linux-kernel - Re: [PATCH v3 0/2] nfsd: allow the use of multiple backchannel slots

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Message-ID: <E97077C4-A730-4755-B637-3EF61CAB44B8@oracle.com>
Date: Wed, 6 Nov 2024 15:37:15 +0000
From: Chuck Lever III <chuck.lever@...cle.com>
To: Sebastian Feld <sebastian.n.feld@...il.com>
CC: Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 0/2] nfsd: allow the use of multiple backchannel slots



> On Nov 6, 2024, at 10:16 AM, Sebastian Feld <sebastian.n.feld@...il.com> wrote:
> 
> On Wed, Oct 30, 2024 at 3:50 PM Jeff Layton <jlayton@...nel.org> wrote:
>> 
>> A few more minor updates to the set to fix some small-ish bugs, and do a
>> bit of cleanup. This seems to test OK for me so far.
>> 
>> Signed-off-by: Jeff Layton <jlayton@...nel.org>
>> ---
>> Changes in v3:
>> - add patch to convert se_flags to single se_dead bool
>> - fix off-by-one bug in handling of NFSD_BC_SLOT_TABLE_MAX
>> - don't reject target highest slot value of 0
>> - Link to v2: https://lore.kernel.org/r/20241029-bcwide-v2-1-e9010b6ef55d@kernel.org
>> 
>> Changes in v2:
>> - take cl_lock when fetching fields from session to be encoded
>> - use fls() instead of bespoke highest_unset_index()
>> - rename variables in several functions with more descriptive names
>> - clamp limit of for loop in update_cb_slot_table()
>> - re-add missing rpc_wake_up_queued_task() call
>> - fix slotid check in decode_cb_sequence4resok()
>> - add new per-session spinlock
>> 
> 
> What does a NFSv4.1 client need to do to be compatible with this change?

Hi Sebastian -

NFSD will continue to use 1 slot if that's all the client can
handle. This is negotiated by the CREATE_SESSION operation.

This is part of the NFSv4.1 protocol as specified in RFC 8881.
If the client complies with that spec, the only thing that
stands in the way of compatibility is implementation bugs.

--
Chuck Lever