linux-kernel - Re: [PATCH v2 1/5] fat: allocate persistent inode numbers

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Message-ID: <CAKYAXd_mxq26bhRYd-YM9OBjYMO12TD4wHxm6PqHBLjgGFHaZg@mail.gmail.com>
Date:	Thu, 6 Sep 2012 22:39:27 +0900
From:	Namjae Jeon <linkinjeon@...il.com>
To:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Cc:	Al Viro <viro@...iv.linux.org.uk>, akpm@...ux-foundation.org,
	bfields@...ldses.org, linux-kernel@...r.kernel.org,
	Namjae Jeon <namjae.jeon@...sung.com>,
	Ravishankar N <ravi.n1@...sung.com>,
	Amit Sahrawat <a.sahrawat@...sung.com>
Subject: Re: [PATCH v2 1/5] fat: allocate persistent inode numbers

2012/9/6 OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>:
> Namjae Jeon <linkinjeon@...il.com> writes:
>
>>>> In this long discusstion about the FAT acceptance over NFS, our belief
>>>> is still that the objective should be to reduce errors as much as
>>>> possible and then if there are certain scenarios - at least that could
>>>> be highlighted as a limitation in Documentation instead of completely
>>>> discarding the usage of FAT over NFS.  So how about puttting rename
>>>> scenario as a limitation ? In ideal scenario how many times this is
>>>> going to happen ?
>>>
>>> My understanding of your patches is to introduce the silent corruption
>>> bug by getting wrong location via ino on some cases, instead of
>>> ESTALE. And make surprise to userland by change ino.
>>>
>>> Why is it safe to change ino? If you are saying to remove the changing
>>> ino on rename, how handle the case of collision?
>> Yes, agreed this would lead to collision. So, If we are choosing
>> 'i_pos' as inode
>> number, We need to have a mechanism to avoid this 'i_pos' being reused.
>>
>> We can have one thing over here. As a part of avoidance for such scenarios -
>> We can return EBUSY for this rename operation. i.e., If the inode is being
>> referenced then in such cases it makes sense to return EBUSY over NFS and
>>  forcus on the large part of the solution which is making FAT stable.
>>
>> Let me know your opinion.
>
> It sounds like sane to provide the limited but stable behavior, with the
> option. But at first, I'd like to see the read-only export but clean
> solution, and make it stable. (I'm not thinking about the implementation
> detail. It may be the stable ino solution, or may not be.)
Hi. OGAWA.
I Agree. Once, I will check whether it is possible to implement
read-only export or not.
And If I face some problem or have some concern, I will discuss about
it with you.

>
> After that, we can make it writable incrementally.
Okay.
Thanks a lot.
> --
> OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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