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Date:   Wed, 26 May 2021 06:58:54 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <yuchao0@huawei.com>
Cc:     linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 2/2] f2fs: support RO feature
Message-ID: <YK5UHr4fV1Hg8MoO@google.com>
References: <20210521190217.2484099-1-jaegeuk@kernel.org>
 <20210521190217.2484099-2-jaegeuk@kernel.org>
 <984caf0c-ddec-930a-cbc6-084c8a9b67e5@huawei.com>
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In-Reply-To: <984caf0c-ddec-930a-cbc6-084c8a9b67e5@huawei.com>
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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".

Thanks,

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