On 2019/4/5 下午8:09, David Sterba wrote:
> On Thu, Apr 04, 2019 at 02:45:29PM +0800, Qu Wenruo wrote:
>> Current delayed ref interface has several problems:
>> - Longer and longer parameter lists
>>   bytenr
>>   num_bytes
>>   parent
>>   ---------- so far so good
>>   ref_root
>>   owner
>>   offset
>>   ---------- I don't feel good now
>>
>> - Different interpretation for the same parameter
>>   Above @owner for data ref is inode number (u64),
>>   while for tree ref, it's level (int).
>>
>>   They are even in different size range.
>>   For level we only need 0~8, while for ino it's
>>   BTRFS_FIRST_FREE_OBJECTID~BTRFS_LAST_FREE_OBJECTID.
>>
>>   And @offset doesn't even makes sense for tree ref.
>>
>>   Such parameter reuse may look clever as an hidden union, but it
>>   destroys code readability.
>>
>> To solve both problems, we introduce a new structure, btrfs_ref to solve
>> them:
>>
>> - Structure instead of long parameter list
>>   This makes later expansion easier, and better documented.
>>
>> - Use btrfs_ref::type to distinguish data and tree ref
>>
>> - Use proper union to store data/tree ref specific structures.
>>
>> - Use separate functions to fill data/tree ref data, with a common generic
>>   function to fill common bytenr/num_bytes members.
>>
>> All parameters will find its place in btrfs_ref, and an extra member,
>> @real_root, inspired by ref-verify code, is newly introduced for later
>> qgroup code, to record which tree is triggered this extent modification.
>>
>> This patch doesn't touch any code, but provides the basis for incoming
>> refactors.
>>
>> Signed-off-by: Qu Wenruo <wqu@suse.com>
>> ---
>>  fs/btrfs/delayed-ref.h | 116 +++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 116 insertions(+)
>>
>> diff --git a/fs/btrfs/delayed-ref.h b/fs/btrfs/delayed-ref.h
>> index 70606da440aa..8eb5b3576759 100644
>> --- a/fs/btrfs/delayed-ref.h
>> +++ b/fs/btrfs/delayed-ref.h
>> @@ -176,6 +176,90 @@ struct btrfs_delayed_ref_root {
>>  	u64 qgroup_to_skip;
>>  };
>>  
>> +enum btrfs_ref_type {
>> +	BTRFS_REF_NOT_SET,
>> +	BTRFS_REF_DATA,
>> +	BTRFS_REF_METADATA,
>> +	BTRFS_REF_LAST,
>> +};
>> +
>> +struct btrfs_data_ref {
>> +	/* For EXTENT_DATA_REF */
>> +
>> +	/* Root who refers to this data extent */
>> +	u64 ref_root;
>> +
>> +	/* Inode who refers to this data extent */
>> +	u64 ino;
>> +
>> +	/*
>> +	 * file_offset - extent_offset
>> +	 *
>> +	 * file_offset is the key.offset of the EXTENT_DATA key.
>> +	 * extent_offset is btrfs_file_extent_offset() of the EXTENT_DATA data.
>> +	 */
>> +	u64 offset;
>> +};
>> +
>> +struct btrfs_tree_ref {
>> +	/*
>> +	 * Level of this tree block
>> +	 *
>> +	 * Shared for skinny (TREE_BLOCK_REF) and normal tree ref.
>> +	 */
>> +	int level;
>> +
>> +	/*
>> +	 * Root who refers to this tree block.
>> +	 *
>> +	 * For TREE_BLOCK_REF (skinny metadata, either inline or keyed)
>> +	 */
>> +	u64 root;
>> +
>> +	/* For non-skinny metadata, no special member needed */
>> +};
>> +
>> +struct btrfs_ref {
> 
> The structure name sounds a bit generic, but I think we can keep it
> short. There are no other btrfs-specific references that could be
> confused, there are 'backrefs', 'delayed-refs' all refering to the
> b-tree references.
> 
>> +	enum btrfs_ref_type type;
>> +	int action;
>> +
>> +	/*
>> +	 * Only use parent pointers as backref (SHARED_BLOCK_REF or
>> +	 * SHARED_DATA_REF) for this extent and its children.
>> +	 * Set for reloc trees.
>> +	 */
>> +	bool only_backreferences:1;
> 
> No bool bitfields please, wasn't this mentioned last time?
> 
Oh, I forgot that one.

Do I need to resend or just edit that commit in my github branch?

Thanks,
Qu