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: Long Li <longli@microsoft.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 3a85df2a9baf22301b139b09c522a0f4fa3428cc..7cee97b93a614736e77414162bdf46c432475a40 100644 (file)
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -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)

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 908d7770d15a316c48604eeadf48abfd52e160da..bee0871d6ddafba07909a4e7c87c2d80b6120d86 100644 (file)
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -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);