target: ->map_task_SG conversion to ->map_control_SG and ->map_data_SG

This patch breaks up the ->map_task_SG() backend call into two seperate
->map_control_SG() and ->map_data_SG() in order to better address
IBLOCK and pSCSI.  IBLOCK only allocates bios for ->map_data_SG(), and
pSCSI will allocate a struct request for both cases.

This patch fixes incorrect usage of ->map_task_SG() for all se_cmd descriptors
in transport_generic_new_cmd() by moving the call into it's proper location
directly inside of transport_allocate_data_tasks()

Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

3 files changed, 36 insertions, 27 deletions

diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c
index 251fc66a8212..7e1234105442 100644
--- a/drivers/target/target_core_iblock.c
+++ b/drivers/target/target_core_iblock.c
@@ -591,7 +591,7 @@ static struct bio *iblock_get_bio(
         return bio;
 }
 
-static int iblock_map_task_SG(struct se_task *task)
+static int iblock_map_data_SG(struct se_task *task)
 {
         struct se_cmd *cmd = task->task_se_cmd;
         struct se_device *dev = cmd->se_dev;
@@ -755,7 +755,7 @@ static struct se_subsystem_api iblock_template = {
         .name                   = "iblock",
         .owner                  = THIS_MODULE,
         .transport_type         = TRANSPORT_PLUGIN_VHBA_PDEV,
-        .map_task_SG            = iblock_map_task_SG,
+        .map_data_SG            = iblock_map_data_SG,
         .attach_hba             = iblock_attach_hba,
         .detach_hba             = iblock_detach_hba,
         .allocate_virtdevice    = iblock_allocate_virtdevice,
diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
index a2ce5998d318..2b7b0da9146d 100644
--- a/drivers/target/target_core_pscsi.c
+++ b/drivers/target/target_core_pscsi.c
@@ -1049,7 +1049,7 @@ static inline struct bio *pscsi_get_bio(int sg_num)
         return bio;
 }
 
-static int __pscsi_map_task_SG(
+static int __pscsi_map_SG(
         struct se_task *task,
         struct scatterlist *task_sg,
         u32 task_sg_num,
@@ -1198,7 +1198,10 @@ fail:
         return ret;
 }
 
-static int pscsi_map_task_SG(struct se_task *task)
+/*
+ * pSCSI maps both ->map_control_SG() and ->map_data_SG() to a single call.
+ */
+static int pscsi_map_SG(struct se_task *task)
 {
         int ret;
 
@@ -1206,13 +1209,13 @@ static int pscsi_map_task_SG(struct se_task *task)
          * Setup the main struct request for the task->task_sg[] payload
          */
 
-        ret = __pscsi_map_task_SG(task, task->task_sg, task->task_sg_nents, 0);
+        ret = __pscsi_map_SG(task, task->task_sg, task->task_sg_nents, 0);
         if (ret >= 0 && task->task_sg_bidi) {
                 /*
                  * If present, set up the extra BIDI-COMMAND SCSI READ
                  * struct request and payload.
                  */
-                ret = __pscsi_map_task_SG(task, task->task_sg_bidi,
+                ret = __pscsi_map_SG(task, task->task_sg_bidi,
                                         task->task_sg_nents, 1);
         }
 
@@ -1340,7 +1343,8 @@ static struct se_subsystem_api pscsi_template = {
         .owner                  = THIS_MODULE,
         .transport_type         = TRANSPORT_PLUGIN_PHBA_PDEV,
         .cdb_none               = pscsi_CDB_none,
-        .map_task_SG            = pscsi_map_task_SG,
+        .map_control_SG         = pscsi_map_SG,
+        .map_data_SG            = pscsi_map_SG,
         .attach_hba             = pscsi_attach_hba,
         .detach_hba             = pscsi_detach_hba,
         .pmode_enable_hba       = pscsi_pmode_enable_hba,
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 55b6588904a4..007cfc164f5e 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -4081,8 +4081,7 @@ static int transport_allocate_data_tasks(
         struct se_device *dev = cmd->se_dev;
         unsigned long flags;
         sector_t sectors;
-        int task_count;
-        int i;
+        int task_count, i, ret;
         sector_t dev_max_sectors = dev->se_sub_dev->se_dev_attrib.max_sectors;
         u32 sector_size = dev->se_sub_dev->se_dev_attrib.block_size;
         struct scatterlist *sg;
@@ -4129,7 +4128,7 @@ static int transport_allocate_data_tasks(
                         task->task_padded_sg = 1;
                 }
 
-                task->task_sg = kmalloc(sizeof(struct scatterlist) * \
+                task->task_sg = kmalloc(sizeof(struct scatterlist) *
                                         task->task_sg_nents, GFP_KERNEL);
                 if (!task->task_sg) {
                         cmd->se_dev->transport->free_task(task);
@@ -4157,6 +4156,20 @@ static int transport_allocate_data_tasks(
                 list_add_tail(&task->t_list, &cmd->t_task_list);
                 spin_unlock_irqrestore(&cmd->t_state_lock, flags);
         }
+        /*
+         * Now perform the memory map of task->task_sg[] into backend
+         * subsystem memory..
+         */
+        list_for_each_entry(task, &cmd->t_task_list, t_list) {
+                if (atomic_read(&task->task_sent))
+                        continue;
+                if (!dev->transport->map_data_SG)
+                        continue;
+
+                ret = dev->transport->map_data_SG(task);
+                if (ret < 0)
+                        return 0;
+        }
 
         return task_count;
 }
@@ -4196,8 +4209,8 @@ transport_allocate_control_task(struct se_cmd *cmd)
         spin_unlock_irqrestore(&cmd->t_state_lock, flags);
 
         if (cmd->se_cmd_flags & SCF_SCSI_CONTROL_SG_IO_CDB) {
-                if (dev->transport->map_task_SG)
-                        ret = dev->transport->map_task_SG(task);
+                if (dev->transport->map_control_SG)
+                        ret = dev->transport->map_control_SG(task);
         } else if (cmd->se_cmd_flags & SCF_SCSI_NON_DATA_CDB) {
                 if (dev->transport->cdb_none)
                         ret = dev->transport->cdb_none(task);
@@ -4239,8 +4252,6 @@ static u32 transport_allocate_tasks(
          */
 int transport_generic_new_cmd(struct se_cmd *cmd)
 {
-        struct se_task *task;
-        struct se_device *dev = cmd->se_dev;
         int ret = 0;
 
         /*
@@ -4254,22 +4265,16 @@ int transport_generic_new_cmd(struct se_cmd *cmd)
                 if (ret < 0)
                         return ret;
         }
-
+        /*
+         * Call transport_new_cmd_obj() to invoke transport_allocate_tasks() for
+         * control or data CDB types, and perform the map to backend subsystem
+         * code from SGL memory allocated here by transport_generic_get_mem(), or
+         * via pre-existing SGL memory setup explictly by fabric module code with
+         * transport_generic_map_mem_to_cmd().
+         */
         ret = transport_new_cmd_obj(cmd);
         if (ret < 0)
                 return ret;
-
-        list_for_each_entry(task, &cmd->t_task_list, t_list) {
-                if (atomic_read(&task->task_sent))
-                        continue;
-                if (!dev->transport->map_task_SG)
-                        continue;
-
-                ret = dev->transport->map_task_SG(task);
-                if (ret < 0)
-                        return ret;
-        }
-
         /*
          * For WRITEs, let the fabric know its buffer is ready..
          * This WRITE struct se_cmd (and all of its associated struct se_task's)