fuse: make the number of max background requests and congestion threshold tunable

The practical values for these limits depend on the design of the
filesystem server so let userspace set them at initialization time.

Signed-off-by: Csaba Henk <csaba@gluster.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
diff --git a/include/linux/fuse.h b/include/linux/fuse.h
index cf593bf..b3700f0 100644
--- a/include/linux/fuse.h
+++ b/include/linux/fuse.h
@@ -30,6 +30,10 @@
  *  - add umask flag to input argument of open, mknod and mkdir
  *  - add notification messages for invalidation of inodes and
  *    directory entries
+ *
+ * 7.13
+ *  - make max number of background requests and congestion threshold
+ *    tunables
  */
 
 #ifndef _LINUX_FUSE_H
@@ -41,7 +45,7 @@
 #define FUSE_KERNEL_VERSION 7
 
 /** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 12
+#define FUSE_KERNEL_MINOR_VERSION 13
 
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1
@@ -427,7 +431,8 @@
 	__u32	minor;
 	__u32	max_readahead;
 	__u32	flags;
-	__u32	unused;
+	__u16   max_background;
+	__u16   congestion_threshold;
 	__u32	max_write;
 };