[Ocfs2-devel] [patch 09/11] ocfs2: llseek requires ocfs2 inode lock for the file in SEEK_END

[Jensen]

On 2014/2/8 6:44, Mark Fasheh wrote:
> On Thu, Feb 06, 2014 at 03:50:29PM -0800, Andrew Morton wrote:
>> On Thu, 6 Feb 2014 15:42:53 -0800 Mark Fasheh <mfasheh at suse.de> wrote:
>>
>>> On Fri, Jan 24, 2014 at 12:47:09PM -0800, akpm at linux-foundation.org wrote:
>>>> From: Jensen <shencanquan at huawei.com>
>>>> Subject: ocfs2: llseek requires ocfs2 inode lock for the file in SEEK_END
>>>>
>>>> llseek requires ocfs2 inode lock for updating the file size in SEEK_END. 
>>>> because the file size maybe update on another node.
>>>>
>>>> This bug can be reproduce the following scenario: at first, we dd a test
>>>> fileA, the file size is 10k.
>>> Basically, you want to amke SEEK_END cluster-aware. This patch would be the
>>> right way to do it.
>> Sunil was worried about the performance impact.  Correctness beats
>> performance, but some quantitative testing would be useful?
> Performance is my primary concern as well. I thought of writing it up but
> realized I don't really have any evidence off the top of my head one way or
> the other that this might slow us down.
>
> That said, I kind of question the usefulness of this patch - we got
> along pretty well so far without locking in lseek and some random dd(1) test
> doesn't really provide a great end-user reason for why we should do this.
>
> I will note that gfs2 locks for SEEK_END.
>
>
> Testing would help to answer this, yes. Jensen is this something you can do?
> I'm not sure exactly what we would run yet though, I have to think about
> that (or maybe someone can suggest something).
>
> Thanks,
> 	--Mark
>
   ocfs2 is a cluster file system.  as like read/write/open/rmdir/unlink interface which think of cluster-aware. I think the seek interface need
   cluster-aware. May be it has the performance impact. but it's correctness is more important than performance.

  Thanks,
                  --Jensen

> --
> Mark Fasheh
>
> .
>