[Ocfs2-tools-devel] [PATCH 06/22] libocfs2: Make ocfs2_init_group_desc aware of discontig group.

[Tao Ma]

Joel Becker wrote:
> On Thu, Apr 01, 2010 at 04:01:23PM +0800, Tao Ma wrote:
>   
>> Joel Becker wrote:
>>     
>>> On Thu, Apr 01, 2010 at 12:41:10PM +0800, Tao Ma wrote:
>>>       
>>>> Pass a parameter named suballoc to ocfs2_init_group_desc
>>>> so that it can init bg_size properly.
>>>>         
>>> 	I hate passing this parameter around.  I don't know how to make
>>> it better.
>>>       
>> yeah, the only way is that we can add a new member in ocfs2_group_desc, 
>> but that are only 2 reserved field(1 le32 and one le64), so I don't want 
>> to waste them.
>>
>> Another way is that we separate bg_chain to a __le8
>> -	__le16  bg_chain;
>> +	__le8	bg_chain;
>> +	__le8	bg_flags;
>>     
>  
> 	You're at least partially right.  In the kernel code, I rely on
> the fact that we know we are a block or cluster allocator before
> deciding to trust bg_list.l_next_free_rec.  Then I use l_next_free_rec
> to decide if we're discontig.  However, our filesystem is (almost
> always) self-describing.  We don't just set i_refcount_loc, we also set
> REFCOUNT_FL.
> 	It's better if we have a way to know the group descriptor is
> discontiguous without knowing the inode and superblock.  Then the
> feature tests are mere sanity.
> 	We can add bg_flags as you describe above.  Another option is to
> see that bg_bitmap + bg_size == offsetof(bg_list).  Both work.  The
> former is more descriptive, the latter is less invasive.  Which works
> for you?  Mark?
>   
oh yes, it seems be better. That also means that we now are heavily 
dependent on bg_size which used to be an auxiliary one. ;)

Regards,
Tao