Re: [PATCH v3 1/2] btrfs: Add support to do stack item key operation

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

Hi David,

Any further comment?

Thanks,
Qu

Qu Wenruo wrote on 2015/10/07 09:22 +0800:
> Hi David,
>
> I'm sorry that I didn't get the point of your previous comment.
>
> Maybe the parameter/function name don't follow BTRFS_STACK_GETSET_FUNC
> macro, but IMHO that's OK, as btrfs_item_key_to_cpu() is not an accessor
> following that macro definition.
> It's called even before we get needed data structure, so I think the
> declaration should be OK.
>
> BTW, I really hope the fix can be merged before v4.3, as such fix is
> quite small, while the bug itself impacts qgroup quite a lot.
>
> Thanks,
> Qu
>
> Qu Wenruo wrote on 2015/10/07 09:08 +0800:
>> Normal btrfs_item_key_to_cpu() will need extent buffer to do it, and
>> there is not stack version to handle in memory leaf.
>>
>> Add btrfs_stack_item_key_to_cpu() function for such operation, which
>> will provide the basis for later qgroup fix.
>>
>> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
>> ---
>> v2:
>>    Change the char* parameter to struct btrfs_header *, as a leaf always
>>    has a header.
>> v3:
>>    Fix a bug caused in type change of stack_leaf.
>> ---
>>   fs/btrfs/ctree.h | 20 ++++++++++++++++++++
>>   1 file changed, 20 insertions(+)
>>
>> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
>> index 938efe3..b824fe2 100644
>> --- a/fs/btrfs/ctree.h
>> +++ b/fs/btrfs/ctree.h
>> @@ -2683,6 +2683,17 @@ static inline void btrfs_item_key(struct
>> extent_buffer *eb,
>>       read_eb_member(eb, item, struct btrfs_item, key, disk_key);
>>   }
>>
>> +static inline void btrfs_stack_item_key(struct btrfs_header *stack_leaf,
>> +                    struct btrfs_disk_key *disk_key,
>> +                    int nr)
>> +{
>> +    unsigned long item_offset = btrfs_item_nr_offset(nr);
>> +    struct btrfs_item *item;
>> +
>> +    item = (struct btrfs_item *)((char *)(stack_leaf) + item_offset);
>> +    memcpy(disk_key, &item->key, sizeof(*disk_key));
>> +}
>> +
>>   static inline void btrfs_set_item_key(struct extent_buffer *eb,
>>                      struct btrfs_disk_key *disk_key, int nr)
>>   {
>> @@ -2785,6 +2796,15 @@ static inline void btrfs_item_key_to_cpu(struct
>> extent_buffer *eb,
>>       btrfs_disk_key_to_cpu(key, &disk_key);
>>   }
>>
>> +static inline void btrfs_stack_item_key_to_cpu(struct btrfs_header
>> *stack_leaf,
>> +                           struct btrfs_key *key,
>> +                           int nr)
>> +{
>> +    struct btrfs_disk_key disk_key;
>> +    btrfs_stack_item_key(stack_leaf, &disk_key, nr);
>> +    btrfs_disk_key_to_cpu(key, &disk_key);
>> +}
>> +
>>   static inline void btrfs_dir_item_key_to_cpu(struct extent_buffer *eb,
>>                         struct btrfs_dir_item *item,
>>                         struct btrfs_key *key)
>>
> --
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