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Date:   Fri, 1 Oct 2021 16:53:27 -0400
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     Dai Ngo <dai.ngo@oracle.com>
Cc:     chuck.lever@oracle.com, linux-nfs@vger.kernel.org,
        linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH RFC v5 0/2] nfsd: Initial implementation of NFSv4
 Courteous Server
Message-ID: <20211001205327.GN959@fieldses.org>
References: <20210929005641.60861-1-dai.ngo@oracle.com>
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On Tue, Sep 28, 2021 at 08:56:39PM -0400, Dai Ngo wrote:
> 
> Hi Bruce,
> 
> This series of patches implement the NFSv4 Courteous Server.

Apologies, I keep meaning to get back to this and haven't yet.

I do notice I'm seeing a timeout on pynfs 4.0 test OPEN18.

--b.

> 
> A server which does not immediately expunge the state on lease expiration
> is known as a Courteous Server.  A Courteous Server continues to recognize
> previously generated state tokens as valid until conflict arises between
> the expired state and the requests from another client, or the server
> reboots.
> 
> The v2 patch includes the following:
> 
> . add new callback, lm_expire_lock, to lock_manager_operations to
>   allow the lock manager to take appropriate action with conflict lock.
> 
> . handle conflicts of NFSv4 locks with NFSv3/NLM and local locks.
> 
> . expire courtesy client after 24hr if client has not reconnected.
> 
> . do not allow expired client to become courtesy client if there are
>   waiters for client's locks.
> 
> . modify client_info_show to show courtesy client and seconds from
>   last renew.
> 
> . fix a problem with NFSv4.1 server where the it keeps returning
>   SEQ4_STATUS_CB_PATH_DOWN in the successful SEQUENCE reply, after
>   the courtesy client re-connects, causing the client to keep sending
>   BCTS requests to server.
> 
> The v3 patch includes the following:
> 
> . modified posix_test_lock to check and resolve conflict locks
>   to handle NLM TEST and NFSv4 LOCKT requests.
> 
> . separate out fix for back channel stuck in SEQ4_STATUS_CB_PATH_DOWN.
> 
> The v4 patch includes:
> 
> . rework nfsd_check_courtesy to avoid dead lock of fl_lock and client_lock
>   by asking the laudromat thread to destroy the courtesy client.
> 
> . handle NFSv4 share reservation conflicts with courtesy client. This
>   includes conflicts between access mode and deny mode and vice versa.
> 
> . drop the patch for back channel stuck in SEQ4_STATUS_CB_PATH_DOWN.
> 
> The v5 patch includes:
> 
> . fix recursive locking of file_rwsem from posix_lock_file. 
> 
> . retest with LOCKDEP enabled.
> 
> NOTE: I will submit pynfs tests for courteous server including tests
> for share reservation conflicts in a separate patch.
>