2010/5/14 Benny Halevy <bhalevy@xxxxxxxxxxx>:
> On May. 13, 2010, 19:04 +0300, "William A. (Andy) Adamson" <androsadamson@xxxxxxxxx> wrote:
>> On Thu, May 13, 2010 at 11:31 AM, Boaz Harrosh <bharrosh@xxxxxxxxxxx> wrote:
>>> On 05/13/2010 06:17 PM, William A. (Andy) Adamson wrote:
>>>> On Thu, May 13, 2010 at 10:40 AM, Benny Halevy <bhalevy@xxxxxxxxxxx> wrote:
>>>>> On May. 13, 2010, 17:19 +0300, "William A. (Andy) Adamson" <androsadamson@xxxxxxxxx> wrote:
>>>>>> On Thu, May 13, 2010 at 4:40 AM, Boaz Harrosh <bharrosh@xxxxxxxxxxx> wrote:
>>>>>>> I've tested the patch:
>>>>>>> FIXME: async layout return
>>>>>>>
>>>>>>> And there is a missing small hunk
>>>>>>>
>>>>>>> I have tested with this patch and it is a very good patch
>>>>>>> that should also go into 2.6.33. It is necessary in the rare
>>>>>>> case when one inode have more then one open_context.
>>>>>>
>>>>>> Do you mean more than one open context per open owner?
>>>>>
>>>>> What we see is one "regular" open context and one which is the layout_commit_ctx
>>>>
>>>> Isn't that a BUG?
>>>>
>>>> Here is what we're seeing:
>>>>
>>>> nfs_file_release->nfs_release->nfs_file_clear_open_context->__put_nfs_open_context->
>>>> NFS_PROTO(inode)->close_context->nfs4_close_sync->__nfs4_close->pnfs_layoutcommit_inode,
>>>>
>>>> This is the same code that Boaz's 'missing small hunk' adds the wait
>>>> to the pnfs_layout_commit_inode to. This is good, because when
>>>> __nfs4_close is called with sync, every thing must be sent/returned
>>>> prior to the nfs_do_close call.
>>>>
>>>> But there is still a problem. Here is the __nfs4_close call (with out
>>>> the wait that Boaz added)
>>>>
>>>> if (nfsi->layoutcommit_ctx)
>>>> pnfs_layoutcommit_inode(state->inode, 0);
>>>> if (has_layout(nfsi) && nfsi->layout.roc_iomode) {
>>>> struct nfs4_pnfs_layout_segment range;
>>>>
>>>> range.iomode = nfsi->layout.roc_iomode;
>>>> range.offset = 0;
>>>> range.length = NFS4_MAX_UINT64;
>>>> pnfs_return_layout(state->inode, &range, NULL,
>>>> RETURN_FILE);
>>>>
>>>> Note that a pnfs_return_layout which is always 'sync' (async with wait
>>>> for completion). So the (currently) async LAYOUTCOMMIT call returns,
>>>> and a LAYOUTRETURN is put on the wire
>>>>
>>>> Then the LAYOUTCOMMIT rpc_call_done routine calls
>>>> pnfs_layoutcommit_done which calls put_nfs_open_context. If the open
>>>> context is different from the open context that was put by
>>>> nfs_file_release, then
>>>>
>>>> pnfs_layoutcommit_done->put_nfs_open_context-> ..... ->__nfs4_close
>>>> and the return on close LAYOUTRETURN is sent again!
>>>>
>>>> Of couse this second LAYOUTRETURN either gets a zero stateid, or uses
>>>> the same stateid as the first LAYOUTRETURN, and the reply to the
>>>> second LAYOUTRETURN will result in a NFS4ERR_BAD_STATEID .....
>>>>
>>>> This will occur whether the LAYOUTCOMMIT is async or sync as they both
>>>> call pnfs_layoutcommit_done.
>>>>
>>>> I need to understand why there are two open contexts. On the face of
>>>> it, it seems wrong.
>>>>
>>>> We also add a pointer to the open context in the nfs_write_data, and
>>>> in the pnfs_layoutcommit_data. Do we take a reference on the open data
>>>> in theses cases? .
>>>>
>>>> -->Andy
>>>>
>>>>
>>>
>>> Yes on all acounts. This is what Benny's patch is fixing please try it out
>>> it is most important (Add my small fix)
>>
>> Is this what you mean?
>>
>> With Benny's patch, with return-on-close set and the layoutcommit_ctx
>> different from the open context that caused the __nfs4_close:
>>
>> The (now) sync LAYOUTCOMMIT triggered from the nfs_file_release
>> __nfs4_close() will complete prior to calling the return-on-close
>> LAYOUTRETURN call. Since pnfs_layoutcommit_done is still called,
>> put_nfs_open_context will be call on the layoutconmit_ctx (saved in
>> pnfs_layoutcommit_data->ctx) and __nfs4_close will be called.
>>
>> In _this_ instance of calling __nfs4_close (from
>> pnfs_layoutcommit_done), the nfsi->layoutcommit_ctx pointer is null so
>> the pnfs_layoutcommit_inode call is skipped, and pnfs_return_layout
>> is called. Since it is also a sync call, pnfs_layoutcommit_done does
>> not return until it is complete. So the layout is returned, the layout
>> is freed (all layout segments 'cause the range covers the whole file)
>> and pnfs_layoutcommit_inode returns to the FIRST __nfs4_close (from
>> nfs_file_release)
>>
>> Now since return-on-close is set, pnfs_layout_return is called (in the
>> nfs_file_release __nfs4_close). This LAYOUTRETURN call will never go
>> on the wire because the first pnfs_layout_return (from the
>> pnfs_layoutcommit_done __nfs4_close) has removed the layout segment,
>> and all is well.
>>
>> Sheese.
>
> Yeah :-/
> I'm feeling increasingly uncomfortable with the current implementation
> and we're planning to come up with the state-machine based model
> for the Bakeathon and test it there. Ideally, this will be stable enough
> that we can get the gist of it into pnfs-submit.
>
> Benny
>
Is there any document about the state-machine based model?
>>
>> --->Andy
>>
>>
>>>
>>> And about the multiple contexts I don't understand as well but the fact of it
>>> is that an nfs_inode has an list_head of open_contexts and we must deal properly
>>> with when that happens. (BTW with 2.6.34 Kernel it happens regularly as in
>>> prev kernels it almost never trigger.)
>>>
>>> Benny's patch takes care of that and I've done heavy testing of it I can see cases
>>> of more then one contexts and it works correctly.
>>>
>>> But I too would like to understand when is it that an inode can have more then
>>> one open_context
>>>
>>> Boaz
>>>
>>>>
>>>>>
>>>>> Benny
>>>>>
>>>>>>
>>>>>> -->Andy
>>>>>>
>>>>>>>
>>>>>>> (For some reason I see that happening much more in 2.6.34
>>>>>>> I don't understand why)
>>>>>>>
>>>>>>> Boaz
>>>>>>> ---
>>>>>>> git diff --stat -p -M
>>>>>>> fs/nfs/nfs4state.c | 2 +-
>>>>>>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>>>>>>
>>>>>>> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
>>>>>>> index 15c8bc8..6dbe893 100644
>>>>>>> --- a/fs/nfs/nfs4state.c
>>>>>>> +++ b/fs/nfs/nfs4state.c
>>>>>>> @@ -590,7 +590,7 @@ static void __nfs4_close(struct path *path, struct nfs4_state *state, fmode_t fm
>>>>>>> struct nfs_inode *nfsi = NFS_I(state->inode);
>>>>>>>
>>>>>>> if (nfsi->layoutcommit_ctx)
>>>>>>> - pnfs_layoutcommit_inode(state->inode, 0);
>>>>>>> + pnfs_layoutcommit_inode(state->inode, wait);
>>>>>>> if (has_layout(nfsi) && nfsi->layout.roc_iomode) {
>>>>>>> struct nfs4_pnfs_layout_segment range;
>>>>>>>
>>>>>>> --
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>>>>>
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>>>
>>>
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--
Zhang Jingwang
National Research Centre for High Performance Computers
Institute of Computing Technology, Chinese Academy of Sciences
No. 6, South Kexueyuan Road, Haidian District
Beijing, China
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