Re: [PATCH 1/1] liveupdate: luo_file: Add internal APIs for file preservation

[Pranjal Shrivastava <praan@google.com>]

On Sat, Jun 13, 2026 at 01:25:20AM +0000, Samiullah Khawaja wrote:
> From: Pasha Tatashin <pasha.tatashin@soleen.com>
> 
> Live update orchestrator file handlers depend on the preservation of
> other files. To make sure that the dependency is preserved, the file
> handlers needs to fetch the preservation token of the preserved
> dependency. Similarly during restore, a file handler wants to fetch the
> restored file of the dependency.
> 
> Add APIs that allows fetching token of dependency during preservation,
> and fetching the restored file dependency during restore.
> 
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> Signed-off-by: Samiullah Khawaja <skhawaja@google.com>
> ---
>  include/linux/liveupdate.h       | 21 ++++++++++
>  kernel/liveupdate/luo_file.c     | 69 ++++++++++++++++++++++++++++++++
>  kernel/liveupdate/luo_internal.h | 17 ++++++++
>  3 files changed, 107 insertions(+)
>
[...]
> +EXPORT_SYMBOL_GPL(liveupdate_get_token_outgoing);
> +
> +/**
> + * liveupdate_get_file_incoming - Retrieves a preserved file for in-kernel use.
> + * @s:      The incoming liveupdate session (restored from the previous kernel).
> + * @token:  The unique token identifying the file to retrieve.
> + * @filep:  On success, this will be populated with a pointer to the retrieved
> + *          'struct file'.
> + *
> + * Provides a kernel-internal API for other subsystems to retrieve their
> + * preserved files after a live update. This function is a simple wrapper
> + * around luo_retrieve_file(), allowing callers to find a file by its token.
> + *
> + * The caller receives a new reference to the file and must call fput() when it
> + * is no longer needed. The file's lifetime is managed by LUO and any userspace
> + * file descriptors.
> + *
> + * Context: It must be called with session mutex acquired of a restored session.
> + * Return: 0 on success. Returns -ENOENT if no file with the matching token is
> + *         found, or any other negative errno on failure.
> + */
> +int liveupdate_get_file_incoming(struct liveupdate_session *s, u64 token,
> +				 struct file **filep)
> +{
> +	return luo_retrieve_file(luo_file_set_from_session_locked(s),
> +				 token, filep);
> +}
> +EXPORT_SYMBOL_GPL(liveupdate_get_file_incoming);

Thanks for modifying the comment (as discussed in [1]). 
This looks good now, along with the EXPORT_SYMBOL_GPL.

Reviewed-by: Pranjal Shrivastava <praan@google.com>

Thanks,
Praan

[1] https://lore.kernel.org/all/agr6yoyYYq2QFxjL@google.com/