ext4

Linux v6.6: fs/ext4/super.c
Linux v6.6: fs/ext4/inode.c
Linux v6.6: fs/ext4/extents.c
Linux v6.6: fs/ext4/namei.c

static int ext4_fill_super(struct super_block *sb, struct fs_context *fc)
{
	struct ext4_fs_context *ctx = fc->fs_private;
	struct ext4_sb_info *sbi;
	const char *descr;
	int ret;

	sbi = ext4_alloc_sbi(sb);
	if (!sbi)
		return -ENOMEM;

	fc->s_fs_info = sbi;

	/* Cleanup superblock name */
	strreplace(sb->s_id, '/', '!');

	sbi->s_sb_block = 1;	/* Default super block location */
	if (ctx->spec & EXT4_SPEC_s_sb_block)
		sbi->s_sb_block = ctx->s_sb_block;

	ret = __ext4_fill_super(fc, sb);
	if (ret < 0)
		goto free_sbi;

	sbi->s_desc_per_block_bits = ilog2(EXT4_DESC_PER_BLOCK(sb));

	return 0;
}

static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
{
	struct ext4_super_block *es = NULL;
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	ext4_fsblk_t logical_sb_block;
	struct inode *root;
	int needs_recovery;
	int err;
	ext4_group_t first_not_zeroed;
	struct ext4_fs_context *ctx = fc->fs_private;
	int silent = fc->sb_flags & SB_SILENT;

	/* Set defaults for the variables that will be set during parsing */
	if (!(ctx->spec & EXT4_SPEC_JOURNAL_IOPRIO))
		ctx->journal_ioprio = DEFAULT_JOURNAL_IOPRIO;

	sbi->s_inode_readahead_blks = EXT4_DEF_INODE_READAHEAD_BLKS;
	sbi->s_sectors_written_start =
		part_stat_read(sb->s_bdev, sectors[STAT_WRITE]);

	err = ext4_load_super(sb, &logical_sb_block, silent);
	if (err)
		goto out_fail;

	es = sbi->s_es;
	sbi->s_kbytes_written = le64_to_cpu(es->s_kbytes_written);

	err = ext4_init_metadata_csum(sb, es);
	if (err)
		goto failed_mount;

	ext4_set_def_opts(sb, es);

	sbi->s_resuid = make_kuid(&init_user_ns, le16_to_cpu(es->s_def_resuid));
	sbi->s_resgid = make_kgid(&init_user_ns, le16_to_cpu(es->s_def_resgid));

int ext4_map_blocks(handle_t *handle, struct inode *inode,
		    struct ext4_map_blocks *map, int flags)
{
	struct extent_status es;
	int retval;
	int ret = 0;
#ifdef ES_AGGRESSIVE_TEST
	struct ext4_map_blocks orig_map;

	memcpy(&orig_map, map, sizeof(*map));
#endif

	map->m_flags = 0;
	ext_debug(inode, "flag 0x%x, max_blocks %u, logical block %lu\n",
		  flags, map->m_len, (unsigned long) map->m_lblk);

	/*
	 * ext4_map_blocks returns an int, and m_len is an unsigned int
	 */
	if (unlikely(map->m_len > INT_MAX))
		map->m_len = INT_MAX;

	/* We can handle the block number less than EXT_MAX_BLOCKS */
	if (unlikely(map->m_lblk >= EXT_MAX_BLOCKS))
		return -EFSCORRUPTED;

	/* Lookup extent status tree firstly */
	if (!(EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY) &&
	    ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
		if (ext4_es_is_written(&es) || ext4_es_is_unwritten(&es)) {
			map->m_pblk = ext4_es_pblock(&es) +
					map->m_lblk - es.es_lblk;
			map->m_flags |= ext4_es_is_written(&es) ?
					EXT4_MAP_MAPPED : EXT4_MAP_UNWRITTEN;
			retval = es.es_len - (map->m_lblk - es.es_lblk);
			if (retval > map->m_len)
				retval = map->m_len;
			map->m_len = retval;
		} else if (ext4_es_is_delayed(&es) || ext4_es_is_hole(&es)) {

found:
	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
		ret = check_block_validity(inode, map);
		if (ret != 0)
			return ret;
	}

	/* If it is only a block(s) look up */
	if ((flags & EXT4_GET_BLOCKS_CREATE) == 0)
		return retval;

	/*
	 * Returns if the blocks have already allocated
	 *
	 * Note that if blocks have been preallocated
	 * ext4_ext_get_block() returns the create = 0
	 * with buffer head unmapped.
	 */
	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED)
		/*
		 * If we need to convert extent to unwritten
		 * we continue and do the actual work in
		 * ext4_ext_map_blocks()
		 */
		if (!(flags & EXT4_GET_BLOCKS_CONVERT_UNWRITTEN))
			return retval;

	/*
	 * Here we clear m_flags because after allocating an new extent,
	 * it will be set again.
	 */
	map->m_flags &= ~EXT4_MAP_FLAGS;

	/*
	 * New blocks allocate and/or writing to unwritten extent
	 * will possibly result in updating i_data, so we take
	 * the write lock of i_data_sem, and call get_block()
	 * with create == 1 flag.
	 */
	down_write(&EXT4_I(inode)->i_data_sem);

	/*
	 * We need to check for EXT4 here because migrate
	 * could have changed the inode type in between
	 */
	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
		retval = ext4_ext_map_blocks(handle, inode, map, flags);
	} else {
		retval = ext4_ind_map_blocks(handle, inode, map, flags);

	return journal_inode;
}

static int ext4_journal_bmap(journal_t *journal, sector_t *block)
{
	struct ext4_map_blocks map;
	int ret;

	if (journal->j_inode == NULL)
		return 0;

	map.m_lblk = *block;
	map.m_len = 1;
	ret = ext4_map_blocks(NULL, journal->j_inode, &map, 0);
	if (ret <= 0) {
		ext4_msg(journal->j_inode->i_sb, KERN_CRIT,
			 "journal bmap failed: block %llu ret %d\n",
			 *block, ret);
		jbd2_journal_abort(journal, ret ? ret : -EIO);
		return ret;
	}
	*block = map.m_pblk;
	return 0;
}

static journal_t *ext4_open_inode_journal(struct super_block *sb,
					  unsigned int journal_inum)
{
	struct inode *journal_inode;
	journal_t *journal;

	journal_inode = ext4_get_journal_inode(sb, journal_inum);
	if (IS_ERR(journal_inode))
		return ERR_CAST(journal_inode);

	journal = jbd2_journal_init_inode(journal_inode);
	if (IS_ERR(journal)) {
		ext4_msg(sb, KERN_ERR, "Could not load journal inode");
		iput(journal_inode);
		return ERR_CAST(journal);