Re: [f2fs-dev] [PATCH 2/2] f2fs: support RO feature

[Chao Yu <yuchao0@huawei.com>]

On 2021/5/22 3:02, Jaegeuk Kim wrote:
> Given RO feature in superblock, we don't need to check provisioning/reserve
> spaces and SSA area.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>   fs/f2fs/f2fs.h    |  2 ++
>   fs/f2fs/segment.c |  3 +++
>   fs/f2fs/super.c   | 35 +++++++++++++++++++++++++++++++----
>   3 files changed, 36 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index c0bead0df66a..2c6913261586 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -168,6 +168,7 @@ struct f2fs_mount_info {
>   #define F2FS_FEATURE_SB_CHKSUM		0x0800
>   #define F2FS_FEATURE_CASEFOLD		0x1000
>   #define F2FS_FEATURE_COMPRESSION	0x2000
> +#define F2FS_FEATURE_RO			0x4000
>   
>   #define __F2FS_HAS_FEATURE(raw_super, mask)				\
>   	((raw_super->feature & cpu_to_le32(mask)) != 0)
> @@ -939,6 +940,7 @@ static inline void set_new_dnode(struct dnode_of_data *dn, struct inode *inode,
>   #define	NR_CURSEG_DATA_TYPE	(3)
>   #define NR_CURSEG_NODE_TYPE	(3)
>   #define NR_CURSEG_INMEM_TYPE	(2)
> +#define NR_CURSEG_RO_TYPE	(2)
>   #define NR_CURSEG_PERSIST_TYPE	(NR_CURSEG_DATA_TYPE + NR_CURSEG_NODE_TYPE)
>   #define NR_CURSEG_TYPE		(NR_CURSEG_INMEM_TYPE + NR_CURSEG_PERSIST_TYPE)
>   
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 8668df7870d0..67cec8f858a2 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -4674,6 +4674,9 @@ static int sanity_check_curseg(struct f2fs_sb_info *sbi)
>   {
>   	int i;
>   
> +	if (__F2FS_HAS_FEATURE(sbi->raw_super, F2FS_FEATURE_RO))
> +		return 0;

We need to skip this sanity check because .next_blkoff may point to end position
of image?

> +
>   	/*
>   	 * In LFS/SSR curseg, .next_blkoff should point to an unused blkaddr;
>   	 * In LFS curseg, all blkaddr after .next_blkoff should be unused.
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index b29de80ab60e..312bfab54693 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -1819,7 +1819,11 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
>   static void default_options(struct f2fs_sb_info *sbi)
>   {
>   	/* init some FS parameters */
> -	F2FS_OPTION(sbi).active_logs = NR_CURSEG_PERSIST_TYPE;
> +	if (__F2FS_HAS_FEATURE(sbi->raw_super, F2FS_FEATURE_RO))
> +		F2FS_OPTION(sbi).active_logs = NR_CURSEG_RO_TYPE;
> +	else
> +		F2FS_OPTION(sbi).active_logs = NR_CURSEG_PERSIST_TYPE;
> +
>   	F2FS_OPTION(sbi).inline_xattr_size = DEFAULT_INLINE_XATTR_ADDRS;
>   	F2FS_OPTION(sbi).whint_mode = WHINT_MODE_OFF;
>   	F2FS_OPTION(sbi).alloc_mode = ALLOC_MODE_DEFAULT;
> @@ -1994,6 +1998,11 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>   	err = parse_options(sb, data, true);
>   	if (err)
>   		goto restore_opts;
> +
> +	if (__F2FS_HAS_FEATURE(sbi->raw_super, F2FS_FEATURE_RO) &&
> +					!(*flags & SB_RDONLY))

err = -EROFS; ?

> +		goto restore_opts;
> +
>   	checkpoint_changed =
>   			disable_checkpoint != test_opt(sbi, DISABLE_CHECKPOINT);
>   
> @@ -3137,16 +3146,18 @@ int f2fs_sanity_check_ckpt(struct f2fs_sb_info *sbi)
>   	ovp_segments = le32_to_cpu(ckpt->overprov_segment_count);
>   	reserved_segments = le32_to_cpu(ckpt->rsvd_segment_count);
>   
> +	if (__F2FS_HAS_FEATURE(sbi->raw_super, F2FS_FEATURE_RO))
> +		goto no_reserved;
>   	if (unlikely(fsmeta < F2FS_MIN_META_SEGMENTS ||
>   			ovp_segments == 0 || reserved_segments == 0)) {
>   		f2fs_err(sbi, "Wrong layout: check mkfs.f2fs version");
>   		return 1;
>   	}

Well, why not:

if (!F2FS_HAS_FEATURE(, RO) && unlikely()) {
}

> -
> +no_reserved:
>   	user_block_count = le64_to_cpu(ckpt->user_block_count);
>   	segment_count_main = le32_to_cpu(raw_super->segment_count_main);
>   	log_blocks_per_seg = le32_to_cpu(raw_super->log_blocks_per_seg);
> -	if (!user_block_count || user_block_count >=
> +	if (!user_block_count || user_block_count >

Does this change related to RO feature? if so, let's split condition for
RO feature here?

>   			segment_count_main << log_blocks_per_seg) {
>   		f2fs_err(sbi, "Wrong user_block_count: %u",
>   			 user_block_count);
> @@ -3175,6 +3186,10 @@ int f2fs_sanity_check_ckpt(struct f2fs_sb_info *sbi)
>   		if (le32_to_cpu(ckpt->cur_node_segno[i]) >= main_segs ||
>   			le16_to_cpu(ckpt->cur_node_blkoff[i]) >= blocks_per_seg)
>   			return 1;
> +
> +		if (__F2FS_HAS_FEATURE(sbi->raw_super, F2FS_FEATURE_RO))
> +			goto check_data;
> +
>   		for (j = i + 1; j < NR_CURSEG_NODE_TYPE; j++) {
>   			if (le32_to_cpu(ckpt->cur_node_segno[i]) ==
>   				le32_to_cpu(ckpt->cur_node_segno[j])) {
> @@ -3185,10 +3200,15 @@ int f2fs_sanity_check_ckpt(struct f2fs_sb_info *sbi)
>   			}
>   		}
>   	}
> +check_data:
>   	for (i = 0; i < NR_CURSEG_DATA_TYPE; i++) {
>   		if (le32_to_cpu(ckpt->cur_data_segno[i]) >= main_segs ||
>   			le16_to_cpu(ckpt->cur_data_blkoff[i]) >= blocks_per_seg)
>   			return 1;
> +
> +		if (__F2FS_HAS_FEATURE(sbi->raw_super, F2FS_FEATURE_RO))
> +			goto skip_cross;
> +
>   		for (j = i + 1; j < NR_CURSEG_DATA_TYPE; j++) {
>   			if (le32_to_cpu(ckpt->cur_data_segno[i]) ==
>   				le32_to_cpu(ckpt->cur_data_segno[j])) {
> @@ -3210,7 +3230,7 @@ int f2fs_sanity_check_ckpt(struct f2fs_sb_info *sbi)
>   			}
>   		}
>   	}
> -
> +skip_cross:
>   	sit_bitmap_size = le32_to_cpu(ckpt->sit_ver_bitmap_bytesize);
>   	nat_bitmap_size = le32_to_cpu(ckpt->nat_ver_bitmap_bytesize);
>   
> @@ -3703,6 +3723,13 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>   	if (err)
>   		goto free_options;
>   
> +	if (__F2FS_HAS_FEATURE(sbi->raw_super, F2FS_FEATURE_RO) &&
> +					!f2fs_readonly(sbi->sb)) {
> +		f2fs_info(sbi, "Allow to mount readonly mode only");
> +		err = -EINVAL;
> +		goto free_options;
> +	}

How about relocating this to parse_options() like other features did, then
we don't need to handle this in both fill_super() and remount()?

Thanks,

> +
>   	sb->s_maxbytes = max_file_blocks(NULL) <<
>   				le32_to_cpu(raw_super->log_blocksize);
>   	sb->s_max_links = F2FS_LINK_MAX;
>