Commit 1944f6ab authored Jun 25, 2025 by Stefan Metzmacher Committed by Steve French Jun 25, 2025

smb: client: let smbd_post_send_iter() respect the peers max_send_size and transmit all data



We should not send smbdirect_data_transfer messages larger than
the negotiated max_send_size, typically 1364 bytes, which means
24 bytes of the smbdirect_data_transfer header + 1340 payload bytes.

This happened when doing an SMB2 write with more than 1340 bytes
(which is done inline as it's below rdma_readwrite_threshold).

It means the peer resets the connection.

When testing between cifs.ko and ksmbd.ko something like this
is logged:

client:

    CIFS: VFS: RDMA transport re-established
    siw: got TERMINATE. layer 1, type 2, code 2
    siw: got TERMINATE. layer 1, type 2, code 2
    siw: got TERMINATE. layer 1, type 2, code 2
    siw: got TERMINATE. layer 1, type 2, code 2
    siw: got TERMINATE. layer 1, type 2, code 2
    siw: got TERMINATE. layer 1, type 2, code 2
    siw: got TERMINATE. layer 1, type 2, code 2
    siw: got TERMINATE. layer 1, type 2, code 2
    siw: got TERMINATE. layer 1, type 2, code 2
    CIFS: VFS: \\carina Send error in SessSetup = -11
    smb2_reconnect: 12 callbacks suppressed
    CIFS: VFS: reconnect tcon failed rc = -11
    CIFS: VFS: reconnect tcon failed rc = -11
    CIFS: VFS: reconnect tcon failed rc = -11
    CIFS: VFS: SMB: Zero rsize calculated, using minimum value 65536

and:

    CIFS: VFS: RDMA transport re-established
    siw: got TERMINATE. layer 1, type 2, code 2
    CIFS: VFS: smbd_recv:1894 disconnected
    siw: got TERMINATE. layer 1, type 2, code 2

The ksmbd dmesg is showing things like:

    smb_direct: Recv error. status='local length error (1)' opcode=128
    smb_direct: disconnected
    smb_direct: Recv error. status='local length error (1)' opcode=128
    ksmbd: smb_direct: disconnected
    ksmbd: sock_read failed: -107

As smbd_post_send_iter() limits the transmitted number of bytes
we need loop over it in order to transmit the whole iter.

Reviewed-by: David Howells <dhowells@redhat.com>
Tested-by: David Howells <dhowells@redhat.com>
Tested-by: Meetakshi Setiya <msetiya@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: linux-cifs@vger.kernel.org
Cc: <stable+noautosel@kernel.org> # sp->max_send_size should be info->max_send_size in backports
Fixes: 3d78fe73 ("cifs: Build the RDMA SGE list directly from an iterator")
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

parent ff8abbd2

fs/smb/client/smbdirect.c

+27 −4

Original line number	Diff line number	Diff line
		@@ -907,8 +907,10 @@ static int smbd_post_send_iter(struct smbd_connection *info,
		.local_dma_lkey = sc->ib.pd->local_dma_lkey,
		.direction = DMA_TO_DEVICE,
		};
		size_t payload_len = umin(*_remaining_data_length,
		sp->max_send_size - sizeof(*packet));

		rc = smb_extract_iter_to_rdma(iter, *_remaining_data_length,
		rc = smb_extract_iter_to_rdma(iter, payload_len,
		&extract);
		if (rc < 0)
		goto err_dma;
		@@ -1013,6 +1015,27 @@ static int smbd_post_send_empty(struct smbd_connection *info)
		return smbd_post_send_iter(info, NULL, &remaining_data_length);
		}

		static int smbd_post_send_full_iter(struct smbd_connection *info,
		struct iov_iter *iter,
		int *_remaining_data_length)
		{
		int rc = 0;

		/*
		* smbd_post_send_iter() respects the
		* negotiated max_send_size, so we need to
		* loop until the full iter is posted
		*/

		while (iov_iter_count(iter) > 0) {
		rc = smbd_post_send_iter(info, iter, _remaining_data_length);
		if (rc < 0)
		break;
		}

		return rc;
		}

		/*
		* Post a receive request to the transport
		* The remote peer can only send data when a receive request is posted
		@@ -2032,13 +2055,13 @@ int smbd_send(struct TCP_Server_Info *server,
		klen += rqst->rq_iov[i].iov_len;
		iov_iter_kvec(&iter, ITER_SOURCE, rqst->rq_iov, rqst->rq_nvec, klen);

		rc = smbd_post_send_iter(info, &iter, &remaining_data_length);
		rc = smbd_post_send_full_iter(info, &iter, &remaining_data_length);
		if (rc < 0)
		break;

		if (iov_iter_count(&rqst->rq_iter) > 0) {
		/* And then the data pages if there are any */
		rc = smbd_post_send_iter(info, &rqst->rq_iter,
		rc = smbd_post_send_full_iter(info, &rqst->rq_iter,
		&remaining_data_length);
		if (rc < 0)
		break;