Re: [PATCH v3 05/22] btrfs-progs: Introduce function to setup temporary superblock

[Liu Bo <bo.li.liu@oracle.com>]

On Fri, Jan 29, 2016 at 01:03:15PM +0800, Qu Wenruo wrote:
> Introduce a new function, setup_temp_super(), to setup temporary super
> for make_btrfs_v2().
> 
> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>  utils.c | 117 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 117 insertions(+)
> 
> diff --git a/utils.c b/utils.c
> index bc10293..ed5476d 100644
> --- a/utils.c
> +++ b/utils.c
> @@ -212,6 +212,98 @@ static int reserve_free_space(struct cache_tree *free_tree, u64 len,
>  	return 0;
>  }
>  
> +static inline int write_temp_super(int fd, struct btrfs_super_block *sb,
> +				   u64 sb_bytenr)
> +{
> +	u32 crc = ~(u32)0;
> +	int ret;
> +
> +	crc = btrfs_csum_data(NULL, (char *)sb + BTRFS_CSUM_SIZE, crc,
> +			      BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
> +	btrfs_csum_final(crc, (char *)&sb->csum[0]);
> +	ret = pwrite(fd, sb, BTRFS_SUPER_INFO_SIZE, sb_bytenr);
> +	if (ret < BTRFS_SUPER_INFO_SIZE)
> +		ret = (ret < 0 ? -errno : -EIO);
> +	else
> +		ret = 0;
> +	return ret;
> +}
> +
> +/*
> + * Setup temporary superblock at cfg->super_bynter
> + * Needed info are extracted from cfg, and root_bytenr, chunk_bytenr
> + *
> + * For now sys chunk array will be empty and dev_item is empty
> + * too.
> + * They will be re-initialized at temp chunk tree setup.
> + */
> +static int setup_temp_super(int fd, struct btrfs_mkfs_config *cfg,
> +			    u64 root_bytenr, u64 chunk_bytenr)
> +{
> +	unsigned char chunk_uuid[BTRFS_UUID_SIZE];
> +	char super_buf[BTRFS_SUPER_INFO_SIZE];
> +	struct btrfs_super_block *super = (struct btrfs_super_block *)super_buf;
> +	int ret;
> +
> +	/*
> +	 * We rely on cfg->chunk_uuid and cfg->fs_uuid to pass uuid
> +	 * for other functions.
> +	 * Caller must allocation space for them
> +	 */
> +	BUG_ON(!cfg->chunk_uuid || !cfg->fs_uuid);
> +	memset(super_buf, 0, BTRFS_SUPER_INFO_SIZE);
> +	cfg->num_bytes = round_down(cfg->num_bytes, cfg->sectorsize);
> +
> +	if (cfg->fs_uuid && *cfg->fs_uuid) {
> +		if (uuid_parse(cfg->fs_uuid, super->fsid) != 0) {
> +			error("cound not parse UUID: %s", cfg->fs_uuid);
> +			ret = -EINVAL;
> +			goto out;
> +		}
> +		if (!test_uuid_unique(cfg->fs_uuid)) {
> +			error("non-unique UUID: %s", cfg->fs_uuid);
> +			ret = -EINVAL;
> +			goto out;
> +		}
> +	} else {
> +		uuid_generate(super->fsid);
> +		uuid_unparse(super->fsid, cfg->fs_uuid);
> +	}
> +	uuid_generate(chunk_uuid);
> +	uuid_unparse(chunk_uuid, cfg->chunk_uuid);
> +
> +	btrfs_set_super_bytenr(super, cfg->super_bytenr);
> +	btrfs_set_super_num_devices(super, 1);
> +	btrfs_set_super_magic(super, BTRFS_MAGIC);
> +	btrfs_set_super_generation(super, 1);
> +	btrfs_set_super_root(super, root_bytenr);
> +	btrfs_set_super_chunk_root(super, chunk_bytenr);
> +	btrfs_set_super_total_bytes(super, cfg->num_bytes);
> +	/*
> +	 * Temporary btrfs will only has 6 tree roots:
> +	 * chunk tree, root tree, extent_tree, device tree, fs tree
> +	 * and csum tree.
> +	 */
> +	btrfs_set_super_bytes_used(super, 6 * cfg->nodesize);
> +	btrfs_set_super_sectorsize(super, cfg->sectorsize);
> +	btrfs_set_super_leafsize(super, cfg->nodesize);
> +	btrfs_set_super_nodesize(super, cfg->nodesize);
> +	btrfs_set_super_stripesize(super, cfg->stripesize);
> +	btrfs_set_super_csum_type(super, BTRFS_CSUM_TYPE_CRC32);
> +	btrfs_set_super_chunk_root(super, chunk_bytenr);
> +	btrfs_set_super_cache_generation(super, -1);
> +	btrfs_set_super_incompat_flags(super, cfg->features);
> +	if (cfg->label)
> +		strncpy(super->label, cfg->label, BTRFS_LABEL_SIZE - 1);

Why not use __strncpy_null?

Thanks,

-liubo

> +
> +	/* Sys chunk array will be re-initialized at chunk tree init time */
> +	super->sys_chunk_array_size = 0;
> +
> +	ret = write_temp_super(fd, super, cfg->super_bytenr);
> +out:
> +	return ret;
> +}
> +
>  /*
>   * Improved version of make_btrfs().
>   *
> @@ -230,6 +322,10 @@ static int make_convert_btrfs(int fd, struct btrfs_mkfs_config *cfg,
>  	struct cache_tree *used = &cctx->used;
>  	u64 sys_chunk_start;
>  	u64 meta_chunk_start;
> +	/* chunk tree bytenr, in system chunk */
> +	u64 chunk_bytenr;
> +	/* metadata trees bytenr, in metadata chunk */
> +	u64 root_bytenr;
>  	int ret;
>  
>  	/* Shouldn't happen */
> @@ -260,6 +356,27 @@ static int make_convert_btrfs(int fd, struct btrfs_mkfs_config *cfg,
>  	if (ret < 0)
>  		goto out;
>  
> +	/*
> +	 * Inside the allocate metadata chunk, its layout will be:
> +	 *  | offset		| contents	|
> +	 *  -------------------------------------
> +	 *  | +0		| tree root	|
> +	 *  | +nodesize		| extent root	|
> +	 *  | +nodesize * 2	| device root	|
> +	 *  | +nodesize * 3	| fs tree	|
> +	 *  | +nodesize * 4	| csum tree	|
> +	 *  -------------------------------------
> +	 * Inside the allocated system chunk, its layout will be:
> +	 *  | offset		| contents	|
> +	 *  -------------------------------------
> +	 *  | +0		| chunk root	|
> +	 *  -------------------------------------
> +	 */
> +	chunk_bytenr = sys_chunk_start;
> +	root_bytenr = meta_chunk_start;
> +	ret = setup_temp_super(fd, cfg, root_bytenr, chunk_bytenr);
> +	if (ret < 0)
> +		goto out;
>  out:
>  	return ret;
>  }
> -- 
> 2.7.0
> 
> 
> 
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