smb: client: let smbd_post_send_iter() call ib_dma_map_single() for the header first

This will simplify further changes, the important part is that
request->num_sge >= 1 is only set if request->sge[0].* is valid.

Note that ib_dma_sync_single_for_device() is called in
smbd_post_send() for each sge, so the device will still
see the packet header even if it's modified after calling
ib_dma_map_single().

Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Long Li <longli@microsoft.com>
Acked-by: 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>

1 files changed, 21 insertions, 22 deletions

diff --git a/fs/smb/client/smbdirect.c b/fs/smb/client/smbdirect.c
index 1d81ead875d0..316f398c70f4 100644
--- a/fs/smb/client/smbdirect.c
+++ b/fs/smb/client/smbdirect.c
@@ -1158,10 +1158,30 @@ wait_send_queue:
 	request->socket = sc;
 	memset(request->sge, 0, sizeof(request->sge));
 
+	/* Map the packet to DMA */
+	header_length = sizeof(struct smbdirect_data_transfer);
+	/* If this is a packet without payload, don't send padding */
+	if (!iter)
+		header_length = offsetof(struct smbdirect_data_transfer, padding);
+
+	packet = smbdirect_send_io_payload(request);
+	request->sge[0].addr = ib_dma_map_single(sc->ib.dev,
+						 (void *)packet,
+						 header_length,
+						 DMA_TO_DEVICE);
+	if (ib_dma_mapping_error(sc->ib.dev, request->sge[0].addr)) {
+		rc = -EIO;
+		goto err_dma;
+	}
+
+	request->sge[0].length = header_length;
+	request->sge[0].lkey = sc->ib.pd->local_dma_lkey;
+	request->num_sge = 1;
+
 	/* Fill in the data payload to find out how much data we can add */
 	if (iter) {
 		struct smb_extract_to_rdma extract = {
-			.nr_sge		= 1,
+			.nr_sge		= request->num_sge,
 			.max_sge	= SMBDIRECT_SEND_IO_MAX_SGE,
 			.sge		= request->sge,
 			.device		= sc->ib.dev,
@@ -1180,11 +1200,9 @@ wait_send_queue:
 		*_remaining_data_length -= data_length;
 	} else {
 		data_length = 0;
-		request->num_sge = 1;
 	}
 
 	/* Fill in the packet header */
-	packet = smbdirect_send_io_payload(request);
 	packet->credits_requested = cpu_to_le16(sp->send_credit_target);
 
 	new_credits = manage_credits_prior_sending(sc);
@@ -1211,25 +1229,6 @@ wait_send_queue:
 		     le32_to_cpu(packet->data_length),
 		     le32_to_cpu(packet->remaining_data_length));
 
-	/* Map the packet to DMA */
-	header_length = sizeof(struct smbdirect_data_transfer);
-	/* If this is a packet without payload, don't send padding */
-	if (!data_length)
-		header_length = offsetof(struct smbdirect_data_transfer, padding);
-
-	request->sge[0].addr = ib_dma_map_single(sc->ib.dev,
-						 (void *)packet,
-						 header_length,
-						 DMA_TO_DEVICE);
-	if (ib_dma_mapping_error(sc->ib.dev, request->sge[0].addr)) {
-		rc = -EIO;
-		request->sge[0].addr = 0;
-		goto err_dma;
-	}
-
-	request->sge[0].length = header_length;
-	request->sge[0].lkey = sc->ib.pd->local_dma_lkey;
-
 	rc = smbd_post_send(sc, request);
 	if (!rc)
 		return 0;