fuse: add submount support to <uapi/linux/fuse.h>

- Add fuse_attr.flags

- Add FUSE_ATTR_SUBMOUNT

  This is a flag for fuse_attr.flags that indicates that the given entry
  resides on a different filesystem than the parent, and as such should
  have a different st_dev.

- Add FUSE_SUBMOUNTS

  The client sets this flag if it supports automounting directories.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

include/uapi/linux/fuse.h

@@ -172,6 +172,9 @@
  *  - add FUSE_WRITE_KILL_PRIV flag
  *  - add FUSE_SETUPMAPPING and FUSE_REMOVEMAPPING
  *  - add map_alignment to fuse_init_out, add FUSE_MAP_ALIGNMENT flag
+ *
+ *  7.32
+ *  - add flags to fuse_attr, add FUSE_ATTR_SUBMOUNT, add FUSE_SUBMOUNTS
  */
 
 #ifndef _LINUX_FUSE_H
@@ -207,7 +210,7 @@
 #define FUSE_KERNEL_VERSION 7
 
 /** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 31
+#define FUSE_KERNEL_MINOR_VERSION 32
 
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1
@@ -231,7 +234,7 @@ struct fuse_attr {
 	uint32_t	gid;
 	uint32_t	rdev;
 	uint32_t	blksize;
-	uint32_t	padding;
+	uint32_t	flags;
 };
 
 struct fuse_kstatfs {
@@ -316,6 +319,7 @@ struct fuse_file_lock {
  * FUSE_MAP_ALIGNMENT: init_out.map_alignment contains log2(byte alignment) for
  *		       foffset and moffset fields in struct
  *		       fuse_setupmapping_out and fuse_removemapping_one.
+ * FUSE_SUBMOUNTS: kernel supports auto-mounting directory submounts
  */
 #define FUSE_ASYNC_READ		(1 << 0)
 #define FUSE_POSIX_LOCKS	(1 << 1)
@@ -344,6 +348,7 @@ struct fuse_file_lock {
 #define FUSE_NO_OPENDIR_SUPPORT (1 << 24)
 #define FUSE_EXPLICIT_INVAL_DATA (1 << 25)
 #define FUSE_MAP_ALIGNMENT	(1 << 26)
+#define FUSE_SUBMOUNTS		(1 << 27)
 
 /**
  * CUSE INIT request/reply flags
@@ -419,6 +424,13 @@ struct fuse_file_lock {
  */
 #define FUSE_FSYNC_FDATASYNC	(1 << 0)
 
+/**
+ * fuse_attr flags
+ *
+ * FUSE_ATTR_SUBMOUNT: Object is a submount root
+ */
+#define FUSE_ATTR_SUBMOUNT      (1 << 0)
+
 enum fuse_opcode {
 	FUSE_LOOKUP		= 1,
 	FUSE_FORGET		= 2,  /* no reply */