linux-ext4 - Re: [PATCH 5 2/4] Return 32/64-bit dir name hash according to usage type

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Message-ID: <4F981A04.1090802@redhat.com>
Date:	Wed, 25 Apr 2012 10:36:36 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Bernd Schubert <bernd.schubert@...m.fraunhofer.de>
CC:	Andreas Dilger <adilger@...mcloud.com>, linux-ext4@...r.kernel.org,
	Fan Yong <yong.fan@...mcloud.com>, bfields@...hat.com
Subject: Re: [PATCH 5 2/4] Return 32/64-bit dir name hash according to usage
 type

On 4/25/12 10:12 AM, Bernd Schubert wrote:
> On 04/25/2012 05:05 PM, Eric Sandeen wrote:
>> On 4/24/12 5:24 PM, Andreas Dilger wrote:
>>> On 2012-04-24, at 4:07 PM, Bernd Schubert wrote:
>>>>> 1) For SEEK_END, we now return -EINVAL for a positive offset
>>>>> (i.e. past EOF)
>>>> 
>>>> I definitely introduces that one, as I cannot see how an
>>>> application might ever run into it. Especially as ext4
>>>> directories cannot shrink. So if an application tries to exceed
>>>> the directory size limit, it looks to me as some of attempt to
>>>> break something or as an error in the application. However, if
>>>> there should be the slightest chance to break existing
>>>> applications relying on that, we need to remove that.
>>> 
>>> I think the other reason to avoid SEEK_END + n is that since
>>> SEEK_END for a hash offset is (signed) MAX_LONG, so if one seeks
>>> beyond that it will wrap to a negative offset.
>> 
>> Makes sense.
>> 
>> Wishing this had been done as a separate patch, though, since it's
>> really addressing a separate issue from the $SUBJECT, and could
>> have used specific documentation of the change.  Nitpicky I know,
>> but it helps.
> 
> Sorry, my fault. 

No worries, I should have reviewed sooner too :)

> Maybe we should simply document it in the code? And
> how do we proceed in general. Shall I write a patch to use
> generic_file_llseek() and update that function to take more
> arguments? I don't think that would go into 3.4.

Unless there is obviously _wrong_ behavior to be fixed I don't think it's needed for 3.4.

We could maybe do one patch to make it lockless again, if there's good confidence in that, since it's sort of a "regression."

Trying to munge things into the upstream seek function would be post-3.4, I'm sure, if it turns out it can be done at all.

Thanks,
-Eric

> Thanks, Bernd

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