fuse: add retrieve request

Userspace filesystem can request data to be retrieved from the inode's
mapping.  This request is synchronous and the retrieved data is queued
as a new request.  If the write to the fuse device returns an error
then the retrieve request was not completed and a reply will not be
sent.

Only present pages are returned in the retrieve reply.  Retrieving
stops when it finds a non-present page and only data prior to that is
returned.

This request doesn't change the dirty state of pages.

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

1 files changed, 21 insertions, 0 deletions

diff --git a/include/linux/fuse.h b/include/linux/fuse.h
index a90bd49834a..c3c578e0983 100644
--- a/include/linux/fuse.h
+++ b/include/linux/fuse.h
@@ -40,6 +40,7 @@
  *
  * 7.15
  *  - add store notify
+ *  - add retrieve notify
  */
 
 #ifndef _LINUX_FUSE_H
@@ -254,6 +255,7 @@ enum fuse_opcode {
 	FUSE_DESTROY       = 38,
 	FUSE_IOCTL         = 39,
 	FUSE_POLL          = 40,
+	FUSE_NOTIFY_REPLY  = 41,
 
 	/* CUSE specific operations */
 	CUSE_INIT          = 4096,
@@ -264,6 +266,7 @@ enum fuse_notify_code {
 	FUSE_NOTIFY_INVAL_INODE = 2,
 	FUSE_NOTIFY_INVAL_ENTRY = 3,
 	FUSE_NOTIFY_STORE = 4,
+	FUSE_NOTIFY_RETRIEVE = 5,
 	FUSE_NOTIFY_CODE_MAX,
 };
 
@@ -579,4 +582,22 @@ struct fuse_notify_store_out {
 	__u32	padding;
 };
 
+struct fuse_notify_retrieve_out {
+	__u64	notify_unique;
+	__u64	nodeid;
+	__u64	offset;
+	__u32	size;
+	__u32	padding;
+};
+
+/* Matches the size of fuse_write_in */
+struct fuse_notify_retrieve_in {
+	__u64	dummy1;
+	__u64	offset;
+	__u32	size;
+	__u32	dummy2;
+	__u64	dummy3;
+	__u64	dummy4;
+};
+
 #endif /* _LINUX_FUSE_H */