+/*
+ * Return request in fuse_file->reserved_req. However that may
+ * currently be in use. If that is the case, wait for it to become
+ * available.
+ */
+static struct fuse_req *get_reserved_req(struct fuse_conn *fc,
+ struct file *file)
+{
+ struct fuse_req *req = NULL;
+ struct fuse_file *ff = file->private_data;
+
+ do {
+ wait_event(fc->blocked_waitq, ff->reserved_req);
+ spin_lock(&fc->lock);
+ if (ff->reserved_req) {
+ req = ff->reserved_req;
+ ff->reserved_req = NULL;
+ get_file(file);
+ req->stolen_file = file;
+ }
+ spin_unlock(&fc->lock);
+ } while (!req);
+
+ return req;
+}
+
+/*
+ * Put stolen request back into fuse_file->reserved_req
+ */
+static void put_reserved_req(struct fuse_conn *fc, struct fuse_req *req)
+{
+ struct file *file = req->stolen_file;
+ struct fuse_file *ff = file->private_data;
+
+ spin_lock(&fc->lock);
+ fuse_request_init(req);
+ BUG_ON(ff->reserved_req);
+ ff->reserved_req = req;
+ wake_up(&fc->blocked_waitq);
+ spin_unlock(&fc->lock);
+ fput(file);
+}
+
+/*
+ * Gets a requests for a file operation, always succeeds
+ *
+ * This is used for sending the FLUSH request, which must get to
+ * userspace, due to POSIX locks which may need to be unlocked.
+ *
+ * If allocation fails due to OOM, use the reserved request in
+ * fuse_file.
+ *
+ * This is very unlikely to deadlock accidentally, since the
+ * filesystem should not have it's own file open. If deadlock is
+ * intentional, it can still be broken by "aborting" the filesystem.
+ */
+struct fuse_req *fuse_get_req_nofail(struct fuse_conn *fc, struct file *file)
+{
+ struct fuse_req *req;
+
+ atomic_inc(&fc->num_waiting);
+ wait_event(fc->blocked_waitq, !fc->blocked);
+ req = fuse_request_alloc();
+ if (!req)
+ req = get_reserved_req(fc, file);
+
+ fuse_req_init_context(req);
+ req->waiting = 1;
+ return req;
+}
+