[SCSI] Support devices with protection information

Implement support for DMA of protection information for devices that
are data integrity capable.

 - Add support for mapping an extra scatter-gather list containing
   the protection information.

 - Allocate protection scsi_data_buffer if host is DIX (integrity DMA)
   capable.

 - Accessor function for checking whether a device has protection
   enabled.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

3 files changed, 59 insertions, 3 deletions

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 5276e73c58fc..ee6be596503d 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -197,11 +197,43 @@ static void
 scsi_pool_free_command(struct scsi_host_cmd_pool *pool,
                          struct scsi_cmnd *cmd)
 {
+        if (cmd->prot_sdb)
+                kmem_cache_free(scsi_sdb_cache, cmd->prot_sdb);
+
         kmem_cache_free(pool->sense_slab, cmd->sense_buffer);
         kmem_cache_free(pool->cmd_slab, cmd);
 }
 
 /**
+ * scsi_host_alloc_command - internal function to allocate command
+ * @shost:      SCSI host whose pool to allocate from
+ * @gfp_mask:   mask for the allocation
+ *
+ * Returns a fully allocated command with sense buffer and protection
+ * data buffer (where applicable) or NULL on failure
+ */
+static struct scsi_cmnd *
+scsi_host_alloc_command(struct Scsi_Host *shost, gfp_t gfp_mask)
+{
+        struct scsi_cmnd *cmd;
+
+        cmd = scsi_pool_alloc_command(shost->cmd_pool, gfp_mask);
+        if (!cmd)
+                return NULL;
+
+        if (scsi_host_get_prot(shost) >= SHOST_DIX_TYPE0_PROTECTION) {
+                cmd->prot_sdb = kmem_cache_zalloc(scsi_sdb_cache, gfp_mask);
+
+                if (!cmd->prot_sdb) {
+                        scsi_pool_free_command(shost->cmd_pool, cmd);
+                        return NULL;
+                }
+        }
+
+        return cmd;
+}
+
+/**
  * __scsi_get_command - Allocate a struct scsi_cmnd
  * @shost: host to transmit command
  * @gfp_mask: allocation mask
@@ -214,7 +246,7 @@ struct scsi_cmnd *__scsi_get_command(struct Scsi_Host *shost, gfp_t gfp_mask)
         struct scsi_cmnd *cmd;
         unsigned char *buf;
 
-        cmd = scsi_pool_alloc_command(shost->cmd_pool, gfp_mask);
+        cmd = scsi_host_alloc_command(shost, gfp_mask);
 
         if (unlikely(!cmd)) {
                 unsigned long flags;
@@ -457,7 +489,7 @@ int scsi_setup_command_freelist(struct Scsi_Host *shost)
         /*
          * Get one backup command for this host.
          */
-        cmd = scsi_pool_alloc_command(shost->cmd_pool, gfp_mask);
+        cmd = scsi_host_alloc_command(shost, gfp_mask);
         if (!cmd) {
                 scsi_put_host_cmd_pool(gfp_mask);
                 shost->cmd_pool = NULL;
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index fe77ccacf319..a47c05d7829a 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -65,7 +65,7 @@ static struct scsi_host_sg_pool scsi_sg_pools[] = {
 };
 #undef SP
 
-static struct kmem_cache *scsi_sdb_cache;
+struct kmem_cache *scsi_sdb_cache;
 
 static void scsi_run_queue(struct request_queue *q);
 
@@ -787,6 +787,9 @@ void scsi_release_buffers(struct scsi_cmnd *cmd)
                 kmem_cache_free(scsi_sdb_cache, bidi_sdb);
                 cmd->request->next_rq->special = NULL;
         }
+
+        if (scsi_prot_sg_count(cmd))
+                scsi_free_sgtable(cmd->prot_sdb);
 }
 EXPORT_SYMBOL(scsi_release_buffers);
 
@@ -1072,6 +1075,26 @@ int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask)
                         goto err_exit;
         }
 
+        if (blk_integrity_rq(cmd->request)) {
+                struct scsi_data_buffer *prot_sdb = cmd->prot_sdb;
+                int ivecs, count;
+
+                BUG_ON(prot_sdb == NULL);
+                ivecs = blk_rq_count_integrity_sg(cmd->request);
+
+                if (scsi_alloc_sgtable(prot_sdb, ivecs, gfp_mask)) {
+                        error = BLKPREP_DEFER;
+                        goto err_exit;
+                }
+
+                count = blk_rq_map_integrity_sg(cmd->request,
+                                                prot_sdb->table.sgl);
+                BUG_ON(unlikely(count > ivecs));
+
+                cmd->prot_sdb = prot_sdb;
+                cmd->prot_sdb->table.nents = count;
+        }
+
         return BLKPREP_OK ;
 
 err_exit:
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index b33e72516ef8..79f0f7511204 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -77,6 +77,7 @@ extern void scsi_exit_queue(void);
 struct request_queue;
 struct request;
 extern int scsi_prep_fn(struct request_queue *, struct request *);
+extern struct kmem_cache *scsi_sdb_cache;
 
 /* scsi_proc.c */
 #ifdef CONFIG_SCSI_PROC_FS