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Re: [PATCH] xfs_mdrestore: initialize sb prior to xfs_sb_from_disk()

To: Dave Chinner <david@xxxxxxxxxxxxx>, Eric Sandeen <sandeen@xxxxxxxxxx>
Subject: Re: [PATCH] xfs_mdrestore: initialize sb prior to xfs_sb_from_disk()
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Thu, 05 Jun 2014 21:53:19 -0500
Cc: xfs-oss <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20140606014256.GD4453@dastard>
References: <5390F89C.2050305@xxxxxxxxxx> <20140605235633.GC4453@dastard> <53910482.1030909@xxxxxxxxxx> <20140606014256.GD4453@dastard>
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On 6/5/14, 8:42 PM, Dave Chinner wrote:
> On Thu, Jun 05, 2014 at 07:00:02PM -0500, Eric Sandeen wrote:
>> On 6/5/14, 6:56 PM, Dave Chinner wrote:
>>> On Thu, Jun 05, 2014 at 06:09:16PM -0500, Eric Sandeen wrote:
>>
>> ...
>>
>>>> But ... should we maybe just do this once and for all in
>>>> xfs_sb_from_disk?  I'm not sure leaving it up to every
>>>> caller is a good idea, unless somebody ahs a reason to
>>>> pre-populate some fields - I can't imagine why that would
>>>> be, though...
>>>
>>> We don't ever read in the CRC field into the in-memory structures
>>> because it has no meaning in memory. Simiarly, we don't ever write
>>> the CRC field from the in-core structure because we always
>>> re-calculate it in the IO path if CRCs are configured. That is
>>> consistent behaviour across the entire code-base.
>>
>> <snip stuff>
>>
>>> Perhaps we should move the memset() to within xfs_sb_from_disk()
>>> to make this explicit?
>>
>> Yes, that's what I meant by "this" in "do this once and for all" - 
>> sorry, that wasn't clear.  memset(0) in xfs_sb_from_disk().
> 
> I didn't read it clearly. my fault.
> 
>> Yeah, the more I think about it, the more I think that's probably
>> the obviously correct thing to do.

Actually, a memset() seems like overkill - every field except
sb_crc is explicitly filled in in the function.

Maybe better to just set sb_crc to 0, with a comment as to why?
I think I'll whip that one up.

-Eric

> *nod*
> 
> Cheers,
> 
> Dave.
> 

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