[PATCH 2/2] f2fs: support RO feature

[Jaegeuk Kim <jaegeuk@kernel.org>]

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;
+
 	/*
 	 * 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))
+		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;
 	}
-
+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 >
 			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;
+	}
+
 	sb->s_maxbytes = max_file_blocks(NULL) <<
 				le32_to_cpu(raw_super->log_blocksize);
 	sb->s_max_links = F2FS_LINK_MAX;
-- 
2.31.1.818.g46aad6cb9e-goog