[PATCH 2/9] fuse: add FOPEN_CACHE_DIR

[Miklos Szeredi]

Add flag returned by OPENDIR request to allow kernel to cache directory
contents in page cache.  The effect of FOPEN_CACHE_DIR is twofold:

 a) if not already cached, it writes entries into the cache

 b) if already cached, it allows reading entries from the cache

The FOPEN_KEEP_CACHE has the same effect as on regular files: unless this
flag is given the cache is cleared upon completion of open.

So FOPEN_KEEP_CACHE and FOPEN_KEEP_CACHE flags should be used together to
make use of the directory caching facility introduced in the following
patches.

The FUSE_AUTO_INVAL_DATA flag returned in INIT reply also has the same
affect on the directory cache as it has on data cache for regular files.

Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
---
 include/uapi/linux/fuse.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 92fa24c24c92..e30e3a6868cd 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -116,6 +116,9 @@
  *
  *  7.27
  *  - add FUSE_ABORT_ERROR
+ *
+ *  7.28
+ *  - add FOPEN_CACHE_DIR
  */
 
 #ifndef _LINUX_FUSE_H
@@ -151,7 +154,7 @@
 #define FUSE_KERNEL_VERSION 7
 
 /** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 27
+#define FUSE_KERNEL_MINOR_VERSION 28
 
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1
@@ -219,10 +222,12 @@ struct fuse_file_lock {
  * FOPEN_DIRECT_IO: bypass page cache for this open file
  * FOPEN_KEEP_CACHE: don't invalidate the data cache on open
  * FOPEN_NONSEEKABLE: the file is not seekable
+ * FOPEN_CACHE_DIR: allow caching this directory
  */
 #define FOPEN_DIRECT_IO		(1 << 0)
 #define FOPEN_KEEP_CACHE	(1 << 1)
 #define FOPEN_NONSEEKABLE	(1 << 2)
+#define FOPEN_CACHE_DIR		(1 << 3)
 
 /**
  * INIT request/reply flags
-- 
2.14.3