[SCSI] zfcp: Report scatter-gather limits to SCSI and block layer

Instead of dealing with large segments in the scatter-gather lists in
zfcp_qdio.c, report the limits to the upper layers. With these limits
in place, the code for mapping large data blocks to multiple sbales
can be removed.

Reviewed-by: Swen Schillig <swen@vnet.ibm.com>
Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

5 files changed, 19 insertions, 34 deletions

diff --git a/drivers/s390/scsi/zfcp_aux.c b/drivers/s390/scsi/zfcp_aux.c
index 1e6183a86ce5..abf33db647ff 100644
--- a/drivers/s390/scsi/zfcp_aux.c
+++ b/drivers/s390/scsi/zfcp_aux.c
@@ -545,6 +545,10 @@ struct zfcp_adapter *zfcp_adapter_enqueue(struct ccw_device *ccw_device)
                                &zfcp_sysfs_adapter_attrs))
                 goto failed;
 
+        /* report size limit per scatter-gather segment */
+        adapter->dma_parms.max_segment_size = ZFCP_QDIO_SBALE_LEN;
+        adapter->ccw_device->dev.dma_parms = &adapter->dma_parms;
+
         if (!zfcp_adapter_scsi_register(adapter))
                 return adapter;
 
diff --git a/drivers/s390/scsi/zfcp_def.h b/drivers/s390/scsi/zfcp_def.h
index 7131c7db1f04..72132c13f45b 100644
--- a/drivers/s390/scsi/zfcp_def.h
+++ b/drivers/s390/scsi/zfcp_def.h
@@ -205,6 +205,7 @@ struct zfcp_adapter {
         struct work_struct      scan_work;
         struct service_level    service_level;
         struct workqueue_struct *work_queue;
+        struct device_dma_parameters dma_parms;
 };
 
 struct zfcp_port {
diff --git a/drivers/s390/scsi/zfcp_qdio.c b/drivers/s390/scsi/zfcp_qdio.c
index dbfa312a7f50..aa68515abe21 100644
--- a/drivers/s390/scsi/zfcp_qdio.c
+++ b/drivers/s390/scsi/zfcp_qdio.c
@@ -206,35 +206,6 @@ static void zfcp_qdio_undo_sbals(struct zfcp_qdio *qdio,
         zfcp_qdio_zero_sbals(sbal, first, count);
 }
 
-static int zfcp_qdio_fill_sbals(struct zfcp_qdio *qdio,
-                                struct zfcp_qdio_req *q_req,
-                                unsigned int sbtype, void *start_addr,
-                                unsigned int total_length)
-{
-        struct qdio_buffer_element *sbale;
-        unsigned long remaining, length;
-        void *addr;
-
-        /* split segment up */
-        for (addr = start_addr, remaining = total_length; remaining > 0;
-             addr += length, remaining -= length) {
-                sbale = zfcp_qdio_sbale_next(qdio, q_req, sbtype);
-                if (!sbale) {
-                        atomic_inc(&qdio->req_q_full);
-                        zfcp_qdio_undo_sbals(qdio, q_req);
-                        return -EINVAL;
-                }
-
-                /* new piece must not exceed next page boundary */
-                length = min(remaining,
-                             (PAGE_SIZE - ((unsigned long)addr &
-                                           (PAGE_SIZE - 1))));
-                sbale->addr = addr;
-                sbale->length = length;
-        }
-        return 0;
-}
-
 /**
  * zfcp_qdio_sbals_from_sg - fill SBALs from scatter-gather list
  * @fsf_req: request to be processed
@@ -248,7 +219,7 @@ int zfcp_qdio_sbals_from_sg(struct zfcp_qdio *qdio, struct zfcp_qdio_req *q_req,
                             int max_sbals)
 {
         struct qdio_buffer_element *sbale;
-        int retval, bytes = 0;
+        int bytes = 0;
 
         /* figure out last allowed SBAL */
         zfcp_qdio_sbal_limit(qdio, q_req, max_sbals);
@@ -258,10 +229,16 @@ int zfcp_qdio_sbals_from_sg(struct zfcp_qdio *qdio, struct zfcp_qdio_req *q_req,
         sbale->flags |= sbtype;
 
         for (; sg; sg = sg_next(sg)) {
-                retval = zfcp_qdio_fill_sbals(qdio, q_req, sbtype,
-                                              sg_virt(sg), sg->length);
-                if (retval < 0)
-                        return retval;
+                sbale = zfcp_qdio_sbale_next(qdio, q_req, sbtype);
+                if (!sbale) {
+                        atomic_inc(&qdio->req_q_full);
+                        zfcp_qdio_undo_sbals(qdio, q_req);
+                        return -EINVAL;
+                }
+
+                sbale->addr = sg_virt(sg);
+                sbale->length = sg->length;
+
                 bytes += sg->length;
         }
 
diff --git a/drivers/s390/scsi/zfcp_qdio.h b/drivers/s390/scsi/zfcp_qdio.h
index 8cca54631e1e..f2b5a363bb84 100644
--- a/drivers/s390/scsi/zfcp_qdio.h
+++ b/drivers/s390/scsi/zfcp_qdio.h
@@ -11,6 +11,8 @@
 
 #include <asm/qdio.h>
 
+#define ZFCP_QDIO_SBALE_LEN     PAGE_SIZE
+
 /**
  * struct zfcp_qdio_queue - qdio queue buffer, zfcp index and free count
  * @sbal: qdio buffers
diff --git a/drivers/s390/scsi/zfcp_scsi.c b/drivers/s390/scsi/zfcp_scsi.c
index d13eb9a6408a..066b0507a639 100644
--- a/drivers/s390/scsi/zfcp_scsi.c
+++ b/drivers/s390/scsi/zfcp_scsi.c
@@ -682,6 +682,7 @@ struct zfcp_data zfcp_data = {
                 .use_clustering          = 1,
                 .sdev_attrs              = zfcp_sysfs_sdev_attrs,
                 .max_sectors             = (ZFCP_MAX_SBALES_PER_REQ * 8),
+                .dma_boundary            = ZFCP_QDIO_SBALE_LEN - 1,
                 .shost_attrs             = zfcp_sysfs_shost_attrs,
         },
 };