target: Allow sbc_ops->execute_rw() to accept SGLs + data_direction

COMPARE_AND_WRITE expects to be able to send down a DMA_FROM_DEVICE
to obtain the necessary READ payload for comparision against the
first half of the WRITE payload containing the verify user data.

Currently virtual backends expect to internally reference SGLs,
SGL nents, and data_direction, so change IBLOCK, FILEIO and RD
sbc_ops->execute_rw() to accept this values as function parameters.

Also add default sbc_execute_rw() handler for the typical case for
cmd->execute_rw() submission using cmd->t_data_sg, cmd->t_data_nents,
and cmd->data_direction).

v2 Changes:
  - Add SCF_COMPARE_AND_WRITE command flag
  - Use sbc_execute_rw() for normal cmd->execute_rw() submission
    with expected se_cmd members.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Martin Petersen <martin.petersen@oracle.com>
Cc: Chris Mason <chris.mason@fusionio.com>
Cc: James Bottomley <JBottomley@Parallels.com>
Cc: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Nicholas Bellinger <nab@daterainc.com>

1 files changed, 2 insertions, 4 deletions

diff --git a/drivers/target/target_core_rd.c b/drivers/target/target_core_rd.c
index 51127d15d5c5..958d17ad1c90 100644
--- a/drivers/target/target_core_rd.c
+++ b/drivers/target/target_core_rd.c
@@ -280,11 +280,9 @@ static struct rd_dev_sg_table *rd_get_sg_table(struct rd_dev *rd_dev, u32 page)
 }
 
 static sense_reason_t
-rd_execute_rw(struct se_cmd *cmd)
+rd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
+	      enum dma_data_direction data_direction)
 {
-	struct scatterlist *sgl = cmd->t_data_sg;
-	u32 sgl_nents = cmd->t_data_nents;
-	enum dma_data_direction data_direction = cmd->data_direction;
 	struct se_device *se_dev = cmd->se_dev;
 	struct rd_dev *dev = RD_DEV(se_dev);
 	struct rd_dev_sg_table *table;