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Re: [PATCH 51/50] xfs: add xfs sb v4 support for dirent filetype field

To: Mark Tinguely <tinguely@xxxxxxx>
Subject: Re: [PATCH 51/50] xfs: add xfs sb v4 support for dirent filetype field
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Tue, 20 Aug 2013 09:45:37 -0500
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <52137D3D.8060205@xxxxxxx>
References: <1376304611-22994-1-git-send-email-david@xxxxxxxxxxxxx> <20130819201940.516942026@xxxxxxx> <5212AA1D.3000809@xxxxxxxxxxx> <52137D3D.8060205@xxxxxxx>
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On 8/20/13 9:29 AM, Mark Tinguely wrote:
> On 08/19/13 18:28, Eric Sandeen wrote:
>> On 8/19/13 3:19 PM, Mark Tinguely wrote:
>> <an attachment that doesn't show up on reply, moving d_type support
>> to v4 superblocks ;)>
>> Thanks, Mark!
>> Has you been able to test this at all?

Hi Mark -

> There is no test for this feature. 

no xfstest, I know.  :)

> Yes I did my version of testing.
> First adding each type of inode type and verifying it. Then fsstress
> testing using the same seed for sb v4+feature, v4 plain, v5+feature.
> The resulting directory and checked with xfs_db. fsstress was chosen
> because how it manipulate directory items.
>> I do still owe a promised xfstest - but for that, we'll need at
>> least mkfs &  xfs_repair support.
> Dave made changes so that xfs_repair will run (find the correct
> directory items) but the feature verification and repairs has not
> been done, so technically this is an incomplete feature.

Right, but Dave's patches only recognize it as a valid feature
on V5 superblocks; V4 will take a bit more logic, won't it?
Won't repair see this as an invalid feature flag on V4 even
with Dave's patches?

>> Did you patch up mkfs to do basic tests of your kernelspace patch?
> yes. to the directory area in mkfs per suggestion.
> The tests run the same on the v5 and v4 - ummm, it is the same
> directory code. see above.
>> Talking to Dave, he reminds me of a few things this needs, if it's 
>> going to be complete&  compatible on V4:
>> * mkfs.xfs commandline option support&  manpage updates
> yes
>> * xfs_db support (including version friendly-text output)
> yes, xfsprogs v4/v5 uses the same directory code, Dave's patches
> support xfs_db. It works for v4/v5.


>> * XFS_IOC_FSGEOM support so that xfs_info can report the
>> difference * xfs_repair needs to know that it's a valid feature on
>> V4
> okay, it will run xfs_repair to the same level as v5. AND ...As
> pointed out, there is no xfs_repair support to verify/correct the
> feature in v5 and therefore v4 - (again it is the same directory
> code). As is, this feature is incomplete. That could keep the kernel
> portion from moving forward.
>> Some of that may overlap w/ things still needed on V5, but some is
>> unique to allowing it on V4.
>> Mark, do you plan to do some of those unique-to-V4 parts, too?
> Yes.

Ok, cool.

>> As an aside: I would support getting this feature onto V4
>> superblocks, after we have confidence that all the bits are done,
>> tested, and robust.
>> I still would really like to see it go forward in parallel on V5,
>> and not be blocked by the extra work needed for proper V4
>> integration.
> understood - now documented.  Hi Linus.

I'm Eric ;)

> This feature uses shared directory code. It has to be turned on using
> a mkfs to be used. No one will accidentally get this feature.
> The feature and implementation are good. The directory code is common
> - the feature added changes to that directory code. If the
> implementation is bad it will trash the v4/v5 directories the same -
> no matter if the feature is turned on or off. If you are so afraid of
> the common code may break any directories, then this feature should
> be held back for more testing.

I'm not overly fearful...

> All that I insist is this nice feature be added to the mainstream
> filesystem at the same time as the experimental filesystem. There is
> NO TECHNICAL reason that this feature is not supported mainstream
> filesystem.

No, not technical... (although, there is also no technical reason that
V4 and V5 must go in at the same time, so we're into the realm of
opinion & preference here)

One reason I'd argue for V5 potentially prior to V4 is that V4 requires
a few more code changes over and above V5.  If those V4 changes lag,
it it might make sense to separate them.  If they don't lag, great.

> I repeat, if you have technical concerns for the feature's
> implementation and its impact on v4 filesystems because it uses
> common directory code, then it should be held back for more testing.

I'm not trying to pick a fight.  I just want to make sure that all
the new work unique to having it on V4 is identified & owned...


>> Thanks, -Eric
> --Mark.

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