linux-kernel - Re: [PATCH v6 06/20] liveupdate: luo_file: implement file systems callbacks

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Message-ID: <mafs05xb744pb.fsf@kernel.org>
Date: Tue, 18 Nov 2025 18:43:12 +0100
From: Pratyush Yadav <pratyush@...nel.org>
To: David Matlack <dmatlack@...gle.com>
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Subject: Re: [PATCH v6 06/20] liveupdate: luo_file: implement file systems
 callbacks

On Tue, Nov 18 2025, David Matlack wrote:

> On 2025-11-15 06:33 PM, Pasha Tatashin wrote:
>> This patch implements the core mechanism for managing preserved
>> files throughout the live update lifecycle. It provides the logic to
>> invoke the file handler callbacks (preserve, unpreserve, freeze,
>> unfreeze, retrieve, and finish) at the appropriate stages.
>> 
>> During the reboot phase, luo_file_freeze() serializes the final
>> metadata for each file (handler compatible string, token, and data
>> handle) into a memory region preserved by KHO. In the new kernel,
>> luo_file_deserialize() reconstructs the in-memory file list from this
>> data, preparing the session for retrieval.
>> 
>> Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
>
>> +int liveupdate_register_file_handler(struct liveupdate_file_handler *h);
>
> Should there be a way to unregister a file handler?
>
> If VFIO is built as module then I think it  would need to be able to
> unregister its file handler when the module is unloaded to avoid leaking
> pointers to its text in LUO.

Good point. We also need when using FLB. You would first do
liveupdate_register_file_handler(), and then do
liveupdate_register_flb(). If the latter fails, you would want to
unregister the file handler too.

-- 
Regards,
Pratyush Yadav