liveupdate: defer session block allocation and physical address setting

Currently, luo_session_setup_outgoing() allocates the session block and
sets its physical address in the header immediately. With upcoming
dynamic block-based session management, this makes the first block
different from the rest. Move the allocation to where it is first needed.

Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Link: https://patch.msgid.link/20260603154402.468928-9-pasha.tatashin@soleen.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

3 files changed, 45 insertions, 29 deletions

diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c
index 69b00e7d0f8f..1b2bda22902d 100644
--- a/kernel/liveupdate/luo_core.c
+++ b/kernel/liveupdate/luo_core.c
@@ -165,9 +165,7 @@ static int __init luo_state_setup(void)
 	strscpy(luo_ser->compatible, LUO_ABI_COMPATIBLE, sizeof(luo_ser->compatible));
 	luo_ser->liveupdate_num = luo_global.liveupdate_num + 1;
 
-	err = luo_session_setup_outgoing(&luo_ser->sessions_pa);
-	if (err)
-		goto exit_free_luo_ser;
+	luo_session_setup_outgoing(&luo_ser->sessions_pa);
 
 	err = luo_flb_setup_outgoing(&luo_ser->flbs_pa);
 	if (err)
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
index fe22086bfbeb..ee18f9a11b91 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -79,7 +79,7 @@ extern struct rw_semaphore luo_register_rwlock;
 
 int luo_session_create(const char *name, struct file **filep);
 int luo_session_retrieve(const char *name, struct file **filep);
-int __init luo_session_setup_outgoing(u64 *sessions_pa);
+void __init luo_session_setup_outgoing(u64 *sessions_pa);
 int __init luo_session_setup_incoming(u64 sessions_pa);
 int luo_session_serialize(void);
 int luo_session_deserialize(void);
diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
index 1cd315e0f6de..2411849a34e3 100644
--- a/kernel/liveupdate/luo_session.c
+++ b/kernel/liveupdate/luo_session.c
@@ -108,15 +108,16 @@ static DECLARE_RWSEM(luo_session_serialize_rwsem);
 
 /**
  * struct luo_session_header - Header struct for managing LUO sessions.
- * @count:      The number of sessions currently tracked in the @list.
- * @list:       The head of the linked list of `struct luo_session` instances.
- * @rwsem:      A read-write semaphore providing synchronized access to the
- *              session list and other fields in this structure.
- * @header_ser: The header data of serialization array.
- * @ser:        The serialized session data (an array of
- *              `struct luo_session_ser`).
- * @active:     Set to true when first initialized. If previous kernel did not
- *              send session data, active stays false for incoming.
+ * @count:       The number of sessions currently tracked in the @list.
+ * @list:        The head of the linked list of `struct luo_session` instances.
+ * @rwsem:       A read-write semaphore providing synchronized access to the
+ *               session list and other fields in this structure.
+ * @header_ser:  The header data of serialization array.
+ * @ser:         The serialized session data (an array of
+ *               `struct luo_session_ser`).
+ * @sessions_pa: Points to the location of sessions_pa within struct luo_ser.
+ * @active:      Set to true when first initialized. If previous kernel did not
+ *               send session data, active stays false for incoming.
  */
 struct luo_session_header {
 	long count;
@@ -124,6 +125,7 @@ struct luo_session_header {
 	struct rw_semaphore rwsem;
 	struct luo_session_header_ser *header_ser;
 	struct luo_session_ser *ser;
+	u64 *sessions_pa;
 	bool active;
 };
 
@@ -171,10 +173,30 @@ static void luo_session_free(struct luo_session *session)
 	kfree(session);
 }
 
+static int luo_session_grow_ser(struct luo_session_header *sh)
+{
+	struct luo_session_header_ser *header_ser;
+
+	if (sh->count == LUO_SESSION_MAX)
+		return -ENOMEM;
+
+	if (sh->header_ser)
+		return 0;
+
+	header_ser = kho_alloc_preserve(LUO_SESSION_PGCNT << PAGE_SHIFT);
+	if (IS_ERR(header_ser))
+		return PTR_ERR(header_ser);
+
+	sh->header_ser = header_ser;
+	sh->ser = (void *)(header_ser + 1);
+	return 0;
+}
+
 static int luo_session_insert(struct luo_session_header *sh,
 			      struct luo_session *session)
 {
 	struct luo_session *it;
+	int err;
 
 	guard(rwsem_write)(&sh->rwsem);
 
@@ -183,8 +205,9 @@ static int luo_session_insert(struct luo_session_header *sh,
 	 * for new session.
 	 */
 	if (sh == &luo_session_global.outgoing) {
-		if (sh->count == LUO_SESSION_MAX)
-			return -ENOMEM;
+		err = luo_session_grow_ser(sh);
+		if (err)
+			return err;
 	}
 
 	/*
@@ -524,21 +547,10 @@ int luo_session_retrieve(const char *name, struct file **filep)
 	return err;
 }
 
-int __init luo_session_setup_outgoing(u64 *sessions_pa)
+void __init luo_session_setup_outgoing(u64 *sessions_pa)
 {
-	struct luo_session_header_ser *header_ser;
-
-	header_ser = kho_alloc_preserve(LUO_SESSION_PGCNT << PAGE_SHIFT);
-	if (IS_ERR(header_ser))
-		return PTR_ERR(header_ser);
-
-	*sessions_pa = virt_to_phys(header_ser);
-
-	luo_session_global.outgoing.header_ser = header_ser;
-	luo_session_global.outgoing.ser = (void *)(header_ser + 1);
+	luo_session_global.outgoing.sessions_pa = sessions_pa;
 	luo_session_global.outgoing.active = true;
-
-	return 0;
 }
 
 int __init luo_session_setup_incoming(u64 sessions_pa)
@@ -644,6 +656,8 @@ int luo_session_serialize(void)
 
 	down_write(&luo_session_serialize_rwsem);
 	down_write(&sh->rwsem);
+	*sh->sessions_pa = 0;
+
 	list_for_each_entry(session, &sh->list, list) {
 		err = luo_session_freeze_one(session, &sh->ser[i]);
 		if (err)
@@ -653,7 +667,11 @@ int luo_session_serialize(void)
 			sizeof(sh->ser[i].name));
 		i++;
 	}
-	sh->header_ser->count = sh->count;
+
+	if (sh->header_ser && sh->count > 0) {
+		sh->header_ser->count = sh->count;
+		*sh->sessions_pa = virt_to_phys(sh->header_ser);
+	}
 	up_write(&sh->rwsem);
 
 	return 0;