From 5ceb0b05cb48e6cfa2c81160df9f1212623e86eb Mon Sep 17 00:00:00 2001
From: Luis Henriques <luis@igalia.com>
Date: Thu, 22 May 2025 15:15:15 +0100
Subject: fuse: add support to FUSE_NOTIFY_INC_EPOCH

This patch adds support for the FUSE INC_EPOCH notify.  This new operation
simply increments the FUSE connection epoch value, allowing to invalidate
all the dentries next time they are revalidated.

Signed-off-by: Luis Henriques <luis@igalia.com>
---
 include/fuse_kernel.h   |  6 +++++-
 include/fuse_lowlevel.h | 14 ++++++++++++++
 lib/fuse_lowlevel.c     | 13 +++++++++++++
 lib/fuse_versionscript  |  1 +
 4 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/include/fuse_kernel.h b/include/fuse_kernel.h
index 42db04c..122d658 100644
--- a/include/fuse_kernel.h
+++ b/include/fuse_kernel.h
@@ -232,6 +232,9 @@
  *
  *  7.43
  *  - add FUSE_REQUEST_TIMEOUT
+ *
+ *  7.44
+ *  - add FUSE_NOTIFY_INC_EPOCH
  */
 
 #ifndef _LINUX_FUSE_H
@@ -267,7 +270,7 @@
 #define FUSE_KERNEL_VERSION 7
 
 /** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 42
+#define FUSE_KERNEL_MINOR_VERSION 44
 
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1
@@ -671,6 +674,7 @@ enum fuse_notify_code {
 	FUSE_NOTIFY_RETRIEVE = 5,
 	FUSE_NOTIFY_DELETE = 6,
 	FUSE_NOTIFY_RESEND = 7,
+	FUSE_NOTIFY_INC_EPOCH = 8,
 	FUSE_NOTIFY_CODE_MAX,
 };
 
diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
index 138a784..82f4a8d 100644
--- a/include/fuse_lowlevel.h
+++ b/include/fuse_lowlevel.h
@@ -1744,6 +1744,20 @@ int fuse_lowlevel_notify_poll(struct fuse_pollhandle *ph);
 int fuse_lowlevel_notify_inval_inode(struct fuse_session *se, fuse_ino_t ino,
 				     off_t off, off_t len);
 
+/**
+ * Notify to increment the epoch for the current
+ *
+ * Each fuse connection has an 'epoch', which is initialized during INIT.
+ * Caching will then be validated against the epoch value: if the current epoch
+ * is higher than an object being revalidated, the object is invalid.
+ *
+ * This function simply increment the current epoch value.
+ *
+ * @param se the session object
+ * @return zero for success, -errno for failure
+ */
+int fuse_lowlevel_notify_increment_epoch(struct fuse_session *se);
+
 /**
  * Notify to invalidate parent attributes and the dentry matching parent/name
  *
diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
index 5568786..13c05c6 100644
--- a/lib/fuse_lowlevel.c
+++ b/lib/fuse_lowlevel.c
@@ -2973,6 +2973,19 @@ int fuse_lowlevel_notify_inval_inode(struct fuse_session *se, fuse_ino_t ino,
 	return send_notify_iov(se, FUSE_NOTIFY_INVAL_INODE, iov, 2);
 }
 
+int fuse_lowlevel_notify_increment_epoch(struct fuse_session *se)
+{
+	struct iovec iov[1];
+
+	if (!se)
+		return -EINVAL;
+
+	if (se->conn.proto_minor < 44)
+		return -ENOSYS;
+
+	return send_notify_iov(se, FUSE_NOTIFY_INC_EPOCH, iov, 1);
+}
+
 /**
  * Notify parent attributes and the dentry matching parent/name
  *
diff --git a/lib/fuse_versionscript b/lib/fuse_versionscript
index ab57d7c..2d8884d 100644
--- a/lib/fuse_versionscript
+++ b/lib/fuse_versionscript
@@ -208,6 +208,7 @@ FUSE_3.18 {
 		fuse_set_feature_flag;
 		fuse_unset_feature_flag;
 		fuse_get_feature_flag;
+		fuse_lowlevel_notify_increment_epoch;
 
 		# Not part of public API, for internal test use only
 		fuse_convert_to_conn_want_ext;
-- 
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