target: Reset data_length for COMPARE_AND_WRITE to NoLB * block_size

This patch resets se_cmd->data_length for COMPARE_AND_WRITE emulation
within sbc_compare_and_write() to NoLB * block_size in order to address
a bug with FILEIO backends where a I/O failure will occur when data_length
does not match the I/O size being actually dispatched for the individual
per block READs + WRITEs.

This is done late enough in sbc_compare_and_write() after the memory
allocations have occured in transport_generic_new_cmd() to not cause
any unwanted side-effects.

Reported-by: Thomas Glanzmann <thomas@glanzmann.de>
Tested-by: Thomas Glanzmann <thomas@glanzmann.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/target/target_core_sbc.c b/drivers/target/target_core_sbc.c
index 6c17295e8d7c..a9dca116011e 100644
--- a/drivers/target/target_core_sbc.c
+++ b/drivers/target/target_core_sbc.c
@@ -508,6 +508,12 @@ sbc_compare_and_write(struct se_cmd *cmd)
                 cmd->transport_complete_callback = NULL;
                 return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
         }
+        /*
+         * Reset cmd->data_length to individual block_size in order to not
+         * confuse backend drivers that depend on this value matching the
+         * size of the I/O being submitted.
+         */
+        cmd->data_length = cmd->t_task_nolb * dev->dev_attrib.block_size;
 
         ret = cmd->execute_rw(cmd, cmd->t_bidi_data_sg, cmd->t_bidi_data_nents,
                               DMA_FROM_DEVICE);