IB/srp: Use a fake scatterlist for non-SG SCSI commands

Since the SCSI midlayer is moving towards entirely getting rid of
commands with use_sg == 0, we should treat this case as an exception.
Therefore, change the IB SRP initiator to create a fake scatterlist
for these commands with sg_init_one().  This simplifies the flow of
DMA mapping and unmapping, since SRP can just use dma_map_sg() and
dma_unmap_sg() unconditionally, rather than having to choose between
the dma_{map,unmap}_sg() and dma_{map,unmap}_single() variants.

Signed-off-by: Roland Dreier <rolandd@cisco.com>

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index a13dcdf90a4f11d4c886fa2b5486fc84d4c19b7b..61924cc30e55c55369cb4eadf191fc2f0ad0daaf 100644 (file)
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -503,8 +503,10 @@ err:
 static int srp_map_data(struct scsi_cmnd *scmnd, struct srp_target_port *target,
                        struct srp_request *req)
 {
+       struct scatterlist *scat;
        struct srp_cmd *cmd = req->cmd->buf;
-       int len;
+       int len, nents, count;
+       int i;
        u8 fmt;
 
        if (!scmnd->request_buffer || scmnd->sc_data_direction == DMA_NONE)
@@ -517,82 +519,66 @@ static int srp_map_data(struct scsi_cmnd *scmnd, struct srp_target_port *target,
                return -EINVAL;
        }
 
-       if (scmnd->use_sg) {
-               struct scatterlist *scat = scmnd->request_buffer;
-               int n;
-               int i;
-
-               n = dma_map_sg(target->srp_host->dev->dma_device,
-                              scat, scmnd->use_sg, scmnd->sc_data_direction);
+       /*
+        * This handling of non-SG commands can be killed when the
+        * SCSI midlayer no longer generates non-SG commands.
+        */
+       if (likely(scmnd->use_sg)) {
+               nents = scmnd->use_sg;
+               scat  = scmnd->request_buffer;
+       } else {
+               nents = 1;
+               scat  = &req->fake_sg;
+               sg_init_one(scat, scmnd->request_buffer, scmnd->request_bufflen);
+       }
 
-               if (n == 1) {
-                       struct srp_direct_buf *buf = (void *) cmd->add_data;
+       count = dma_map_sg(target->srp_host->dev->dma_device, scat, nents,
+                          scmnd->sc_data_direction);
 
-                       fmt = SRP_DATA_DESC_DIRECT;
+       if (count == 1) {
+               struct srp_direct_buf *buf = (void *) cmd->add_data;
 
-                       buf->va  = cpu_to_be64(sg_dma_address(scat));
-                       buf->key = cpu_to_be32(target->srp_host->mr->rkey);
-                       buf->len = cpu_to_be32(sg_dma_len(scat));
+               fmt = SRP_DATA_DESC_DIRECT;
 
-                       len = sizeof (struct srp_cmd) +
-                               sizeof (struct srp_direct_buf);
-               } else {
-                       struct srp_indirect_buf *buf = (void *) cmd->add_data;
-                       u32 datalen = 0;
+               buf->va  = cpu_to_be64(sg_dma_address(scat));
+               buf->key = cpu_to_be32(target->srp_host->mr->rkey);
+               buf->len = cpu_to_be32(sg_dma_len(scat));
 
-                       fmt = SRP_DATA_DESC_INDIRECT;
+               len = sizeof (struct srp_cmd) +
+                       sizeof (struct srp_direct_buf);
+       } else {
+               struct srp_indirect_buf *buf = (void *) cmd->add_data;
+               u32 datalen = 0;
 
-                       if (scmnd->sc_data_direction == DMA_TO_DEVICE)
-                               cmd->data_out_desc_cnt = n;
-                       else
-                               cmd->data_in_desc_cnt = n;
+               fmt = SRP_DATA_DESC_INDIRECT;
 
-                       buf->table_desc.va  = cpu_to_be64(req->cmd->dma +
-                                                         sizeof *cmd +
-                                                         sizeof *buf);
-                       buf->table_desc.key =
+               if (scmnd->sc_data_direction == DMA_TO_DEVICE)
+                       cmd->data_out_desc_cnt = count;
+               else
+                       cmd->data_in_desc_cnt = count;
+
+               buf->table_desc.va  = cpu_to_be64(req->cmd->dma +
+                                                 sizeof *cmd +
+                                                 sizeof *buf);
+               buf->table_desc.key =
+                       cpu_to_be32(target->srp_host->mr->rkey);
+               buf->table_desc.len =
+                       cpu_to_be32(count * sizeof (struct srp_direct_buf));
+
+               for (i = 0; i < count; ++i) {
+                       buf->desc_list[i].va  = cpu_to_be64(sg_dma_address(&scat[i]));
+                       buf->desc_list[i].key =
                                cpu_to_be32(target->srp_host->mr->rkey);
-                       buf->table_desc.len =
-                               cpu_to_be32(n * sizeof (struct srp_direct_buf));
-
-                       for (i = 0; i < n; ++i) {
-                               buf->desc_list[i].va  = cpu_to_be64(sg_dma_address(&scat[i]));
-                               buf->desc_list[i].key =
-                                       cpu_to_be32(target->srp_host->mr->rkey);
-                               buf->desc_list[i].len = cpu_to_be32(sg_dma_len(&scat[i]));
-
-                               datalen += sg_dma_len(&scat[i]);
-                       }
+                       buf->desc_list[i].len = cpu_to_be32(sg_dma_len(&scat[i]));
 
-                       buf->len = cpu_to_be32(datalen);
-
-                       len = sizeof (struct srp_cmd) +
-                               sizeof (struct srp_indirect_buf) +
-                               n * sizeof (struct srp_direct_buf);
-               }
-       } else {
-               struct srp_direct_buf *buf = (void *) cmd->add_data;
-               dma_addr_t dma;
-
-               dma = dma_map_single(target->srp_host->dev->dma_device,
-                                    scmnd->request_buffer, scmnd->request_bufflen,
-                                    scmnd->sc_data_direction);
-               if (dma_mapping_error(dma)) {
-                       printk(KERN_WARNING PFX "unable to map %p/%d (dir %d)\n",
-                              scmnd->request_buffer, (int) scmnd->request_bufflen,
-                              scmnd->sc_data_direction);
-                       return -EINVAL;
+                       datalen += sg_dma_len(&scat[i]);
                }
 
-               pci_unmap_addr_set(req, direct_mapping, dma);
+               buf->len = cpu_to_be32(datalen);
 
-               buf->va  = cpu_to_be64(dma);
-               buf->key = cpu_to_be32(target->srp_host->mr->rkey);
-               buf->len = cpu_to_be32(scmnd->request_bufflen);
-
-               fmt = SRP_DATA_DESC_DIRECT;
-
-               len = sizeof (struct srp_cmd) + sizeof (struct srp_direct_buf);
+               len = sizeof (struct srp_cmd) +
+                       sizeof (struct srp_indirect_buf) +
+                       count * sizeof (struct srp_direct_buf);
        }
 
        if (scmnd->sc_data_direction == DMA_TO_DEVICE)
@@ -600,7 +586,6 @@ static int srp_map_data(struct scsi_cmnd *scmnd, struct srp_target_port *target,
        else
                cmd->buf_fmt = fmt;
 
-
        return len;
 }
 
@@ -608,20 +593,28 @@ static void srp_unmap_data(struct scsi_cmnd *scmnd,
                           struct srp_target_port *target,
                           struct srp_request *req)
 {
+       struct scatterlist *scat;
+       int nents;
+
        if (!scmnd->request_buffer ||
            (scmnd->sc_data_direction != DMA_TO_DEVICE &&
             scmnd->sc_data_direction != DMA_FROM_DEVICE))
-           return;
+               return;
 
-       if (scmnd->use_sg)
-               dma_unmap_sg(target->srp_host->dev->dma_device,
-                            (struct scatterlist *) scmnd->request_buffer,
-                            scmnd->use_sg, scmnd->sc_data_direction);
-       else
-               dma_unmap_single(target->srp_host->dev->dma_device,
-                                pci_unmap_addr(req, direct_mapping),
-                                scmnd->request_bufflen,
-                                scmnd->sc_data_direction);
+       /*
+        * This handling of non-SG commands can be killed when the
+        * SCSI midlayer no longer generates non-SG commands.
+        */
+       if (likely(scmnd->use_sg)) {
+               nents = scmnd->use_sg;
+               scat  = (struct scatterlist *) scmnd->request_buffer;
+       } else {
+               nents = 1;
+               scat  = (struct scatterlist *) scmnd->request_buffer;
+       }
+
+       dma_unmap_sg(target->srp_host->dev->dma_device, scat, nents,
+                    scmnd->sc_data_direction);
 }
 
 static void srp_process_rsp(struct srp_target_port *target, struct srp_rsp *rsp)

diff --git a/drivers/infiniband/ulp/srp/ib_srp.h b/drivers/infiniband/ulp/srp/ib_srp.h
index 4e7727df32f12d9f17de6b1032851d600af91ef6..bd7f7c3115de8f0078ce17f66655c0ce5acb0081 100644 (file)
--- a/drivers/infiniband/ulp/srp/ib_srp.h
+++ b/drivers/infiniband/ulp/srp/ib_srp.h
@@ -38,6 +38,7 @@
 #include <linux/types.h>
 #include <linux/list.h>
 #include <linux/mutex.h>
+#include <linux/scatterlist.h>
 
 #include <scsi/scsi_host.h>
 #include <scsi/scsi_cmnd.h>
@@ -94,7 +95,11 @@ struct srp_request {
        struct scsi_cmnd       *scmnd;
        struct srp_iu          *cmd;
        struct srp_iu          *tsk_mgmt;
-       DECLARE_PCI_UNMAP_ADDR(direct_mapping)
+       /*
+        * Fake scatterlist used when scmnd->use_sg==0.  Can be killed
+        * when the SCSI midlayer no longer generates non-SG commands.
+        */
+       struct scatterlist      fake_sg;
        struct completion       done;
        short                   next;
        u8                      cmd_done;