smb: client: let recv_done() queue a refill when the peer is low on credits

In captures I saw that Windows was granting 191 credits in a batch
when its peer posted a lot of messages. We are asking for a
credit target of 255 and 191 is 252*3/4.

So we also use that logic in order to fill the
recv buffers available to the peer.

Fixes: 02548c4 ("smb: client: queue post_recv_credits_work also if the peer raises the credit target")
Cc: <stable@vger.kernel.org> # 6.18.x
Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Long Li <longli@microsoft.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: metze-samba

fs/smb/client/smbdirect.c

@@ -663,6 +663,7 @@ static void recv_done(struct ib_cq *cq, struct ib_wc *wc)
 		container_of(wc->wr_cqe, struct smbdirect_recv_io, cqe);
 	struct smbdirect_socket *sc = response->socket;
 	struct smbdirect_socket_parameters *sp = &sc->parameters;
+	int current_recv_credits;
 	u16 old_recv_credit_target;
 	u32 data_offset = 0;
 	u32 data_length = 0;
@@ -747,7 +748,8 @@ static void recv_done(struct ib_cq *cq, struct ib_wc *wc)
 		}
 
 		atomic_dec(&sc->recv_io.posted.count);
-		atomic_dec(&sc->recv_io.credits.count);
+		current_recv_credits = atomic_dec_return(&sc->recv_io.credits.count);
+
 		old_recv_credit_target = sc->recv_io.credits.target;
 		sc->recv_io.credits.target =
 			le16_to_cpu(data_transfer->credits_requested);
@@ -783,7 +785,8 @@ static void recv_done(struct ib_cq *cq, struct ib_wc *wc)
 		 * reassembly queue and wake up the reading thread
 		 */
 		if (data_length) {
-			if (sc->recv_io.credits.target > old_recv_credit_target)
+			if (current_recv_credits <= (sc->recv_io.credits.target / 4) ||
+			    sc->recv_io.credits.target > old_recv_credit_target)
 				queue_work(sc->workqueue, &sc->recv_io.posted.refill_work);
 
 			enqueue_reassembly(sc, response, data_length);