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Subject: Re: [f2fs-dev] [PATCH 2/2 v3] f2fs: support RO feature
To:     Jaegeuk Kim <jaegeuk@kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-f2fs-devel@lists.sourceforge.net>
References: <20210521190217.2484099-1-jaegeuk@kernel.org>
 <20210521190217.2484099-2-jaegeuk@kernel.org> <YK5UOfzwdZni7c5W@google.com>
 <YK5edM0igwfd47LV@google.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <9070633e-39ef-6e13-6467-534541d917b7@huawei.com>
Date:   Thu, 27 May 2021 09:19:20 +0800
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On 2021/5/26 22:43, 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>
> ---
> Change log from v2:
>   - allow curseg updates
>   - fix some bugs
> 
>   fs/f2fs/f2fs.h    |  2 ++
>   fs/f2fs/segment.c |  4 ++++
>   fs/f2fs/super.c   | 37 +++++++++++++++++++++++++++++++------
>   3 files changed, 37 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index eaf57b5f3c4b..9ad502f92529 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)
> @@ -940,6 +941,7 @@ 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..02e0c38be7eb 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -4683,6 +4683,10 @@ static int sanity_check_curseg(struct f2fs_sb_info *sbi)
>   		struct seg_entry *se = get_seg_entry(sbi, curseg->segno);
>   		unsigned int blkofs = curseg->next_blkoff;
>   
> +		if (F2FS_HAS_FEATURE(sbi, F2FS_FEATURE_RO) &&
> +			i != CURSEG_HOT_DATA && i != CURSEG_HOT_NODE)
> +			continue;
> +
>   		sanity_check_seg_type(sbi, curseg->seg_type);
>   
>   		if (f2fs_test_bit(blkofs, se->cur_valid_map))
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index e70aca8f97bd..6788e7b71e27 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -555,7 +555,7 @@ static int parse_options(struct super_block *sb, char *options, bool is_remount)
>   	int ret;
>   
>   	if (!options)
> -		return 0;
> +		goto default_check;
>   
>   	while ((p = strsep(&options, ",")) != NULL) {
>   		int token;
> @@ -1090,6 +1090,7 @@ static int parse_options(struct super_block *sb, char *options, bool is_remount)
>   			return -EINVAL;
>   		}
>   	}
> +default_check:
>   #ifdef CONFIG_QUOTA
>   	if (f2fs_check_quota_options(sbi))
>   		return -EINVAL;
> @@ -1162,6 +1163,11 @@ static int parse_options(struct super_block *sb, char *options, bool is_remount)
>   	 */
>   	if (F2FS_OPTION(sbi).active_logs != NR_CURSEG_TYPE)
>   		F2FS_OPTION(sbi).whint_mode = WHINT_MODE_OFF;
> +
> +	if (F2FS_HAS_FEATURE(sbi, F2FS_FEATURE_RO) && !f2fs_readonly(sbi->sb)) {
> +		f2fs_err(sbi, "Allow to mount readonly mode only");
> +		return -EROFS;
> +	}
>   	return 0;
>   }
>   
> @@ -1819,7 +1825,11 @@ 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, 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;
> @@ -2001,6 +2011,11 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>   	if (f2fs_readonly(sb) && (*flags & SB_RDONLY))
>   		goto skip;
>   
> +	if (F2FS_HAS_FEATURE(sbi, F2FS_FEATURE_RO) && !(*flags & SB_RDONLY)) {
> +		err = -EROFS;
> +		goto restore_opts;
> +	}

remount() -> parse_options() will fail due to below check, so it doesn't need
to check again? Am I missing something?

@@ -1162,6 +1163,11 @@

  static int parse_options(struct super_block *sb, char *options, bool is_remount)

  	 */
  	if (F2FS_OPTION(sbi).active_logs != NR_CURSEG_TYPE)
  		F2FS_OPTION(sbi).whint_mode = WHINT_MODE_OFF;
+
+	if (F2FS_HAS_FEATURE(sbi, F2FS_FEATURE_RO) && !f2fs_readonly(sbi->sb)) {
+		f2fs_err(sbi, "Allow to mount readonly mode only");
+		return -EROFS;
+	}
  	return 0;
  }

Thanks,

> +
>   #ifdef CONFIG_QUOTA
>   	if (!f2fs_readonly(sb) && (*flags & SB_RDONLY)) {
>   		err = dquot_suspend(sb, -1);
> @@ -3134,14 +3149,15 @@ 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 (unlikely(fsmeta < F2FS_MIN_META_SEGMENTS ||
> +	if (!F2FS_HAS_FEATURE(sbi, F2FS_FEATURE_RO) &&
> +			unlikely(fsmeta < F2FS_MIN_META_SEGMENTS ||
>   			ovp_segments == 0 || reserved_segments == 0)) {
>   		f2fs_err(sbi, "Wrong layout: check mkfs.f2fs version");
>   		return 1;
>   	}
> -
>   	user_block_count = le64_to_cpu(ckpt->user_block_count);
> -	segment_count_main = le32_to_cpu(raw_super->segment_count_main);
> +	segment_count_main = le32_to_cpu(raw_super->segment_count_main) +
> +			(F2FS_HAS_FEATURE(sbi, F2FS_FEATURE_RO) ? 1 : 0);
>   	log_blocks_per_seg = le32_to_cpu(raw_super->log_blocks_per_seg);
>   	if (!user_block_count || user_block_count >=
>   			segment_count_main << log_blocks_per_seg) {
> @@ -3172,6 +3188,10 @@ 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, 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])) {
> @@ -3182,10 +3202,15 @@ 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, 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])) {
> @@ -3207,7 +3232,7 @@ 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);
>   
>