Commit bd813720 authored by Lee Duncan's avatar Lee Duncan Committed by Martin K. Petersen
Browse files

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: default avatarBodo Stroesser <bstroesser@ts.fujitsu.com>
Signed-off-by: default avatarLee Duncan <lduncan@suse.com>
Reviewed-by: default avatarHannes Reinecke <hare@suse.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 51b910c3

drivers/target/target_core_pscsi.c

+24 −2
Original line number Diff line number Diff line
@@ -689,8 +689,29 @@ after_mode_sense: 
	}

after_mode_select:



	if (scsi_status == SAM_STAT_CHECK_CONDITION)

	if (scsi_status == SAM_STAT_CHECK_CONDITION) {

		transport_copy_sense_to_cmd(cmd, req_sense);



		/*

		 * check for TAPE device reads with

		 * FM/EOM/ILI set, so that we can get data

		 * back despite framework assumption that a

		 * check condition means there is no data

		 */

		if (sd->type == TYPE_TAPE &&

		    cmd->data_direction == DMA_FROM_DEVICE) {

			/*

			 * is sense data valid, fixed format,

			 * and have FM, EOM, or ILI set?

			 */

			if (req_sense[0] == 0xf0 &&	/* valid, fixed format */

			    req_sense[2] & 0xe0 &&	/* FM, EOM, or ILI */

			    (req_sense[2] & 0xf) == 0) { /* key==NO_SENSE */

				pr_debug("Tape FM/EOM/ILI status detected. Treat as normal read.\n");

				cmd->se_cmd_flags |= SCF_TREAT_READ_AS_NORMAL;

			}

		}

	}

}



enum {
@@ -1061,7 +1082,8 @@ static void pscsi_req_done(struct request *req, blk_status_t status) 


	switch (host_byte(result)) {

	case DID_OK:

		target_complete_cmd(cmd, scsi_status);

		target_complete_cmd_with_length(cmd, scsi_status,

			cmd->data_length - scsi_req(req)->resid_len);

		break;

	default:

		pr_debug("PSCSI Host Byte exception at cmd: %p CDB:"

drivers/target/target_core_transport.c

+37 −6
Original line number Diff line number Diff line
@@ -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.

	 */

	if (cmd->se_cmd_flags & SCF_TRANSPORT_TASK_SENSE) {

	 * 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) {

		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,

include/target/target_core_base.h

+1 −0
Original line number Diff line number Diff line
@@ -143,6 +143,7 @@ enum se_cmd_flags_table { 
	SCF_ACK_KREF			= 0x00400000,

	SCF_USE_CPUID			= 0x00800000,

	SCF_TASK_ATTR_SET		= 0x01000000,

	SCF_TREAT_READ_AS_NORMAL	= 0x02000000,

};



/*

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