Re: [Patch v2 13/19] CIFS: SMBD: Use registered memory RDMA read for SMB write

Leon Romanovsky
2017-08-23T13:52:00Z

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On Sun, Aug 20, 2017 at 12:04:37PM -0700, Long Li wrote:
> From: Long Li <longli@microsoft.com>
>
> When sending I/O, if size is larger than rdma_readwrite_threshold we prepare to send SMB WRITE packet for a RDMA read via memory registration. The actual I/O is done out-of-the-band, so modify the relevant fields in the packet accordingly.
>
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
> fs/cifs/smb2pdu.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 44 insertions(+), 1 deletion(-)
>
> diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
> index 5cc5f6c..5581afd 100644
> --- a/fs/cifs/smb2pdu.c
> +++ b/fs/cifs/smb2pdu.c
> @@ -48,6 +48,7 @@
> #include "smb2glob.h"
> #include "cifspdu.h"
> #include "cifs_spnego.h"
> +#include "smbdirect.h"
>
> /*
> * The following table defines the expected "StructureSize" of SMB2 requests
> @@ -2716,6 +2717,41 @@ smb2_async_writev(struct cifs_writedata *wdata,
> offsetof(struct smb2_write_req, Buffer) - 4);
> req->RemainingBytes = 0;
>
> + /*
> + * If we want to do a server RDMA read, fill in and append
> + * smbd_buffer_descriptor_v1 to the end of write request
> + */
> + if (server->rdma && wdata->bytes >
> + server->smbd_conn->rdma_readwrite_threshold) {
> +
> + struct smbd_buffer_descriptor_v1 *v1;
> + bool need_invalidate = server->dialect == SMB30_PROT_ID;
> +
> + wdata->mr = smbd_register_mr(
> + server->smbd_conn, wdata->pages,
> + wdata->nr_pages, wdata->tailsz,
> + false, need_invalidate);
> + if (!wdata->mr) {
> + rc = -ENOBUFS;
> + goto async_writev_out;
> + }
> + req->Length = 0;
> + req->DataOffset = 0;
> + req->RemainingBytes =

Wow, we have CamelCase variables in linux kernel. It will help if you
start your patchset with small cleanup to convert those variables from
CamelCase to normal names.

Thanks

> + (wdata->nr_pages-1)*PAGE_SIZE + wdata->tailsz;
> + req->Channel = SMB2_CHANNEL_RDMA_V1_INVALIDATE;
> + if (need_invalidate)
> + req->Channel = SMB2_CHANNEL_RDMA_V1;
> + req->WriteChannelInfoOffset =
> + offsetof(struct smb2_write_req, Buffer) - 4;
> + req->WriteChannelInfoLength =
> + sizeof(struct smbd_buffer_descriptor_v1);
> + v1 = (struct smbd_buffer_descriptor_v1 *) &req->Buffer[0];
> + v1->offset = wdata->mr->mr->iova;
> + v1->token = wdata->mr->mr->rkey;
> + v1->length = wdata->mr->mr->length;
> + }
> +
> /* 4 for rfc1002 length field and 1 for Buffer */
> iov[0].iov_len = 4;
> iov[0].iov_base = req;
> @@ -2729,10 +2765,17 @@ smb2_async_writev(struct cifs_writedata *wdata,
> rqst.rq_pagesz = wdata->pagesz;
> rqst.rq_tailsz = wdata->tailsz;
>
> + if (wdata->mr) {
> + iov[1].iov_len += sizeof(struct smbd_buffer_descriptor_v1);
> + rqst.rq_npages = 0;
> + }
> +
> cifs_dbg(FYI, "async write at %llu %u bytes\n",
> wdata->offset, wdata->bytes);
>
> - req->Length = cpu_to_le32(wdata->bytes);
> + /* For RDMA read, I/O size is in RemainingBytes not in Length */
> + if (!wdata->mr)
> + req->Length = cpu_to_le32(wdata->bytes);
>
> inc_rfc1001_len(&req->hdr, wdata->bytes - 1 /* Buffer */);
>
> --
> 2.7.4
>

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