Commit bd3dcc6a authored by Long Li's avatar Long Li Committed by Steve French
Browse files

CIFS: SMBD: Upper layer performs SMB read via RDMA write through memory registration 



If I/O size is larger than rdma_readwrite_threshold, use RDMA write for
SMB read by specifying channel SMB2_CHANNEL_RDMA_V1 or
SMB2_CHANNEL_RDMA_V1_INVALIDATE in the SMB packet, depending on SMB dialect
used. Append a smbd_buffer_descriptor_v1 to the end of the SMB packet and fill
in other values to indicate this SMB read uses RDMA write.

There is no need to read from the transport for incoming payload. At the time
SMB read response comes back, the data is already transferred and placed in the
pages by RDMA hardware.

When SMB read is finished, deregister the memory regions if RDMA write is used
for this SMB read. smbd_deregister_mr may need to do local invalidation and
sleep, if server remote invalidation is not used.

There are situations where the MID may not be created on I/O failure, under
which memory region is deregistered when read data context is released.

Signed-off-by: default avatarLong Li <longli@microsoft.com>
Signed-off-by: default avatarSteve French <smfrench@gmail.com>
Reviewed-by: default avatarPavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: default avatarRonnie Sahlberg <lsahlber@redhat.com>
parent 74dcf418

fs/cifs/file.c

+15 −2
Original line number Diff line number Diff line
@@ -42,7 +42,7 @@ 
#include "cifs_debug.h"

#include "cifs_fs_sb.h"

#include "fscache.h"



#include "smbdirect.h"



static inline int cifs_convert_flags(unsigned int flags)

{
@@ -2902,7 +2902,12 @@ cifs_readdata_release(struct kref *refcount) 
{

	struct cifs_readdata *rdata = container_of(refcount,

					struct cifs_readdata, refcount);



#ifdef CONFIG_CIFS_SMB_DIRECT

	if (rdata->mr) {

		smbd_deregister_mr(rdata->mr);

		rdata->mr = NULL;

	}

#endif

	if (rdata->cfile)

		cifsFileInfo_put(rdata->cfile);
@@ -3031,6 +3036,10 @@ uncached_fill_pages(struct TCP_Server_Info *server, 
		}

		if (iter)

			result = copy_page_from_iter(page, 0, n, iter);

#ifdef CONFIG_CIFS_SMB_DIRECT

		else if (rdata->mr)

			result = n;

#endif

		else

			result = cifs_read_page_from_socket(server, page, n);

		if (result < 0)
@@ -3598,6 +3607,10 @@ readpages_fill_pages(struct TCP_Server_Info *server, 


		if (iter)

			result = copy_page_from_iter(page, 0, n, iter);

#ifdef CONFIG_CIFS_SMB_DIRECT

		else if (rdata->mr)

			result = n;

#endif

		else

			result = cifs_read_page_from_socket(server, page, n);

		if (result < 0)

fs/cifs/smb2pdu.c

+44 −1
Original line number Diff line number Diff line
@@ -2458,7 +2458,40 @@ smb2_new_read_req(void **buf, unsigned int *total_len, 
	req->MinimumCount = 0;

	req->Length = cpu_to_le32(io_parms->length);

	req->Offset = cpu_to_le64(io_parms->offset);

#ifdef CONFIG_CIFS_SMB_DIRECT

	/*

	 * If we want to do a RDMA write, fill in and append

	 * smbd_buffer_descriptor_v1 to the end of read request

	 */

	if (server->rdma && rdata &&

		rdata->bytes >= server->smbd_conn->rdma_readwrite_threshold) {



		struct smbd_buffer_descriptor_v1 *v1;

		bool need_invalidate =

			io_parms->tcon->ses->server->dialect == SMB30_PROT_ID;



		rdata->mr = smbd_register_mr(

				server->smbd_conn, rdata->pages,

				rdata->nr_pages, rdata->tailsz,

				true, need_invalidate);

		if (!rdata->mr)

			return -ENOBUFS;



		req->Channel = SMB2_CHANNEL_RDMA_V1_INVALIDATE;

		if (need_invalidate)

			req->Channel = SMB2_CHANNEL_RDMA_V1;

		req->ReadChannelInfoOffset =

			offsetof(struct smb2_read_plain_req, Buffer);

		req->ReadChannelInfoLength =

			sizeof(struct smbd_buffer_descriptor_v1);

		v1 = (struct smbd_buffer_descriptor_v1 *) &req->Buffer[0];

		v1->offset = rdata->mr->mr->iova;

		v1->token = rdata->mr->mr->rkey;

		v1->length = rdata->mr->mr->length;



		*total_len += sizeof(*v1) - 1;

	}

#endif

	if (request_type & CHAINED_REQUEST) {

		if (!(request_type & END_OF_CHAIN)) {

			/* next 8-byte aligned request */
@@ -2537,7 +2570,17 @@ smb2_readv_callback(struct mid_q_entry *mid) 
		if (rdata->result != -ENODATA)

			rdata->result = -EIO;

	}



#ifdef CONFIG_CIFS_SMB_DIRECT

	/*

	 * If this rdata has a memmory registered, the MR can be freed

	 * MR needs to be freed as soon as I/O finishes to prevent deadlock

	 * because they have limited number and are used for future I/Os

	 */

	if (rdata->mr) {

		smbd_deregister_mr(rdata->mr);

		rdata->mr = NULL;

	}

#endif

	if (rdata->result)

		cifs_stats_fail_inc(tcon, SMB2_READ_HE);

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