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Subject: Re: [f2fs-dev] [PATCH 2/2] f2fs: support RO feature
To:     Jaegeuk Kim <jaegeuk@kernel.org>, Chao Yu <yuchao0@huawei.com>
Cc:     linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net
References: <20210521190217.2484099-1-jaegeuk@kernel.org>
 <20210521190217.2484099-2-jaegeuk@kernel.org>
 <984caf0c-ddec-930a-cbc6-084c8a9b67e5@huawei.com>
 <YK5UHr4fV1Hg8MoO@google.com>
From:   Chao Yu <chao@kernel.org>
Message-ID: <ebbc8cae-7e1f-f9f4-17b8-c59f99c7f043@kernel.org>
Date:   Wed, 26 May 2021 23:06:29 +0800
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On 2021/5/26 21:58, Jaegeuk Kim wrote:
> On 05/26, Chao Yu wrote:
>> 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?
> 
> Since we only use hot data and node. Let me check them only.
> 
>>
>>> +
>>>    	/*
>>>    	 * 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; ?
> 
> Done.
> 
>>
>>> +		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()) {
>> }
> 
> Done.
> 
>>
>>> -
>>> +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?
> 
> Done.
> 
>>
>>>    			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()?
> 
> Done. But not sure what you mean "we don't need to handle both".

Oh, I mean both fill_super() and remount() will call parse_options(),
so if we want to avoid mounting ro image with rw mountoption, we just
need to add one condition check in parse_option().

Thanks,

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