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

To: Mark Tinguely <tinguely@xxxxxxx>
Subject: Re: [PATCH] xfs: reserve fields in inode for parent ptr and alloc policy
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Wed, 10 Apr 2013 15:40:28 -0500
Cc: Rich Johnston <rjohnston@xxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <5165CC39.2090108@xxxxxxx>
References: <20130410182438.268267840@xxxxxxx> <5165B5CB.2070203@xxxxxxxxxxx> <5165BFF4.8020601@xxxxxxx> <5165CC39.2090108@xxxxxxx>
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On 4/10/13 3:31 PM, Mark Tinguely wrote:
> 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
>>

> 
> The allocation policies is based on work by Dave:
> 
>     http://oss.sgi.com/archives/xfs/2009-02/msg00250.html
> 
> --Mark.
> 

Great, thanks guys.  I had forgotten about that TBH.  Just wondered
if you had it in the works, or reserving just in case, or . . . 

-Eric

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