[PATCH-v2 06/12] target: Add memory allocation for bidirectional commands

[Nicholas A. Bellinger]

From: Nicholas Bellinger <n...@daterainc.com>

This adds transport_generic_get_mem_bidi() to perform scatterlist
allocation for bidirectional commands.

Also, update transport_generic_new_cmd() to call this new function
when SCF_BIDI has been set.

v2 Changes:
  - Use SCF_COMPARE_AND_WRITE instead of CDB based check for
    calculating length in transport_generic_get_mem_bidi().
  - Use SCF_COMPARE_AND_WRITE in transport_generic_new_cmd()
    for determing when to call transport_generic_get_mem_bidi()

Cc: Christoph Hellwig <h...@lst.de>
Cc: Hannes Reinecke <h...@suse.de>
Cc: Martin Petersen <martin.peter...@oracle.com>
Cc: Chris Mason <chris.ma...@fusionio.com>
Cc: James Bottomley <jbottom...@parallels.com>
Cc: Nicholas Bellinger <n...@linux-iscsi.org>
Signed-off-by: Nicholas Bellinger <n...@daterainc.com>
---
 drivers/target/target_core_transport.c |   54 ++++++++++++++++++++++++++++++++
 1 files changed, 54 insertions(+), 0 deletions(-)

diff --git a/drivers/target/target_core_transport.c 
b/drivers/target/target_core_transport.c
index 781859e..967dac7 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -2092,6 +2092,53 @@ void transport_kunmap_data_sg(struct se_cmd *cmd)
 EXPORT_SYMBOL(transport_kunmap_data_sg);
 
 static int
+transport_generic_get_mem_bidi(struct se_cmd *cmd)
+{
+       struct se_device *dev = cmd->se_dev;
+       struct page *page;
+       gfp_t zero_flag;
+       u32 length;
+       unsigned int nents;
+       int i = 0;
+
+       if (cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE)
+               length = cmd->t_task_nolb * dev->dev_attrib.block_size;
+       else
+               length = cmd->data_length;
+
+       nents = DIV_ROUND_UP(length, PAGE_SIZE);
+       cmd->t_bidi_data_sg = kmalloc(sizeof(struct scatterlist) * nents, 
GFP_KERNEL);
+       if (!cmd->t_bidi_data_sg)
+               return -ENOMEM;
+
+       cmd->t_bidi_data_nents = nents;
+       sg_init_table(cmd->t_bidi_data_sg, nents);
+
+       zero_flag = cmd->se_cmd_flags & SCF_SCSI_DATA_CDB ? 0 : __GFP_ZERO;
+
+       while (length) {
+               u32 page_len = min_t(u32, length, PAGE_SIZE);
+               page = alloc_page(GFP_KERNEL | zero_flag);
+               if (!page)
+                       goto out;
+
+               sg_set_page(&cmd->t_bidi_data_sg[i], page, page_len, 0);
+               length -= page_len;
+               i++;
+       }
+       return 0;
+
+out:
+       while (i > 0) {
+               i--;
+               __free_page(sg_page(&cmd->t_bidi_data_sg[i]));
+       }
+       kfree(cmd->t_bidi_data_sg);
+       cmd->t_bidi_data_sg = NULL;
+       return -ENOMEM;
+}
+
+static int
 transport_generic_get_mem(struct se_cmd *cmd)
 {
        u32 length = cmd->data_length;
@@ -2149,6 +2196,13 @@ transport_generic_new_cmd(struct se_cmd *cmd)
         */
        if (!(cmd->se_cmd_flags & SCF_PASSTHROUGH_SG_TO_MEM_NOALLOC) &&
            cmd->data_length) {
+               if ((cmd->se_cmd_flags & SCF_BIDI) ||
+                   (cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE)) {
+                       ret = transport_generic_get_mem_bidi(cmd);
+                       if (ret < 0)
+                               return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
+               }
+
                ret = transport_generic_get_mem(cmd);
                if (ret < 0)
                        return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
-- 
1.7.2.5

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