[PATCH v8 13/18] liveupdate: luo_file: add private argument to store runtime state

[Pasha Tatashin <pasha.tatashin@soleen.com>]

From: Pratyush Yadav <ptyadav@amazon.de>

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.

Signed-off-by: Pratyush Yadav <ptyadav@amazon.de>
Co-developed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 include/linux/liveupdate.h   | 5 +++++
 kernel/liveupdate/luo_file.c | 9 +++++++++
 2 files changed, 14 insertions(+)

diff --git a/include/linux/liveupdate.h b/include/linux/liveupdate.h
index 122ad8f16ff9..a7f6ee5b6771 100644
--- a/include/linux/liveupdate.h
+++ b/include/linux/liveupdate.h
@@ -27,6 +27,10 @@ struct file;
  *                    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.
@@ -36,6 +40,7 @@ struct liveupdate_file_op_args {
 	bool retrieved;
 	struct file *file;
 	u64 serialized_data;
+	void *private_data;
 };
 
 /**
diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
index e9727cb1275a..ddff87917b21 100644
--- a/kernel/liveupdate/luo_file.c
+++ b/kernel/liveupdate/luo_file.c
@@ -129,6 +129,10 @@ static LIST_HEAD(luo_file_handler_list);
  *                 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.
@@ -155,6 +159,7 @@ struct luo_file {
 	struct liveupdate_file_handler *fh;
 	struct file *file;
 	u64 serialized_data;
+	void *private_data;
 	bool retrieved;
 	struct mutex mutex;
 	struct list_head list;
@@ -298,6 +303,7 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd)
 		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++;
 
@@ -344,6 +350,7 @@ void luo_file_unpreserve_files(struct luo_file_set *file_set)
 		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);
@@ -370,6 +377,7 @@ static int luo_file_freeze_one(struct luo_file_set *file_set,
 		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)
@@ -390,6 +398,7 @@ static void luo_file_unfreeze_one(struct luo_file_set *file_set,
 		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);
 	}
-- 
2.52.0.460.gd25c4c69ec-goog