diff mbox

btrfs-progs: mkfs: Replace number with enum

Message ID 20170628095924.3276-1-gujx@cn.fujitsu.com (mailing list archive)
State New, archived
Headers show

Commit Message

Gu Jinxiang June 28, 2017, 9:59 a.m. UTC 
For code maintainability and scalability,
replace hardcoded constant with a meaningful enum.

Signed-off-by: Gu Jinxiang <gujx@cn.fujitsu.com>
---
 mkfs/common.c | 47 ++++++++++++++++++++++++-----------------------
 mkfs/common.h | 14 +++++++++++++-
 2 files changed, 37 insertions(+), 24 deletions(-)

Comments

David Sterba Aug. 21, 2017, 5:39 p.m. UTC | #1 
On Wed, Jun 28, 2017 at 05:59:24PM +0800, Gu Jinxiang wrote:
> For code maintainability and scalability,
> replace hardcoded constant with a meaningful enum.
> 
> Signed-off-by: Gu Jinxiang <gujx@cn.fujitsu.com>

Sorry for late reply. Patch applied with some tweaks, the added enum
names are too generic, so I've added some prefix.
> ---
>  mkfs/common.c | 47 ++++++++++++++++++++++++-----------------------
>  mkfs/common.h | 14 +++++++++++++-
>  2 files changed, 37 insertions(+), 24 deletions(-)
> 
> diff --git a/mkfs/common.c b/mkfs/common.c
> index e4785c5..f34c4eb 100644
> --- a/mkfs/common.c
> +++ b/mkfs/common.c
> @@ -93,18 +93,18 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>  	uuid_generate(super.dev_item.uuid);
>  	uuid_generate(chunk_tree_uuid);
>  
> -	cfg->blocks[0] = BTRFS_SUPER_INFO_OFFSET;
> -	for (i = 1; i < 7; i++) {
> +	cfg->blocks[SUPER_BLOCK] = BTRFS_SUPER_INFO_OFFSET;
> +	for (i = 1; i < BLOCK_COUNT; i++) {
>  		cfg->blocks[i] = BTRFS_SUPER_INFO_OFFSET + 1024 * 1024 +
>  			cfg->nodesize * i;
>  	}
>  
> -	btrfs_set_super_bytenr(&super, cfg->blocks[0]);
> +	btrfs_set_super_bytenr(&super, cfg->blocks[SUPER_BLOCK]);
>  	btrfs_set_super_num_devices(&super, 1);
>  	btrfs_set_super_magic(&super, BTRFS_MAGIC_PARTIAL);
>  	btrfs_set_super_generation(&super, 1);
> -	btrfs_set_super_root(&super, cfg->blocks[1]);
> -	btrfs_set_super_chunk_root(&super, cfg->blocks[3]);
> +	btrfs_set_super_root(&super, cfg->blocks[ROOT_TREE]);
> +	btrfs_set_super_chunk_root(&super, cfg->blocks[CHUNK_TREE]);
>  	btrfs_set_super_total_bytes(&super, num_bytes);
>  	btrfs_set_super_bytes_used(&super, 6 * cfg->nodesize);
>  	btrfs_set_super_sectorsize(&super, cfg->sectorsize);
> @@ -121,7 +121,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>  	/* create the tree of root objects */
>  	memset(buf->data, 0, cfg->nodesize);
>  	buf->len = cfg->nodesize;
> -	btrfs_set_header_bytenr(buf, cfg->blocks[1]);
> +	btrfs_set_header_bytenr(buf, cfg->blocks[ROOT_TREE]);
>  	btrfs_set_header_nritems(buf, 4);
>  	btrfs_set_header_generation(buf, 1);
>  	btrfs_set_header_backref_rev(buf, BTRFS_MIXED_BACKREF_REV);
> @@ -151,7 +151,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>  	nritems = 0;
>  
>  	itemoff = __BTRFS_LEAF_DATA_SIZE(cfg->nodesize) - sizeof(root_item);
> -	btrfs_set_root_bytenr(&root_item, cfg->blocks[2]);
> +	btrfs_set_root_bytenr(&root_item, cfg->blocks[EXTENT_TREE]);
>  	btrfs_set_disk_key_objectid(&disk_key, BTRFS_EXTENT_TREE_OBJECTID);
>  	btrfs_set_item_key(buf, &disk_key, nritems);
>  	btrfs_set_item_offset(buf, btrfs_item_nr(nritems), itemoff);
> @@ -162,7 +162,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>  	nritems++;
>  
>  	itemoff = itemoff - sizeof(root_item);
> -	btrfs_set_root_bytenr(&root_item, cfg->blocks[4]);
> +	btrfs_set_root_bytenr(&root_item, cfg->blocks[DEV_TREE]);
>  	btrfs_set_disk_key_objectid(&disk_key, BTRFS_DEV_TREE_OBJECTID);
>  	btrfs_set_item_key(buf, &disk_key, nritems);
>  	btrfs_set_item_offset(buf, btrfs_item_nr(nritems), itemoff);
> @@ -174,7 +174,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>  	nritems++;
>  
>  	itemoff = itemoff - sizeof(root_item);
> -	btrfs_set_root_bytenr(&root_item, cfg->blocks[5]);
> +	btrfs_set_root_bytenr(&root_item, cfg->blocks[FS_TREE]);
>  	btrfs_set_disk_key_objectid(&disk_key, BTRFS_FS_TREE_OBJECTID);
>  	btrfs_set_item_key(buf, &disk_key, nritems);
>  	btrfs_set_item_offset(buf, btrfs_item_nr(nritems), itemoff);
> @@ -186,7 +186,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>  	nritems++;
>  
>  	itemoff = itemoff - sizeof(root_item);
> -	btrfs_set_root_bytenr(&root_item, cfg->blocks[6]);
> +	btrfs_set_root_bytenr(&root_item, cfg->blocks[CSUM_TREE]);
>  	btrfs_set_disk_key_objectid(&disk_key, BTRFS_CSUM_TREE_OBJECTID);
>  	btrfs_set_item_key(buf, &disk_key, nritems);
>  	btrfs_set_item_offset(buf, btrfs_item_nr(nritems), itemoff);
> @@ -199,7 +199,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>  
>  
>  	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
> -	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[1]);
> +	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[ROOT_TREE]);
>  	if (ret != cfg->nodesize) {
>  		ret = (ret < 0 ? -errno : -EIO);
>  		goto out;
> @@ -210,7 +210,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>  		cfg->nodesize - sizeof(struct btrfs_header));
>  	nritems = 0;
>  	itemoff = __BTRFS_LEAF_DATA_SIZE(cfg->nodesize);
> -	for (i = 1; i < 7; i++) {
> +	for (i = 1; i < BLOCK_COUNT; i++) {
>  		item_size = sizeof(struct btrfs_extent_item);
>  		if (!skinny_metadata)
>  			item_size += sizeof(struct btrfs_tree_block_info);
> @@ -267,11 +267,11 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>  		btrfs_set_item_size(buf, btrfs_item_nr(nritems), 0);
>  		nritems++;
>  	}
> -	btrfs_set_header_bytenr(buf, cfg->blocks[2]);
> +	btrfs_set_header_bytenr(buf, cfg->blocks[EXTENT_TREE]);
>  	btrfs_set_header_owner(buf, BTRFS_EXTENT_TREE_OBJECTID);
>  	btrfs_set_header_nritems(buf, nritems);
>  	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
> -	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[2]);
> +	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[EXTENT_TREE]);
>  	if (ret != cfg->nodesize) {
>  		ret = (ret < 0 ? -errno : -EIO);
>  		goto out;
> @@ -354,11 +354,11 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>  	ptr += item_size;
>  	btrfs_set_super_sys_array_size(&super, array_size);
>  
> -	btrfs_set_header_bytenr(buf, cfg->blocks[3]);
> +	btrfs_set_header_bytenr(buf, cfg->blocks[CHUNK_TREE]);
>  	btrfs_set_header_owner(buf, BTRFS_CHUNK_TREE_OBJECTID);
>  	btrfs_set_header_nritems(buf, nritems);
>  	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
> -	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[3]);
> +	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[CHUNK_TREE]);
>  	if (ret != cfg->nodesize) {
>  		ret = (ret < 0 ? -errno : -EIO);
>  		goto out;
> @@ -393,11 +393,11 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>  				    BTRFS_MKFS_SYSTEM_GROUP_SIZE);
>  	nritems++;
>  
> -	btrfs_set_header_bytenr(buf, cfg->blocks[4]);
> +	btrfs_set_header_bytenr(buf, cfg->blocks[DEV_TREE]);
>  	btrfs_set_header_owner(buf, BTRFS_DEV_TREE_OBJECTID);
>  	btrfs_set_header_nritems(buf, nritems);
>  	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
> -	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[4]);
> +	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[DEV_TREE]);
>  	if (ret != cfg->nodesize) {
>  		ret = (ret < 0 ? -errno : -EIO);
>  		goto out;
> @@ -406,11 +406,11 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>  	/* create the FS root */
>  	memset(buf->data + sizeof(struct btrfs_header), 0,
>  		cfg->nodesize - sizeof(struct btrfs_header));
> -	btrfs_set_header_bytenr(buf, cfg->blocks[5]);
> +	btrfs_set_header_bytenr(buf, cfg->blocks[FS_TREE]);
>  	btrfs_set_header_owner(buf, BTRFS_FS_TREE_OBJECTID);
>  	btrfs_set_header_nritems(buf, 0);
>  	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
> -	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[5]);
> +	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[FS_TREE]);
>  	if (ret != cfg->nodesize) {
>  		ret = (ret < 0 ? -errno : -EIO);
>  		goto out;
> @@ -418,11 +418,11 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>  	/* finally create the csum root */
>  	memset(buf->data + sizeof(struct btrfs_header), 0,
>  		cfg->nodesize - sizeof(struct btrfs_header));
> -	btrfs_set_header_bytenr(buf, cfg->blocks[6]);
> +	btrfs_set_header_bytenr(buf, cfg->blocks[CSUM_TREE]);
>  	btrfs_set_header_owner(buf, BTRFS_CSUM_TREE_OBJECTID);
>  	btrfs_set_header_nritems(buf, 0);
>  	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
> -	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[6]);
> +	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[CSUM_TREE]);
>  	if (ret != cfg->nodesize) {
>  		ret = (ret < 0 ? -errno : -EIO);
>  		goto out;
> @@ -433,7 +433,8 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>  	memcpy(buf->data, &super, sizeof(super));
>  	buf->len = BTRFS_SUPER_INFO_SIZE;
>  	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
> -	ret = pwrite(fd, buf->data, BTRFS_SUPER_INFO_SIZE, cfg->blocks[0]);
> +	ret = pwrite(fd, buf->data, BTRFS_SUPER_INFO_SIZE,
> +			cfg->blocks[SUPER_BLOCK]);
>  	if (ret != BTRFS_SUPER_INFO_SIZE) {
>  		ret = (ret < 0 ? -errno : -EIO);
>  		goto out;
> diff --git a/mkfs/common.h b/mkfs/common.h
> index 666a75b..4d8a314 100644
> --- a/mkfs/common.h
> +++ b/mkfs/common.h
> @@ -28,6 +28,18 @@
>  #define BTRFS_MKFS_SYSTEM_GROUP_SIZE SZ_4M
>  #define BTRFS_MKFS_SMALL_VOLUME_SIZE SZ_1G
>  
> +/* roots: root tree, extent tree, chunk tree, dev tree, fs tree, csum tree */
> +enum btrfs_mkfs_block {
> +	SUPER_BLOCK = 0,
> +	ROOT_TREE,
> +	EXTENT_TREE,
> +	CHUNK_TREE,
> +	DEV_TREE,
> +	FS_TREE,
> +	CSUM_TREE,
> +	BLOCK_COUNT
> +};
> +
>  struct btrfs_mkfs_config {
>  	/* Label of the new filesystem */
>  	const char *label;
> @@ -43,7 +55,7 @@ struct btrfs_mkfs_config {
>  	/* Output fields, set during creation */
>  
>  	/* Logical addresses of superblock [0] and other tree roots */
> -	u64 blocks[8];
> +	u64 blocks[BLOCK_COUNT];
>  	char fs_uuid[BTRFS_UUID_UNPARSED_SIZE];
>  	char chunk_uuid[BTRFS_UUID_UNPARSED_SIZE];
>  
> -- 
> 2.9.4
> 
> 
> 
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David Sterba Aug. 22, 2017, 2:04 p.m. UTC | #2 
On Mon, Aug 21, 2017 at 07:39:49PM +0200, David Sterba wrote:
> > +/* roots: root tree, extent tree, chunk tree, dev tree, fs tree, csum tree */
> > +enum btrfs_mkfs_block {
> > +	SUPER_BLOCK = 0,
> > +	ROOT_TREE,
> > +	EXTENT_TREE,
> > +	CHUNK_TREE,
> > +	DEV_TREE,
> > +	FS_TREE,
> > +	CSUM_TREE,
> > +	BLOCK_COUNT

BLOCK_COUNT is 7

> > +};
> > +
> >  struct btrfs_mkfs_config {
> >  	/* Label of the new filesystem */
> >  	const char *label;
> > @@ -43,7 +55,7 @@ struct btrfs_mkfs_config {
> >  	/* Output fields, set during creation */
> >  
> >  	/* Logical addresses of superblock [0] and other tree roots */
> > -	u64 blocks[8];
> > +	u64 blocks[BLOCK_COUNT];

This replaces 8 with 7 then, so the fs_uuid gets overwritten, can be
also caught by simply running 'make test-mkfs'.

> >  	char fs_uuid[BTRFS_UUID_UNPARSED_SIZE];
> >  	char chunk_uuid[BTRFS_UUID_UNPARSED_SIZE];
> >  
> > -- 
> > 2.9.4
> > 
> > 
> > 
> > --
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> > the body of a message to majordomo@vger.kernel.org
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Gu Jinxiang Aug. 23, 2017, 2:32 a.m. UTC | #3 
> -----Original Message-----

> From: David Sterba [mailto:dsterba@suse.cz]

> Sent: Tuesday, August 22, 2017 10:04 PM

> To: Gu, Jinxiang/顾 金香 <gujx@cn.fujitsu.com>; linux-btrfs@vger.kernel.org

> Subject: Re: [PATCH] btrfs-progs: mkfs: Replace number with enum

> 

> On Mon, Aug 21, 2017 at 07:39:49PM +0200, David Sterba wrote:

> > > +/* roots: root tree, extent tree, chunk tree, dev tree, fs tree,

> > > +csum tree */ enum btrfs_mkfs_block {

> > > +	SUPER_BLOCK = 0,

> > > +	ROOT_TREE,

> > > +	EXTENT_TREE,

> > > +	CHUNK_TREE,

> > > +	DEV_TREE,

> > > +	FS_TREE,

> > > +	CSUM_TREE,

> > > +	BLOCK_COUNT

> 

> BLOCK_COUNT is 7


> 

> > > +};

> > > +

> > >  struct btrfs_mkfs_config {

> > >  	/* Label of the new filesystem */

> > >  	const char *label;

> > > @@ -43,7 +55,7 @@ struct btrfs_mkfs_config {

> > >  	/* Output fields, set during creation */

> > >

> > >  	/* Logical addresses of superblock [0] and other tree roots */

> > > -	u64 blocks[8];

> > > +	u64 blocks[BLOCK_COUNT];

> 

> This replaces 8 with 7 then, so the fs_uuid gets overwritten, can be also caught by simply running 'make test-mkfs'.


I made this change because block[7] is never used. I have run 'make test-mkfs', and get no error.
Why need to make a u64 left before fs_uuid?

> 

> > >  	char fs_uuid[BTRFS_UUID_UNPARSED_SIZE];

> > >  	char chunk_uuid[BTRFS_UUID_UNPARSED_SIZE];

> > >

> > > --

> > > 2.9.4

> > >

> > >

> > >

> > > --

> > > To unsubscribe from this list: send the line "unsubscribe

> > > linux-btrfs" in the body of a message to majordomo@vger.kernel.org

> > > More majordomo info at  http://vger.kernel.org/majordomo-info.html

> > --

> > To unsubscribe from this list: send the line "unsubscribe linux-btrfs"

> > in the body of a message to majordomo@vger.kernel.org More majordomo

> > info at  http://vger.kernel.org/majordomo-info.html

>
diff mbox

Patch

diff --git a/mkfs/common.c b/mkfs/common.c
index e4785c5..f34c4eb 100644
--- a/mkfs/common.c
+++ b/mkfs/common.c
@@ -93,18 +93,18 @@  int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	uuid_generate(super.dev_item.uuid);
 	uuid_generate(chunk_tree_uuid);
 
-	cfg->blocks[0] = BTRFS_SUPER_INFO_OFFSET;
-	for (i = 1; i < 7; i++) {
+	cfg->blocks[SUPER_BLOCK] = BTRFS_SUPER_INFO_OFFSET;
+	for (i = 1; i < BLOCK_COUNT; i++) {
 		cfg->blocks[i] = BTRFS_SUPER_INFO_OFFSET + 1024 * 1024 +
 			cfg->nodesize * i;
 	}
 
-	btrfs_set_super_bytenr(&super, cfg->blocks[0]);
+	btrfs_set_super_bytenr(&super, cfg->blocks[SUPER_BLOCK]);
 	btrfs_set_super_num_devices(&super, 1);
 	btrfs_set_super_magic(&super, BTRFS_MAGIC_PARTIAL);
 	btrfs_set_super_generation(&super, 1);
-	btrfs_set_super_root(&super, cfg->blocks[1]);
-	btrfs_set_super_chunk_root(&super, cfg->blocks[3]);
+	btrfs_set_super_root(&super, cfg->blocks[ROOT_TREE]);
+	btrfs_set_super_chunk_root(&super, cfg->blocks[CHUNK_TREE]);
 	btrfs_set_super_total_bytes(&super, num_bytes);
 	btrfs_set_super_bytes_used(&super, 6 * cfg->nodesize);
 	btrfs_set_super_sectorsize(&super, cfg->sectorsize);
@@ -121,7 +121,7 @@  int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	/* create the tree of root objects */
 	memset(buf->data, 0, cfg->nodesize);
 	buf->len = cfg->nodesize;
-	btrfs_set_header_bytenr(buf, cfg->blocks[1]);
+	btrfs_set_header_bytenr(buf, cfg->blocks[ROOT_TREE]);
 	btrfs_set_header_nritems(buf, 4);
 	btrfs_set_header_generation(buf, 1);
 	btrfs_set_header_backref_rev(buf, BTRFS_MIXED_BACKREF_REV);
@@ -151,7 +151,7 @@  int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	nritems = 0;
 
 	itemoff = __BTRFS_LEAF_DATA_SIZE(cfg->nodesize) - sizeof(root_item);
-	btrfs_set_root_bytenr(&root_item, cfg->blocks[2]);
+	btrfs_set_root_bytenr(&root_item, cfg->blocks[EXTENT_TREE]);
 	btrfs_set_disk_key_objectid(&disk_key, BTRFS_EXTENT_TREE_OBJECTID);
 	btrfs_set_item_key(buf, &disk_key, nritems);
 	btrfs_set_item_offset(buf, btrfs_item_nr(nritems), itemoff);
@@ -162,7 +162,7 @@  int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	nritems++;
 
 	itemoff = itemoff - sizeof(root_item);
-	btrfs_set_root_bytenr(&root_item, cfg->blocks[4]);
+	btrfs_set_root_bytenr(&root_item, cfg->blocks[DEV_TREE]);
 	btrfs_set_disk_key_objectid(&disk_key, BTRFS_DEV_TREE_OBJECTID);
 	btrfs_set_item_key(buf, &disk_key, nritems);
 	btrfs_set_item_offset(buf, btrfs_item_nr(nritems), itemoff);
@@ -174,7 +174,7 @@  int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	nritems++;
 
 	itemoff = itemoff - sizeof(root_item);
-	btrfs_set_root_bytenr(&root_item, cfg->blocks[5]);
+	btrfs_set_root_bytenr(&root_item, cfg->blocks[FS_TREE]);
 	btrfs_set_disk_key_objectid(&disk_key, BTRFS_FS_TREE_OBJECTID);
 	btrfs_set_item_key(buf, &disk_key, nritems);
 	btrfs_set_item_offset(buf, btrfs_item_nr(nritems), itemoff);
@@ -186,7 +186,7 @@  int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	nritems++;
 
 	itemoff = itemoff - sizeof(root_item);
-	btrfs_set_root_bytenr(&root_item, cfg->blocks[6]);
+	btrfs_set_root_bytenr(&root_item, cfg->blocks[CSUM_TREE]);
 	btrfs_set_disk_key_objectid(&disk_key, BTRFS_CSUM_TREE_OBJECTID);
 	btrfs_set_item_key(buf, &disk_key, nritems);
 	btrfs_set_item_offset(buf, btrfs_item_nr(nritems), itemoff);
@@ -199,7 +199,7 @@  int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 
 
 	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
-	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[1]);
+	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[ROOT_TREE]);
 	if (ret != cfg->nodesize) {
 		ret = (ret < 0 ? -errno : -EIO);
 		goto out;
@@ -210,7 +210,7 @@  int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 		cfg->nodesize - sizeof(struct btrfs_header));
 	nritems = 0;
 	itemoff = __BTRFS_LEAF_DATA_SIZE(cfg->nodesize);
-	for (i = 1; i < 7; i++) {
+	for (i = 1; i < BLOCK_COUNT; i++) {
 		item_size = sizeof(struct btrfs_extent_item);
 		if (!skinny_metadata)
 			item_size += sizeof(struct btrfs_tree_block_info);
@@ -267,11 +267,11 @@  int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 		btrfs_set_item_size(buf, btrfs_item_nr(nritems), 0);
 		nritems++;
 	}
-	btrfs_set_header_bytenr(buf, cfg->blocks[2]);
+	btrfs_set_header_bytenr(buf, cfg->blocks[EXTENT_TREE]);
 	btrfs_set_header_owner(buf, BTRFS_EXTENT_TREE_OBJECTID);
 	btrfs_set_header_nritems(buf, nritems);
 	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
-	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[2]);
+	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[EXTENT_TREE]);
 	if (ret != cfg->nodesize) {
 		ret = (ret < 0 ? -errno : -EIO);
 		goto out;
@@ -354,11 +354,11 @@  int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	ptr += item_size;
 	btrfs_set_super_sys_array_size(&super, array_size);
 
-	btrfs_set_header_bytenr(buf, cfg->blocks[3]);
+	btrfs_set_header_bytenr(buf, cfg->blocks[CHUNK_TREE]);
 	btrfs_set_header_owner(buf, BTRFS_CHUNK_TREE_OBJECTID);
 	btrfs_set_header_nritems(buf, nritems);
 	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
-	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[3]);
+	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[CHUNK_TREE]);
 	if (ret != cfg->nodesize) {
 		ret = (ret < 0 ? -errno : -EIO);
 		goto out;
@@ -393,11 +393,11 @@  int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 				    BTRFS_MKFS_SYSTEM_GROUP_SIZE);
 	nritems++;
 
-	btrfs_set_header_bytenr(buf, cfg->blocks[4]);
+	btrfs_set_header_bytenr(buf, cfg->blocks[DEV_TREE]);
 	btrfs_set_header_owner(buf, BTRFS_DEV_TREE_OBJECTID);
 	btrfs_set_header_nritems(buf, nritems);
 	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
-	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[4]);
+	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[DEV_TREE]);
 	if (ret != cfg->nodesize) {
 		ret = (ret < 0 ? -errno : -EIO);
 		goto out;
@@ -406,11 +406,11 @@  int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	/* create the FS root */
 	memset(buf->data + sizeof(struct btrfs_header), 0,
 		cfg->nodesize - sizeof(struct btrfs_header));
-	btrfs_set_header_bytenr(buf, cfg->blocks[5]);
+	btrfs_set_header_bytenr(buf, cfg->blocks[FS_TREE]);
 	btrfs_set_header_owner(buf, BTRFS_FS_TREE_OBJECTID);
 	btrfs_set_header_nritems(buf, 0);
 	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
-	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[5]);
+	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[FS_TREE]);
 	if (ret != cfg->nodesize) {
 		ret = (ret < 0 ? -errno : -EIO);
 		goto out;
@@ -418,11 +418,11 @@  int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	/* finally create the csum root */
 	memset(buf->data + sizeof(struct btrfs_header), 0,
 		cfg->nodesize - sizeof(struct btrfs_header));
-	btrfs_set_header_bytenr(buf, cfg->blocks[6]);
+	btrfs_set_header_bytenr(buf, cfg->blocks[CSUM_TREE]);
 	btrfs_set_header_owner(buf, BTRFS_CSUM_TREE_OBJECTID);
 	btrfs_set_header_nritems(buf, 0);
 	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
-	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[6]);
+	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[CSUM_TREE]);
 	if (ret != cfg->nodesize) {
 		ret = (ret < 0 ? -errno : -EIO);
 		goto out;
@@ -433,7 +433,8 @@  int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	memcpy(buf->data, &super, sizeof(super));
 	buf->len = BTRFS_SUPER_INFO_SIZE;
 	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
-	ret = pwrite(fd, buf->data, BTRFS_SUPER_INFO_SIZE, cfg->blocks[0]);
+	ret = pwrite(fd, buf->data, BTRFS_SUPER_INFO_SIZE,
+			cfg->blocks[SUPER_BLOCK]);
 	if (ret != BTRFS_SUPER_INFO_SIZE) {
 		ret = (ret < 0 ? -errno : -EIO);
 		goto out;
diff --git a/mkfs/common.h b/mkfs/common.h
index 666a75b..4d8a314 100644
--- a/mkfs/common.h
+++ b/mkfs/common.h
@@ -28,6 +28,18 @@ 
 #define BTRFS_MKFS_SYSTEM_GROUP_SIZE SZ_4M
 #define BTRFS_MKFS_SMALL_VOLUME_SIZE SZ_1G
 
+/* roots: root tree, extent tree, chunk tree, dev tree, fs tree, csum tree */
+enum btrfs_mkfs_block {
+	SUPER_BLOCK = 0,
+	ROOT_TREE,
+	EXTENT_TREE,
+	CHUNK_TREE,
+	DEV_TREE,
+	FS_TREE,
+	CSUM_TREE,
+	BLOCK_COUNT
+};
+
 struct btrfs_mkfs_config {
 	/* Label of the new filesystem */
 	const char *label;
@@ -43,7 +55,7 @@  struct btrfs_mkfs_config {
 	/* Output fields, set during creation */
 
 	/* Logical addresses of superblock [0] and other tree roots */
-	u64 blocks[8];
+	u64 blocks[BLOCK_COUNT];
 	char fs_uuid[BTRFS_UUID_UNPARSED_SIZE];
 	char chunk_uuid[BTRFS_UUID_UNPARSED_SIZE];