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FAILED: Patch "smb: server: make use of smbdirect_socket.send_io.bcredits" failed to apply to 6.6-stable tree

PATCH Sasha Levin 1 participant 1 message Mar 1

Subsystems (4)
Stable branch SMB client (CIFS) Kernel SMB3 server (ksmbd) Smbdirect (RDMA Stream Transport with Read/Write-Offload, MS-SMBD)
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Sasha Levin

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The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From 34abd408c8ba24d7c97bd02ba874d8c714f49db1 Mon Sep 17 00:00:00 2001
From: Stefan Metzmacher <[email protected]>
Date: Thu, 22 Jan 2026 18:16:45 +0100
Subject: [PATCH] smb: server: make use of smbdirect_socket.send_io.bcredits

It turns out that our code will corrupt the stream of reassabled data transfer messages when we trigger an immendiate (empty) send.

In order to fix this we'll have a single 'batch' credit per connection. And code getting that credit is free to use as much messages until remaining_length reaches 0, then the batch credit it given back and the next logical send can happen.

Cc <[email protected]> # 6.18.x
Cc Namjae Jeon <[email protected]>
Cc Steve French <[email protected]>
Cc Tom Talpey <[email protected]>
Cc [email protected]
Cc [email protected]
Signed-off-by Stefan Metzmacher <[email protected]>
Acked-by Namjae Jeon <[email protected]>
Signed-off-by Steve French <[email protected]>
---
 fs/smb/server/transport_rdma.c | 53 ++++++++++++++++++++++++++++++++--
 1 file changed, 51 insertions(+), 2 deletions(-)
fs/smb/server/transport_rdma.c +51 -2
index 4a473df1f2b3a..38248b6a1b5ca 100644
@@ -221,6 +221,7 @@ static void smb_direct_disconnect_wake_up_all(struct smbdirect_socket *sc)
 	 * in order to notice the broken connection.
 	 */
 	wake_up_all(&sc->status_wait);
+	wake_up_all(&sc->send_io.bcredits.wait_queue);
 	wake_up_all(&sc->send_io.lcredits.wait_queue);
 	wake_up_all(&sc->send_io.credits.wait_queue);
 	wake_up_all(&sc->send_io.pending.zero_wait_queue);

@@ -1152,6 +1153,7 @@ static void smb_direct_send_ctx_init(struct smbdirect_send_batch *send_ctx,
 	send_ctx->wr_cnt = 0;
 	send_ctx->need_invalidate_rkey = need_invalidate_rkey;
 	send_ctx->remote_key = remote_key;
+	send_ctx->credit = 0;
 }
 
 static int smb_direct_flush_send_list(struct smbdirect_socket *sc,

@@ -1159,10 +1161,10 @@ static int smb_direct_flush_send_list(struct smbdirect_socket *sc,
 				      bool is_last)
 {
 	struct smbdirect_send_io *first, *last;
-	int ret;
+	int ret = 0;
 
 	if (list_empty(&send_ctx->msg_list))
-		return 0;
+		goto release_credit;
 
 	first = list_first_entry(&send_ctx->msg_list,
 				 struct smbdirect_send_io,

@@ -1204,6 +1206,13 @@ static int smb_direct_flush_send_list(struct smbdirect_socket *sc,
 		smb_direct_free_sendmsg(sc, last);
 	}
 
+release_credit:
+	if (is_last && !ret && send_ctx->credit) {
+		atomic_add(send_ctx->credit, &sc->send_io.bcredits.count);
+		send_ctx->credit = 0;
+		wake_up(&sc->send_io.bcredits.wait_queue);
+	}
+
 	return ret;
 }
 

@@ -1229,6 +1238,25 @@ static int wait_for_credits(struct smbdirect_socket *sc,
 	} while (true);
 }
 
+static int wait_for_send_bcredit(struct smbdirect_socket *sc,
+				 struct smbdirect_send_batch *send_ctx)
+{
+	int ret;
+
+	if (send_ctx->credit)
+		return 0;
+
+	ret = wait_for_credits(sc,
+			       &sc->send_io.bcredits.wait_queue,
+			       &sc->send_io.bcredits.count,
+			       1);
+	if (ret)
+		return ret;
+
+	send_ctx->credit = 1;
+	return 0;
+}
+
 static int wait_for_send_lcredit(struct smbdirect_socket *sc,
 				 struct smbdirect_send_batch *send_ctx)
 {

@@ -1430,6 +1458,16 @@ static int smb_direct_post_send_data(struct smbdirect_socket *sc,
 	struct smbdirect_send_io *msg;
 	int data_length;
 	struct scatterlist sg[SMBDIRECT_SEND_IO_MAX_SGE - 1];
+	struct smbdirect_send_batch _send_ctx;
+
+	if (!send_ctx) {
+		smb_direct_send_ctx_init(&_send_ctx, false, 0);
+		send_ctx = &_send_ctx;
+	}
+
+	ret = wait_for_send_bcredit(sc, send_ctx);
+	if (ret)
+		goto bcredit_failed;
 
 	ret = wait_for_send_lcredit(sc, send_ctx);
 	if (ret)

@@ -1482,6 +1520,13 @@ static int smb_direct_post_send_data(struct smbdirect_socket *sc,
 	ret = post_sendmsg(sc, send_ctx, msg);
 	if (ret)
 		goto err;
+
+	if (send_ctx == &_send_ctx) {
+		ret = smb_direct_flush_send_list(sc, send_ctx, true);
+		if (ret)
+			goto err;
+	}
+
 	return 0;
 err:
 	smb_direct_free_sendmsg(sc, msg);

@@ -1490,6 +1535,9 @@ static int smb_direct_post_send_data(struct smbdirect_socket *sc,
 credit_failed:
 	atomic_inc(&sc->send_io.lcredits.count);
 lcredit_failed:
+	atomic_add(send_ctx->credit, &sc->send_io.bcredits.count);
+	send_ctx->credit = 0;
+bcredit_failed:
 	return ret;
 }
 

@@ -1961,6 +2009,7 @@ static int smb_direct_send_negotiate_response(struct smbdirect_socket *sc,
 		resp->max_fragmented_size =
 				cpu_to_le32(sp->max_fragmented_recv_size);
 
+		atomic_set(&sc->send_io.bcredits.count, 1);
 		sc->recv_io.expected = SMBDIRECT_EXPECT_DATA_TRANSFER;
 		sc->status = SMBDIRECT_SOCKET_CONNECTED;
 	}
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