[PATCH 1/1] liveupdate: luo_file: Add documentation for dependencies

[Samiullah Khawaja]

Add documentation for dependencies between FDs preserved by File
Handlers. This supplements the previously added
liveupdate_get_token_outgoing() and liveupdate_get_file_incoming()
internal APIs to allow File Handlers to resolve dependencies.

Signed-off-by: Samiullah Khawaja <skhawaja at google.com>
---
 kernel/liveupdate/luo_file.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
index dbae0715220b..0a4994377c98 100644
--- a/kernel/liveupdate/luo_file.c
+++ b/kernel/liveupdate/luo_file.c
@@ -91,6 +91,21 @@
  *    again later. If the issue cannot be resolved, these resources will be held
  *    by LUO until the next live update cycle, at which point they will be
  *    discarded.
+ *
+ * Dependencies:
+ *
+ * Preserved files may have dependencies on other files that also need to be
+ * preserved during a live update. A file handler can resolve these dependencies
+ * by querying the token of the dependency. That token can then be serialized
+ * and used to fetch the dependency during the retrieve() callback in the next
+ * kernel.
+ *
+ * Some of these dependencies can be resolved late during File Handler freeze()
+ * callback, but some of these might need resolution during File Handler
+ * preserve() callback based on the constraints such as immutability and
+ * performance. This introduces an order of preservation. Note that the order of
+ * preservation of dependencies can be safely relaxed later, but it cannot be
+ * enforced later.
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-- 
2.55.0.1003.g10538fe699-goog