target/iblock: pass WRITE_SAME to device if possible

This patch has iblock pass the WRITE_SAME command to
the device for offloading if possible. It is similar to what is
done for UNMAP/discards, except that we export a large max write same
value to the initiator, and then rely on the block layer to
break it up into multiple requests if it cannot fit into one.

v2.

- Drop file backend changes and move helper function to
iblock backend.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c
index abe4eb997a84..026a758e5778 100644
--- a/drivers/target/target_core_iblock.c
+++ b/drivers/target/target_core_iblock.c
@@ -413,8 +413,39 @@ iblock_execute_unmap(struct se_cmd *cmd, sector_t lba, sector_t nolb)
 }
 
 static sense_reason_t
+iblock_execute_write_same_direct(struct block_device *bdev, struct se_cmd *cmd)
+{
+        struct se_device *dev = cmd->se_dev;
+        struct scatterlist *sg = &cmd->t_data_sg[0];
+        struct page *page = NULL;
+        int ret;
+
+        if (sg->offset) {
+                page = alloc_page(GFP_KERNEL);
+                if (!page)
+                        return TCM_OUT_OF_RESOURCES;
+                sg_copy_to_buffer(sg, cmd->t_data_nents, page_address(page),
+                                  dev->dev_attrib.block_size);
+        }
+
+        ret = blkdev_issue_write_same(bdev,
+                                target_to_linux_sector(dev, cmd->t_task_lba),
+                                target_to_linux_sector(dev,
+                                        sbc_get_write_same_sectors(cmd)),
+                                GFP_KERNEL, page ? page : sg_page(sg));
+        if (page)
+                __free_page(page);
+        if (ret)
+                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
+
+        target_complete_cmd(cmd, GOOD);
+        return 0;
+}
+
+static sense_reason_t
 iblock_execute_write_same(struct se_cmd *cmd)
 {
+        struct block_device *bdev = IBLOCK_DEV(cmd->se_dev)->ibd_bd;
         struct iblock_req *ibr;
         struct scatterlist *sg;
         struct bio *bio;
@@ -439,6 +470,9 @@ iblock_execute_write_same(struct se_cmd *cmd)
                 return TCM_INVALID_CDB_FIELD;
         }
 
+        if (bdev_write_same(bdev))
+                return iblock_execute_write_same_direct(bdev, cmd);
+
         ibr = kzalloc(sizeof(struct iblock_req), GFP_KERNEL);
         if (!ibr)
                 goto fail;