virtio-fs: let -ENOMEM bubble up or burst gently

Currently, when the enqueueing of a request or forget operation fails
with -ENOMEM, the enqueueing is retried after a timeout. This patch
removes this behavior and treats -ENOMEM in these scenarios like any
other error. By bubbling up the error to user space in the case of a
request, and by dropping the operation in case of a forget. This
behavior matches that of the FUSE layer above, and also simplifies the
error handling. The latter will come in handy for upcoming patches that
optimize the retrying of operations in case of -ENOSPC.
Signed-off-by: Peter-Jan Gootzen <pgootzen@nvidia.com>
Reviewed-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Yoray Zack <yorayz@nvidia.com>
Message-Id: <20240517190435.152096-2-pgootzen@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

fs/fuse/virtio_fs.c

@@ -447,7 +447,7 @@ static void virtio_fs_request_dispatch_work(struct work_struct *work)
 
 		ret = virtio_fs_enqueue_req(fsvq, req, true);
 		if (ret < 0) {
-			if (ret == -ENOMEM || ret == -ENOSPC) {
+			if (ret == -ENOSPC) {
 				spin_lock(&fsvq->lock);
 				list_add_tail(&req->list, &fsvq->queued_reqs);
 				schedule_delayed_work(&fsvq->dispatch_work,
@@ -494,7 +494,7 @@ static int send_forget_request(struct virtio_fs_vq *fsvq,
 
 	ret = virtqueue_add_outbuf(vq, &sg, 1, forget, GFP_ATOMIC);
 	if (ret < 0) {
-		if (ret == -ENOMEM || ret == -ENOSPC) {
+		if (ret == -ENOSPC) {
 			pr_debug("virtio-fs: Could not queue FORGET: err=%d. Will try later\n",
 				 ret);
 			list_add_tail(&forget->list, &fsvq->queued_reqs);
@@ -1367,7 +1367,7 @@ __releases(fiq->lock)
 	fsvq = &fs->vqs[queue_id];
 	ret = virtio_fs_enqueue_req(fsvq, req, false);
 	if (ret < 0) {
-		if (ret == -ENOMEM || ret == -ENOSPC) {
+		if (ret == -ENOSPC) {
 			/*
 			 * Virtqueue full. Retry submission from worker
 			 * context as we might be holding fc->bg_lock.