liveupdate: luo_file: add private argument to store runtime state

Currently file handlers only get the serialized_data field to store their
state. This field has a pointer to the serialized state of the file, and
it becomes a part of LUO file's serialized state.

File handlers can also need some runtime state to track information that
shouldn't make it in the serialized data.

One such example is a vmalloc pointer. While kho_preserve_vmalloc()
preserves the memory backing a vmalloc allocation, it does not store the
original vmap pointer, since that has no use being passed to the next
kernel. The pointer is needed to free the memory in case the file is
unpreserved.

Provide a private field in struct luo_file and pass it to all the
callbacks. The field's can be set by preserve, and must be freed by
unpreserve.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Pratyush Yadav <[e-mail]>
Co-developed-by: Pasha Tatashin <[e-mail]>
Signed-off-by: Pasha Tatashin <[e-mail]>
Reviewed-by: Mike Rapoport (Microsoft) <[e-mail]>
Tested-by: David Matlack <[e-mail]>
Cc: Aleksander Lobakin <[e-mail]>
Cc: Alexander Graf <[e-mail]>
Cc: Alice Ryhl <[e-mail]>
Cc: Andriy Shevchenko <[e-mail]>
Cc: anish kumar <[e-mail]>
Cc: Anna Schumaker <[e-mail]>
Cc: Bartosz Golaszewski <[e-mail]>
Cc: Bjorn Helgaas <[e-mail]>
Cc: Borislav Betkov <[e-mail]>
Cc: Chanwoo Choi <[e-mail]>
Cc: Chen Ridong <[e-mail]>
Cc: Chris Li <[e-mail]>
Cc: Christian Brauner <[e-mail]>
Cc: Daniel Wagner <[e-mail]>
Cc: Danilo Krummrich <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: David Hildenbrand <[e-mail]>
Cc: David Jeffery <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: Guixin Liu <[e-mail]>
Cc: "H. Peter Anvin" <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Cc: Ilpo Järvinen <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Ira Weiny <[e-mail]>
Cc: Jann Horn <[e-mail]>
Cc: Jason Gunthorpe <[e-mail]>
Cc: Jens Axboe <[e-mail]>
Cc: Joanthan Cameron <[e-mail]>
Cc: Joel Granados <[e-mail]>
Cc: Johannes Weiner <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Cc: Lennart Poettering <[e-mail]>
Cc: Leon Romanovsky <[e-mail]>
Cc: Leon Romanovsky <[e-mail]>
Cc: Lukas Wunner <[e-mail]>
Cc: Marc Rutland <[e-mail]>
Cc: Masahiro Yamada <[e-mail]>
Cc: Matthew Maurer <[e-mail]>
Cc: Miguel Ojeda <[e-mail]>
Cc: Myugnjoo Ham <[e-mail]>
Cc: Parav Pandit <[e-mail]>
Cc: Pratyush Yadav <[e-mail]>
Cc: Randy Dunlap <[e-mail]>
Cc: Roman Gushchin <[e-mail]>
Cc: Saeed Mahameed <[e-mail]>
Cc: Samiullah Khawaja <[e-mail]>
Cc: Song Liu <[e-mail]>
Cc: Steven Rostedt <[e-mail]>
Cc: Stuart Hayes <[e-mail]>
Cc: Tejun Heo <[e-mail]>
Cc: Thomas Gleinxer <[e-mail]>
Cc: Thomas Weißschuh <[e-mail]>
Cc: Vincent Guittot <[e-mail]>
Cc: William Tu <[e-mail]>
Cc: Yoann Congal <[e-mail]>
Cc: Zhu Yanjun <[e-mail]>
Cc: Zijun Hu <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

include/linux/liveupdate.h

···
  *                    this to the file being operated on.
  * @serialized_data:  The opaque u64 handle, preserve/prepare/freeze may update
  *                    this field.
+ * @private_data:     Private data for the file used to hold runtime state that
+ *                    is not preserved. Set by the handler's .preserve()
+ *                    callback, and must be freed in the handler's
+ *                    .unpreserve() callback.
  *
  * This structure bundles all parameters for the file operation callbacks.
  * The 'data' and 'file' fields are used for both input and output.
···
 	bool retrieved;
 	struct file *file;
 	u64 serialized_data;
+	void *private_data;
 };
 
 /**

kernel/liveupdate/luo_file.c

···
  *                 This handle is passed back to the handler's .freeze(),
  *                 .retrieve(), and .finish() callbacks, allowing it to track
  *                 and update its serialized state across phases.
+ * @private_data:  Pointer to the private data for the file used to hold runtime
+ *                 state that is not preserved. Set by the handler's .preserve()
+ *                 callback, and must be freed in the handler's .unpreserve()
+ *                 callback.
  * @retrieved:     A flag indicating whether a user/kernel in the new kernel has
  *                 successfully called retrieve() on this file. This prevents
  *                 multiple retrieval attempts.
···
 	struct liveupdate_file_handler *fh;
 	struct file *file;
 	u64 serialized_data;
+	void *private_data;
 	bool retrieved;
 	struct mutex mutex;
 	struct list_head list;
···
 		goto err_kfree;
 
 	luo_file->serialized_data = args.serialized_data;
+	luo_file->private_data = args.private_data;
 	list_add_tail(&luo_file->list, &file_set->files_list);
 	file_set->count++;
 
···
 		args.handler = luo_file->fh;
 		args.file = luo_file->file;
 		args.serialized_data = luo_file->serialized_data;
+		args.private_data = luo_file->private_data;
 		luo_file->fh->ops->unpreserve(&args);
 
 		list_del(&luo_file->list);
···
 		args.handler = luo_file->fh;
 		args.file = luo_file->file;
 		args.serialized_data = luo_file->serialized_data;
+		args.private_data = luo_file->private_data;
 
 		err = luo_file->fh->ops->freeze(&args);
 		if (!err)
···
 		args.handler = luo_file->fh;
 		args.file = luo_file->file;
 		args.serialized_data = luo_file->serialized_data;
+		args.private_data = luo_file->private_data;
 
 		luo_file->fh->ops->unfreeze(&args);
 	}