linux-kernel - [RFC PATCH 1/3] luo: Extract file object logic

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Message-ID: 
 <176928013535.26405.5652761027502265757.stgit@skinsburskii-cloud-desktop.internal.cloudapp.net>
Date: Sat, 24 Jan 2026 18:42:15 +0000
From: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
To: pasha.tatashin@...een.com, rppt@...nel.org, pratyush@...nel.org,
 kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
 decui@...rosoft.com, longli@...rosoft.com
Cc: linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 1/3] luo: Extract file object logic

Split file object related logic out of the liveupdate implementation so it
can be reused by other kernel subsystems.

This is a preparatory change for enabling use of the luo infrastructure
outside of liveupdate. No functional change intended.

Signed-off-by: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
---
 include/linux/liveupdate.h       |    3 ++
 kernel/liveupdate/luo_file.c     |   55 ++++++++++++++++++++++++++++++++------
 kernel/liveupdate/luo_internal.h |    2 +
 kernel/liveupdate/luo_session.c  |    2 +
 4 files changed, 51 insertions(+), 11 deletions(-)

diff --git a/include/linux/liveupdate.h b/include/linux/liveupdate.h
index a7f6ee5b6771..0e6e0a1b1489 100644
--- a/include/linux/liveupdate.h
+++ b/include/linux/liveupdate.h
@@ -112,6 +112,9 @@ int liveupdate_reboot(void);
 int liveupdate_register_file_handler(struct liveupdate_file_handler *fh);
 int liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh);
 
+int liveupdate_session_create(char *name, struct file **filep);
+void liveupdate_session_destroy(char *name, struct file *file);
+
 #else /* CONFIG_LIVEUPDATE */
 
 static inline bool liveupdate_enabled(void)
diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
index a32a777f6df8..e46aeb29ab4d 100644
--- a/kernel/liveupdate/luo_file.c
+++ b/kernel/liveupdate/luo_file.c
@@ -250,12 +250,11 @@ static bool luo_token_is_used(struct luo_file_set *file_set, u64 token)
  *         -ENOMEM on memory allocation failure.
  *         Other erros might be returned by .preserve().
  */
-int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd)
+static int luo_preserve_file(struct luo_file_set *file_set, u64 token, struct file *file)
 {
 	struct liveupdate_file_op_args args = {0};
 	struct liveupdate_file_handler *fh;
 	struct luo_file *luo_file;
-	struct file *file;
 	int err;
 
 	if (luo_token_is_used(file_set, token))
@@ -264,13 +263,9 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd)
 	if (file_set->count == LUO_FILE_MAX)
 		return -ENOSPC;
 
-	file = fget(fd);
-	if (!file)
-		return -EBADF;
-
 	err = luo_alloc_files_mem(file_set);
 	if (err)
-		goto  err_fput;
+		return err;
 
 	err = -ENOENT;
 	luo_list_for_each_private(fh, &luo_file_handler_list, list) {
@@ -313,8 +308,22 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd)
 	kfree(luo_file);
 err_free_files_mem:
 	luo_free_files_mem(file_set);
-err_fput:
-	fput(file);
+
+	return err;
+}
+
+int luo_preserve_fd(struct luo_file_set *file_set, u64 token, int fd)
+{
+	struct file *file;
+	int err;
+
+	file = fget(fd);
+	if (!file)
+		return -EBADF;
+
+	err = luo_preserve_file(file_set, token, file);
+	if (err)
+		fput(file);
 
 	return err;
 }
@@ -861,6 +870,34 @@ int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)
 	return err;
 }
 
+int liveupdate_session_create(char *name, struct file **filep)
+{
+	struct luo_session *session;
+	int err;
+
+	err = luo_session_create(name, filep);
+	if (err)
+		return err;
+
+	session = (*filep)->private_data;
+
+	/* Not need to guard here, session is not yet visible to others */
+	err = luo_preserve_file(&session->file_set, 0, *filep);
+	if (err)
+		goto err_preserve;
+
+	return 0;
+
+err_preserve:
+	fput(*filep);
+	return err;
+}
+
+void liveupdate_session_destroy(char *name, struct file *file)
+{
+	fput(file);
+}
+
 /**
  * liveupdate_unregister_file_handler - Unregister a liveupdate file handler
  * @fh: The file handler to unregister
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
index c8973b543d1d..b14391f1514f 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -93,7 +93,7 @@ int luo_session_deserialize(void);
 bool luo_session_quiesce(void);
 void luo_session_resume(void);
 
-int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd);
+int luo_preserve_fd(struct luo_file_set *file_set, u64 token, int fd);
 void luo_file_unpreserve_files(struct luo_file_set *file_set);
 int luo_file_freeze(struct luo_file_set *file_set,
 		    struct luo_file_set_ser *file_set_ser);
diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
index dbdbc3bd7929..641186d41a22 100644
--- a/kernel/liveupdate/luo_session.c
+++ b/kernel/liveupdate/luo_session.c
@@ -234,7 +234,7 @@ static int luo_session_preserve_fd(struct luo_session *session,
 	int err;
 
 	guard(mutex)(&session->mutex);
-	err = luo_preserve_file(&session->file_set, argp->token, argp->fd);
+	err = luo_preserve_fd(&session->file_set, argp->token, argp->fd);
 	if (err)
 		return err;