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From:   Benjamin Coddington <bcodding@redhat.com>
To:     Olga Kornievskaia <olga.kornievskaia@gmail.com>
Cc:     trond.myklebust@hammerspace.com, anna.schumaker@netapp.com,
        linux-nfs@vger.kernel.org
Subject: Re: [PATCH 1/1] NFSv4.1: fix zero value filehandle in post open
 getattr
Date:   Thu, 13 Jul 2023 18:12:56 -0400
Message-ID: <A05D90E0-6D74-4948-B948-852B1448DD3C@redhat.com>
In-Reply-To: <CAN-5tyGa1dV1A5RgZsMCQzFHDV63=LDJq0DTpg8aJ=UCO+k+Og@mail.gmail.com>
References: <20230713195416.30414-1-olga.kornievskaia@gmail.com>
 <A0663B9C-F005-4089-ABD6-542F77EE43ED@redhat.com>
 <CAN-5tyGa1dV1A5RgZsMCQzFHDV63=LDJq0DTpg8aJ=UCO+k+Og@mail.gmail.com>
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On 13 Jul 2023, at 17:27, Olga Kornievskaia wrote:

> On Thu, Jul 13, 2023 at 5:09 PM Benjamin Coddington <bcodding@redhat.com> wrote:
>>
>> On 13 Jul 2023, at 15:54, Olga Kornievskaia wrote:
>>
>>> From: Olga Kornievskaia <kolga@netapp.com>
>>>
>>> Currently, if the OPEN compound experiencing an error and needs to
>>> get the file attributes separately, it will send a stand alone
>>> GETATTR but it would use the filehandle from the results of
>>> the OPEN compound. In case of the CLAIM_FH OPEN, nfs_openres's fh
>>> is zero value. That generate a GETATTR that's sent with a zero
>>> value filehandle, and results in the server returning an error.
>>>
>>> Instead, for the CLAIM_FH OPEN, take the filehandle that was used
>>> in the PUTFH of the OPEN compound.
>>>
>>> Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
>>> ---
>>>  fs/nfs/nfs4proc.c | 6 +++++-
>>>  1 file changed, 5 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
>>> index 8edc610dc1d3..0b1b49f01c5b 100644
>>> --- a/fs/nfs/nfs4proc.c
>>> +++ b/fs/nfs/nfs4proc.c
>>> @@ -2703,8 +2703,12 @@ static int _nfs4_proc_open(struct nfs4_opendata *data,
>>>                       return status;
>>>       }
>>>       if (!(o_res->f_attr->valid & NFS_ATTR_FATTR)) {
>>> +             struct nfs_fh *fh = &o_res->fh;
>>> +
>>>               nfs4_sequence_free_slot(&o_res->seq_res);
>>> -             nfs4_proc_getattr(server, &o_res->fh, o_res->f_attr, NULL);
>>> +             if (o_arg->claim == NFS4_OPEN_CLAIM_FH)
>>> +                     fh = NFS_FH(d_inode(data->dentry));
>>> +             nfs4_proc_getattr(server, fh, o_res->f_attr, NULL);
>>>       }
>>>       return 0;
>>>  }
>>
>> Looks good, but why not just use o_arg->fh?  Maybe also an opportunity
>> to fix the whitespace damage a few lines before this hunk too.
>>
>
> I did try it first. I had 2 problems with it. First of o_arg->fh is a
> "const struct" so it wouldn't allow me to be assigned without casting.
> Ok so perhaps it's not a big deal that we are going against the
> "const". Second of all, when I did do that, it produced the following
> warning and so I thought perhaps I should really use the original fh
> instead of what's in the args:

Oh maybe because this is the error path and nfs4_opendata is getting cleaned
up in nfs4_open_release()?  The comments in nfs4_open_release are a bit
confusing, but I think for the cases where we need to re-use the opendata we
are doing a kref_get on it.  Maybe we need a kref_get on the opendata for
this case?

.. I suspect we'd have the o_res.fh from nfs4_opendata_get_inode().  Out of
time, will check back in tomorrow.

Ben