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, 19 insertions, 0 deletions

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index ffd670bb8c8c..6176e444c76e 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -816,10 +816,29 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
         return err;
 }
 
+static int fuse_notify_poll(struct fuse_conn *fc, unsigned int size,
+                            struct fuse_copy_state *cs)
+{
+        struct fuse_notify_poll_wakeup_out outarg;
+        int err;
+
+        if (size != sizeof(outarg))
+                return -EINVAL;
+
+        err = fuse_copy_one(cs, &outarg, sizeof(outarg));
+        if (err)
+                return err;
+
+        return fuse_notify_poll_wakeup(fc, &outarg);
+}
+
 static int fuse_notify(struct fuse_conn *fc, enum fuse_notify_code code,
                        unsigned int size, struct fuse_copy_state *cs)
 {
         switch (code) {
+        case FUSE_NOTIFY_POLL:
+                return fuse_notify_poll(fc, size, cs);
+
         default:
                 return -EINVAL;
         }