fuse: implement poll support

Implement poll support.  Polled files are indexed using kh in a RB
tree rooted at fuse_conn->polled_files.

Client should send FUSE_NOTIFY_POLL notification once after processing
FUSE_POLL which has FUSE_POLL_SCHEDULE_NOTIFY set.  Sending
notification unconditionally after the latest poll or everytime file
content might have changed is inefficient but won't cause malfunction.

fuse_file_poll() can sleep and requires patches from the following
thread which allows f_op->poll() to sleep.

  http://thread.gmane.org/gmane.linux.kernel/726176

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

1 files changed, 25 insertions, 0 deletions

diff --git a/include/linux/fuse.h b/include/linux/fuse.h
index abde9949e2c0..5650cf033e73 100644
--- a/include/linux/fuse.h
+++ b/include/linux/fuse.h
@@ -163,6 +163,13 @@ struct fuse_file_lock {
 
 #define FUSE_IOCTL_MAX_IOV      256
 
+/**
+ * Poll flags
+ *
+ * FUSE_POLL_SCHEDULE_NOTIFY: request poll notify
+ */
+#define FUSE_POLL_SCHEDULE_NOTIFY (1 << 0)
+
 enum fuse_opcode {
         FUSE_LOOKUP        = 1,
         FUSE_FORGET        = 2,  /* no reply */
@@ -201,9 +208,11 @@ enum fuse_opcode {
         FUSE_BMAP          = 37,
         FUSE_DESTROY       = 38,
         FUSE_IOCTL         = 39,
+        FUSE_POLL          = 40,
 };
 
 enum fuse_notify_code {
+        FUSE_NOTIFY_POLL   = 1,
         FUSE_NOTIFY_CODE_MAX,
 };
 
@@ -421,6 +430,22 @@ struct fuse_ioctl_out {
         __u32   out_iovs;
 };
 
+struct fuse_poll_in {
+        __u64   fh;
+        __u64   kh;
+        __u32   flags;
+        __u32   padding;
+};
+
+struct fuse_poll_out {
+        __u32   revents;
+        __u32   padding;
+};
+
+struct fuse_notify_poll_wakeup_out {
+        __u64   kh;
+};
+
 struct fuse_in_header {
         __u32   len;
         __u32   opcode;