[PATCH] fuse: add O_ASYNC support to FUSE device
This adds asynchronous notification to FUSE - a FUSE server can request
O_ASYNC on a /dev/fuse file descriptor and receive SIGIO when there is input
available.
One subtlety - fuse_dev_fasync, which is called when O_ASYNC is requested,
does no locking, unlink the other methods. I think it's unnecessary, as the
fuse_conn.fasync list is manipulated only by fasync_helper and kill_fasync,
which provide their own locking. It would also be wrong to use the fuse_lock,
as it's a spin lock and fasync_helper can sleep. My one concern with this is
the fuse_conn going away underneath fuse_dev_fasync - sys_fcntl takes a
reference on the file struct, so this seems not to be a problem.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index b2e8613..438770f 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -317,6 +317,7 @@
list_add_tail(&req->list, &fc->pending);
req->state = FUSE_REQ_PENDING;
wake_up(&fc->waitq);
+ kill_fasync(&fc->fasync, SIGIO, POLL_IN);
}
/*
@@ -901,6 +902,7 @@
end_requests(fc, &fc->pending);
end_requests(fc, &fc->processing);
wake_up_all(&fc->waitq);
+ kill_fasync(&fc->fasync, SIGIO, POLL_IN);
}
spin_unlock(&fuse_lock);
}
@@ -917,12 +919,24 @@
end_requests(fc, &fc->processing);
}
spin_unlock(&fuse_lock);
- if (fc)
+ if (fc) {
+ fasync_helper(-1, file, 0, &fc->fasync);
kobject_put(&fc->kobj);
+ }
return 0;
}
+static int fuse_dev_fasync(int fd, struct file *file, int on)
+{
+ struct fuse_conn *fc = fuse_get_conn(file);
+ if (!fc)
+ return -ENODEV;
+
+ /* No locking - fasync_helper does its own locking */
+ return fasync_helper(fd, file, on, &fc->fasync);
+}
+
const struct file_operations fuse_dev_operations = {
.owner = THIS_MODULE,
.llseek = no_llseek,
@@ -932,6 +946,7 @@
.writev = fuse_dev_writev,
.poll = fuse_dev_poll,
.release = fuse_dev_release,
+ .fasync = fuse_dev_fasync,
};
static struct miscdevice fuse_miscdevice = {
