scsi: target: transport should handle st FM/EOM/ILI reads
When a tape drive is exported via LIO using the pscsi module, a read
that requests more bytes per block than the tape can supply returns an
empty buffer. This is because the pscsi pass-through target module sees
the "ILI" illegal length bit set and thinks there is no reason to return
the data.
This is a long-standing transport issue, since it assumes that no data
need be returned under a check condition, which isn't always the case
for tape.
Add in a check for tape reads with the ILI, EOM, or FM bits set, with a
sense code of NO_SENSE, treating such cases as if the read
succeeded. The layered tape driver then "does the right thing" when it
gets such a response.
Signed-off-by: Bodo Stroesser <bstroesser@ts.fujitsu.com>
Signed-off-by: Lee Duncan <lduncan@suse.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 3500aa5..bde14f4 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -779,7 +779,9 @@ EXPORT_SYMBOL(target_complete_cmd);
void target_complete_cmd_with_length(struct se_cmd *cmd, u8 scsi_status, int length)
{
- if (scsi_status == SAM_STAT_GOOD && length < cmd->data_length) {
+ if ((scsi_status == SAM_STAT_GOOD ||
+ cmd->se_cmd_flags & SCF_TREAT_READ_AS_NORMAL) &&
+ length < cmd->data_length) {
if (cmd->se_cmd_flags & SCF_UNDERFLOW_BIT) {
cmd->residual_count += cmd->data_length - length;
} else {
@@ -2084,12 +2086,24 @@ static void transport_complete_qf(struct se_cmd *cmd)
goto queue_status;
}
- if (cmd->se_cmd_flags & SCF_TRANSPORT_TASK_SENSE)
+ /*
+ * Check if we need to send a sense buffer from
+ * the struct se_cmd in question. We do NOT want
+ * to take this path of the IO has been marked as
+ * needing to be treated like a "normal read". This
+ * is the case if it's a tape read, and either the
+ * FM, EOM, or ILI bits are set, but there is no
+ * sense data.
+ */
+ if (!(cmd->se_cmd_flags & SCF_TREAT_READ_AS_NORMAL) &&
+ cmd->se_cmd_flags & SCF_TRANSPORT_TASK_SENSE)
goto queue_status;
switch (cmd->data_direction) {
case DMA_FROM_DEVICE:
- if (cmd->scsi_status)
+ /* queue status if not treating this as a normal read */
+ if (cmd->scsi_status &&
+ !(cmd->se_cmd_flags & SCF_TREAT_READ_AS_NORMAL))
goto queue_status;
trace_target_cmd_complete(cmd);
@@ -2194,9 +2208,15 @@ static void target_complete_ok_work(struct work_struct *work)
/*
* Check if we need to send a sense buffer from
- * the struct se_cmd in question.
+ * the struct se_cmd in question. We do NOT want
+ * to take this path of the IO has been marked as
+ * needing to be treated like a "normal read". This
+ * is the case if it's a tape read, and either the
+ * FM, EOM, or ILI bits are set, but there is no
+ * sense data.
*/
- if (cmd->se_cmd_flags & SCF_TRANSPORT_TASK_SENSE) {
+ if (!(cmd->se_cmd_flags & SCF_TREAT_READ_AS_NORMAL) &&
+ cmd->se_cmd_flags & SCF_TRANSPORT_TASK_SENSE) {
WARN_ON(!cmd->scsi_status);
ret = transport_send_check_condition_and_sense(
cmd, 0, 1);
@@ -2238,7 +2258,18 @@ static void target_complete_ok_work(struct work_struct *work)
queue_rsp:
switch (cmd->data_direction) {
case DMA_FROM_DEVICE:
- if (cmd->scsi_status)
+ /*
+ * if this is a READ-type IO, but SCSI status
+ * is set, then skip returning data and just
+ * return the status -- unless this IO is marked
+ * as needing to be treated as a normal read,
+ * in which case we want to go ahead and return
+ * the data. This happens, for example, for tape
+ * reads with the FM, EOM, or ILI bits set, with
+ * no sense data.
+ */
+ if (cmd->scsi_status &&
+ !(cmd->se_cmd_flags & SCF_TREAT_READ_AS_NORMAL))
goto queue_status;
atomic_long_add(cmd->data_length,
