fuse: add helper for asynchronous writes

This patch adds a new helper function fuse_write_fill() which makes it
possible to send WRITE requests asynchronously.

A new flag for WRITE requests is also added which indicates that this a write
from the page cache, and not a "normal" file write.

This patch is in preparation for writable mmap support.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 5657cca..8b64a63 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -219,6 +219,10 @@
 		struct fuse_init_in init_in;
 		struct fuse_init_out init_out;
 		struct fuse_read_in read_in;
+		struct {
+			struct fuse_write_in in;
+			struct fuse_write_out out;
+		} write;
 		struct fuse_lk_in lk_in;
 	} misc;