pblocks;
> +	unsigned int blocks_per_sec = sbi->blocks_per_seg * sbi->segs_per_sec;

Ditto,

>   	u64 len;
>   	int ret;
>   
> @@ -3827,6 +3880,13 @@ static int check_swap_activate_fast(struct swap_info_struct *sis,
>   		pblock = map.m_pblk;
>   		nr_pblocks = map.m_len;
>   
> +		if ((pblock - SM_I(sbi)->main_blkaddr) & (blocks_per_sec - 1) ||
> +			nr_pblocks & (blocks_per_sec - 1)) {
> +			pr_err("swapon: swapfile isn't section-aligned\n");

Ditto,

> +			ret = -EINVAL;
> +			goto out;
> +		}
> +
>   		if (cur_lblock + nr_pblocks >= sis->max)
>   			nr_pblocks = sis->max - cur_lblock;
>   
> @@ -3878,6 +3938,9 @@ static int check_swap_activate(struct swap_info_struct *sis,
>   	if (PAGE_SIZE == F2FS_BLKSIZE)
>   		return check_swap_activate_fast(sis, swap_file, span);
>   
> +	if (f2fs_check_file_aligned(inode))

ret = f2fs_check_file_aligned();
if (ret)
	return ret;

Thanks,

> +		return -EINVAL;
> +
>   	blocks_per_page = bytes_to_blks(inode, PAGE_SIZE);
>   
>   	/*