Complete patchset is available here:
https://github.com/dubeyko/ssdfs-driver/tree/master/patchset/linux-kernel-6.18.0

This patch implements commit superblock logic.

Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>
---
 fs/ssdfs/super.c | 2796 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 2796 insertions(+)

diff --git a/fs/ssdfs/super.c b/fs/ssdfs/super.c
index f430eee9aaf0..853d64d220ae 100644
--- a/fs/ssdfs/super.c
+++ b/fs/ssdfs/super.c
@@ -394,6 +394,2802 @@ static int ssdfs_remount_fs(struct fs_context *fc, struct super_block *sb)
 	return err;
 }
 
+static inline
+bool unfinished_read_data_requests_exist(struct ssdfs_fs_info *fsi)
+{
+	u64 read_requests = 0;
+
+	spin_lock(&fsi->volume_state_lock);
+	read_requests = fsi->read_user_data_requests;
+	spin_unlock(&fsi->volume_state_lock);
+
+	return read_requests > 0;
+}
+
+static inline
+void wait_unfinished_read_data_requests(struct ssdfs_fs_info *fsi)
+{
+	if (unfinished_read_data_requests_exist(fsi)) {
+		wait_queue_head_t *wq = &fsi->finish_user_data_read_wq;
+		u64 old_read_requests, new_read_requests;
+		int number_of_tries = 0;
+		int err;
+
+		while (number_of_tries < SSDFS_UNMOUNT_NUMBER_OF_TRIES) {
+			spin_lock(&fsi->volume_state_lock);
+			old_read_requests = fsi->read_user_data_requests;
+			spin_unlock(&fsi->volume_state_lock);
+
+			DEFINE_WAIT_FUNC(wait, woken_wake_function);
+			add_wait_queue(wq, &wait);
+			if (unfinished_read_data_requests_exist(fsi)) {
+				wait_woken(&wait, TASK_INTERRUPTIBLE, HZ);
+			}
+			remove_wait_queue(wq, &wait);
+
+			if (!unfinished_read_data_requests_exist(fsi))
+				break;
+
+			spin_lock(&fsi->volume_state_lock);
+			new_read_requests = fsi->read_user_data_requests;
+			spin_unlock(&fsi->volume_state_lock);
+
+			if (old_read_requests != new_read_requests) {
+				if (number_of_tries > 0)
+					number_of_tries--;
+			} else
+				number_of_tries++;
+		}
+
+		if (unfinished_read_data_requests_exist(fsi)) {
+			spin_lock(&fsi->volume_state_lock);
+			new_read_requests = fsi->read_user_data_requests;
+			spin_unlock(&fsi->volume_state_lock);
+
+			SSDFS_WARN("there are unfinished requests: "
+				   "unfinished_read_data_requests %llu, "
+				   "number_of_tries %d, err %d\n",
+				   new_read_requests,
+				   number_of_tries, err);
+		}
+	}
+}
+
+static inline
+bool unfinished_user_data_requests_exist(struct ssdfs_fs_info *fsi)
+{
+	u64 flush_requests = 0;
+
+	spin_lock(&fsi->volume_state_lock);
+	flush_requests = fsi->flushing_user_data_requests;
+	spin_unlock(&fsi->volume_state_lock);
+
+	return flush_requests > 0;
+}
+
+#ifdef CONFIG_SSDFS_DEBUG
+static inline
+void ssdfs_show_unfinished_user_data_requests(struct ssdfs_fs_info *fsi)
+{
+	bool is_empty;
+	struct list_head *this, *next;
+
+	spin_lock(&fsi->requests_lock);
+	is_empty = list_empty_careful(&fsi->user_data_requests_list);
+	if (!is_empty) {
+		list_for_each_safe(this, next, &fsi->user_data_requests_list) {
+			struct ssdfs_segment_request *req;
+
+			req = list_entry(this, struct ssdfs_segment_request,
+					 list);
+
+			if (!req) {
+				SSDFS_ERR_DBG("empty request ptr\n");
+				continue;
+			}
+
+			SSDFS_ERR_DBG("request: "
+				      "class %#x, cmd %#x, "
+				      "type %#x, refs_count %u, "
+				      "seg %llu, extent (start %u, len %u)\n",
+				      req->private.class, req->private.cmd,
+				      req->private.type,
+				      atomic_read(&req->private.refs_count),
+				      req->place.start.seg_id,
+				      req->place.start.blk_index,
+				      req->place.len);
+		}
+	}
+	spin_unlock(&fsi->requests_lock);
+
+	if (is_empty) {
+		SSDFS_ERR_DBG("list is empty\n");
+		return;
+	}
+}
+#endif /* CONFIG_SSDFS_DEBUG */
+
+static inline
+void wait_unfinished_user_data_requests(struct ssdfs_fs_info *fsi)
+{
+	if (unfinished_user_data_requests_exist(fsi)) {
+		wait_queue_head_t *wq = &fsi->finish_user_data_flush_wq;
+		u64 old_flush_requests, new_flush_requests;
+		int number_of_tries = 0;
+		int err;
+
+		while (number_of_tries < SSDFS_UNMOUNT_NUMBER_OF_TRIES) {
+			spin_lock(&fsi->volume_state_lock);
+			old_flush_requests =
+				fsi->flushing_user_data_requests;
+			spin_unlock(&fsi->volume_state_lock);
+
+			DEFINE_WAIT_FUNC(wait, woken_wake_function);
+			add_wait_queue(wq, &wait);
+			if (unfinished_user_data_requests_exist(fsi)) {
+				wait_woken(&wait, TASK_INTERRUPTIBLE, HZ);
+			}
+			remove_wait_queue(wq, &wait);
+
+			if (!unfinished_user_data_requests_exist(fsi))
+				break;
+
+			spin_lock(&fsi->volume_state_lock);
+			new_flush_requests =
+				fsi->flushing_user_data_requests;
+			spin_unlock(&fsi->volume_state_lock);
+
+			if (old_flush_requests != new_flush_requests) {
+				if (number_of_tries > 0)
+					number_of_tries--;
+			} else
+				number_of_tries++;
+		}
+
+		if (unfinished_user_data_requests_exist(fsi)) {
+			spin_lock(&fsi->volume_state_lock);
+			new_flush_requests =
+				fsi->flushing_user_data_requests;
+			spin_unlock(&fsi->volume_state_lock);
+
+			SSDFS_WARN("there are unfinished requests: "
+				   "unfinished_user_data_requests %llu, "
+				   "number_of_tries %d, err %d\n",
+				   new_flush_requests,
+				   number_of_tries, err);
+
+#ifdef CONFIG_SSDFS_DEBUG
+			ssdfs_show_unfinished_user_data_requests(fsi);
+#endif /* CONFIG_SSDFS_DEBUG */
+		}
+	}
+}
+
+static int ssdfs_sync_fs(struct super_block *sb, int wait)
+{
+	struct ssdfs_fs_info *fsi;
+	int err = 0;
+
+	fsi = SSDFS_FS_I(sb);
+
+#ifdef CONFIG_SSDFS_TRACK_API_CALL
+	SSDFS_ERR("sb %p\n", sb);
+#else
+	SSDFS_DBG("sb %p\n", sb);
+#endif /* CONFIG_SSDFS_TRACK_API_CALL */
+
+#ifdef CONFIG_SSDFS_SHOW_CONSUMED_MEMORY
+	SSDFS_ERR("SYNCFS is starting...\n");
+	ssdfs_check_memory_leaks();
+#endif /* CONFIG_SSDFS_SHOW_CONSUMED_MEMORY */
+
+	atomic_set(&fsi->global_fs_state, SSDFS_METADATA_GOING_FLUSHING);
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("SSDFS_METADATA_GOING_FLUSHING\n");
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	wake_up_all(&fsi->pending_wq);
+	wait_unfinished_user_data_requests(fsi);
+
+	atomic_set(&fsi->global_fs_state, SSDFS_METADATA_UNDER_FLUSH);
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("SSDFS_METADATA_UNDER_FLUSH\n");
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	down_write(&fsi->volume_sem);
+
+	if (fsi->fs_feature_compat &
+			SSDFS_HAS_INVALID_EXTENTS_TREE_COMPAT_FLAG) {
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("flush invalidated extents btree\n");
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		err = ssdfs_invextree_flush(fsi);
+		if (err) {
+			SSDFS_ERR("fail to flush invalidated extents btree: "
+				  "err %d\n", err);
+		}
+	}
+
+	if (fsi->fs_feature_compat & SSDFS_HAS_SHARED_EXTENTS_COMPAT_FLAG) {
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("flush shared extents btree\n");
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		err = ssdfs_shextree_flush(fsi);
+		if (err) {
+			SSDFS_ERR("fail to flush shared extents btree: "
+				  "err %d\n", err);
+		}
+	}
+
+	if (fsi->fs_feature_compat & SSDFS_HAS_INODES_TREE_COMPAT_FLAG) {
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("flush inodes btree\n");
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		err = ssdfs_inodes_btree_flush(fsi->inodes_tree);
+		if (err) {
+			SSDFS_ERR("fail to flush inodes btree: "
+				  "err %d\n", err);
+		}
+	}
+
+	if (fsi->fs_feature_compat & SSDFS_HAS_SHARED_DICT_COMPAT_FLAG) {
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("flush shared dictionary\n");
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		err = ssdfs_shared_dict_btree_flush(fsi->shdictree);
+		if (err) {
+			SSDFS_ERR("fail to flush shared dictionary: "
+				  "err %d\n", err);
+		}
+	}
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("process the snapshots creation\n");
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	err = ssdfs_execute_create_snapshots(fsi);
+	if (err) {
+		SSDFS_ERR("fail to process the snapshots creation\n");
+	}
+
+	if (fsi->fs_feature_compat & SSDFS_HAS_SNAPSHOTS_TREE_COMPAT_FLAG) {
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("flush snapshots btree\n");
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		err = ssdfs_snapshots_btree_flush(fsi);
+		if (err) {
+			SSDFS_ERR("fail to flush snapshots btree: "
+				  "err %d\n", err);
+		}
+	}
+
+	if (fsi->fs_feature_compat & SSDFS_HAS_SEGBMAP_COMPAT_FLAG) {
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("flush segment bitmap\n");
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		err = ssdfs_segbmap_flush(fsi->segbmap);
+		if (err) {
+			SSDFS_ERR("fail to flush segment bitmap: "
+				  "err %d\n", err);
+		}
+	}
+
+	if (fsi->fs_feature_compat & SSDFS_HAS_MAPTBL_COMPAT_FLAG) {
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("flush mapping table\n");
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		err = ssdfs_maptbl_flush(fsi->maptbl);
+		if (err) {
+			SSDFS_ERR("fail to flush mapping table: "
+				  "err %d\n", err);
+		}
+	}
+
+	up_write(&fsi->volume_sem);
+
+	atomic_set(&fsi->global_fs_state, SSDFS_REGULAR_FS_OPERATIONS);
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("SSDFS_REGULAR_FS_OPERATIONS\n");
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	wake_up_all(&fsi->pending_wq);
+
+#ifdef CONFIG_SSDFS_SHOW_CONSUMED_MEMORY
+	SSDFS_ERR("SYNCFS has been finished...\n");
+	ssdfs_check_memory_leaks();
+#endif /* CONFIG_SSDFS_SHOW_CONSUMED_MEMORY */
+
+#ifdef CONFIG_SSDFS_TRACK_API_CALL
+	SSDFS_ERR("finished\n");
+#endif /* CONFIG_SSDFS_TRACK_API_CALL */
+
+	if (unlikely(err))
+		goto fail_sync_fs;
+
+	trace_ssdfs_sync_fs(sb, wait);
+
+	return 0;
+
+fail_sync_fs:
+	trace_ssdfs_sync_fs_exit(sb, wait, err);
+	return err;
+}
+
+static struct inode *ssdfs_nfs_get_inode(struct super_block *sb,
+					 u64 ino, u32 generation)
+{
+	struct inode *inode;
+
+	if (ino < SSDFS_ROOT_INO)
+		return ERR_PTR(-ESTALE);
+
+	inode = ssdfs_iget(sb, ino);
+	if (IS_ERR(inode))
+		return ERR_CAST(inode);
+	if (generation && inode->i_generation != generation) {
+		iput(inode);
+		return ERR_PTR(-ESTALE);
+	}
+	return inode;
+}
+
+static struct dentry *ssdfs_fh_to_dentry(struct super_block *sb,
+					 struct fid *fid,
+					 int fh_len, int fh_type)
+{
+	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
+				    ssdfs_nfs_get_inode);
+}
+
+static struct dentry *ssdfs_fh_to_parent(struct super_block *sb,
+					 struct fid *fid,
+					 int fh_len, int fh_type)
+{
+	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
+				    ssdfs_nfs_get_inode);
+}
+
+static struct dentry *ssdfs_get_parent(struct dentry *child)
+{
+	struct qstr dotdot = QSTR_INIT("..", 2);
+	ino_t ino;
+	int err;
+
+	down_read(&SSDFS_I(d_inode(child))->lock);
+	err = ssdfs_inode_by_name(d_inode(child), &dotdot, &ino);
+	up_read(&SSDFS_I(d_inode(child))->lock);
+
+	if (unlikely(err))
+		return ERR_PTR(err);
+
+	return d_obtain_alias(ssdfs_iget(child->d_sb, ino));
+}
+
+static const struct export_operations ssdfs_export_ops = {
+	.get_parent	= ssdfs_get_parent,
+	.fh_to_dentry	= ssdfs_fh_to_dentry,
+	.fh_to_parent	= ssdfs_fh_to_parent,
+};
+
+static const struct super_operations ssdfs_super_operations = {
+	.alloc_inode	= ssdfs_alloc_inode,
+	.destroy_inode	= ssdfs_destroy_inode,
+	.evict_inode	= ssdfs_evict_inode,
+	.write_inode	= ssdfs_write_inode,
+	.statfs		= ssdfs_statfs,
+	.show_options	= ssdfs_show_options,
+	.put_super	= ssdfs_put_super,
+	.sync_fs	= ssdfs_sync_fs,
+};
+
+static inline
+u32 ssdfs_sb_payload_size(struct folio_batch *batch)
+{
+	struct ssdfs_maptbl_cache_header *hdr;
+	struct folio *folio;
+	void *kaddr;
+	u16 fragment_bytes_count;
+	u32 bytes_count = 0;
+	int i;
+
+	for (i = 0; i < folio_batch_count(batch); i++) {
+		folio = batch->folios[i];
+
+		ssdfs_folio_lock(folio);
+		kaddr = kmap_local_folio(folio, 0);
+		hdr = (struct ssdfs_maptbl_cache_header *)kaddr;
+		fragment_bytes_count = le16_to_cpu(hdr->bytes_count);
+		kunmap_local(kaddr);
+		ssdfs_folio_unlock(folio);
+
+#ifdef CONFIG_SSDFS_DEBUG
+		WARN_ON(fragment_bytes_count > PAGE_SIZE);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		bytes_count += fragment_bytes_count;
+	}
+
+	return bytes_count;
+}
+
+static u32 ssdfs_define_sb_log_size(struct super_block *sb)
+{
+	struct ssdfs_fs_info *fsi;
+	size_t hdr_size = sizeof(struct ssdfs_segment_header);
+	u32 inline_capacity;
+	u32 log_size = 0;
+	u32 payload_size;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!sb);
+
+	SSDFS_DBG("sb %p\n", sb);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	fsi = SSDFS_FS_I(sb);
+	payload_size = ssdfs_sb_payload_size(&fsi->maptbl_cache.batch);
+	inline_capacity = PAGE_SIZE - hdr_size;
+
+	if (payload_size > inline_capacity) {
+		log_size += PAGE_SIZE;
+		log_size += atomic_read(&fsi->maptbl_cache.bytes_count);
+		log_size += PAGE_SIZE;
+	} else {
+		log_size += PAGE_SIZE;
+		log_size += PAGE_SIZE;
+	}
+
+	log_size = (log_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
+
+	return log_size;
+}
+
+static int ssdfs_snapshot_sb_log_payload(struct super_block *sb,
+					 struct ssdfs_sb_log_payload *payload)
+{
+	struct ssdfs_fs_info *fsi;
+	struct folio *sfolio, *dfolio;
+	unsigned folios_count;
+	unsigned i;
+	int err = 0;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!sb || !payload);
+	BUG_ON(folio_batch_count(&payload->maptbl_cache.batch) != 0);
+
+	SSDFS_DBG("sb %p, payload %p\n",
+		  sb, payload);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	fsi = SSDFS_FS_I(sb);
+
+	down_read(&fsi->maptbl_cache.lock);
+
+	folios_count = folio_batch_count(&fsi->maptbl_cache.batch);
+
+	for (i = 0; i < folios_count; i++) {
+		dfolio = ssdfs_super_add_batch_folio(&payload->maptbl_cache.batch,
+						     get_order(PAGE_SIZE));
+		if (unlikely(IS_ERR_OR_NULL(dfolio))) {
+			err = !dfolio ? -ENOMEM : PTR_ERR(dfolio);
+			SSDFS_ERR("fail to add folio into batch: "
+				  "index %u, err %d\n",
+				  i, err);
+			goto finish_maptbl_snapshot;
+		}
+
+		sfolio = fsi->maptbl_cache.batch.folios[i];
+		if (unlikely(!sfolio)) {
+			err = -ERANGE;
+			SSDFS_ERR("source folio is absent: index %u\n",
+				  i);
+			goto finish_maptbl_snapshot;
+		}
+
+		ssdfs_folio_lock(sfolio);
+		ssdfs_folio_lock(dfolio);
+		__ssdfs_memcpy_folio(dfolio, 0, PAGE_SIZE,
+				     sfolio, 0, PAGE_SIZE,
+				     PAGE_SIZE);
+		ssdfs_folio_unlock(dfolio);
+		ssdfs_folio_unlock(sfolio);
+	}
+
+	payload->maptbl_cache.bytes_count =
+		atomic_read(&fsi->maptbl_cache.bytes_count);
+
+finish_maptbl_snapshot:
+	up_read(&fsi->maptbl_cache.lock);
+
+	if (unlikely(err))
+		ssdfs_super_folio_batch_release(&payload->maptbl_cache.batch);
+
+	return err;
+}
+
+static inline
+int ssdfs_write_padding_block(struct super_block *sb,
+			      struct folio *folio,
+			      loff_t offset)
+{
+	struct ssdfs_fs_info *fsi;
+	struct ssdfs_padding_header *hdr;
+	size_t hdr_size = sizeof(struct ssdfs_padding_header);
+	int err = 0;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!sb || !folio);
+	BUG_ON(!SSDFS_FS_I(sb)->devops);
+	BUG_ON(!SSDFS_FS_I(sb)->devops->write_block);
+
+	SSDFS_DBG("offset %llu\n", offset);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	fsi = SSDFS_FS_I(sb);
+
+	/* ->writepage() calls put_folio() */
+	ssdfs_folio_get(folio);
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("folio %p, count %d\n",
+		  folio, folio_ref_count(folio));
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	ssdfs_folio_lock(folio);
+
+	err = __ssdfs_memset_folio(folio, hdr_size, folio_size(folio),
+				   0xdada, folio_size(folio) - hdr_size);
+	if (unlikely(err)) {
+		SSDFS_ERR("fail to prepare padding block: err %d\n", err);
+		ssdfs_folio_unlock(folio);
+		goto unlock_folio;
+	}
+
+	hdr = (struct ssdfs_padding_header *)kmap_local_folio(folio, 0);
+	hdr->magic.common = cpu_to_le32(SSDFS_SUPER_MAGIC);
+	hdr->magic.key = cpu_to_le16(SSDFS_PADDING_HDR_MAGIC);
+	hdr->magic.version.major = SSDFS_MAJOR_REVISION;
+	hdr->magic.version.minor = SSDFS_MINOR_REVISION;
+	hdr->blob = cpu_to_le64(SSDFS_PADDING_BLOB);
+	hdr->check.bytes = cpu_to_le16(folio_size(folio));
+	hdr->check.flags = cpu_to_le16(0);
+	hdr->check.csum = cpu_to_le32(0xdada);
+	kunmap_local(hdr);
+
+	folio_mark_uptodate(folio);
+	folio_set_dirty(folio);
+
+	ssdfs_folio_unlock(folio);
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("offset %llu\n", offset);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	err = fsi->devops->write_block(sb, offset, folio);
+	if (err) {
+		SSDFS_ERR("fail to write segment header: "
+			  "offset %llu, size %zu\n",
+			  (u64)offset, folio_size(folio));
+	}
+
+	ssdfs_folio_lock(folio);
+	folio_clear_uptodate(folio);
+unlock_folio:
+	ssdfs_folio_unlock(folio);
+
+	return err;
+}
+
+static int ssdfs_write_padding(struct super_block *sb,
+				loff_t offset, loff_t size)
+{
+	struct folio *folio;
+	loff_t written = 0;
+	int err = 0;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!sb);
+	BUG_ON(!SSDFS_FS_I(sb)->devops);
+	BUG_ON(!SSDFS_FS_I(sb)->devops->write_block);
+
+	SSDFS_DBG("offset %llu, size %llu\n", offset, size);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	if (size == 0 || size % PAGE_SIZE) {
+		SSDFS_ERR("invalid size %llu\n", size);
+		return -EINVAL;
+	}
+
+	folio = ssdfs_super_alloc_folio(GFP_KERNEL | __GFP_ZERO,
+					get_order(PAGE_SIZE));
+	if (IS_ERR_OR_NULL(folio)) {
+		err = (folio == NULL ? -ENOMEM : PTR_ERR(folio));
+		SSDFS_ERR("unable to allocate memory folio\n");
+		return err;
+	}
+
+	while (written < size) {
+		offset = offset + written;
+
+		err = ssdfs_write_padding_block(sb, folio, offset);
+		if (unlikely(err)) {
+			SSDFS_ERR("fail to write padding block: "
+				  "offset %llu\n", offset);
+			goto free_folio;
+		}
+
+		written += folio_size(folio);
+	}
+
+free_folio:
+	ssdfs_super_free_folio(folio);
+
+	return err;
+}
+
+static inline
+int ssdfs_write_padding_in_sb_segs_pair(struct super_block *sb,
+					u32 log_page)
+{
+	struct ssdfs_fs_info *fsi;
+	u64 cur_peb;
+	u32 pages_per_peb;
+	loff_t peb_offset;
+	loff_t padding_offset;
+	loff_t padding_size;
+	int i;
+	int err;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!sb);
+	BUG_ON(!SSDFS_FS_I(sb)->devops);
+	BUG_ON(!SSDFS_FS_I(sb)->devops->write_block);
+
+	SSDFS_DBG("log_page %u,\n", log_page);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	fsi = SSDFS_FS_I(sb);
+
+	/*
+	 * Superblock segment uses 4KB page always.
+	 * It needs to calculate pages_per_peb value.
+	 */
+	pages_per_peb = fsi->erasesize / PAGE_SIZE;
+
+	for (i = 0; i < SSDFS_SB_SEG_COPY_MAX; i++) {
+		cur_peb = fsi->sb_pebs[SSDFS_CUR_SB_SEG][i];
+
+		padding_size = pages_per_peb - log_page;
+		padding_size <<= PAGE_SHIFT;
+
+		peb_offset = cur_peb * fsi->pages_per_peb;
+		peb_offset <<= fsi->log_pagesize;
+
+		padding_offset = log_page;
+		padding_offset <<= PAGE_SHIFT;
+		padding_offset += peb_offset;
+
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("cur_peb %llu, padding_offset %llu, "
+			  "padding_size %llu\n",
+			  cur_peb, (u64)padding_offset,
+			  (u64)padding_size);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		err = ssdfs_write_padding(sb, padding_offset, padding_size);
+		if (unlikely(err)) {
+			SSDFS_ERR("fail to write padding: "
+				  "padding_offset %llu, "
+				  "padding_size %llu, "
+				  "err %d\n",
+				  padding_offset,
+				  padding_size,
+				  err);
+			return err;
+		}
+	}
+
+	return 0;
+}
+
+static int ssdfs_define_next_sb_log_place(struct super_block *sb,
+					  struct ssdfs_peb_extent *last_sb_log)
+{
+	struct ssdfs_fs_info *fsi;
+	u32 offset;
+	u32 log_size;
+	u64 cur_peb, prev_peb;
+	u64 cur_leb;
+	u32 pages_per_peb;
+	int i;
+	int err = 0;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!sb || !last_sb_log);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	fsi = SSDFS_FS_I(sb);
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("sb %p, last_sb_log %p\n",
+		  sb, last_sb_log);
+	SSDFS_DBG("fsi->sbi.last_log: (leb_id %llu, peb_id %llu, "
+		  "page_offset %u, pages_count %u), "
+		  "last_sb_log: (leb_id %llu, peb_id %llu, "
+		  "page_offset %u, pages_count %u)\n",
+		  fsi->sbi.last_log.leb_id,
+		  fsi->sbi.last_log.peb_id,
+		  fsi->sbi.last_log.page_offset,
+		  fsi->sbi.last_log.pages_count,
+		  last_sb_log->leb_id,
+		  last_sb_log->peb_id,
+		  last_sb_log->page_offset,
+		  last_sb_log->pages_count);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	/*
+	 * Superblock segment uses 4KB page always.
+	 * It needs to calculate pages_per_peb value.
+	 */
+	pages_per_peb = fsi->erasesize / PAGE_SIZE;
+
+	offset = fsi->sbi.last_log.page_offset;
+
+	log_size = ssdfs_define_sb_log_size(sb);
+	if (log_size > pages_per_peb) {
+		SSDFS_ERR("log_size %u > pages_per_peb %u\n",
+			  log_size, pages_per_peb);
+		return -ERANGE;
+	}
+
+	log_size = max_t(u32, log_size, fsi->sbi.last_log.pages_count);
+
+	if (offset > pages_per_peb || offset > (UINT_MAX - log_size)) {
+		SSDFS_ERR("inconsistent metadata state: "
+			  "last_sb_log.page_offset %u, "
+			  "pages_per_peb %u, log_size %u\n",
+			  offset, pages_per_peb, log_size);
+		return -EINVAL;
+	}
+
+	for (err = -EINVAL, i = 0; i < SSDFS_SB_SEG_COPY_MAX; i++) {
+		cur_peb = fsi->sb_pebs[SSDFS_CUR_SB_SEG][i];
+		prev_peb = fsi->sb_pebs[SSDFS_PREV_SB_SEG][i];
+		cur_leb = fsi->sb_lebs[SSDFS_CUR_SB_SEG][i];
+
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("cur_peb %llu, prev_peb %llu, "
+			  "last_sb_log.peb_id %llu, log_size %u, "
+			  "err %d\n",
+			  cur_peb, prev_peb,
+			  fsi->sbi.last_log.peb_id,
+			  log_size, err);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		if (fsi->sbi.last_log.peb_id == cur_peb) {
+			offset += fsi->sbi.last_log.pages_count;
+
+			if (offset > pages_per_peb) {
+				SSDFS_ERR("inconsistent metadata state: "
+					  "last_sb_log.page_offset %u, "
+					  "pages_per_peb %u, log_size %u\n",
+					  offset, pages_per_peb,
+					  fsi->sbi.last_log.pages_count);
+				return -EIO;
+			} else if (offset == pages_per_peb) {
+#ifdef CONFIG_SSDFS_DEBUG
+				SSDFS_DBG("sb PEB %llu is full: "
+					  "offset %u, log_size %u, "
+					  "pages_per_peb %u\n",
+					  cur_peb, offset,
+					  fsi->sbi.last_log.pages_count,
+					  pages_per_peb);
+#endif /* CONFIG_SSDFS_DEBUG */
+				return -EFBIG;
+			} else if ((offset + log_size) > pages_per_peb) {
+				err  = ssdfs_write_padding_in_sb_segs_pair(sb,
+									offset);
+				if (unlikely(err)) {
+					SSDFS_ERR("fail to write padding: "
+						  "err %d\n", err);
+					return err;
+				}
+
+#ifdef CONFIG_SSDFS_DEBUG
+				SSDFS_DBG("sb PEB %llu is full: "
+					  "offset %u, log_size %u, "
+					  "pages_per_peb %u\n",
+					  cur_peb, offset,
+					  fsi->sbi.last_log.pages_count,
+					  pages_per_peb);
+#endif /* CONFIG_SSDFS_DEBUG */
+				return -EFBIG;
+			}
+
+			last_sb_log->leb_id = cur_leb;
+			last_sb_log->peb_id = cur_peb;
+			last_sb_log->page_offset = offset;
+			last_sb_log->pages_count = log_size;
+
+			err = 0;
+			break;
+		} else if (fsi->sbi.last_log.peb_id != cur_peb &&
+			   fsi->sbi.last_log.peb_id == prev_peb) {
+
+			last_sb_log->leb_id = cur_leb;
+			last_sb_log->peb_id = cur_peb;
+			last_sb_log->page_offset = 0;
+			last_sb_log->pages_count = log_size;
+
+			err = 0;
+			break;
+		} else {
+			/* continue to check */
+			err = -ERANGE;
+		}
+	}
+
+	if (err) {
+		SSDFS_ERR("inconsistent metadata state: "
+			  "cur_peb %llu, prev_peb %llu, "
+			  "last_sb_log.peb_id %llu\n",
+			  cur_peb, prev_peb, fsi->sbi.last_log.peb_id);
+		return err;
+	}
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("last_sb_log->leb_id %llu, "
+		  "last_sb_log->peb_id %llu, "
+		  "last_sb_log->page_offset %u, "
+		  "last_sb_log->pages_count %u\n",
+		  last_sb_log->leb_id,
+		  last_sb_log->peb_id,
+		  last_sb_log->page_offset,
+		  last_sb_log->pages_count);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	for (i = 0; i < SSDFS_SB_SEG_COPY_MAX; i++) {
+		last_sb_log->leb_id = fsi->sb_lebs[SSDFS_CUR_SB_SEG][i];
+		last_sb_log->peb_id = fsi->sb_pebs[SSDFS_CUR_SB_SEG][i];
+		err = ssdfs_can_write_sb_log(sb, last_sb_log);
+		if (err) {
+			SSDFS_DBG("possibly logical block has data: "
+				  "PEB %llu: "
+				  "last_sb_log->page_offset %u, "
+				  "last_sb_log->pages_count %u\n",
+				  last_sb_log->peb_id,
+				  last_sb_log->page_offset,
+				  last_sb_log->pages_count);
+		}
+	}
+
+	last_sb_log->leb_id = cur_leb;
+	last_sb_log->peb_id = cur_peb;
+
+	if (fsi->sb_snapi.need_snapshot_sb) {
+		struct ssdfs_peb_extent *last_sb_snap_log;
+
+		last_sb_snap_log = &fsi->sb_snapi.last_log;
+
+		offset = last_sb_snap_log->page_offset;
+
+		if (offset >= pages_per_peb) {
+			SSDFS_ERR("inconsistent metadata state: "
+				  "last_sb_snap_log.page_offset %u, "
+				  "pages_per_peb %u\n",
+				  offset, pages_per_peb);
+			return -EINVAL;
+		}
+
+		offset += last_sb_snap_log->pages_count;
+
+		if (offset >= pages_per_peb) {
+			SSDFS_ERR("inconsistent metadata state: "
+				  "last_sb_snap_log.page_offset %u, "
+				  "last_sb_snap_log.pages_count %u, "
+				  "pages_per_peb %u\n",
+				  last_sb_snap_log->page_offset,
+				  last_sb_snap_log->pages_count,
+				  pages_per_peb);
+			return -ERANGE;
+		}
+
+		last_sb_snap_log->page_offset = offset;
+
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("last_sb_snap_log (page_offset %u, pages_count %u)\n",
+			  last_sb_snap_log->page_offset,
+			  last_sb_snap_log->pages_count);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		err = ssdfs_can_write_sb_log(sb, last_sb_snap_log);
+		if (err) {
+			SSDFS_DBG("possibly logical block has data: "
+				  "PEB %llu: "
+				  "last_sb_log->page_offset %u, "
+				  "last_sb_log->pages_count %u\n",
+				  last_sb_log->peb_id,
+				  last_sb_log->page_offset,
+				  last_sb_log->pages_count);
+		}
+	}
+
+	return 0;
+}
+
+#ifndef CONFIG_SSDFS_FIXED_SUPERBLOCK_SEGMENTS_SET
+static u64 ssdfs_correct_start_leb_id(struct ssdfs_fs_info *fsi,
+				      int seg_type, u64 leb_id)
+{
+	struct completion *init_end;
+	struct ssdfs_maptbl_peb_relation pebr;
+	struct ssdfs_maptbl_peb_descriptor *ptr;
+	u8 peb_type = SSDFS_MAPTBL_UNKNOWN_PEB_TYPE;
+	u32 pebs_per_seg;
+	u64 seg_id;
+	u64 cur_leb;
+	u64 peb_id1, peb_id2;
+	u64 found_peb_id;
+	u64 peb_id_off;
+	u16 pebs_per_fragment;
+	u16 pebs_per_stripe;
+	u16 stripes_per_fragment;
+	u64 calculated_leb_id = leb_id;
+	int i;
+	int err;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!fsi);
+
+	SSDFS_DBG("fsi %p, seg_type %#x, leb_id %llu\n",
+		  fsi, seg_type, leb_id);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	found_peb_id = leb_id;
+	peb_type = SEG2PEB_TYPE(seg_type);
+	pebs_per_seg = fsi->pebs_per_seg;
+
+	seg_id = ssdfs_get_seg_id_for_leb_id(fsi, leb_id);
+	if (unlikely(seg_id >= U64_MAX)) {
+		SSDFS_ERR("invalid seg_id: "
+			  "leb_id %llu\n", leb_id);
+		return -ERANGE;
+	}
+
+	err = ssdfs_maptbl_define_fragment_info(fsi, leb_id,
+						&pebs_per_fragment,
+						&pebs_per_stripe,
+						&stripes_per_fragment);
+	if (unlikely(err)) {
+		SSDFS_ERR("fail to define fragment info: "
+			  "err %d\n", err);
+		return err;
+	}
+
+	for (i = 0; i < pebs_per_seg; i++) {
+		cur_leb = ssdfs_get_leb_id_for_peb_index(fsi, seg_id, i);
+		if (cur_leb >= U64_MAX) {
+			SSDFS_ERR("fail to convert PEB index into LEB ID: "
+				  "seg %llu, peb_index %u\n",
+				  seg_id, i);
+			return -ERANGE;
+		}
+
+		err = ssdfs_maptbl_convert_leb2peb(fsi, cur_leb,
+						   peb_type, &pebr,
+						   &init_end);
+		if (err == -EAGAIN) {
+			err = SSDFS_WAIT_COMPLETION(init_end);
+			if (unlikely(err)) {
+				SSDFS_ERR("maptbl init failed: "
+					  "err %d\n", err);
+				goto finish_leb_id_correction;
+			}
+
+			err = ssdfs_maptbl_convert_leb2peb(fsi, cur_leb,
+							   peb_type, &pebr,
+							   &init_end);
+		}
+
+		if (err == -ENODATA) {
+#ifdef CONFIG_SSDFS_DEBUG
+			SSDFS_DBG("LEB is not mapped: leb_id %llu\n",
+				  cur_leb);
+#endif /* CONFIG_SSDFS_DEBUG */
+			goto finish_leb_id_correction;
+		} else if (unlikely(err)) {
+			SSDFS_ERR("fail to convert LEB to PEB: "
+				  "leb_id %llu, peb_type %#x, err %d\n",
+				  cur_leb, peb_type, err);
+			goto finish_leb_id_correction;
+		}
+
+		ptr = &pebr.pebs[SSDFS_MAPTBL_MAIN_INDEX];
+		peb_id1 = ptr->peb_id;
+		ptr = &pebr.pebs[SSDFS_MAPTBL_RELATION_INDEX];
+		peb_id2 = ptr->peb_id;
+
+		if (peb_id1 < U64_MAX)
+			found_peb_id = max_t(u64, peb_id1, found_peb_id);
+
+		if (peb_id2 < U64_MAX)
+			found_peb_id = max_t(u64, peb_id2, found_peb_id);
+
+		peb_id_off = found_peb_id % pebs_per_stripe;
+		if (peb_id_off >= (pebs_per_stripe / 2)) {
+			calculated_leb_id = found_peb_id / pebs_per_stripe;
+			calculated_leb_id++;
+			calculated_leb_id *= pebs_per_stripe;
+		} else {
+			calculated_leb_id = found_peb_id;
+			calculated_leb_id++;
+		}
+
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("found_peb_id %llu, pebs_per_stripe %u, "
+			  "calculated_leb_id %llu\n",
+			  found_peb_id, pebs_per_stripe,
+			  calculated_leb_id);
+#endif /* CONFIG_SSDFS_DEBUG */
+	}
+
+finish_leb_id_correction:
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("leb_id %llu, calculated_leb_id %llu\n",
+		  leb_id, calculated_leb_id);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	return calculated_leb_id;
+}
+#endif /* CONFIG_SSDFS_FIXED_SUPERBLOCK_SEGMENTS_SET */
+
+#ifndef CONFIG_SSDFS_FIXED_SUPERBLOCK_SEGMENTS_SET
+static int __ssdfs_reserve_clean_segment(struct ssdfs_fs_info *fsi,
+					 int sb_seg_type,
+					 u64 start_search_id,
+					 u64 *reserved_seg)
+{
+	struct ssdfs_segment_bmap *segbmap = fsi->segbmap;
+	u64 start_seg = start_search_id;
+	u64 end_seg = U64_MAX;
+	struct ssdfs_maptbl_peb_relation pebr;
+	struct completion *end;
+	u8 peb_type = SSDFS_MAPTBL_SBSEG_PEB_TYPE;
+	u64 leb_id;
+	int err = 0;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!reserved_seg);
+	BUG_ON(sb_seg_type >= SSDFS_SB_SEG_COPY_MAX);
+
+	SSDFS_DBG("fsi %p, sb_seg_type %#x, start_search_id %llu\n",
+		  fsi, sb_seg_type, start_search_id);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	switch (sb_seg_type) {
+	case SSDFS_MAIN_SB_SEG:
+	case SSDFS_COPY_SB_SEG:
+		err = ssdfs_segment_detect_search_range(fsi,
+							&start_seg,
+							&end_seg);
+		if (err == -ENOENT) {
+#ifdef CONFIG_SSDFS_DEBUG
+			SSDFS_DBG("unable to find fragment for search: "
+				  "start_seg %llu, end_seg %llu\n",
+				  start_seg, end_seg);
+#endif /* CONFIG_SSDFS_DEBUG */
+			return err;
+		} else if (unlikely(err)) {
+			SSDFS_ERR("fail to define a search range: "
+				  "start_seg %llu, err %d\n",
+				  start_seg, err);
+			return err;
+		}
+		break;
+
+	default:
+		BUG();
+	};
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("start_seg %llu, end_seg %llu\n",
+		  start_seg, end_seg);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	err = ssdfs_segbmap_reserve_clean_segment(segbmap,
+						  start_seg, end_seg,
+						  reserved_seg, &end);
+	if (err == -EAGAIN) {
+		err = SSDFS_WAIT_COMPLETION(end);
+		if (unlikely(err)) {
+			SSDFS_ERR("segbmap init failed: "
+				  "err %d\n", err);
+			goto finish_search;
+		}
+
+		err = ssdfs_segbmap_reserve_clean_segment(segbmap,
+							  start_seg, end_seg,
+							  reserved_seg,
+							  &end);
+	}
+
+	if (err == -ENODATA) {
+		err = -ENOENT;
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("unable to reserve segment: "
+			  "type %#x, start_seg %llu, end_seg %llu\n",
+			  sb_seg_type, start_seg, end_seg);
+#endif /* CONFIG_SSDFS_DEBUG */
+		goto finish_search;
+	} else if (unlikely(err)) {
+		SSDFS_ERR("fail to reserve segment: "
+			  "type %#x, start_seg %llu, "
+			   "end_seg %llu, err %d\n",
+			  sb_seg_type, start_seg, end_seg, err);
+		goto finish_search;
+	}
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("reserved_seg %llu\n", *reserved_seg);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	leb_id = ssdfs_get_leb_id_for_peb_index(fsi, *reserved_seg, i);
+	if (leb_id >= U64_MAX) {
+		err = -ERANGE;
+		SSDFS_ERR("fail to convert PEB index into LEB ID: "
+			  "seg %llu, peb_index %u\n",
+			  *reserved_seg, i);
+		goto finish_search;
+	}
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("leb_id %llu\n", leb_id);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	err = ssdfs_maptbl_map_leb2peb(fsi, leb_id, peb_type,
+					&pebr, &end);
+	if (err == -EAGAIN) {
+		err = SSDFS_WAIT_COMPLETION(end);
+		if (unlikely(err)) {
+			SSDFS_ERR("maptbl init failed: "
+				  "err %d\n", err);
+			goto finish_search;
+		}
+
+		err = ssdfs_maptbl_map_leb2peb(fsi, leb_id,
+						peb_type,
+						&pebr, &end);
+	}
+
+	if (unlikely(err)) {
+		SSDFS_ERR("fail to map LEB to PEB: "
+			  "reserved_seg %llu, leb_id %llu, "
+			  "err %d\n",
+			  *reserved_seg, leb_id, err);
+		goto finish_search;
+	}
+
+finish_search:
+	if (err == -ENOENT)
+		*reserved_seg = end_seg;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("reserved_seg %llu\n", *reserved_seg);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	return err;
+}
+#endif /* CONFIG_SSDFS_FIXED_SUPERBLOCK_SEGMENTS_SET */
+
+#ifndef CONFIG_SSDFS_FIXED_SUPERBLOCK_SEGMENTS_SET
+static int ssdfs_reserve_clean_segment(struct super_block *sb,
+					int sb_seg_type, u64 start_leb,
+					u64 *reserved_seg)
+{
+	struct ssdfs_fs_info *fsi = SSDFS_FS_I(sb);
+	u64 start_search_id;
+	u64 cur_id;
+	int err;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!reserved_seg);
+	BUG_ON(sb_seg_type >= SSDFS_SB_SEG_COPY_MAX);
+
+	SSDFS_DBG("sb %p, sb_seg_type %#x, start_leb %llu\n",
+		  sb, sb_seg_type, start_leb);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	*reserved_seg = U64_MAX;
+
+	start_leb = ssdfs_correct_start_leb_id(fsi,
+						SSDFS_SB_SEG_TYPE,
+						start_leb);
+
+	start_search_id = SSDFS_LEB2SEG(fsi, start_leb);
+	if (start_search_id >= fsi->nsegs)
+		start_search_id = 0;
+
+	cur_id = start_search_id;
+
+	while (cur_id < fsi->nsegs) {
+		err = __ssdfs_reserve_clean_segment(fsi, sb_seg_type,
+						    cur_id, reserved_seg);
+		if (err == -ENOENT) {
+			err = 0;
+			cur_id = *reserved_seg;
+#ifdef CONFIG_SSDFS_DEBUG
+			SSDFS_DBG("cur_id %llu\n", cur_id);
+#endif /* CONFIG_SSDFS_DEBUG */
+			continue;
+		} else if (unlikely(err)) {
+			SSDFS_ERR("fail to find a new segment: "
+				  "cur_id %llu, err %d\n",
+				  cur_id, err);
+			return err;
+		} else {
+#ifdef CONFIG_SSDFS_DEBUG
+			SSDFS_DBG("found seg_id %llu\n", *reserved_seg);
+#endif /* CONFIG_SSDFS_DEBUG */
+			return 0;
+		}
+	}
+
+	cur_id = 0;
+
+	while (cur_id < start_search_id) {
+		err = __ssdfs_reserve_clean_segment(fsi, sb_seg_type,
+						    cur_id, reserved_seg);
+		if (err == -ENOENT) {
+			err = 0;
+			cur_id = *reserved_seg;
+#ifdef CONFIG_SSDFS_DEBUG
+			SSDFS_DBG("cur_id %llu\n", cur_id);
+#endif /* CONFIG_SSDFS_DEBUG */
+			continue;
+		} else if (unlikely(err)) {
+			SSDFS_ERR("fail to find a new segment: "
+				  "cur_id %llu, err %d\n",
+				  cur_id, err);
+			return err;
+		} else {
+#ifdef CONFIG_SSDFS_DEBUG
+			SSDFS_DBG("found seg_id %llu\n", *reserved_seg);
+#endif /* CONFIG_SSDFS_DEBUG */
+			return 0;
+		}
+	}
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("no free space for a new segment\n");
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	return -ENOSPC;
+}
+#endif /* CONFIG_SSDFS_FIXED_SUPERBLOCK_SEGMENTS_SET */
+
+typedef u64 sb_pebs_array[SSDFS_SB_CHAIN_MAX][SSDFS_SB_SEG_COPY_MAX];
+
+static int ssdfs_erase_dirty_prev_sb_segs(struct ssdfs_fs_info *fsi,
+					  u64 prev_leb)
+{
+	struct completion *init_end;
+	u8 peb_type = SSDFS_MAPTBL_UNKNOWN_PEB_TYPE;
+	u32 pebs_per_seg;
+	u64 seg_id;
+	u64 cur_leb;
+	int err;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!fsi);
+
+	SSDFS_DBG("fsi %p, prev_leb %llu\n",
+		  fsi, prev_leb);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	peb_type = SEG2PEB_TYPE(SSDFS_SB_SEG_TYPE);
+	pebs_per_seg = fsi->pebs_per_seg;
+
+	seg_id = SSDFS_LEB2SEG(fsi, prev_leb);
+	if (seg_id >= U64_MAX) {
+		SSDFS_ERR("invalid seg_id for leb_id %llu\n",
+			  prev_leb);
+		return -ERANGE;
+	}
+
+	cur_leb = ssdfs_get_leb_id_for_peb_index(fsi, seg_id, 0);
+	if (cur_leb >= U64_MAX) {
+		SSDFS_ERR("invalid leb_id for seg_id %llu\n",
+			  seg_id);
+		return -ERANGE;
+	}
+
+	err = ssdfs_maptbl_erase_reserved_peb_now(fsi,
+						  cur_leb,
+						  peb_type,
+						  &init_end);
+	if (err == -EAGAIN) {
+		err = SSDFS_WAIT_COMPLETION(init_end);
+		if (unlikely(err)) {
+			SSDFS_ERR("maptbl init failed: "
+				  "err %d\n", err);
+			return err;
+		}
+
+		err = ssdfs_maptbl_erase_reserved_peb_now(fsi,
+							  cur_leb,
+							  peb_type,
+							  &init_end);
+	}
+
+	if (unlikely(err)) {
+		SSDFS_ERR("fail to erase reserved dirty PEB: "
+			  "leb_id %llu, err %d\n",
+			  cur_leb, err);
+		return err;
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_SSDFS_FIXED_SUPERBLOCK_SEGMENTS_SET
+static int ssdfs_move_on_first_peb_next_sb_seg(struct super_block *sb,
+						int sb_seg_type,
+						sb_pebs_array *sb_lebs,
+						sb_pebs_array *sb_pebs)
+{
+	struct ssdfs_fs_info *fsi = SSDFS_FS_I(sb);
+	u64 prev_leb, cur_leb, next_leb, reserved_leb;
+	u64 prev_peb, cur_peb, next_peb, reserved_peb;
+	loff_t offset;
+	int err = 0;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!sb || !sb_lebs || !sb_pebs);
+
+	if (sb_seg_type >= SSDFS_SB_SEG_COPY_MAX) {
+		SSDFS_ERR("invalid sb_seg_type %#x\n",
+			  sb_seg_type);
+		return -EINVAL;
+	}
+
+	SSDFS_DBG("sb %p, sb_seg_type %#x\n", sb, sb_seg_type);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	prev_leb = (*sb_lebs)[SSDFS_PREV_SB_SEG][sb_seg_type];
+	cur_leb = (*sb_lebs)[SSDFS_CUR_SB_SEG][sb_seg_type];
+	next_leb = (*sb_lebs)[SSDFS_NEXT_SB_SEG][sb_seg_type];
+	reserved_leb = (*sb_lebs)[SSDFS_RESERVED_SB_SEG][sb_seg_type];
+
+	prev_peb = (*sb_pebs)[SSDFS_PREV_SB_SEG][sb_seg_type];
+	cur_peb = (*sb_pebs)[SSDFS_CUR_SB_SEG][sb_seg_type];
+	next_peb = (*sb_pebs)[SSDFS_NEXT_SB_SEG][sb_seg_type];
+	reserved_peb = (*sb_pebs)[SSDFS_RESERVED_SB_SEG][sb_seg_type];
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("cur_peb %llu, next_peb %llu, "
+		  "cur_leb %llu, next_leb %llu\n",
+		  cur_peb, next_peb, cur_leb, next_leb);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	(*sb_lebs)[SSDFS_CUR_SB_SEG][sb_seg_type] = next_leb;
+	(*sb_pebs)[SSDFS_CUR_SB_SEG][sb_seg_type] = next_peb;
+
+	if (prev_leb >= U64_MAX) {
+		(*sb_lebs)[SSDFS_PREV_SB_SEG][sb_seg_type] = cur_leb;
+		(*sb_pebs)[SSDFS_PREV_SB_SEG][sb_seg_type] = cur_peb;
+
+		(*sb_lebs)[SSDFS_NEXT_SB_SEG][sb_seg_type] = reserved_leb;
+		(*sb_pebs)[SSDFS_NEXT_SB_SEG][sb_seg_type] = reserved_peb;
+
+		(*sb_lebs)[SSDFS_RESERVED_SB_SEG][sb_seg_type] = U64_MAX;
+		(*sb_pebs)[SSDFS_RESERVED_SB_SEG][sb_seg_type] = U64_MAX;
+	} else {
+		err = ssdfs_erase_dirty_prev_sb_segs(fsi, prev_leb);
+		if (unlikely(err)) {
+			SSDFS_ERR("fail erase dirty PEBs: "
+				  "prev_leb %llu, err %d\n",
+				  prev_leb, err);
+			goto finish_move_sb_seg;
+		}
+
+		(*sb_lebs)[SSDFS_NEXT_SB_SEG][sb_seg_type] = prev_leb;
+		(*sb_pebs)[SSDFS_NEXT_SB_SEG][sb_seg_type] = prev_peb;
+
+		(*sb_lebs)[SSDFS_RESERVED_SB_SEG][sb_seg_type] = U64_MAX;
+		(*sb_pebs)[SSDFS_RESERVED_SB_SEG][sb_seg_type] = U64_MAX;
+
+		(*sb_lebs)[SSDFS_PREV_SB_SEG][sb_seg_type] = cur_leb;
+		(*sb_pebs)[SSDFS_PREV_SB_SEG][sb_seg_type] = cur_peb;
+	}
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("cur_leb %llu, cur_peb %llu, "
+		  "next_leb %llu, next_peb %llu, "
+		  "reserved_leb %llu, reserved_peb %llu, "
+		  "prev_leb %llu, prev_peb %llu\n",
+		  (*sb_lebs)[SSDFS_CUR_SB_SEG][sb_seg_type],
+		  (*sb_pebs)[SSDFS_CUR_SB_SEG][sb_seg_type],
+		  (*sb_lebs)[SSDFS_NEXT_SB_SEG][sb_seg_type],
+		  (*sb_pebs)[SSDFS_NEXT_SB_SEG][sb_seg_type],
+		  (*sb_lebs)[SSDFS_RESERVED_SB_SEG][sb_seg_type],
+		  (*sb_pebs)[SSDFS_RESERVED_SB_SEG][sb_seg_type],
+		  (*sb_lebs)[SSDFS_PREV_SB_SEG][sb_seg_type],
+		  (*sb_pebs)[SSDFS_PREV_SB_SEG][sb_seg_type]);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	if (fsi->is_zns_device) {
+		cur_peb = (*sb_pebs)[SSDFS_CUR_SB_SEG][sb_seg_type];
+		offset = cur_peb * fsi->erasesize;
+
+		err = fsi->devops->open_zone(fsi->sb, offset);
+		if (unlikely(err)) {
+			SSDFS_ERR("fail to open zone: "
+				  "offset %llu, err %d\n",
+				  offset, err);
+			return err;
+		}
+	}
+
+finish_move_sb_seg:
+	return err;
+}
+#else
+static int ssdfs_move_on_first_peb_next_sb_seg(struct super_block *sb,
+						int sb_seg_type,
+						sb_pebs_array *sb_lebs,
+						sb_pebs_array *sb_pebs)
+{
+	struct ssdfs_fs_info *fsi = SSDFS_FS_I(sb);
+	struct ssdfs_segment_bmap *segbmap = fsi->segbmap;
+	struct ssdfs_maptbl_cache *maptbl_cache = &fsi->maptbl_cache;
+	u64 prev_leb, cur_leb, next_leb, reserved_leb;
+	u64 prev_peb, cur_peb, next_peb, reserved_peb;
+	u64 new_leb = U64_MAX, new_peb = U64_MAX;
+	u64 reserved_seg;
+	u64 prev_seg, cur_seg;
+	struct ssdfs_maptbl_peb_relation pebr;
+	u8 peb_type = SSDFS_MAPTBL_SBSEG_PEB_TYPE;
+	struct completion *end = NULL;
+	int err = 0;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!sb || !sb_lebs || !sb_pebs);
+
+	if (sb_seg_type >= SSDFS_SB_SEG_COPY_MAX) {
+		SSDFS_ERR("invalid sb_seg_type %#x\n",
+			  sb_seg_type);
+		return -EINVAL;
+	}
+
+	SSDFS_DBG("sb %p, sb_seg_type %#x\n", sb, sb_seg_type);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	prev_leb = (*sb_lebs)[SSDFS_PREV_SB_SEG][sb_seg_type];
+	cur_leb = (*sb_lebs)[SSDFS_CUR_SB_SEG][sb_seg_type];
+	next_leb = (*sb_lebs)[SSDFS_NEXT_SB_SEG][sb_seg_type];
+	reserved_leb = (*sb_lebs)[SSDFS_RESERVED_SB_SEG][sb_seg_type];
+
+	prev_peb = (*sb_pebs)[SSDFS_PREV_SB_SEG][sb_seg_type];
+	cur_peb = (*sb_pebs)[SSDFS_CUR_SB_SEG][sb_seg_type];
+	next_peb = (*sb_pebs)[SSDFS_NEXT_SB_SEG][sb_seg_type];
+	reserved_peb = (*sb_pebs)[SSDFS_RESERVED_SB_SEG][sb_seg_type];
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("cur_peb %llu, next_peb %llu, "
+		  "cur_leb %llu, next_leb %llu\n",
+		  cur_peb, next_peb, cur_leb, next_leb);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	err = ssdfs_reserve_clean_segment(sb, sb_seg_type, cur_leb,
+					  &reserved_seg);
+	if (unlikely(err)) {
+		SSDFS_ERR("fail to reserve clean segment: err %d\n", err);
+		goto finish_move_sb_seg;
+	}
+
+	new_leb = ssdfs_get_leb_id_for_peb_index(fsi, reserved_seg, 0);
+	if (new_leb >= U64_MAX) {
+		err = -ERANGE;
+		SSDFS_ERR("fail to convert PEB index into LEB ID: "
+			  "seg %llu\n", reserved_seg);
+		goto finish_move_sb_seg;
+	}
+
+	err = ssdfs_maptbl_convert_leb2peb(fsi, new_leb,
+					   peb_type,
+					   &pebr, &end);
+	if (err == -EAGAIN) {
+		err = SSDFS_WAIT_COMPLETION(end);
+		if (unlikely(err)) {
+			SSDFS_ERR("maptbl init failed: "
+				  "err %d\n", err);
+			goto finish_move_sb_seg;
+		}
+
+		err = ssdfs_maptbl_convert_leb2peb(fsi, new_leb,
+						   peb_type,
+						   &pebr, &end);
+	}
+
+	if (unlikely(err)) {
+		SSDFS_ERR("fail to convert LEB %llu to PEB: err %d\n",
+			  new_leb, err);
+		goto finish_move_sb_seg;
+	}
+
+	new_peb = pebr.pebs[SSDFS_MAPTBL_MAIN_INDEX].peb_id;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(new_peb == U64_MAX);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	(*sb_lebs)[SSDFS_PREV_SB_SEG][sb_seg_type] = cur_leb;
+	(*sb_pebs)[SSDFS_PREV_SB_SEG][sb_seg_type] = cur_peb;
+
+	(*sb_lebs)[SSDFS_CUR_SB_SEG][sb_seg_type] = next_leb;
+	(*sb_pebs)[SSDFS_CUR_SB_SEG][sb_seg_type] = next_peb;
+
+	(*sb_lebs)[SSDFS_NEXT_SB_SEG][sb_seg_type] = reserved_leb;
+	(*sb_pebs)[SSDFS_NEXT_SB_SEG][sb_seg_type] = reserved_peb;
+
+	(*sb_lebs)[SSDFS_RESERVED_SB_SEG][sb_seg_type] = new_leb;
+	(*sb_pebs)[SSDFS_RESERVED_SB_SEG][sb_seg_type] = new_peb;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("cur_leb %llu, cur_peb %llu, "
+		  "next_leb %llu, next_peb %llu, "
+		  "reserved_leb %llu, reserved_peb %llu, "
+		  "new_leb %llu, new_peb %llu\n",
+		  cur_leb, cur_peb,
+		  next_leb, next_peb,
+		  reserved_leb, reserved_peb,
+		  new_leb, new_peb);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	if (prev_leb == U64_MAX)
+		goto finish_move_sb_seg;
+
+	prev_seg = SSDFS_LEB2SEG(fsi, prev_leb);
+	cur_seg = SSDFS_LEB2SEG(fsi, cur_leb);
+
+	if (prev_seg != cur_seg) {
+		err = ssdfs_segbmap_change_state(segbmap, prev_seg,
+						 SSDFS_SEG_DIRTY, &end);
+		if (err == -EAGAIN) {
+			err = SSDFS_WAIT_COMPLETION(end);
+			if (unlikely(err)) {
+				SSDFS_ERR("segbmap init failed: "
+					  "err %d\n", err);
+				goto finish_move_sb_seg;
+			}
+
+			err = ssdfs_segbmap_change_state(segbmap, prev_seg,
+							 SSDFS_SEG_DIRTY, &end);
+		}
+
+		if (unlikely(err)) {
+			SSDFS_ERR("fail to change segment state: "
+				  "seg %llu, state %#x, err %d\n",
+				  prev_seg, SSDFS_SEG_DIRTY, err);
+			goto finish_move_sb_seg;
+		}
+	}
+
+	err = ssdfs_maptbl_wait_and_change_peb_state(fsi, prev_leb, peb_type,
+						SSDFS_MAPTBL_DIRTY_PEB_STATE);
+	if (unlikely(err)) {
+		SSDFS_ERR("fail to change the PEB state: "
+			  "leb_id %llu, new_state %#x, err %d\n",
+			  prev_leb, SSDFS_MAPTBL_DIRTY_PEB_STATE, err);
+		goto finish_move_sb_seg;
+	}
+
+	err = ssdfs_maptbl_cache_forget_leb2peb(maptbl_cache, prev_leb,
+						SSDFS_PEB_STATE_CONSISTENT);
+	if (unlikely(err)) {
+		SSDFS_ERR("fail to forget prev_leb %llu, err %d\n",
+			  prev_leb, err);
+		goto finish_move_sb_seg;
+	}
+
+finish_move_sb_seg:
+	return err;
+}
+#endif /* CONFIG_SSDFS_FIXED_SUPERBLOCK_SEGMENTS_SET */
+
+static int ssdfs_move_on_next_sb_seg(struct super_block *sb,
+				     int sb_seg_type,
+				     sb_pebs_array *sb_lebs,
+				     sb_pebs_array *sb_pebs)
+{
+	struct ssdfs_fs_info *fsi = SSDFS_FS_I(sb);
+	u64 cur_leb, next_leb;
+	u64 cur_peb;
+	u8 peb_type = SSDFS_MAPTBL_SBSEG_PEB_TYPE;
+	int err;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!sb || !sb_lebs || !sb_pebs);
+
+	if (sb_seg_type >= SSDFS_SB_SEG_COPY_MAX) {
+		SSDFS_ERR("invalid sb_seg_type %#x\n",
+			  sb_seg_type);
+		return -EINVAL;
+	}
+
+	SSDFS_DBG("sb %p, sb_seg_type %#x\n", sb, sb_seg_type);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	cur_leb = (*sb_lebs)[SSDFS_CUR_SB_SEG][sb_seg_type];
+	cur_peb = (*sb_pebs)[SSDFS_CUR_SB_SEG][sb_seg_type];
+
+	next_leb = cur_leb + 1;
+
+	err = ssdfs_maptbl_wait_and_change_peb_state(fsi, cur_leb, peb_type,
+						SSDFS_MAPTBL_USED_PEB_STATE);
+	if (unlikely(err)) {
+		SSDFS_ERR("fail to change the PEB state: "
+			  "leb_id %llu, new_state %#x, err %d\n",
+			  cur_leb, SSDFS_MAPTBL_USED_PEB_STATE, err);
+		return err;
+	}
+
+	err = ssdfs_move_on_first_peb_next_sb_seg(sb, sb_seg_type,
+						sb_lebs, sb_pebs);
+	if (unlikely(err)) {
+		SSDFS_ERR("fail to move on next sb segment: "
+			  "sb_seg_type %#x, cur_leb %llu, "
+			  "cur_peb %llu, err %d\n",
+			  sb_seg_type, cur_leb,
+			  cur_peb, err);
+		return err;
+	}
+
+	return 0;
+}
+
+static int ssdfs_snapshot_new_sb_pebs_array(struct super_block *sb)
+{
+	struct ssdfs_fs_info *fsi;
+	struct ssdfs_peb_extent *last_log;
+	struct ssdfs_segment_request *req;
+	struct ssdfs_requests_queue *rq;
+	u64 offset;
+	u32 log_blocks;
+	int err;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!sb);
+
+	SSDFS_DBG("sb %p", sb);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	fsi = SSDFS_FS_I(sb);
+
+	fsi->sb_snapi.need_snapshot_sb = true;
+
+	last_log = &fsi->sb_snapi.last_log;
+	offset = last_log->page_offset + last_log->pages_count;
+	log_blocks = last_log->pages_count;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("last_log (page_offset %u, pages_count %u)\n",
+		  last_log->page_offset, last_log->pages_count);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	if (offset > fsi->pages_per_peb) {
+		SSDFS_ERR("last log has inconsistent state: "
+			  "offset %llu > pages_per_peb %u\n",
+			  offset, fsi->pages_per_peb);
+		return -ERANGE;
+	} else if ((offset + log_blocks) > fsi->pages_per_peb) {
+		req = ssdfs_request_alloc();
+		if (IS_ERR_OR_NULL(req)) {
+			err = (req == NULL ? -ENOMEM : PTR_ERR(req));
+			SSDFS_ERR("fail to allocate segment request: err %d\n",
+				  err);
+			return err;
+		}
+
+		ssdfs_request_init(req, fsi->pagesize);
+		ssdfs_get_request(req);
+
+		ssdfs_request_prepare_internal_data(SSDFS_GLOBAL_FSCK_REQ,
+					SSDFS_FSCK_ERASE_RE_WRITE_SB_SNAP_SEG,
+					SSDFS_REQ_ASYNC_NO_FREE, req);
+
+		rq = &fsi->global_fsck.rq;
+		ssdfs_requests_queue_add_tail_inc(fsi, rq, req);
+		fsi->sb_snapi.req = req;
+		wake_up_all(&fsi->global_fsck.wait_queue);
+
+		last_log->page_offset = 0;
+
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("last_log (page_offset %u, pages_count %u)\n",
+			  last_log->page_offset, last_log->pages_count);
+#endif /* CONFIG_SSDFS_DEBUG */
+	}
+
+	return 0;
+}
+
+static int ssdfs_move_on_next_sb_segs_pair(struct super_block *sb)
+{
+	struct ssdfs_fs_info *fsi = SSDFS_FS_I(sb);
+	sb_pebs_array sb_lebs;
+	sb_pebs_array sb_pebs;
+	size_t array_size;
+	int i;
+	int err = 0;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("sb %p", sb);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	if (!(fsi->fs_feature_compat & SSDFS_HAS_SEGBMAP_COMPAT_FLAG) ||
+	    !(fsi->fs_feature_compat & SSDFS_HAS_MAPTBL_COMPAT_FLAG)) {
+		SSDFS_ERR("volume hasn't segbmap or maptbl\n");
+		return -EIO;
+	}
+
+	array_size = sizeof(u64);
+	array_size *= SSDFS_SB_CHAIN_MAX;
+	array_size *= SSDFS_SB_SEG_COPY_MAX;
+
+	down_read(&fsi->sb_segs_sem);
+	ssdfs_memcpy(sb_lebs, 0, array_size,
+		     fsi->sb_lebs, 0, array_size,
+		     array_size);
+	ssdfs_memcpy(sb_pebs, 0, array_size,
+		     fsi->sb_pebs, 0, array_size,
+		     array_size);
+	up_read(&fsi->sb_segs_sem);
+
+	for (i = 0; i < SSDFS_SB_SEG_COPY_MAX; i++) {
+		err = ssdfs_move_on_next_sb_seg(sb, i, &sb_lebs, &sb_pebs);
+		if (unlikely(err)) {
+			SSDFS_ERR("fail to move on next sb PEB: err %d\n",
+				  err);
+			return err;
+		}
+	}
+
+	down_write(&fsi->sb_segs_sem);
+	ssdfs_memcpy(fsi->sb_lebs, 0, array_size,
+		     sb_lebs, 0, array_size,
+		     array_size);
+	ssdfs_memcpy(fsi->sb_pebs, 0, array_size,
+		     sb_pebs, 0, array_size,
+		     array_size);
+	up_write(&fsi->sb_segs_sem);
+
+	err = ssdfs_snapshot_new_sb_pebs_array(sb);
+	if (unlikely(err)) {
+		SSDFS_ERR("fail to prepare snapshot of new superblock chain: "
+			  "err %d\n", err);
+		return err;
+	}
+
+	return 0;
+}
+
+static
+int ssdfs_prepare_sb_log(struct super_block *sb,
+			 struct ssdfs_peb_extent *last_sb_log)
+{
+	int err;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!sb || !last_sb_log);
+
+	SSDFS_DBG("sb %p, last_sb_log %p\n",
+		  sb, last_sb_log);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	err = ssdfs_define_next_sb_log_place(sb, last_sb_log);
+	switch (err) {
+	case -EFBIG: /* current sb segment is exhausted */
+	case -EIO: /* current sb segment is corrupted */
+		err = ssdfs_move_on_next_sb_segs_pair(sb);
+		if (err) {
+			SSDFS_ERR("fail to move on next sb segs pair: err %d\n",
+				  err);
+			return err;
+		}
+		err = ssdfs_define_next_sb_log_place(sb, last_sb_log);
+		if (unlikely(err)) {
+			SSDFS_ERR("unable to define next sb log place: err %d\n",
+				  err);
+			return err;
+		}
+		break;
+
+	default:
+		if (err) {
+			SSDFS_ERR("unable to define next sb log place: err %d\n",
+				  err);
+			return err;
+		}
+		break;
+	}
+
+	return 0;
+}
+
+static void
+ssdfs_prepare_maptbl_cache_descriptor(struct ssdfs_metadata_descriptor *desc,
+				      u32 offset,
+				      struct ssdfs_payload_content *payload,
+				      u32 payload_size)
+{
+	unsigned i;
+	u32 csum = ~0;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!desc || !payload);
+
+	SSDFS_DBG("desc %p, offset %u, payload %p\n",
+		  desc, offset, payload);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	desc->offset = cpu_to_le32(offset);
+	desc->size = cpu_to_le32(payload_size);
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(payload_size >= U16_MAX);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	desc->check.bytes = cpu_to_le16((u16)payload_size);
+	desc->check.flags = cpu_to_le16(SSDFS_CRC32);
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(folio_batch_count(&payload->batch) == 0);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	for (i = 0; i < folio_batch_count(&payload->batch); i++) {
+		struct folio *folio = payload->batch.folios[i];
+		struct ssdfs_maptbl_cache_header *hdr;
+		void *kaddr;
+		u16 bytes_count;
+
+#ifdef CONFIG_SSDFS_DEBUG
+		BUG_ON(!folio);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		ssdfs_folio_lock(folio);
+		kaddr = kmap_local_folio(folio, 0);
+
+		hdr = (struct ssdfs_maptbl_cache_header *)kaddr;
+		bytes_count = le16_to_cpu(hdr->bytes_count);
+
+		csum = crc32(csum, kaddr, bytes_count);
+
+		kunmap_local(kaddr);
+		ssdfs_folio_unlock(folio);
+	}
+
+	desc->check.csum = cpu_to_le32(csum);
+}
+
+static
+int ssdfs_prepare_snapshot_rules_for_commit(struct ssdfs_fs_info *fsi,
+					struct ssdfs_metadata_descriptor *desc,
+					u32 offset)
+{
+	struct ssdfs_snapshot_rules_header *hdr;
+	size_t hdr_size = sizeof(struct ssdfs_snapshot_rules_header);
+	size_t info_size = sizeof(struct ssdfs_snapshot_rule_info);
+	struct ssdfs_snapshot_rule_item *item = NULL;
+	u32 payload_off;
+	u32 item_off;
+	u32 pagesize = fsi->pagesize;
+	u16 items_count = 0;
+	u16 items_capacity = 0;
+	u32 area_size = 0;
+	struct list_head *this, *next;
+	u32 csum = ~0;
+	int err = 0;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!fsi || !desc);
+
+	SSDFS_DBG("fsi %p, offset %u\n",
+		  fsi, offset);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	if (is_ssdfs_snapshot_rules_list_empty(&fsi->snapshots.rules_list)) {
+		SSDFS_DBG("snapshot rules list is empty\n");
+		return -ENODATA;
+	}
+
+	payload_off = offsetof(struct ssdfs_log_footer, payload);
+	hdr = SSDFS_SNRU_HDR((u8 *)fsi->sbi.vs_buf + payload_off);
+	memset(hdr, 0, hdr_size);
+	area_size = pagesize - payload_off;
+	item_off = payload_off + hdr_size;
+
+	items_capacity = (u16)((area_size - hdr_size) / info_size);
+	area_size = min_t(u32, area_size, (u32)items_capacity * info_size);
+
+	spin_lock(&fsi->snapshots.rules_list.lock);
+	list_for_each_safe(this, next, &fsi->snapshots.rules_list.list) {
+		item = list_entry(this, struct ssdfs_snapshot_rule_item, list);
+
+		err = ssdfs_memcpy(fsi->sbi.vs_buf, item_off, pagesize,
+				   &item->rule, 0, info_size,
+				   info_size);
+		if (unlikely(err)) {
+			SSDFS_ERR("fail to copy: err %d\n", err);
+			goto finish_copy_items;
+		}
+
+		item_off += info_size;
+		items_count++;
+	}
+finish_copy_items:
+	spin_unlock(&fsi->snapshots.rules_list.lock);
+
+	if (unlikely(err))
+		return err;
+
+	hdr->magic = cpu_to_le32(SSDFS_SNAPSHOT_RULES_MAGIC);
+	hdr->item_size = cpu_to_le16(info_size);
+	hdr->flags = cpu_to_le16(0);
+
+	if (items_count == 0 || items_count > items_capacity) {
+		SSDFS_ERR("invalid items number: "
+			  "items_count %u, items_capacity %u, "
+			  "area_size %u, item_size %zu\n",
+			  items_count, items_capacity,
+			  area_size, info_size);
+		return -ERANGE;
+	}
+
+	hdr->items_count = cpu_to_le16(items_count);
+	hdr->items_capacity = cpu_to_le16(items_capacity);
+	hdr->area_size = cpu_to_le32(area_size);
+
+	desc->offset = cpu_to_le32(offset);
+	desc->size = cpu_to_le32(area_size);
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(area_size >= U16_MAX);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	desc->check.bytes = cpu_to_le16(area_size);
+	desc->check.flags = cpu_to_le16(SSDFS_CRC32);
+
+	csum = crc32(csum, hdr, area_size);
+	desc->check.csum = cpu_to_le32(csum);
+
+	return 0;
+}
+
+static int __ssdfs_commit_sb_log(struct super_block *sb,
+				 u64 timestamp, u64 cno,
+				 struct ssdfs_peb_extent *last_sb_log,
+				 struct ssdfs_sb_log_payload *payload)
+{
+	struct ssdfs_fs_info *fsi;
+	struct ssdfs_metadata_descriptor hdr_desc[SSDFS_SEG_HDR_DESC_MAX];
+	struct ssdfs_metadata_descriptor footer_desc[SSDFS_LOG_FOOTER_DESC_MAX];
+	size_t desc_size = sizeof(struct ssdfs_metadata_descriptor);
+	size_t hdr_array_bytes = desc_size * SSDFS_SEG_HDR_DESC_MAX;
+	size_t footer_array_bytes = desc_size * SSDFS_LOG_FOOTER_DESC_MAX;
+	struct ssdfs_metadata_descriptor *cur_hdr_desc;
+	struct folio *folio;
+	struct ssdfs_segment_header *hdr;
+	size_t hdr_size = sizeof(struct ssdfs_segment_header);
+	struct ssdfs_log_footer *footer;
+	size_t footer_size = sizeof(struct ssdfs_log_footer);
+#ifdef CONFIG_SSDFS_DEBUG
+	void *kaddr = NULL;
+#endif /* CONFIG_SSDFS_DEBUG */
+	loff_t peb_offset;
+	loff_t sb_offset, sb_snap_offset;
+	u32 flags = 0;
+	u32 written = 0;
+	u64 seg_id;
+	u32 log_pages_count;
+	unsigned i;
+	int err;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!sb || !last_sb_log);
+	BUG_ON(!SSDFS_FS_I(sb)->devops);
+	BUG_ON(!SSDFS_FS_I(sb)->devops->write_block);
+	BUG_ON((last_sb_log->page_offset + last_sb_log->pages_count) >
+		(ULLONG_MAX >> PAGE_SHIFT));
+	BUG_ON((last_sb_log->leb_id * SSDFS_FS_I(sb)->pebs_per_seg) >=
+		SSDFS_FS_I(sb)->nsegs);
+	BUG_ON(last_sb_log->peb_id >
+		div_u64(ULLONG_MAX, SSDFS_FS_I(sb)->pages_per_peb));
+	BUG_ON((last_sb_log->peb_id * SSDFS_FS_I(sb)->pages_per_peb) >
+		(ULLONG_MAX >> SSDFS_FS_I(sb)->log_pagesize));
+
+	SSDFS_DBG("sb %p, last_sb_log->leb_id %llu, last_sb_log->peb_id %llu, "
+		  "last_sb_log->page_offset %u, last_sb_log->pages_count %u\n",
+		  sb, last_sb_log->leb_id, last_sb_log->peb_id,
+		  last_sb_log->page_offset, last_sb_log->pages_count);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	fsi = SSDFS_FS_I(sb);
+	hdr = SSDFS_SEG_HDR(fsi->sbi.vh_buf);
+	footer = SSDFS_LF(fsi->sbi.vs_buf);
+
+	memset(hdr_desc, 0, hdr_array_bytes);
+	memset(footer_desc, 0, footer_array_bytes);
+
+	sb_offset = (loff_t)last_sb_log->page_offset << PAGE_SHIFT;
+	sb_offset += PAGE_SIZE;
+
+	cur_hdr_desc = &hdr_desc[SSDFS_MAPTBL_CACHE_INDEX];
+	ssdfs_prepare_maptbl_cache_descriptor(cur_hdr_desc, (u32)sb_offset,
+					     &payload->maptbl_cache,
+					     payload->maptbl_cache.bytes_count);
+
+	sb_offset += payload->maptbl_cache.bytes_count;
+
+	cur_hdr_desc = &hdr_desc[SSDFS_LOG_FOOTER_INDEX];
+	cur_hdr_desc->offset = cpu_to_le32(sb_offset);
+	cur_hdr_desc->size = cpu_to_le32(footer_size);
+
+	ssdfs_memcpy(hdr->desc_array, 0, hdr_array_bytes,
+		     hdr_desc, 0, hdr_array_bytes,
+		     hdr_array_bytes);
+
+	hdr->peb_migration_id[SSDFS_PREV_MIGRATING_PEB] =
+					SSDFS_PEB_UNKNOWN_MIGRATION_ID;
+	hdr->peb_migration_id[SSDFS_CUR_MIGRATING_PEB] =
+					SSDFS_PEB_UNKNOWN_MIGRATION_ID;
+
+	seg_id = ssdfs_get_seg_id_for_leb_id(fsi, last_sb_log->leb_id);
+
+	log_pages_count = PAGE_SIZE; /* header size */
+	log_pages_count += payload->maptbl_cache.bytes_count;
+	log_pages_count += PAGE_SIZE; /* footer size */
+	log_pages_count >>= PAGE_SHIFT;
+
+	err = ssdfs_prepare_segment_header_for_commit(fsi,
+						     seg_id,
+						     last_sb_log->leb_id,
+						     last_sb_log->peb_id,
+						     U64_MAX,
+						     log_pages_count,
+						     SSDFS_SB_SEG_TYPE,
+						     SSDFS_LOG_HAS_FOOTER |
+						     SSDFS_LOG_HAS_MAPTBL_CACHE,
+						     timestamp, cno,
+						     hdr);
+	if (err) {
+		SSDFS_ERR("fail to prepare segment header: err %d\n", err);
+		return err;
+	}
+
+	sb_offset += offsetof(struct ssdfs_log_footer, payload);
+	cur_hdr_desc = &footer_desc[SSDFS_SNAPSHOT_RULES_AREA_INDEX];
+
+	err = ssdfs_prepare_snapshot_rules_for_commit(fsi, cur_hdr_desc,
+						      (u32)sb_offset);
+	if (err == -ENODATA) {
+		err = 0;
+		SSDFS_DBG("snapshot rules list is empty\n");
+	} else if (err) {
+		SSDFS_ERR("fail to prepare snapshot rules: err %d\n", err);
+		return err;
+	} else
+		flags |= SSDFS_LOG_FOOTER_HAS_SNAPSHOT_RULES;
+
+	ssdfs_memcpy(footer->desc_array, 0, footer_array_bytes,
+		     footer_desc, 0, footer_array_bytes,
+		     footer_array_bytes);
+
+	err = ssdfs_prepare_log_footer_for_commit(fsi, PAGE_SIZE,
+						  log_pages_count,
+						  flags, timestamp,
+						  cno, footer);
+	if (err) {
+		SSDFS_ERR("fail to prepare log footer: err %d\n", err);
+		return err;
+	}
+
+	folio = ssdfs_super_alloc_folio(GFP_KERNEL | __GFP_ZERO,
+					get_order(PAGE_SIZE));
+	if (IS_ERR_OR_NULL(folio)) {
+		err = (folio == NULL ? -ENOMEM : PTR_ERR(folio));
+		SSDFS_ERR("unable to allocate memory folio\n");
+		return err;
+	}
+
+	/* ->writepage() calls put_folio() */
+	ssdfs_folio_get(folio);
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("folio %p, count %d\n",
+		  folio, folio_ref_count(folio));
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	/* write segment header */
+	ssdfs_folio_lock(folio);
+	__ssdfs_memcpy_to_folio(folio, 0, PAGE_SIZE,
+				fsi->sbi.vh_buf, 0, hdr_size,
+				hdr_size);
+	folio_mark_uptodate(folio);
+	folio_set_dirty(folio);
+	ssdfs_folio_unlock(folio);
+
+	peb_offset = last_sb_log->peb_id * fsi->pages_per_peb;
+	peb_offset <<= fsi->log_pagesize;
+	sb_offset = (loff_t)last_sb_log->page_offset << PAGE_SHIFT;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(peb_offset > (ULLONG_MAX - (sb_offset + PAGE_SIZE)));
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	sb_offset += peb_offset;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("offset %llu\n", sb_offset);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	err = fsi->devops->write_block(sb, sb_offset, folio);
+	if (err) {
+		SSDFS_ERR("fail to write segment header: "
+			  "offset %llu, size %zu\n",
+			  (u64)sb_offset, hdr_size);
+		goto cleanup_after_failure;
+	}
+
+	if (fsi->sb_snapi.need_snapshot_sb) {
+		struct ssdfs_peb_extent *last_sb_snap_log;
+
+		last_sb_snap_log = &fsi->sb_snapi.last_log;
+
+		peb_offset = last_sb_snap_log->peb_id * fsi->pages_per_peb;
+		peb_offset <<= fsi->log_pagesize;
+		sb_snap_offset =
+			(loff_t)last_sb_snap_log->page_offset << PAGE_SHIFT;
+
+#ifdef CONFIG_SSDFS_DEBUG
+		BUG_ON(peb_offset > (ULLONG_MAX - (sb_snap_offset + PAGE_SIZE)));
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		sb_snap_offset += peb_offset;
+
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("offset %llu\n", sb_snap_offset);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		/* ->writepage() calls put_folio() */
+		ssdfs_folio_get(folio);
+
+		ssdfs_folio_lock(folio);
+		hdr = SSDFS_SEG_HDR(kmap_local_folio(folio, 0));
+		hdr->seg_id = cpu_to_le64(SSDFS_INITIAL_SNAPSHOT_SEG_ID);
+		hdr->leb_id = cpu_to_le64(SSDFS_INITIAL_SNAPSHOT_SEG_LEB_ID);
+		hdr->peb_id = cpu_to_le64(SSDFS_INITIAL_SNAPSHOT_SEG_PEB_ID);
+		hdr->seg_type = cpu_to_le16(SSDFS_INITIAL_SNAPSHOT_SEG_TYPE);
+		hdr->seg_flags = cpu_to_le32(SSDFS_LOG_HAS_FOOTER);
+		hdr->volume_hdr.check.bytes =
+			cpu_to_le16(sizeof(struct ssdfs_segment_header));
+		hdr->volume_hdr.check.flags = cpu_to_le16(SSDFS_CRC32);
+		err = ssdfs_calculate_csum(&hdr->volume_hdr.check,
+					   hdr,
+					   sizeof(struct ssdfs_segment_header));
+		if (unlikely(err)) {
+			SSDFS_ERR("unable to calculate checksum: err %d\n", err);
+		} else {
+			folio_mark_uptodate(folio);
+			folio_set_dirty(folio);
+		}
+		kunmap_local(hdr);
+		ssdfs_folio_unlock(folio);
+
+		if (err)
+			goto cleanup_after_failure;
+
+		err = fsi->devops->write_block(sb, sb_snap_offset, folio);
+		if (err) {
+			SSDFS_ERR("fail to write segment header: "
+				  "offset %llu, size %zu\n",
+				  (u64)sb_snap_offset,
+				  hdr_size);
+			goto cleanup_after_failure;
+		}
+	}
+
+	ssdfs_folio_lock(folio);
+	folio_clear_uptodate(folio);
+	ssdfs_folio_unlock(folio);
+
+	sb_offset += PAGE_SIZE;
+	written = 0;
+
+	for (i = 0; i < folio_batch_count(&payload->maptbl_cache.batch); i++) {
+		struct folio *payload_folio =
+				payload->maptbl_cache.batch.folios[i];
+
+#ifdef CONFIG_SSDFS_DEBUG
+		BUG_ON(!payload_folio);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		/* ->writepage() calls put_folio() */
+		ssdfs_folio_get(payload_folio);
+
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("folio %p, count %d\n",
+			  payload_folio,
+			  folio_ref_count(payload_folio));
+
+		kaddr = kmap_local_folio(payload_folio, 0);
+		SSDFS_DBG("PAYLOAD FOLIO %d\n", i);
+		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET,
+				     kaddr, PAGE_SIZE);
+		kunmap_local(kaddr);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		ssdfs_folio_lock(payload_folio);
+		folio_mark_uptodate(payload_folio);
+		folio_set_dirty(payload_folio);
+		ssdfs_folio_unlock(payload_folio);
+
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("offset %llu\n", sb_offset);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		err = fsi->devops->write_block(sb, sb_offset, payload_folio);
+		if (err) {
+			SSDFS_ERR("fail to write maptbl cache page: "
+				  "offset %llu, folio_index %u, size %zu\n",
+				  (u64)sb_offset, i, PAGE_SIZE);
+			goto cleanup_after_failure;
+		}
+
+		ssdfs_folio_lock(payload_folio);
+		folio_clear_uptodate(payload_folio);
+		ssdfs_folio_unlock(payload_folio);
+
+		sb_offset += PAGE_SIZE;
+	}
+
+	/* TODO: write metadata payload */
+
+	/* ->writepage() calls put_folio() */
+	ssdfs_folio_get(folio);
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("folio %p, count %d\n",
+		  folio, folio_ref_count(folio));
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	/* write log footer */
+	ssdfs_folio_lock(folio);
+	__ssdfs_memset_folio(folio, 0, PAGE_SIZE,
+			     0, PAGE_SIZE);
+	__ssdfs_memcpy_to_folio(folio, 0, PAGE_SIZE,
+				fsi->sbi.vs_buf, 0, fsi->sbi.vs_buf_size,
+				PAGE_SIZE);
+	folio_mark_uptodate(folio);
+	folio_set_dirty(folio);
+	ssdfs_folio_unlock(folio);
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("offset %llu\n", sb_offset);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	err = fsi->devops->write_block(sb, sb_offset, folio);
+	if (err) {
+		SSDFS_ERR("fail to write log footer: "
+			  "offset %llu, size %zu\n",
+			  (u64)sb_offset, fsi->sbi.vs_buf_size);
+		goto cleanup_after_failure;
+	}
+
+	if (fsi->sb_snapi.need_snapshot_sb) {
+		sb_snap_offset += PAGE_SIZE;
+
+		/* ->writepage() calls put_folio() */
+		ssdfs_folio_get(folio);
+
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("offset %llu\n", sb_snap_offset);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		ssdfs_folio_lock(folio);
+		folio_mark_uptodate(folio);
+		folio_set_dirty(folio);
+		ssdfs_folio_unlock(folio);
+
+		err = fsi->devops->write_block(sb, sb_snap_offset, folio);
+		if (err) {
+			SSDFS_ERR("fail to write log footer: "
+				  "offset %llu, size %zu\n",
+				  (u64)sb_snap_offset, fsi->sbi.vs_buf_size);
+			goto cleanup_after_failure;
+		}
+	}
+
+	ssdfs_folio_lock(folio);
+	folio_clear_uptodate(folio);
+	ssdfs_folio_unlock(folio);
+
+	fsi->sb_snapi.need_snapshot_sb = false;
+
+	ssdfs_super_free_folio(folio);
+	return 0;
+
+cleanup_after_failure:
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("folio %p, count %d\n",
+		  folio, folio_ref_count(folio));
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	ssdfs_super_free_folio(folio);
+
+	return err;
+}
+
+static int
+__ssdfs_commit_sb_log_inline(struct super_block *sb,
+			     u64 timestamp, u64 cno,
+			     struct ssdfs_peb_extent *last_sb_log,
+			     struct ssdfs_sb_log_payload *payload,
+			     u32 payload_size)
+{
+	struct ssdfs_fs_info *fsi;
+	struct ssdfs_metadata_descriptor hdr_desc[SSDFS_SEG_HDR_DESC_MAX];
+	struct ssdfs_metadata_descriptor footer_desc[SSDFS_LOG_FOOTER_DESC_MAX];
+	size_t desc_size = sizeof(struct ssdfs_metadata_descriptor);
+	size_t hdr_array_bytes = desc_size * SSDFS_SEG_HDR_DESC_MAX;
+	size_t footer_array_bytes = desc_size * SSDFS_LOG_FOOTER_DESC_MAX;
+	struct ssdfs_metadata_descriptor *cur_hdr_desc;
+	struct folio *folio;
+	struct folio *payload_folio;
+	struct ssdfs_segment_header *hdr;
+	size_t hdr_size = sizeof(struct ssdfs_segment_header);
+	struct ssdfs_log_footer *footer;
+	size_t footer_size = sizeof(struct ssdfs_log_footer);
+	void *kaddr = NULL;
+	loff_t peb_offset;
+	loff_t sb_offset, sb_snap_offset;
+	u32 inline_capacity;
+	void *payload_buf;
+	u32 flags = 0;
+	u64 seg_id;
+	u32 log_pages_count;
+	int err;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!sb || !last_sb_log);
+	BUG_ON(!SSDFS_FS_I(sb)->devops);
+	BUG_ON(!SSDFS_FS_I(sb)->devops->write_block);
+	BUG_ON((last_sb_log->page_offset + last_sb_log->pages_count) >
+		(ULLONG_MAX >> PAGE_SHIFT));
+	BUG_ON((last_sb_log->leb_id * SSDFS_FS_I(sb)->pebs_per_seg) >=
+		SSDFS_FS_I(sb)->nsegs);
+	BUG_ON(last_sb_log->peb_id >
+		    div_u64(ULLONG_MAX, SSDFS_FS_I(sb)->pages_per_peb));
+	BUG_ON((last_sb_log->peb_id * SSDFS_FS_I(sb)->pages_per_peb) >
+				(ULLONG_MAX >> SSDFS_FS_I(sb)->log_pagesize));
+
+	SSDFS_DBG("sb %p, last_sb_log->leb_id %llu, last_sb_log->peb_id %llu, "
+		  "last_sb_log->page_offset %u, last_sb_log->pages_count %u\n",
+		  sb, last_sb_log->leb_id, last_sb_log->peb_id,
+		  last_sb_log->page_offset, last_sb_log->pages_count);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	fsi = SSDFS_FS_I(sb);
+	hdr = SSDFS_SEG_HDR(fsi->sbi.vh_buf);
+	footer = SSDFS_LF(fsi->sbi.vs_buf);
+
+	memset(hdr_desc, 0, hdr_array_bytes);
+	memset(footer_desc, 0, footer_array_bytes);
+
+	sb_offset = (loff_t)last_sb_log->page_offset << PAGE_SHIFT;
+	sb_offset += hdr_size;
+
+	cur_hdr_desc = &hdr_desc[SSDFS_MAPTBL_CACHE_INDEX];
+	ssdfs_prepare_maptbl_cache_descriptor(cur_hdr_desc, (u32)sb_offset,
+					      &payload->maptbl_cache,
+					      payload_size);
+
+	sb_offset += payload_size;
+
+	sb_offset += PAGE_SIZE - 1;
+	sb_offset = (sb_offset >> PAGE_SHIFT) << PAGE_SHIFT;
+
+	cur_hdr_desc = &hdr_desc[SSDFS_LOG_FOOTER_INDEX];
+	cur_hdr_desc->offset = cpu_to_le32(sb_offset);
+	cur_hdr_desc->size = cpu_to_le32(footer_size);
+
+	ssdfs_memcpy(hdr->desc_array, 0, hdr_array_bytes,
+		     hdr_desc, 0, hdr_array_bytes,
+		     hdr_array_bytes);
+
+	hdr->peb_migration_id[SSDFS_PREV_MIGRATING_PEB] =
+					SSDFS_PEB_UNKNOWN_MIGRATION_ID;
+	hdr->peb_migration_id[SSDFS_CUR_MIGRATING_PEB] =
+					SSDFS_PEB_UNKNOWN_MIGRATION_ID;
+
+	seg_id = ssdfs_get_seg_id_for_leb_id(fsi, last_sb_log->leb_id);
+
+	log_pages_count = hdr_size + payload_size;
+	log_pages_count += PAGE_SIZE - 1;
+	log_pages_count = (log_pages_count >> PAGE_SHIFT) << PAGE_SHIFT;
+	log_pages_count += PAGE_SIZE; /* footer size */
+	log_pages_count >>= PAGE_SHIFT;
+
+	err = ssdfs_prepare_segment_header_for_commit(fsi,
+						     seg_id,
+						     last_sb_log->leb_id,
+						     last_sb_log->peb_id,
+						     U64_MAX,
+						     log_pages_count,
+						     SSDFS_SB_SEG_TYPE,
+						     SSDFS_LOG_HAS_FOOTER |
+						     SSDFS_LOG_HAS_MAPTBL_CACHE,
+						     timestamp, cno,
+						     hdr);
+	if (err) {
+		SSDFS_ERR("fail to prepare segment header: err %d\n", err);
+		return err;
+	}
+
+	sb_offset += offsetof(struct ssdfs_log_footer, payload);
+	cur_hdr_desc = &footer_desc[SSDFS_SNAPSHOT_RULES_AREA_INDEX];
+
+	err = ssdfs_prepare_snapshot_rules_for_commit(fsi, cur_hdr_desc,
+						      (u32)sb_offset);
+	if (err == -ENODATA) {
+		err = 0;
+		SSDFS_DBG("snapshot rules list is empty\n");
+	} else if (err) {
+		SSDFS_ERR("fail to prepare snapshot rules: err %d\n", err);
+		return err;
+	} else
+		flags |= SSDFS_LOG_FOOTER_HAS_SNAPSHOT_RULES;
+
+	ssdfs_memcpy(footer->desc_array, 0, footer_array_bytes,
+		     footer_desc, 0, footer_array_bytes,
+		     footer_array_bytes);
+
+	err = ssdfs_prepare_log_footer_for_commit(fsi, PAGE_SIZE,
+						  log_pages_count,
+						  flags, timestamp,
+						  cno, footer);
+	if (err) {
+		SSDFS_ERR("fail to prepare log footer: err %d\n", err);
+		return err;
+	}
+
+	if (folio_batch_count(&payload->maptbl_cache.batch) != 1) {
+		SSDFS_WARN("payload contains several memory folios\n");
+		return -ERANGE;
+	}
+
+	inline_capacity = PAGE_SIZE - hdr_size;
+
+	if (payload_size > inline_capacity) {
+		SSDFS_ERR("payload_size %u > inline_capacity %u\n",
+			  payload_size, inline_capacity);
+		return -ERANGE;
+	}
+
+	payload_buf = ssdfs_super_kmalloc(inline_capacity, GFP_KERNEL);
+	if (!payload_buf) {
+		SSDFS_ERR("fail to allocate payload buffer\n");
+		return -ENOMEM;
+	}
+
+	folio = ssdfs_super_alloc_folio(GFP_KERNEL | __GFP_ZERO,
+					get_order(PAGE_SIZE));
+	if (IS_ERR_OR_NULL(folio)) {
+		err = (folio == NULL ? -ENOMEM : PTR_ERR(folio));
+		SSDFS_ERR("unable to allocate memory folio\n");
+		ssdfs_super_kfree(payload_buf);
+		return err;
+	}
+
+	/* ->writepage() calls put_folio() */
+	ssdfs_folio_get(folio);
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("folio %p, count %d\n",
+		  folio, folio_ref_count(folio));
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	payload_folio = payload->maptbl_cache.batch.folios[0];
+	if (!payload_folio) {
+		err = -ERANGE;
+		SSDFS_ERR("invalid payload folio\n");
+		goto free_payload_buffer;
+	}
+
+	ssdfs_folio_lock(payload_folio);
+	err = __ssdfs_memcpy_from_folio(payload_buf, 0, inline_capacity,
+					payload_folio, 0, PAGE_SIZE,
+					payload_size);
+	ssdfs_folio_unlock(payload_folio);
+
+	if (unlikely(err)) {
+		SSDFS_ERR("fail to copy: err %d\n", err);
+		goto free_payload_buffer;
+	}
+
+	/* write segment header + payload */
+	ssdfs_folio_lock(folio);
+	kaddr = kmap_local_folio(folio, 0);
+	ssdfs_memcpy(kaddr, 0, PAGE_SIZE,
+		     fsi->sbi.vh_buf, 0, hdr_size,
+		     hdr_size);
+	err = ssdfs_memcpy(kaddr, hdr_size, PAGE_SIZE,
+			   payload_buf, 0, inline_capacity,
+			   payload_size);
+	flush_dcache_folio(folio);
+	kunmap_local(kaddr);
+	if (!err) {
+		folio_mark_uptodate(folio);
+		folio_set_dirty(folio);
+	}
+	ssdfs_folio_unlock(folio);
+
+	if (unlikely(err)) {
+		SSDFS_ERR("fail to copy: err %d\n", err);
+		goto free_payload_buffer;
+	}
+
+free_payload_buffer:
+	ssdfs_super_kfree(payload_buf);
+
+	if (unlikely(err))
+		goto cleanup_after_failure;
+
+	peb_offset = last_sb_log->peb_id * fsi->pages_per_peb;
+	peb_offset <<= fsi->log_pagesize;
+	sb_offset = (loff_t)last_sb_log->page_offset << PAGE_SHIFT;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(peb_offset > (ULLONG_MAX - (sb_offset + PAGE_SIZE)));
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	sb_offset += peb_offset;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("offset %llu\n", sb_offset);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	err = fsi->devops->write_block(sb, sb_offset, folio);
+	if (err) {
+		SSDFS_ERR("fail to write segment header: "
+			  "offset %llu, size %zu\n",
+			  (u64)sb_offset, hdr_size + payload_size);
+		goto cleanup_after_failure;
+	}
+
+	if (fsi->sb_snapi.need_snapshot_sb) {
+		struct ssdfs_peb_extent *last_sb_snap_log;
+
+		last_sb_snap_log = &fsi->sb_snapi.last_log;
+
+		peb_offset = last_sb_snap_log->peb_id * fsi->pages_per_peb;
+		peb_offset <<= fsi->log_pagesize;
+		sb_snap_offset =
+			(loff_t)last_sb_snap_log->page_offset << PAGE_SHIFT;
+
+#ifdef CONFIG_SSDFS_DEBUG
+		BUG_ON(peb_offset > (ULLONG_MAX - (sb_snap_offset + PAGE_SIZE)));
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		sb_snap_offset += peb_offset;
+
+		/* ->writepage() calls put_folio() */
+		ssdfs_folio_get(folio);
+
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("offset %llu\n", sb_snap_offset);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		ssdfs_folio_lock(folio);
+		hdr = SSDFS_SEG_HDR(kmap_local_folio(folio, 0));
+		hdr->seg_id = cpu_to_le64(SSDFS_INITIAL_SNAPSHOT_SEG_ID);
+		hdr->leb_id = cpu_to_le64(SSDFS_INITIAL_SNAPSHOT_SEG_LEB_ID);
+		hdr->peb_id = cpu_to_le64(SSDFS_INITIAL_SNAPSHOT_SEG_PEB_ID);
+		hdr->seg_type = cpu_to_le16(SSDFS_INITIAL_SNAPSHOT_SEG_TYPE);
+		hdr->seg_flags = cpu_to_le32(SSDFS_LOG_HAS_FOOTER);
+		hdr->volume_hdr.check.bytes =
+			cpu_to_le16(sizeof(struct ssdfs_segment_header));
+		hdr->volume_hdr.check.flags = cpu_to_le16(SSDFS_CRC32);
+		err = ssdfs_calculate_csum(&hdr->volume_hdr.check,
+					   hdr,
+					   sizeof(struct ssdfs_segment_header));
+		if (unlikely(err)) {
+			SSDFS_ERR("unable to calculate checksum: err %d\n", err);
+		} else {
+			folio_mark_uptodate(folio);
+			folio_set_dirty(folio);
+		}
+		kunmap_local(hdr);
+		ssdfs_folio_unlock(folio);
+
+		if (err)
+			goto cleanup_after_failure;
+
+		err = fsi->devops->write_block(sb, sb_snap_offset, folio);
+		if (err) {
+			SSDFS_ERR("fail to write segment header: "
+				  "offset %llu, size %zu\n",
+				  (u64)sb_snap_offset,
+				  hdr_size + payload_size);
+			goto cleanup_after_failure;
+		}
+	}
+
+	ssdfs_folio_lock(folio);
+	folio_clear_uptodate(folio);
+	ssdfs_folio_unlock(folio);
+
+	/* ->writepage() calls put_folio() */
+	ssdfs_folio_get(folio);
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("folio %p, count %d\n",
+		  folio, folio_ref_count(folio));
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	/* write log footer */
+	ssdfs_folio_lock(folio);
+	__ssdfs_memset_folio(folio, 0, PAGE_SIZE,
+			     0, PAGE_SIZE);
+	__ssdfs_memcpy_to_folio(folio, 0, PAGE_SIZE,
+				fsi->sbi.vs_buf, 0, fsi->sbi.vs_buf_size,
+				PAGE_SIZE);
+	folio_mark_uptodate(folio);
+	folio_set_dirty(folio);
+	ssdfs_folio_unlock(folio);
+
+	sb_offset += PAGE_SIZE;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("offset %llu\n", sb_offset);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	err = fsi->devops->write_block(sb, sb_offset, folio);
+	if (err) {
+		SSDFS_ERR("fail to write log footer: "
+			  "offset %llu, size %zu\n",
+			  (u64)sb_offset, fsi->sbi.vs_buf_size);
+		goto cleanup_after_failure;
+	}
+
+	if (fsi->sb_snapi.need_snapshot_sb) {
+		sb_snap_offset += PAGE_SIZE;
+
+		/* ->writepage() calls put_folio() */
+		ssdfs_folio_get(folio);
+
+#ifdef CONFIG_SSDFS_DEBUG
+		SSDFS_DBG("offset %llu\n", sb_snap_offset);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+		ssdfs_folio_lock(folio);
+		folio_mark_uptodate(folio);
+		folio_set_dirty(folio);
+		ssdfs_folio_unlock(folio);
+
+		err = fsi->devops->write_block(sb, sb_snap_offset, folio);
+		if (err) {
+			SSDFS_ERR("fail to write log footer: "
+				  "offset %llu, size %zu\n",
+				  (u64)sb_snap_offset, fsi->sbi.vs_buf_size);
+			goto cleanup_after_failure;
+		}
+	}
+
+	ssdfs_folio_lock(folio);
+	folio_clear_uptodate(folio);
+	ssdfs_folio_unlock(folio);
+
+	fsi->sb_snapi.need_snapshot_sb = false;
+
+	ssdfs_super_free_folio(folio);
+	return 0;
+
+cleanup_after_failure:
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("folio %p, count %d\n",
+		  folio, folio_ref_count(folio));
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	ssdfs_super_free_folio(folio);
+
+	return err;
+}
+
+static int ssdfs_commit_sb_log(struct super_block *sb,
+				u64 timestamp, u64 cno,
+				struct ssdfs_peb_extent *last_sb_log,
+				struct ssdfs_sb_log_payload *payload)
+{
+	struct ssdfs_fs_info *fsi = SSDFS_FS_I(sb);
+	size_t hdr_size = sizeof(struct ssdfs_segment_header);
+	u32 inline_capacity;
+	u32 payload_size;
+	int err = 0;
+
+#ifdef CONFIG_SSDFS_DEBUG
+	BUG_ON(!sb || !last_sb_log || !payload);
+
+	SSDFS_DBG("sb %p, last_sb_log->leb_id %llu, last_sb_log->peb_id %llu, "
+		  "last_sb_log->page_offset %u, last_sb_log->pages_count %u\n",
+		  sb, last_sb_log->leb_id, last_sb_log->peb_id,
+		  last_sb_log->page_offset, last_sb_log->pages_count);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	inline_capacity = PAGE_SIZE - hdr_size;
+	payload_size = ssdfs_sb_payload_size(&payload->maptbl_cache.batch);
+
+#ifdef CONFIG_SSDFS_DEBUG
+	SSDFS_DBG("inline_capacity %u, payload_size %u\n",
+		  inline_capacity, payload_size);
+#endif /* CONFIG_SSDFS_DEBUG */
+
+	if (fsi->sb_snapi.req != NULL) {
+		struct ssdfs_segment_request *req = fsi->sb_snapi.req;
+
+		switch (atomic_read(&req->result.state)) {
+		case SSDFS_REQ_CREATED:
+		case SSDFS_REQ_STARTED:
+			fsi->sb_snapi.need_snapshot_sb = false;
+			break;
+
+		case SSDFS_REQ_FINISHED:
+			ssdfs_request_free(fsi->sb_snapi.req, NULL);
+			fsi->sb_snapi.req = NULL;
+			break;
+
+		case SSDFS_REQ_FAILED:
+			SSDFS_ERR("erase and re-write request failed\n");
+			ssdfs_request_free(fsi->sb_snapi.req, NULL);
+			fsi->sb_snapi.req = NULL;
+			fsi->sb_snapi.need_snapshot_sb = false;
+			break;
+
+		default:
+			SSDFS_ERR("invalid result's state %#x\n",
+				  atomic_read(&req->result.state));
+			ssdfs_request_free(fsi->sb_snapi.req, NULL);
+			fsi->sb_snapi.req = NULL;
+			fsi->sb_snapi.need_snapshot_sb = false;
+			break;
+		}
+	}
+
+	if (payload_size > inline_capacity) {
+		err = __ssdfs_commit_sb_log(sb, timestamp, cno,
+					    last_sb_log, payload);
+	} else {
+		err = __ssdfs_commit_sb_log_inline(sb, timestamp, cno,
+						   last_sb_log,
+						   payload, payload_size);
+	}
+
+	if (unlikely(err))
+		SSDFS_ERR("fail to commit sb log: err %d\n", err);
+
+	return err;
+}
+
 static
 int ssdfs_commit_super(struct super_block *sb, u16 fs_state,
 			struct ssdfs_peb_extent *last_sb_log,
-- 
2.34.1