Re: [PATCH] btrfs: Move on-disk structure definition to btrfs_tree.h

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

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On 2020/4/7 下午9:14, David Sterba wrote:
> On Tue, Apr 07, 2020 at 04:44:33PM +0800, Qu Wenruo wrote:
>> These structures all are on-disk format. Move them to btrfs_tree.h
>>
>> 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_item structure
>> - btrfs_leaf structure
>> - btrfs_key_ptr structure
>> - btrfs_node structure
>>
>> - BTRFS_INODE_* flags
>>   Move them before btrfs_inode_item definition.
>>
>> Signed-off-by: Qu Wenruo <wqu@suse.com>
>> ---
>> This moved btree_tree.h is more appropriate for btrfs-progs to reuse.
> 
> This actually answers 'why' the change is made so this should be in the
> changelog but I still want to know the reason to move it to the header.
> Do you mean that progs from git would be built #including this header
> directly?
> 
No. As you answered a long long time before, btrfs-progs shouldn't
include global kernel header directly.

Your answer was for case like building btrfs-progs on older kernel, and
I still believe you're right.

For btrfs-progs, I will just cross-port (copy) the header to btrfs-progs.

The re-use part doesn't only limit to btrfs-progs.
In fact, there are already two more projects which can benefit from such
move: grub and u-boot.

This patch is the base stone for later u-boot cross ports.
The idea is to use kernel headers (copy them to related projects), then
re-use a subset of btrfs-progs to implement a full read-only btrfs code
base in u-boot.

Thanks,
Qu


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