diff mbox series

[v4,1/2] btrfs: Move on-disk structure definition to btrfs_tree.h

Message ID 20200415084113.64378-2-wqu@suse.com (mailing list archive)
State New, archived
Headers show
Series btrfs: Reformat and make btrfs_tree.h self-contained | expand

Commit Message

Qu Wenruo April 15, 2020, 8:41 a.m. UTC
These structures all are on-disk format. Move them to btrfs_tree.h

This allows us to sync the header to different projects, who need to
read btrfs filesystem, like U-boot, grub.

With this modification, all on-disk format is definite in btrfs_tree.h,
and can be easily synced to other projects.

This move includes:
- btrfs magic
  It's a surprise that it's not even definied in btrfs_tree.h

- tree block max level
  Move it before btrfs_header definition.

- tree block backref revision
- btrfs_header structure
- btrfs_root_backup structure
- btrfs_super_block structure
- BTRFS_FEATURE_* flags
- BTRFS_(FSID|UUID|LABEL)_SIZE macros
- BTRFS_MAX_METADATA_BLOCKSIZE macro
- BTRFS_NAME_LEN macro

- btrfs_item structure
- btrfs_leaf structure
- btrfs_key_ptr structure
- btrfs_node structure

- btrfs_dev_stat_values
  Since on-disk format btrfs_dev_stats_item needs it.

- BTRFS_INODE_* flags
- BTRFS_QGROUP_LIMIT_* flags

- enum btrfs_compression_type
  With this movement, btrfs_tree is completely self-contained.
  It only needs <linux/types.h> header.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/compression.h          |   9 +-
 fs/btrfs/ctree.h                | 246 -----------------------
 include/uapi/linux/btrfs.h      |  74 +------
 include/uapi/linux/btrfs_tree.h | 338 +++++++++++++++++++++++++++++++-
 4 files changed, 336 insertions(+), 331 deletions(-)

Comments

Christoph Hellwig April 21, 2020, 11:31 a.m. UTC | #1
On Wed, Apr 15, 2020 at 04:41:12PM +0800, Qu Wenruo wrote:
> These structures all are on-disk format. Move them to btrfs_tree.h
> 
> This allows us to sync the header to different projects, who need to
> read btrfs filesystem, like U-boot, grub.

Please use a separate header for that.  btrfs_tree.h is a UAPI header
with strict ABI guarantees.  Just add a fs/btrfs/btrfs_format.h that
can be copied into the projects where is needed.
Qu Wenruo April 21, 2020, 11:41 a.m. UTC | #2
On 2020/4/21 下午7:31, Christoph Hellwig wrote:
> On Wed, Apr 15, 2020 at 04:41:12PM +0800, Qu Wenruo wrote:
>> These structures all are on-disk format. Move them to btrfs_tree.h
>>
>> This allows us to sync the header to different projects, who need to
>> read btrfs filesystem, like U-boot, grub.
> 
> Please use a separate header for that.  btrfs_tree.h is a UAPI header
> with strict ABI guarantees.  Just add a fs/btrfs/btrfs_format.h that
> can be copied into the projects where is needed.
> 
Doesn't on-disk format itself need strict ABI guarantees?

Thus it looks like the perfect location for on-disk format definitions.

Thanks,
Qu
kernel test robot April 23, 2020, 11:32 a.m. UTC | #3
Hi Qu,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on v5.7-rc1]
[also build test ERROR on next-20200423]
[cannot apply to btrfs/next]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Qu-Wenruo/btrfs-Reformat-and-make-btrfs_tree-h-self-contained/20200416-023848
base:    8f3d9f354286745c751374f5f1fcafee6b3f3136
config: x86_64-randconfig-s1-20200423 (attached as .config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   In file included from ./usr/include/linux/btrfs.h:24:0,
                    from <command-line>:32:
>> ./usr/include/linux/btrfs_tree.h:1110:2: error: unknown type name 'u8'
     u8 tree_root_level;
     ^~
   ./usr/include/linux/btrfs_tree.h:1111:2: error: unknown type name 'u8'
     u8 chunk_root_level;
     ^~
   ./usr/include/linux/btrfs_tree.h:1112:2: error: unknown type name 'u8'
     u8 extent_root_level;
     ^~
   ./usr/include/linux/btrfs_tree.h:1113:2: error: unknown type name 'u8'
     u8 fs_root_level;
     ^~
   ./usr/include/linux/btrfs_tree.h:1114:2: error: unknown type name 'u8'
     u8 dev_root_level;
     ^~
   ./usr/include/linux/btrfs_tree.h:1115:2: error: unknown type name 'u8'
     u8 csum_root_level;
     ^~
   ./usr/include/linux/btrfs_tree.h:1117:2: error: unknown type name 'u8'
     u8 unused_8[10];
     ^~
   ./usr/include/linux/btrfs_tree.h:1133:2: error: unknown type name 'u8'
     u8 csum[BTRFS_CSUM_SIZE];
     ^~
   ./usr/include/linux/btrfs_tree.h:1135:2: error: unknown type name 'u8'
     u8 fsid[BTRFS_FSID_SIZE];
     ^~
   ./usr/include/linux/btrfs_tree.h:1162:2: error: unknown type name 'u8'
     u8 root_level;
     ^~
   ./usr/include/linux/btrfs_tree.h:1163:2: error: unknown type name 'u8'
     u8 chunk_root_level;
     ^~
   ./usr/include/linux/btrfs_tree.h:1164:2: error: unknown type name 'u8'
     u8 log_root_level;
     ^~
   ./usr/include/linux/btrfs_tree.h:1173:2: error: unknown type name 'u8'
     u8 metadata_uuid[BTRFS_FSID_SIZE];
     ^~
   ./usr/include/linux/btrfs_tree.h:1177:2: error: unknown type name 'u8'
     u8 sys_chunk_array[BTRFS_SYSTEM_CHUNK_ARRAY_SIZE];
     ^~
   ./usr/include/linux/btrfs_tree.h:1268:2: error: unknown type name 'u8'
     u8 csum[BTRFS_CSUM_SIZE];
     ^~
   ./usr/include/linux/btrfs_tree.h:1269:2: error: unknown type name 'u8'
     u8 fsid[BTRFS_FSID_SIZE]; /* FS specific uuid */
     ^~
   ./usr/include/linux/btrfs_tree.h:1274:2: error: unknown type name 'u8'
     u8 chunk_tree_uuid[BTRFS_UUID_SIZE];
     ^~
   ./usr/include/linux/btrfs_tree.h:1278:2: error: unknown type name 'u8'
     u8 level;
     ^~

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
David Sterba April 24, 2020, 8:24 p.m. UTC | #4
On Tue, Apr 21, 2020 at 07:41:40PM +0800, Qu Wenruo wrote:
> 
> 
> On 2020/4/21 下午7:31, Christoph Hellwig wrote:
> > On Wed, Apr 15, 2020 at 04:41:12PM +0800, Qu Wenruo wrote:
> >> These structures all are on-disk format. Move them to btrfs_tree.h
> >>
> >> This allows us to sync the header to different projects, who need to
> >> read btrfs filesystem, like U-boot, grub.
> > 
> > Please use a separate header for that.  btrfs_tree.h is a UAPI header
> > with strict ABI guarantees.  Just add a fs/btrfs/btrfs_format.h that
> > can be copied into the projects where is needed.
> > 
> Doesn't on-disk format itself need strict ABI guarantees?
> 
> Thus it looks like the perfect location for on-disk format definitions.

Right now I'm not sure if it's a good idea to put the on-disk format to
the UAPI path or not. The exported code is to support the ioctls,
there's an overlap with the on-disk format but providing all the on-disk
structures for general might become an unnecessry burden.

We know that there's a small number of projects that want to sync the
on-disk format so I don't think it's going to be a problem for them to
use a private header.
Christoph Hellwig April 25, 2020, 7:14 a.m. UTC | #5
On Fri, Apr 24, 2020 at 10:24:45PM +0200, David Sterba wrote:
> On Tue, Apr 21, 2020 at 07:41:40PM +0800, Qu Wenruo wrote:
> > 
> > 
> > On 2020/4/21 下午7:31, Christoph Hellwig wrote:
> > > On Wed, Apr 15, 2020 at 04:41:12PM +0800, Qu Wenruo wrote:
> > >> These structures all are on-disk format. Move them to btrfs_tree.h
> > >>
> > >> This allows us to sync the header to different projects, who need to
> > >> read btrfs filesystem, like U-boot, grub.
> > > 
> > > Please use a separate header for that.  btrfs_tree.h is a UAPI header
> > > with strict ABI guarantees.  Just add a fs/btrfs/btrfs_format.h that
> > > can be copied into the projects where is needed.
> > > 
> > Doesn't on-disk format itself need strict ABI guarantees?
> > 
> > Thus it looks like the perfect location for on-disk format definitions.
> 
> Right now I'm not sure if it's a good idea to put the on-disk format to
> the UAPI path or not. The exported code is to support the ioctls,
> there's an overlap with the on-disk format but providing all the on-disk
> structures for general might become an unnecessry burden.
> 
> We know that there's a small number of projects that want to sync the
> on-disk format so I don't think it's going to be a problem for them to
> use a private header.

And the usual way is to just ensure the format header is self-contained
and suitably licensed that they can easily copy it and rely on the
version they checked in.  That avoids the problems of

 a) the tools relying on installed kernel headers new enough for the
    feature they want to support
 b) ifdef magic for newer features in the tools
 c) the need to keep changes to the kernel format header to be backwards
    compatible at the compiler level (as there can be disk format
    compatible changes that still break users, e.g. introducing a named
    union, or splitting / merging struct definitions)
Qu Wenruo April 25, 2020, 7:25 a.m. UTC | #6
On 2020/4/25 下午3:14, Christoph Hellwig wrote:
> On Fri, Apr 24, 2020 at 10:24:45PM +0200, David Sterba wrote:
>> On Tue, Apr 21, 2020 at 07:41:40PM +0800, Qu Wenruo wrote:
>>>
>>>
>>> On 2020/4/21 下午7:31, Christoph Hellwig wrote:
>>>> On Wed, Apr 15, 2020 at 04:41:12PM +0800, Qu Wenruo wrote:
>>>>> These structures all are on-disk format. Move them to btrfs_tree.h
>>>>>
>>>>> This allows us to sync the header to different projects, who need to
>>>>> read btrfs filesystem, like U-boot, grub.
>>>>
>>>> Please use a separate header for that.  btrfs_tree.h is a UAPI header
>>>> with strict ABI guarantees.  Just add a fs/btrfs/btrfs_format.h that
>>>> can be copied into the projects where is needed.
>>>>
>>> Doesn't on-disk format itself need strict ABI guarantees?
>>>
>>> Thus it looks like the perfect location for on-disk format definitions.
>>
>> Right now I'm not sure if it's a good idea to put the on-disk format to
>> the UAPI path or not. The exported code is to support the ioctls,
>> there's an overlap with the on-disk format but providing all the on-disk
>> structures for general might become an unnecessry burden.
>>
>> We know that there's a small number of projects that want to sync the
>> on-disk format so I don't think it's going to be a problem for them to
>> use a private header.
> 
> And the usual way is to just ensure the format header is self-contained
> and suitably licensed that they can easily copy it and rely on the
> version they checked in.  That avoids the problems of
> 
>  a) the tools relying on installed kernel headers new enough for the
>     feature they want to support
>  b) ifdef magic for newer features in the tools
>  c) the need to keep changes to the kernel format header to be backwards
>     compatible at the compiler level (as there can be disk format
>     compatible changes that still break users, e.g. introducing a named
>     union, or splitting / merging struct definitions)
> 
One last question.

Btrfs has one ioctl, which allow users to search btrfs on-disk data.

And the ioctl returns the on-disk data directly to user space, which
means the on-disk format is also used by ioctl.

In that case, do we still need to put the on-disk format internal other
than as a uapi?

Thanks,
Qu
Qu Wenruo April 30, 2020, 7:29 a.m. UTC | #7
On 2020/4/25 下午3:25, Qu Wenruo wrote:
> 
> 
> On 2020/4/25 下午3:14, Christoph Hellwig wrote:
>> On Fri, Apr 24, 2020 at 10:24:45PM +0200, David Sterba wrote:
>>> On Tue, Apr 21, 2020 at 07:41:40PM +0800, Qu Wenruo wrote:
>>>>
>>>>
>>>> On 2020/4/21 下午7:31, Christoph Hellwig wrote:
>>>>> On Wed, Apr 15, 2020 at 04:41:12PM +0800, Qu Wenruo wrote:
>>>>>> These structures all are on-disk format. Move them to btrfs_tree.h
>>>>>>
>>>>>> This allows us to sync the header to different projects, who need to
>>>>>> read btrfs filesystem, like U-boot, grub.
>>>>>
>>>>> Please use a separate header for that.  btrfs_tree.h is a UAPI header
>>>>> with strict ABI guarantees.  Just add a fs/btrfs/btrfs_format.h that
>>>>> can be copied into the projects where is needed.
>>>>>
>>>> Doesn't on-disk format itself need strict ABI guarantees?
>>>>
>>>> Thus it looks like the perfect location for on-disk format definitions.
>>>
>>> Right now I'm not sure if it's a good idea to put the on-disk format to
>>> the UAPI path or not. The exported code is to support the ioctls,
>>> there's an overlap with the on-disk format but providing all the on-disk
>>> structures for general might become an unnecessry burden.
>>>
>>> We know that there's a small number of projects that want to sync the
>>> on-disk format so I don't think it's going to be a problem for them to
>>> use a private header.
>>
>> And the usual way is to just ensure the format header is self-contained
>> and suitably licensed that they can easily copy it and rely on the
>> version they checked in.  That avoids the problems of
>>
>>  a) the tools relying on installed kernel headers new enough for the
>>     feature they want to support
>>  b) ifdef magic for newer features in the tools
>>  c) the need to keep changes to the kernel format header to be backwards
>>     compatible at the compiler level (as there can be disk format
>>     compatible changes that still break users, e.g. introducing a named
>>     union, or splitting / merging struct definitions)
>>
> One last question.
> 
> Btrfs has one ioctl, which allow users to search btrfs on-disk data.
> 
> And the ioctl returns the on-disk data directly to user space, which
> means the on-disk format is also used by ioctl.
> 
> In that case, do we still need to put the on-disk format internal other
> than as a uapi?

After some tries, there are still problems especially for some flags
shared by ioctl and on-disk data.

E.g. We have a qgroup related ioctl, which uses some flag like
BTRFS_QGROUP_LIMIT_MAX_RFER.

But we also use that flag on-disk (obviously, we don't want spend try
time/code to do mapping of these flags).

Putting such flags to ioctl header, then we need to sync two headers to
other projects, while we care nothing about the ioctl part.

Putting such flags to on-disk format header, and put that header inside
fs/btrfs other than uapi, then ioctl doesn't have the definition of such
flags, and break user space programms.

So it looks like we'd better keep a on-disk format uapi header, and put
such flags to on-disk format uapi header, and ioctl header just includes
on-disk format header.

For user space, all needed flags are still kept as is.
For bootloader projects, they only need the on-disk format header.

Any extra ideas/feedback on this?

Thanks,
Qu
diff mbox series

Patch

diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
index d253f7aa8ed5..65f6f31a7ec4 100644
--- a/fs/btrfs/compression.h
+++ b/fs/btrfs/compression.h
@@ -7,6 +7,7 @@ 
 #define BTRFS_COMPRESSION_H
 
 #include <linux/sizes.h>
+#include <linux/btrfs_tree.h>
 
 /*
  * We want to make sure that amount of RAM required to uncompress an extent is
@@ -100,14 +101,6 @@  blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 
 unsigned int btrfs_compress_str2level(unsigned int type, const char *str);
 
-enum btrfs_compression_type {
-	BTRFS_COMPRESS_NONE  = 0,
-	BTRFS_COMPRESS_ZLIB  = 1,
-	BTRFS_COMPRESS_LZO   = 2,
-	BTRFS_COMPRESS_ZSTD  = 3,
-	BTRFS_NR_COMPRESS_TYPES = 4,
-};
-
 struct workspace_manager {
 	struct list_head idle_ws;
 	spinlock_t ws_lock;
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 8aa7b9dac405..4d787d749315 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -49,8 +49,6 @@  extern struct kmem_cache *btrfs_free_space_bitmap_cachep;
 struct btrfs_ordered_sum;
 struct btrfs_ref;
 
-#define BTRFS_MAGIC 0x4D5F53665248425FULL /* ascii _BHRfS_M, no null */
-
 /*
  * Maximum number of mirrors that can be available for all profiles counting
  * the target device of dev-replace as one. During an active device replace
@@ -62,22 +60,8 @@  struct btrfs_ref;
  */
 #define BTRFS_MAX_MIRRORS (4 + 1)
 
-#define BTRFS_MAX_LEVEL 8
-
 #define BTRFS_OLDEST_GENERATION	0ULL
 
-/*
- * the max metadata block size.  This limit is somewhat artificial,
- * but the memmove costs go through the roof for larger blocks.
- */
-#define BTRFS_MAX_METADATA_BLOCKSIZE 65536
-
-/*
- * we can actually store much bigger names, but lets not confuse the rest
- * of linux
- */
-#define BTRFS_NAME_LEN 255
-
 /*
  * Theoretical limit is larger, but we keep this down to a sane
  * value. That should limit greatly the possibility of collisions on
@@ -148,203 +132,6 @@  enum {
 	BTRFS_FS_STATE_DUMMY_FS_INFO,
 };
 
-#define BTRFS_BACKREF_REV_MAX		256
-#define BTRFS_BACKREF_REV_SHIFT		56
-#define BTRFS_BACKREF_REV_MASK		(((u64)BTRFS_BACKREF_REV_MAX - 1) << \
-					 BTRFS_BACKREF_REV_SHIFT)
-
-#define BTRFS_OLD_BACKREF_REV		0
-#define BTRFS_MIXED_BACKREF_REV		1
-
-/*
- * every tree block (leaf or node) starts with this header.
- */
-struct btrfs_header {
-	/* these first four must match the super block */
-	u8 csum[BTRFS_CSUM_SIZE];
-	u8 fsid[BTRFS_FSID_SIZE]; /* FS specific uuid */
-	__le64 bytenr; /* which block this node is supposed to live in */
-	__le64 flags;
-
-	/* allowed to be different from the super from here on down */
-	u8 chunk_tree_uuid[BTRFS_UUID_SIZE];
-	__le64 generation;
-	__le64 owner;
-	__le32 nritems;
-	u8 level;
-} __attribute__ ((__packed__));
-
-/*
- * this is a very generous portion of the super block, giving us
- * room to translate 14 chunks with 3 stripes each.
- */
-#define BTRFS_SYSTEM_CHUNK_ARRAY_SIZE 2048
-
-/*
- * just in case we somehow lose the roots and are not able to mount,
- * we store an array of the roots from previous transactions
- * in the super.
- */
-#define BTRFS_NUM_BACKUP_ROOTS 4
-struct btrfs_root_backup {
-	__le64 tree_root;
-	__le64 tree_root_gen;
-
-	__le64 chunk_root;
-	__le64 chunk_root_gen;
-
-	__le64 extent_root;
-	__le64 extent_root_gen;
-
-	__le64 fs_root;
-	__le64 fs_root_gen;
-
-	__le64 dev_root;
-	__le64 dev_root_gen;
-
-	__le64 csum_root;
-	__le64 csum_root_gen;
-
-	__le64 total_bytes;
-	__le64 bytes_used;
-	__le64 num_devices;
-	/* future */
-	__le64 unused_64[4];
-
-	u8 tree_root_level;
-	u8 chunk_root_level;
-	u8 extent_root_level;
-	u8 fs_root_level;
-	u8 dev_root_level;
-	u8 csum_root_level;
-	/* future and to align */
-	u8 unused_8[10];
-} __attribute__ ((__packed__));
-
-/*
- * the super block basically lists the main trees of the FS
- * it currently lacks any block count etc etc
- */
-struct btrfs_super_block {
-	/* the first 4 fields must match struct btrfs_header */
-	u8 csum[BTRFS_CSUM_SIZE];
-	/* FS specific UUID, visible to user */
-	u8 fsid[BTRFS_FSID_SIZE];
-	__le64 bytenr; /* this block number */
-	__le64 flags;
-
-	/* allowed to be different from the btrfs_header from here own down */
-	__le64 magic;
-	__le64 generation;
-	__le64 root;
-	__le64 chunk_root;
-	__le64 log_root;
-
-	/* this will help find the new super based on the log root */
-	__le64 log_root_transid;
-	__le64 total_bytes;
-	__le64 bytes_used;
-	__le64 root_dir_objectid;
-	__le64 num_devices;
-	__le32 sectorsize;
-	__le32 nodesize;
-	__le32 __unused_leafsize;
-	__le32 stripesize;
-	__le32 sys_chunk_array_size;
-	__le64 chunk_root_generation;
-	__le64 compat_flags;
-	__le64 compat_ro_flags;
-	__le64 incompat_flags;
-	__le16 csum_type;
-	u8 root_level;
-	u8 chunk_root_level;
-	u8 log_root_level;
-	struct btrfs_dev_item dev_item;
-
-	char label[BTRFS_LABEL_SIZE];
-
-	__le64 cache_generation;
-	__le64 uuid_tree_generation;
-
-	/* the UUID written into btree blocks */
-	u8 metadata_uuid[BTRFS_FSID_SIZE];
-
-	/* future expansion */
-	__le64 reserved[28];
-	u8 sys_chunk_array[BTRFS_SYSTEM_CHUNK_ARRAY_SIZE];
-	struct btrfs_root_backup super_roots[BTRFS_NUM_BACKUP_ROOTS];
-} __attribute__ ((__packed__));
-
-/*
- * Compat flags that we support.  If any incompat flags are set other than the
- * ones specified below then we will fail to mount
- */
-#define BTRFS_FEATURE_COMPAT_SUPP		0ULL
-#define BTRFS_FEATURE_COMPAT_SAFE_SET		0ULL
-#define BTRFS_FEATURE_COMPAT_SAFE_CLEAR		0ULL
-
-#define BTRFS_FEATURE_COMPAT_RO_SUPP			\
-	(BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE |	\
-	 BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE_VALID)
-
-#define BTRFS_FEATURE_COMPAT_RO_SAFE_SET	0ULL
-#define BTRFS_FEATURE_COMPAT_RO_SAFE_CLEAR	0ULL
-
-#define BTRFS_FEATURE_INCOMPAT_SUPP			\
-	(BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF |		\
-	 BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL |	\
-	 BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS |		\
-	 BTRFS_FEATURE_INCOMPAT_BIG_METADATA |		\
-	 BTRFS_FEATURE_INCOMPAT_COMPRESS_LZO |		\
-	 BTRFS_FEATURE_INCOMPAT_COMPRESS_ZSTD |		\
-	 BTRFS_FEATURE_INCOMPAT_RAID56 |		\
-	 BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF |		\
-	 BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA |	\
-	 BTRFS_FEATURE_INCOMPAT_NO_HOLES	|	\
-	 BTRFS_FEATURE_INCOMPAT_METADATA_UUID	|	\
-	 BTRFS_FEATURE_INCOMPAT_RAID1C34)
-
-#define BTRFS_FEATURE_INCOMPAT_SAFE_SET			\
-	(BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF)
-#define BTRFS_FEATURE_INCOMPAT_SAFE_CLEAR		0ULL
-
-/*
- * A leaf is full of items. offset and size tell us where to find
- * the item in the leaf (relative to the start of the data area)
- */
-struct btrfs_item {
-	struct btrfs_disk_key key;
-	__le32 offset;
-	__le32 size;
-} __attribute__ ((__packed__));
-
-/*
- * leaves have an item area and a data area:
- * [item0, item1....itemN] [free space] [dataN...data1, data0]
- *
- * The data is separate from the items to get the keys closer together
- * during searches.
- */
-struct btrfs_leaf {
-	struct btrfs_header header;
-	struct btrfs_item items[];
-} __attribute__ ((__packed__));
-
-/*
- * all non-leaf blocks are nodes, they hold only keys and pointers to
- * other blocks
- */
-struct btrfs_key_ptr {
-	struct btrfs_disk_key key;
-	__le64 blockptr;
-	__le64 generation;
-} __attribute__ ((__packed__));
-
-struct btrfs_node {
-	struct btrfs_header header;
-	struct btrfs_key_ptr ptrs[];
-} __attribute__ ((__packed__));
-
 /*
  * btrfs_paths remember the path taken from the root down to the leaf.
  * level 0 is always the leaf, and nodes[1...BTRFS_MAX_LEVEL] will point
@@ -1307,39 +1094,6 @@  do {                                                                   \
        }                                                               \
 } while(0)
 
-/*
- * Inode flags
- */
-#define BTRFS_INODE_NODATASUM		(1 << 0)
-#define BTRFS_INODE_NODATACOW		(1 << 1)
-#define BTRFS_INODE_READONLY		(1 << 2)
-#define BTRFS_INODE_NOCOMPRESS		(1 << 3)
-#define BTRFS_INODE_PREALLOC		(1 << 4)
-#define BTRFS_INODE_SYNC		(1 << 5)
-#define BTRFS_INODE_IMMUTABLE		(1 << 6)
-#define BTRFS_INODE_APPEND		(1 << 7)
-#define BTRFS_INODE_NODUMP		(1 << 8)
-#define BTRFS_INODE_NOATIME		(1 << 9)
-#define BTRFS_INODE_DIRSYNC		(1 << 10)
-#define BTRFS_INODE_COMPRESS		(1 << 11)
-
-#define BTRFS_INODE_ROOT_ITEM_INIT	(1 << 31)
-
-#define BTRFS_INODE_FLAG_MASK						\
-	(BTRFS_INODE_NODATASUM |					\
-	 BTRFS_INODE_NODATACOW |					\
-	 BTRFS_INODE_READONLY |						\
-	 BTRFS_INODE_NOCOMPRESS |					\
-	 BTRFS_INODE_PREALLOC |						\
-	 BTRFS_INODE_SYNC |						\
-	 BTRFS_INODE_IMMUTABLE |					\
-	 BTRFS_INODE_APPEND |						\
-	 BTRFS_INODE_NODUMP |						\
-	 BTRFS_INODE_NOATIME |						\
-	 BTRFS_INODE_DIRSYNC |						\
-	 BTRFS_INODE_COMPRESS |						\
-	 BTRFS_INODE_ROOT_ITEM_INIT)
-
 struct btrfs_map_token {
 	const struct extent_buffer *eb;
 	char *kaddr;
diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index 8134924cfc17..69c2c21e7f7b 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -21,10 +21,10 @@ 
 #define _UAPI_LINUX_BTRFS_H
 #include <linux/types.h>
 #include <linux/ioctl.h>
+#include <linux/btrfs_tree.h>
 
 #define BTRFS_IOCTL_MAGIC 0x94
 #define BTRFS_VOL_NAME_MAX 255
-#define BTRFS_LABEL_SIZE 256
 
 /* this should be 4k */
 #define BTRFS_PATH_NAME_MAX 4087
@@ -55,24 +55,8 @@  struct btrfs_ioctl_vol_args {
 			BTRFS_DEVICE_SPEC_BY_ID |	\
 			BTRFS_SUBVOL_SPEC_BY_ID)
 
-#define BTRFS_FSID_SIZE 16
-#define BTRFS_UUID_SIZE 16
 #define BTRFS_UUID_UNPARSED_SIZE	37
 
-/*
- * flags definition for qgroup limits
- *
- * Used by:
- * struct btrfs_qgroup_limit.flags
- * struct btrfs_qgroup_limit_item.flags
- */
-#define BTRFS_QGROUP_LIMIT_MAX_RFER	(1ULL << 0)
-#define BTRFS_QGROUP_LIMIT_MAX_EXCL	(1ULL << 1)
-#define BTRFS_QGROUP_LIMIT_RSV_RFER	(1ULL << 2)
-#define BTRFS_QGROUP_LIMIT_RSV_EXCL	(1ULL << 3)
-#define BTRFS_QGROUP_LIMIT_RFER_CMPR	(1ULL << 4)
-#define BTRFS_QGROUP_LIMIT_EXCL_CMPR	(1ULL << 5)
-
 struct btrfs_qgroup_limit {
 	__u64	flags;
 	__u64	max_rfer;
@@ -256,43 +240,6 @@  struct btrfs_ioctl_fs_info_args {
 	__u64 reserved[122];			/* pad to 1k */
 };
 
-/*
- * feature flags
- *
- * Used by:
- * struct btrfs_ioctl_feature_flags
- */
-#define BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE		(1ULL << 0)
-/*
- * Older kernels (< 4.9) on big-endian systems produced broken free space tree
- * bitmaps, and btrfs-progs also used to corrupt the free space tree (versions
- * < 4.7.3).  If this bit is clear, then the free space tree cannot be trusted.
- * btrfs-progs can also intentionally clear this bit to ask the kernel to
- * rebuild the free space tree, however this might not work on older kernels
- * that do not know about this bit. If not sure, clear the cache manually on
- * first mount when booting older kernel versions.
- */
-#define BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE_VALID	(1ULL << 1)
-
-#define BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF	(1ULL << 0)
-#define BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL	(1ULL << 1)
-#define BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS	(1ULL << 2)
-#define BTRFS_FEATURE_INCOMPAT_COMPRESS_LZO	(1ULL << 3)
-#define BTRFS_FEATURE_INCOMPAT_COMPRESS_ZSTD	(1ULL << 4)
-
-/*
- * older kernels tried to do bigger metadata blocks, but the
- * code was pretty buggy.  Lets not let them try anymore.
- */
-#define BTRFS_FEATURE_INCOMPAT_BIG_METADATA	(1ULL << 5)
-
-#define BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF	(1ULL << 6)
-#define BTRFS_FEATURE_INCOMPAT_RAID56		(1ULL << 7)
-#define BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA	(1ULL << 8)
-#define BTRFS_FEATURE_INCOMPAT_NO_HOLES		(1ULL << 9)
-#define BTRFS_FEATURE_INCOMPAT_METADATA_UUID	(1ULL << 10)
-#define BTRFS_FEATURE_INCOMPAT_RAID1C34		(1ULL << 11)
-
 struct btrfs_ioctl_feature_flags {
 	__u64 compat_flags;
 	__u64 compat_ro_flags;
@@ -657,25 +604,6 @@  struct btrfs_ioctl_logical_ino_args {
  * Requires logical == extent bytenr. */
 #define BTRFS_LOGICAL_INO_ARGS_IGNORE_OFFSET	(1ULL << 0)
 
-enum btrfs_dev_stat_values {
-	/* disk I/O failure stats */
-	BTRFS_DEV_STAT_WRITE_ERRS, /* EIO or EREMOTEIO from lower layers */
-	BTRFS_DEV_STAT_READ_ERRS, /* EIO or EREMOTEIO from lower layers */
-	BTRFS_DEV_STAT_FLUSH_ERRS, /* EIO or EREMOTEIO from lower layers */
-
-	/* stats for indirect indications for I/O failures */
-	BTRFS_DEV_STAT_CORRUPTION_ERRS, /* checksum error, bytenr error or
-					 * contents is illegal: this is an
-					 * indication that the block was damaged
-					 * during read or write, or written to
-					 * wrong location or read from wrong
-					 * location */
-	BTRFS_DEV_STAT_GENERATION_ERRS, /* an indication that blocks have not
-					 * been written */
-
-	BTRFS_DEV_STAT_VALUES_MAX
-};
-
 /* Reset statistics after reading; needs SYS_ADMIN capability */
 #define	BTRFS_DEV_STATS_RESET		(1ULL << 0)
 
diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h
index 8e322e2c7e78..1170be498c43 100644
--- a/include/uapi/linux/btrfs_tree.h
+++ b/include/uapi/linux/btrfs_tree.h
@@ -2,9 +2,26 @@ 
 #ifndef _BTRFS_CTREE_H_
 #define _BTRFS_CTREE_H_
 
-#include <linux/btrfs.h>
 #include <linux/types.h>
 
+#define BTRFS_MAGIC 0x4D5F53665248425FULL /* ascii _BHRfS_M, no null */
+
+/*
+ * The max metadata block size (node size).
+ *
+ * This limit is somewhat artificial. The memmove and tree block locking cost
+ * go up with larger node size.
+ */
+#define BTRFS_MAX_METADATA_BLOCKSIZE 65536
+
+/*
+ * We can actually store much bigger names, but lets not confuse the rest
+ * of linux.
+ *
+ * btrfs_dir_item::name_len follows this limitation.
+ */
+#define BTRFS_NAME_LEN 255
+
 /*
  * This header contains the structure definitions and constants used
  * by file system objects that can be retrieved using
@@ -281,9 +298,6 @@ 
  * The key is built like this:
  * (UUID_upper_64_bits, BTRFS_UUID_KEY*, UUID_lower_64_bits).
  */
-#if BTRFS_UUID_SIZE != 16
-#error "UUID items require BTRFS_UUID_SIZE == 16!"
-#endif
 #define BTRFS_UUID_KEY_SUBVOL	251	/* for UUIDs assigned to subvols */
 #define BTRFS_UUID_KEY_RECEIVED_SUBVOL	252	/* for UUIDs assigned to
 						 * received subvols */
@@ -326,6 +340,9 @@  enum btrfs_csum_type {
 #define BTRFS_FT_XATTR		8
 #define BTRFS_FT_MAX		9
 
+#define BTRFS_FSID_SIZE 16
+#define BTRFS_UUID_SIZE 16
+
 /*
  * The key defines the order in the tree, and so it also defines (optimal)
  * block layout.
@@ -559,6 +576,39 @@  struct btrfs_timespec {
 	__le32 nsec;
 } __attribute__ ((__packed__));
 
+/*
+ * Inode flags
+ */
+#define BTRFS_INODE_NODATASUM		(1 << 0)
+#define BTRFS_INODE_NODATACOW		(1 << 1)
+#define BTRFS_INODE_READONLY		(1 << 2)
+#define BTRFS_INODE_NOCOMPRESS		(1 << 3)
+#define BTRFS_INODE_PREALLOC		(1 << 4)
+#define BTRFS_INODE_SYNC		(1 << 5)
+#define BTRFS_INODE_IMMUTABLE		(1 << 6)
+#define BTRFS_INODE_APPEND		(1 << 7)
+#define BTRFS_INODE_NODUMP		(1 << 8)
+#define BTRFS_INODE_NOATIME		(1 << 9)
+#define BTRFS_INODE_DIRSYNC		(1 << 10)
+#define BTRFS_INODE_COMPRESS		(1 << 11)
+
+#define BTRFS_INODE_ROOT_ITEM_INIT	(1 << 31)
+
+#define BTRFS_INODE_FLAG_MASK						\
+	(BTRFS_INODE_NODATASUM |					\
+	 BTRFS_INODE_NODATACOW |					\
+	 BTRFS_INODE_READONLY |						\
+	 BTRFS_INODE_NOCOMPRESS |					\
+	 BTRFS_INODE_PREALLOC |						\
+	 BTRFS_INODE_SYNC |						\
+	 BTRFS_INODE_IMMUTABLE |					\
+	 BTRFS_INODE_APPEND |						\
+	 BTRFS_INODE_NODUMP |						\
+	 BTRFS_INODE_NOATIME |						\
+	 BTRFS_INODE_DIRSYNC |						\
+	 BTRFS_INODE_COMPRESS |						\
+	 BTRFS_INODE_ROOT_ITEM_INIT)
+
 struct btrfs_inode_item {
 	/* nfs style generation number */
 	__le64 generation;
@@ -747,6 +797,14 @@  enum {
 	BTRFS_NR_FILE_EXTENT_TYPES = 3,
 };
 
+enum btrfs_compression_type {
+	BTRFS_COMPRESS_NONE  = 0,
+	BTRFS_COMPRESS_ZLIB  = 1,
+	BTRFS_COMPRESS_LZO   = 2,
+	BTRFS_COMPRESS_ZSTD  = 3,
+	BTRFS_NR_COMPRESS_TYPES = 4,
+};
+
 struct btrfs_file_extent_item {
 	/*
 	 * transaction id that created this extent
@@ -803,6 +861,25 @@  struct btrfs_csum_item {
 	__u8 csum;
 } __attribute__ ((__packed__));
 
+enum btrfs_dev_stat_values {
+	/* disk I/O failure stats */
+	BTRFS_DEV_STAT_WRITE_ERRS, /* EIO or EREMOTEIO from lower layers */
+	BTRFS_DEV_STAT_READ_ERRS, /* EIO or EREMOTEIO from lower layers */
+	BTRFS_DEV_STAT_FLUSH_ERRS, /* EIO or EREMOTEIO from lower layers */
+
+	/* stats for indirect indications for I/O failures */
+	BTRFS_DEV_STAT_CORRUPTION_ERRS, /* checksum error, bytenr error or
+					 * contents is illegal: this is an
+					 * indication that the block was damaged
+					 * during read or write, or written to
+					 * wrong location or read from wrong
+					 * location */
+	BTRFS_DEV_STAT_GENERATION_ERRS, /* an indication that blocks have not
+					 * been written */
+
+	BTRFS_DEV_STAT_VALUES_MAX
+};
+
 struct btrfs_dev_stats_item {
 	/*
 	 * grow this item struct at the end for future enhancements and keep
@@ -974,6 +1051,20 @@  struct btrfs_qgroup_info_item {
 	__le64 excl_cmpr;
 } __attribute__ ((__packed__));
 
+/*
+ * flags definition for qgroup limits
+ *
+ * Used by:
+ * struct btrfs_qgroup_limit.flags
+ * struct btrfs_qgroup_limit_item.flags
+ */
+#define BTRFS_QGROUP_LIMIT_MAX_RFER	(1ULL << 0)
+#define BTRFS_QGROUP_LIMIT_MAX_EXCL	(1ULL << 1)
+#define BTRFS_QGROUP_LIMIT_RSV_RFER	(1ULL << 2)
+#define BTRFS_QGROUP_LIMIT_RSV_EXCL	(1ULL << 3)
+#define BTRFS_QGROUP_LIMIT_RFER_CMPR	(1ULL << 4)
+#define BTRFS_QGROUP_LIMIT_EXCL_CMPR	(1ULL << 5)
+
 struct btrfs_qgroup_limit_item {
 	/*
 	 * only updated when any of the other values change
@@ -985,4 +1076,243 @@  struct btrfs_qgroup_limit_item {
 	__le64 rsv_excl;
 } __attribute__ ((__packed__));
 
+/*
+ * just in case we somehow lose the roots and are not able to mount,
+ * we store an array of the roots from previous transactions
+ * in the super.
+ */
+#define BTRFS_NUM_BACKUP_ROOTS 4
+struct btrfs_root_backup {
+	__le64 tree_root;
+	__le64 tree_root_gen;
+
+	__le64 chunk_root;
+	__le64 chunk_root_gen;
+
+	__le64 extent_root;
+	__le64 extent_root_gen;
+
+	__le64 fs_root;
+	__le64 fs_root_gen;
+
+	__le64 dev_root;
+	__le64 dev_root_gen;
+
+	__le64 csum_root;
+	__le64 csum_root_gen;
+
+	__le64 total_bytes;
+	__le64 bytes_used;
+	__le64 num_devices;
+	/* future */
+	__le64 unused_64[4];
+
+	u8 tree_root_level;
+	u8 chunk_root_level;
+	u8 extent_root_level;
+	u8 fs_root_level;
+	u8 dev_root_level;
+	u8 csum_root_level;
+	/* future and to align */
+	u8 unused_8[10];
+} __attribute__ ((__packed__));
+
+/*
+ * this is a very generous portion of the super block, giving us
+ * room to translate 14 chunks with 3 stripes each.
+ */
+#define BTRFS_SYSTEM_CHUNK_ARRAY_SIZE 2048
+
+#define BTRFS_LABEL_SIZE 256
+/*
+ * the super block basically lists the main trees of the FS
+ * it currently lacks any block count etc etc
+ */
+struct btrfs_super_block {
+	/* the first 4 fields must match struct btrfs_header */
+	u8 csum[BTRFS_CSUM_SIZE];
+	/* FS specific UUID, visible to user */
+	u8 fsid[BTRFS_FSID_SIZE];
+	__le64 bytenr; /* this block number */
+	__le64 flags;
+
+	/* allowed to be different from the btrfs_header from here own down */
+	__le64 magic;
+	__le64 generation;
+	__le64 root;
+	__le64 chunk_root;
+	__le64 log_root;
+
+	/* this will help find the new super based on the log root */
+	__le64 log_root_transid;
+	__le64 total_bytes;
+	__le64 bytes_used;
+	__le64 root_dir_objectid;
+	__le64 num_devices;
+	__le32 sectorsize;
+	__le32 nodesize;
+	__le32 __unused_leafsize;
+	__le32 stripesize;
+	__le32 sys_chunk_array_size;
+	__le64 chunk_root_generation;
+	__le64 compat_flags;
+	__le64 compat_ro_flags;
+	__le64 incompat_flags;
+	__le16 csum_type;
+	u8 root_level;
+	u8 chunk_root_level;
+	u8 log_root_level;
+	struct btrfs_dev_item dev_item;
+
+	char label[BTRFS_LABEL_SIZE];
+
+	__le64 cache_generation;
+	__le64 uuid_tree_generation;
+
+	/* the UUID written into btree blocks */
+	u8 metadata_uuid[BTRFS_FSID_SIZE];
+
+	/* future expansion */
+	__le64 reserved[28];
+	u8 sys_chunk_array[BTRFS_SYSTEM_CHUNK_ARRAY_SIZE];
+	struct btrfs_root_backup super_roots[BTRFS_NUM_BACKUP_ROOTS];
+} __attribute__ ((__packed__));
+
+/*
+ * feature flags
+ *
+ * Used by:
+ * struct btrfs_super_block::(compat|compat_ro|incompat)_flags
+ * struct btrfs_ioctl_feature_flags
+ */
+#define BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE		(1ULL << 0)
+
+/*
+ * Older kernels (< 4.9) on big-endian systems produced broken free space tree
+ * bitmaps, and btrfs-progs also used to corrupt the free space tree (versions
+ * < 4.7.3).  If this bit is clear, then the free space tree cannot be trusted.
+ * btrfs-progs can also intentionally clear this bit to ask the kernel to
+ * rebuild the free space tree, however this might not work on older kernels
+ * that do not know about this bit. If not sure, clear the cache manually on
+ * first mount when booting older kernel versions.
+ */
+#define BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE_VALID	(1ULL << 1)
+
+#define BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF	(1ULL << 0)
+#define BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL	(1ULL << 1)
+#define BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS	(1ULL << 2)
+#define BTRFS_FEATURE_INCOMPAT_COMPRESS_LZO	(1ULL << 3)
+#define BTRFS_FEATURE_INCOMPAT_COMPRESS_ZSTD	(1ULL << 4)
+
+/*
+ * older kernels tried to do bigger metadata blocks, but the
+ * code was pretty buggy.  Lets not let them try anymore.
+ */
+#define BTRFS_FEATURE_INCOMPAT_BIG_METADATA	(1ULL << 5)
+
+#define BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF	(1ULL << 6)
+#define BTRFS_FEATURE_INCOMPAT_RAID56		(1ULL << 7)
+#define BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA	(1ULL << 8)
+#define BTRFS_FEATURE_INCOMPAT_NO_HOLES		(1ULL << 9)
+#define BTRFS_FEATURE_INCOMPAT_METADATA_UUID	(1ULL << 10)
+#define BTRFS_FEATURE_INCOMPAT_RAID1C34		(1ULL << 11)
+
+/*
+ * Compat flags that we support.  If any incompat flags are set other than the
+ * ones specified below then we will fail to mount
+ */
+#define BTRFS_FEATURE_COMPAT_SUPP		0ULL
+#define BTRFS_FEATURE_COMPAT_SAFE_SET		0ULL
+#define BTRFS_FEATURE_COMPAT_SAFE_CLEAR		0ULL
+
+#define BTRFS_FEATURE_COMPAT_RO_SUPP			\
+	(BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE |	\
+	 BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE_VALID)
+
+#define BTRFS_FEATURE_COMPAT_RO_SAFE_SET	0ULL
+#define BTRFS_FEATURE_COMPAT_RO_SAFE_CLEAR	0ULL
+
+#define BTRFS_FEATURE_INCOMPAT_SUPP			\
+	(BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF |		\
+	 BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL |	\
+	 BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS |		\
+	 BTRFS_FEATURE_INCOMPAT_BIG_METADATA |		\
+	 BTRFS_FEATURE_INCOMPAT_COMPRESS_LZO |		\
+	 BTRFS_FEATURE_INCOMPAT_COMPRESS_ZSTD |		\
+	 BTRFS_FEATURE_INCOMPAT_RAID56 |		\
+	 BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF |		\
+	 BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA |	\
+	 BTRFS_FEATURE_INCOMPAT_NO_HOLES	|	\
+	 BTRFS_FEATURE_INCOMPAT_METADATA_UUID	|	\
+	 BTRFS_FEATURE_INCOMPAT_RAID1C34)
+
+#define BTRFS_FEATURE_INCOMPAT_SAFE_SET			\
+	(BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF)
+#define BTRFS_FEATURE_INCOMPAT_SAFE_CLEAR		0ULL
+
+#define BTRFS_BACKREF_REV_MAX		256
+#define BTRFS_BACKREF_REV_SHIFT		56
+#define BTRFS_BACKREF_REV_MASK		(((u64)BTRFS_BACKREF_REV_MAX - 1) << \
+					 BTRFS_BACKREF_REV_SHIFT)
+
+#define BTRFS_OLD_BACKREF_REV		0
+#define BTRFS_MIXED_BACKREF_REV		1
+
+#define BTRFS_MAX_LEVEL 8
+
+/*
+ * every tree block (leaf or node) starts with this header.
+ */
+struct btrfs_header {
+	/* these first four must match the super block */
+	u8 csum[BTRFS_CSUM_SIZE];
+	u8 fsid[BTRFS_FSID_SIZE]; /* FS specific uuid */
+	__le64 bytenr; /* which block this node is supposed to live in */
+	__le64 flags;
+
+	/* allowed to be different from the super from here on down */
+	u8 chunk_tree_uuid[BTRFS_UUID_SIZE];
+	__le64 generation;
+	__le64 owner;
+	__le32 nritems;
+	u8 level;
+} __attribute__ ((__packed__));
+
+/*
+ * A leaf is full of items. offset and size tell us where to find
+ * the item in the leaf (relative to the start of the data area)
+ */
+struct btrfs_item {
+	struct btrfs_disk_key key;
+	__le32 offset;
+	__le32 size;
+} __attribute__ ((__packed__));
+
+/*
+ * leaves have an item area and a data area:
+ * [item0, item1....itemN] [free space] [dataN...data1, data0]
+ *
+ * The data is separate from the items to get the keys closer together
+ * during searches.
+ */
+struct btrfs_leaf {
+	struct btrfs_header header;
+	struct btrfs_item items[];
+} __attribute__ ((__packed__));
+
+/*
+ * all non-leaf blocks are nodes, they hold only keys and pointers to
+ * other blocks
+ */
+struct btrfs_key_ptr {
+	struct btrfs_disk_key key;
+	__le64 blockptr;
+	__le64 generation;
+} __attribute__ ((__packed__));
+
+struct btrfs_node {
+	struct btrfs_header header;
+	struct btrfs_key_ptr ptrs[];
+} __attribute__ ((__packed__));
+
 #endif /* _BTRFS_CTREE_H_ */