fuse: add renameat2 support

Support RENAME_EXCHANGE and RENAME_NOREPLACE flags on the userspace ABI.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

include/uapi/linux/fuse.h

@@ -100,6 +100,7 @@
  *  - add reserved space to fuse_init_out
  *  - add FATTR_CTIME
  *  - add ctime and ctimensec to fuse_setattr_in
+ *  - add FUSE_RENAME2 request
  */
 
 #ifndef _LINUX_FUSE_H
@@ -353,6 +354,7 @@ enum fuse_opcode {
 	FUSE_BATCH_FORGET  = 42,
 	FUSE_FALLOCATE     = 43,
 	FUSE_READDIRPLUS   = 44,
+	FUSE_RENAME2       = 45,
 
 	/* CUSE specific operations */
 	CUSE_INIT          = 4096,
@@ -431,6 +433,12 @@ struct fuse_rename_in {
 	uint64_t	newdir;
 };
 
+struct fuse_rename2_in {
+	uint64_t	newdir;
+	uint32_t	flags;
+	uint32_t	padding;
+};
+
 struct fuse_link_in {
 	uint64_t	oldnodeid;
 };