libfuse: add retrieve request

Retrieve data stored in the kernel buffers for a given inode.

2 files changed, 60 insertions, 0 deletions

diff --git a/include/fuse_kernel.h b/include/fuse_kernel.h
index 25d3555..c7c99a5 100644
--- a/include/fuse_kernel.h
+++ b/include/fuse_kernel.h
@@ -66,6 +66,7 @@
  *
  * 7.15
  *  - add store notify
+ *  - add retrieve notify
  */
 
 #ifndef _LINUX_FUSE_H
@@ -285,6 +286,7 @@ enum fuse_opcode {
 	FUSE_DESTROY       = 38,
 	FUSE_IOCTL         = 39,
 	FUSE_POLL          = 40,
+	FUSE_NOTIFY_REPLY  = 41,
 
 	/* CUSE specific operations */
 	CUSE_INIT          = 4096,
@@ -295,6 +297,7 @@ 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,
 };
 
@@ -610,4 +613,22 @@ 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 */
diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
index 0a8fdf1..8f31471 100644
--- a/include/fuse_lowlevel.h
+++ b/include/fuse_lowlevel.h
@@ -902,6 +902,17 @@ struct fuse_lowlevel_ops {
 	void (*write_buf) (fuse_req_t req, fuse_ino_t ino,
 			   struct fuse_bufvec *bufv, off_t off,
 			   struct fuse_file_info *fi);
+
+	/**
+	 * Callback function for the retrieve request
+	 *
+	 * @param cookie user data supplied to fuse_lowlevel_notify_retrieve()
+	 * @param ino the inode number supplied to fuse_lowlevel_notify_retrieve()
+	 * @param offset the offset supplied to fuse_lowlevel_notify_retrieve()
+	 * @param bufv the buffer containing the returned data
+	 */
+	void (*retrieve_reply) (void *cookie, fuse_ino_t ino, off_t offset,
+				struct fuse_bufvec *bufv);
 };
 
 /**
@@ -1248,6 +1259,34 @@ int fuse_lowlevel_notify_inval_entry(struct fuse_chan *ch, fuse_ino_t parent,
 int fuse_lowlevel_notify_store(struct fuse_chan *ch, fuse_ino_t ino,
 			       off_t offset, struct fuse_bufvec *bufv,
 			       enum fuse_buf_copy_flags flags);
+/**
+ * Retrieve data from the kernel buffers
+ *
+ * Retrieve data in the kernel buffers belonging to the given inode.
+ * If successful then the retrieve_reply() method will be called with
+ * the returned data.
+ *
+ * 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.
+ *
+ * If this function returns an error, then the retrieve will not be
+ * completed and no reply will be sent.
+ *
+ * This function doesn't change the dirty state of pages in the kernel
+ * buffer.  For dirty pages the write() method will be called
+ * regardless of having been retrieved previously.
+ *
+ * @param ch the channel through which to send the invalidation
+ * @param ino the inode number
+ * @param size the number of bytes to retrieve
+ * @param offset the starting offset into the file to retrieve from
+ * @param cookie user data to supply to the reply callback
+ * @return zero for success, -errno for failure
+ */
+int fuse_lowlevel_notify_retrieve(struct fuse_chan *ch, fuse_ino_t ino,
+				  size_t size, off_t offset, void *cookie);
+
 
 /* ----------------------------------------------------------- *
  * Utility functions					       *