fuse: set FR_PENDING atomically in fuse_resend()

When fuse_resend() moves the requests from processing lists to pending
list, it uses __set_bit() to set FR_PENDING bit in req->flags.

Using __set_bit() is not safe, because other functions may update
req->flags concurrently (e.g., request_wait_answer() may call
set_bit(FR_INTERRUPTED, &flags)).

Fix it by using set_bit() instead.

Fixes: 760eac7 ("fuse: Introduce a new notification type for resend pending requests")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Author: Hou Tao

fs/fuse/dev.c

@@ -1813,7 +1813,7 @@ static void fuse_resend(struct fuse_conn *fc)
 	spin_unlock(&fc->lock);
 
 	list_for_each_entry_safe(req, next, &to_queue, list) {
-		__set_bit(FR_PENDING, &req->flags);
+		set_bit(FR_PENDING, &req->flags);
 		/* mark the request as resend request */
 		req->in.h.unique |= FUSE_UNIQUE_RESEND;
 	}