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 <w...@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
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