Re: [PATCH] xfs: reserve fields in inode for parent ptr and alloc policy

[Mark Tinguely <tinguely@sgi.com>]

On 04/10/13 14:39, Rich Johnston wrote:
> On 04/10/2013 01:56 PM, Eric Sandeen wrote:
>> On 4/10/13 1:24 PM, Mark Tinguely wrote:
>>> Reserve fields in new inode layout for parent pointer and
>>> allocation policy.
>>> ----
>>> The inode will hold the parent information for the first
>>> link to a file. Information for the other links will be
>>> held in extended attribute entries.
>>>
>>> The "di_parino" is the inode of the parent directory. The
>>> directory information for this entry is located the parent
>>> directory with "di_paroff" offset.
>>>
>>> The di_parino/di_paroff concept code is running.
>>> ----
>>> The "di_allocpolicy" will be used to remember the allocation
>>> policy associated with this inode.
>>
>> can you say more about this allocation policy?
>>
>> -Eric
>
> No its super secret information. ;)
>
> Its on my plate Eric, because Mark was making a change for parent ptrs,
> I asked him to request space for allocation policies also.
>
> I don't have all the details yet but here is a very high level concept.
>
> Identify allocation groups by names (or numbers -- preferably using names
> in user-visible areas), allowing many different areas. Placing the
> allocation
> policy outside of user programs is necessary for this to be successful.
>
> Current thoughts on proposed a layered allocation policies:
>
> Policy for the entire filesystem
> Policy attached to a directory (whose policy would be inherited by
> subdirectories when subdirectories are created)
> Policy for a single file
>
> The policy would define:
>
> where to place file data
> where to place metadata for the files.
> a prefered allocation group for placing file data (for directories).
>
> --Rich
>
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The allocation policies is based on work by Dave:

	http://oss.sgi.com/archives/xfs/2009-02/msg00250.html

--Mark.

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