target/user: Add support for bidirectional commands

Enable TCMU to handle bidirectional SCSI commands. In such cases,
entries in iov[] cover both the Data-In and the Data-Out buffers. The
first iov_cnt entries correspond to the Data-Out buffer, while the
remaining iov_bidi_cnt entries correspond to the Data-In buffer.

Signed-off-by: Ilias Tsitsimpis <iliastsi@arrikto.com>
Signed-off-by: Vangelis Koukis <vkoukis@arrikto.com>
Reviewed-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --git a/Documentation/target/tcmu-design.txt b/Documentation/target/tcmu-design.txt
index 263b907..bef81e4 100644 (file)
--- a/Documentation/target/tcmu-design.txt
+++ b/Documentation/target/tcmu-design.txt
@@ -152,7 +152,7 @@ overall shared memory region, not the entry. The data in/out buffers
 are accessible via tht req.iov[] array. iov_cnt contains the number of
 entries in iov[] needed to describe either the Data-In or Data-Out
 buffers. For bidirectional commands, iov_cnt specifies how many iovec
-entries cover the Data-Out area, and iov_bidi_count specifies how many
+entries cover the Data-Out area, and iov_bidi_cnt specifies how many
 iovec entries immediately after that in iov[] cover the Data-In
 area. Just like other fields, iov.iov_base is an offset from the start
 of the region.

diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 2b0d26e..60330e0 100644 (file)
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -167,6 +167,11 @@ static struct tcmu_cmd *tcmu_alloc_cmd(struct se_cmd *se_cmd)
        tcmu_cmd->tcmu_dev = udev;
        tcmu_cmd->data_length = se_cmd->data_length;
 
+       if (se_cmd->se_cmd_flags & SCF_BIDI) {
+               BUG_ON(!(se_cmd->t_bidi_data_sg && se_cmd->t_bidi_data_nents));
+               tcmu_cmd->data_length += se_cmd->t_bidi_data_sg->length;
+       }
+
        tcmu_cmd->deadline = jiffies + msecs_to_jiffies(TCMU_TIME_OUT);
 
        idr_preload(GFP_KERNEL);
@@ -387,7 +392,8 @@ static int tcmu_queue_cmd_ring(struct tcmu_cmd *tcmu_cmd)
         * b/c size == offsetof one-past-element.
        */
        base_command_size = max(offsetof(struct tcmu_cmd_entry,
-                                        req.iov[se_cmd->t_data_nents + 2]),
+                                        req.iov[se_cmd->t_bidi_data_nents +
+                                                se_cmd->t_data_nents + 2]),
                                sizeof(struct tcmu_cmd_entry));
        command_size = base_command_size
                + round_up(scsi_command_size(se_cmd->t_task_cdb), TCMU_OP_ALIGN_SIZE);
@@ -456,13 +462,19 @@ static int tcmu_queue_cmd_ring(struct tcmu_cmd *tcmu_cmd)
         */
        iov = &entry->req.iov[0];
        iov_cnt = 0;
-       copy_to_data_area = (se_cmd->data_direction == DMA_TO_DEVICE);
+       copy_to_data_area = (se_cmd->data_direction == DMA_TO_DEVICE
+               || se_cmd->se_cmd_flags & SCF_BIDI);
        alloc_and_scatter_data_area(udev, se_cmd->t_data_sg,
                se_cmd->t_data_nents, &iov, &iov_cnt, copy_to_data_area);
        entry->req.iov_cnt = iov_cnt;
-       entry->req.iov_bidi_cnt = 0;
        entry->req.iov_dif_cnt = 0;
 
+       /* Handle BIDI commands */
+       iov_cnt = 0;
+       alloc_and_scatter_data_area(udev, se_cmd->t_bidi_data_sg,
+               se_cmd->t_bidi_data_nents, &iov, &iov_cnt, false);
+       entry->req.iov_bidi_cnt = iov_cnt;
+
        /* All offsets relative to mb_addr, not start of entry! */
        cdb_off = CMDR_OFF + cmd_head + base_command_size;
        memcpy((void *) mb + cdb_off, se_cmd->t_task_cdb, scsi_command_size(se_cmd->t_task_cdb));
@@ -535,8 +547,15 @@ static void tcmu_handle_completion(struct tcmu_cmd *cmd, struct tcmu_cmd_entry *
                               se_cmd->scsi_sense_length);
 
                UPDATE_HEAD(udev->data_tail, cmd->data_length, udev->data_size);
-       }
-       else if (se_cmd->data_direction == DMA_FROM_DEVICE) {
+       } else if (se_cmd->se_cmd_flags & SCF_BIDI) {
+               /* Discard data_out buffer */
+               UPDATE_HEAD(udev->data_tail,
+                       (size_t)se_cmd->t_data_sg->length, udev->data_size);
+
+               /* Get Data-In buffer */
+               gather_and_free_data_area(udev,
+                       se_cmd->t_bidi_data_sg, se_cmd->t_bidi_data_nents);
+       } else if (se_cmd->data_direction == DMA_FROM_DEVICE) {
                gather_and_free_data_area(udev,
                        se_cmd->t_data_sg, se_cmd->t_data_nents);
        } else if (se_cmd->data_direction == DMA_TO_DEVICE) {