Re: Questions Regarding Delegation Claim Behavior

[Chuck Lever <chuck.lever@oracle.com>]

On 5/22/25 11:51 AM, Petro Pavlov wrote:
> Hello,
> 
> My name is Petro Pavlov, I'm a developer at VAST.
> 
> I have a few questions about the delegation claim behavior observed in
> the Linux kernel version 3.10.0-1160.118.1.el7.x86_64.
> 
> I’ve written the following test case:
> 
>  1. Client1 opens *file1* with a write delegation; the server grants
>     both the open and delegation (*delegation1*).

Since you mention a write delegation, I'll assume you are using Linux
as an NFS client, and the server is not Linux, since that kernel version
does not implement server-side write delegation.


>  2. Client1 closes the open but does not return the delegation.
>  3. Client2 opens *file2* and also receives a write delegation
>     (*delegation2*).
>  4. Client1 then issues an open request with CLAIM_DELEGATE_CUR,
>     providing the filename from step 3 *(file2*), but using the
>     delegation stateid from step 1 (*delegation1*).

Would that be a client bug?


>  5. The server begins a recall of *delegation2*, treating the request in
>     step 4 as a normal open rather than returning a BAD_STATEID error.

That seems OK to me. The server has correctly noticed that the
client is opening file2, and delegation2 is associated with a
previous open of file2.

A better place to seek an authoritative answer might be RFC 8881.

The server returns BAD_STATEID if the stateid doesn't pass various
checks as outlined in Section 8.2. I don't see any text requiring the
server to report BAD_STATEID if delegate_stateid does not match the
component4 on a DELEGATE_CUR OPEN -- in fact, Table 19 says that
DELEGATE_CUR considers only the current file handle (the parent
directory) and the component4 argument.


> My understanding is that the server should have verified whether the
> delegation stateid provided actually belongs to the file being opened.
> Since it does not, I expected the server to return a BAD_STATEID error
> instead of proceeding with a standard open.
> 
> From additional tests, it seems the server only checks whether the
> delegation stateid is valid (i.e., whether it was ever granted), but
> does not verify that it is associated with the correct file or client.
> Please see the attached PCAP for reference.
> 
> Questions:
> 
> Is this behavior considered a bug?
> 
> Are there any known plans to address or fix this issue in future kernel
> versions?

AFAICT at the moment, NOTABUG


-- 
Chuck Lever