@@ -244,3 +244,10 @@ following flags are defined:
     nfsd. A case in point is reexport of NFS itself, which can't be done
     safely without coordinating the grace period handling. Other clustered
     and networked filesystems can be problematic here as well.
+
+  EXPORT_OP_STABLE_HANDLES - This filesystem provides filehandles that are
+    stable across the lifetime of a file. This is a hard requirement for export
+    via nfsd. Any filesystem that is eligible to be exported via nfsd must
+    indicate this guarantee by setting this flag. Most disk-based filesystems
+    can do this naturally. Pseudofilesystems that are for local reporting and
+    control (e.g. kernfs, pidfs, nsfs) usually can't support this.

@@ -3,6 +3,7 @@
 #define LINUX_EXPORTFS_H 1
 
 #include <linux/types.h>
+#include <linux/bits.h>
 #include <linux/path.h>
 
 struct dentry;

@@ -277,15 +278,16 @@ struct export_operations {
 			     int nr_iomaps, struct iattr *iattr);
 	int (*permission)(struct handle_to_path_ctx *ctx, unsigned int oflags);
 	struct file * (*open)(const struct path *path, unsigned int oflags);
-#define	EXPORT_OP_NOWCC			(0x1) /* don't collect v3 wcc data */
-#define	EXPORT_OP_NOSUBTREECHK		(0x2) /* no subtree checking */
-#define	EXPORT_OP_CLOSE_BEFORE_UNLINK	(0x4) /* close files before unlink */
-#define EXPORT_OP_REMOTE_FS		(0x8) /* Filesystem is remote */
-#define EXPORT_OP_NOATOMIC_ATTR		(0x10) /* Filesystem cannot supply
+#define EXPORT_OP_NOWCC			BIT(0) /* don't collect v3 wcc data */
+#define EXPORT_OP_NOSUBTREECHK		BIT(1) /* no subtree checking */
+#define EXPORT_OP_CLOSE_BEFORE_UNLINK	BIT(2) /* close files before unlink */
+#define EXPORT_OP_REMOTE_FS		BIT(3) /* Filesystem is remote */
+#define EXPORT_OP_NOATOMIC_ATTR		BIT(4) /* Filesystem cannot supply
 						  atomic attribute updates
 						*/
-#define EXPORT_OP_FLUSH_ON_CLOSE	(0x20) /* fs flushes file data on close */
-#define EXPORT_OP_NOLOCKS		(0x40) /* no file locking support */
+#define EXPORT_OP_FLUSH_ON_CLOSE	BIT(5) /* fs flushes file data on close */
+#define EXPORT_OP_NOLOCKS		BIT(6) /* no file locking support */
+#define EXPORT_OP_STABLE_HANDLES	BIT(7) /* fhs are stable across reboot */
 	unsigned long	flags;
 };