Re: [PATCH v3 17/30] liveupdate: luo_files: luo_ioctl: Unregister all FDs on device close

[Pratyush Yadav <pratyush@kernel.org>]

On Mon, Sep 22 2025, Pasha Tatashin wrote:

> On Wed, Aug 27, 2025 at 11:34 AM Pratyush Yadav <pratyush@kernel.org> wrote:
>>
>> Hi Pasha,
>>
>> On Thu, Aug 07 2025, Pasha Tatashin wrote:
>>
>> > Currently, a file descriptor registered for preservation via the remains
>> > globally registered with LUO until it is explicitly unregistered. This
>> > creates a potential for resource leaks into the next kernel if the
>> > userspace agent crashes or exits without proper cleanup before a live
>> > update is fully initiated.
>> >
>> > This patch ties the lifetime of FD preservation requests to the lifetime
>> > of the open file descriptor for /dev/liveupdate, creating an implicit
>> > "session".
>> >
>> > When the /dev/liveupdate file descriptor is closed (either explicitly
>> > via close() or implicitly on process exit/crash), the .release
>> > handler, luo_release(), is now called. This handler invokes the new
>> > function luo_unregister_all_files(), which iterates through all FDs
>> > that were preserved through that session and unregisters them.
>>
>> Why special case files here? Shouldn't you undo all the serialization
>> done for all the subsystems?
>
> Good point, subsystems should also be cancelled, and system should be
> brought back to normal state. However, with session support, we will
> be dropping only FDs that belong to a specific session when its FD is
> closed, or all FDs+subsystems when closing /dev/liveupdate.

Yeah, that makes sense.

[...]

-- 
Regards,
Pratyush Yadav