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Commit c8e63985 authored by Nicholas Bellinger's avatar Nicholas Bellinger
Browse files

target: Fix COMPARE_AND_WRITE with SG_TO_MEM_NOALLOC handling 



This patch fixes a bug for COMPARE_AND_WRITE handling with
fabrics using SCF_PASSTHROUGH_SG_TO_MEM_NOALLOC.

It adds the missing allocation for cmd->t_bidi_data_sg within
transport_generic_new_cmd() that is used by COMPARE_AND_WRITE
for the initial READ payload, even if the fabric is already
providing a pre-allocated buffer for cmd->t_data_sg.

Also, fix zero-length COMPARE_AND_WRITE handling within the
compare_and_write_callback() and target_complete_ok_work()
to queue the response, skipping the initial READ.

This fixes COMPARE_AND_WRITE emulation with loopback, vhost,
and xen-backend fabric drivers using SG_TO_MEM_NOALLOC.

Reported-by: default avatarChristoph Hellwig <hch@lst.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: <stable@vger.kernel.org> # v3.12+
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
parent 9ac8928e

drivers/target/target_core_sbc.c

+10 −5
Original line number Diff line number Diff line
@@ -321,7 +321,7 @@ sbc_setup_write_same(struct se_cmd *cmd, unsigned char *flags, struct sbc_ops *o 
	return 0;

}



static sense_reason_t xdreadwrite_callback(struct se_cmd *cmd)

static sense_reason_t xdreadwrite_callback(struct se_cmd *cmd, bool success)

{

	unsigned char *buf, *addr;

	struct scatterlist *sg;
@@ -385,7 +385,7 @@ sbc_execute_rw(struct se_cmd *cmd) 
			       cmd->data_direction);

}



static sense_reason_t compare_and_write_post(struct se_cmd *cmd)

static sense_reason_t compare_and_write_post(struct se_cmd *cmd, bool success)

{

	struct se_device *dev = cmd->se_dev;
@@ -408,7 +408,7 @@ static sense_reason_t compare_and_write_post(struct se_cmd *cmd) 
	return TCM_NO_SENSE;

}



static sense_reason_t compare_and_write_callback(struct se_cmd *cmd)

static sense_reason_t compare_and_write_callback(struct se_cmd *cmd, bool success)

{

	struct se_device *dev = cmd->se_dev;

	struct scatterlist *write_sg = NULL, *sg;
@@ -423,10 +423,15 @@ static sense_reason_t compare_and_write_callback(struct se_cmd *cmd) 


	/*

	 * Handle early failure in transport_generic_request_failure(),

	 * which will not have taken ->caw_mutex yet..

	 * which will not have taken ->caw_sem yet..

	 */

	if (!cmd->t_data_sg || !cmd->t_bidi_data_sg)

	if (!success && (!cmd->t_data_sg || !cmd->t_bidi_data_sg))

		return TCM_NO_SENSE;

	/*

	 * Handle special case for zero-length COMPARE_AND_WRITE

	 */

	if (!cmd->data_length)

		goto out;

	/*

	 * Immediately exit + release dev->caw_sem if command has already

	 * been failed with a non-zero SCSI status.

drivers/target/target_core_transport.c

+33 −4
Original line number Diff line number Diff line
@@ -1647,11 +1647,11 @@ void transport_generic_request_failure(struct se_cmd *cmd, 
	transport_complete_task_attr(cmd);

	/*

	 * Handle special case for COMPARE_AND_WRITE failure, where the

	 * callback is expected to drop the per device ->caw_mutex.

	 * callback is expected to drop the per device ->caw_sem.

	 */

	if ((cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE) &&

	     cmd->transport_complete_callback)

		cmd->transport_complete_callback(cmd);

		cmd->transport_complete_callback(cmd, false);



	switch (sense_reason) {

	case TCM_NON_EXISTENT_LUN:
@@ -2048,8 +2048,12 @@ static void target_complete_ok_work(struct work_struct *work) 
	if (cmd->transport_complete_callback) {

		sense_reason_t rc;



		rc = cmd->transport_complete_callback(cmd);

		rc = cmd->transport_complete_callback(cmd, true);

		if (!rc && !(cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE_POST)) {

			if ((cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE) &&

			    !cmd->data_length)

				goto queue_rsp;



			return;

		} else if (rc) {

			ret = transport_send_check_condition_and_sense(cmd,
@@ -2063,6 +2067,7 @@ static void target_complete_ok_work(struct work_struct *work) 
		}

	}



queue_rsp:

	switch (cmd->data_direction) {

	case DMA_FROM_DEVICE:

		spin_lock(&cmd->se_lun->lun_sep_lock);
@@ -2166,6 +2171,16 @@ static inline void transport_reset_sgl_orig(struct se_cmd *cmd) 
static inline void transport_free_pages(struct se_cmd *cmd)

{

	if (cmd->se_cmd_flags & SCF_PASSTHROUGH_SG_TO_MEM_NOALLOC) {

		/*

		 * Release special case READ buffer payload required for

		 * SG_TO_MEM_NOALLOC to function with COMPARE_AND_WRITE

		 */

		if (cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE) {

			transport_free_sgl(cmd->t_bidi_data_sg,

					   cmd->t_bidi_data_nents);

			cmd->t_bidi_data_sg = NULL;

			cmd->t_bidi_data_nents = 0;

		}

		transport_reset_sgl_orig(cmd);

		return;

	}
@@ -2318,6 +2333,7 @@ sense_reason_t 
transport_generic_new_cmd(struct se_cmd *cmd)

{

	int ret = 0;

	bool zero_flag = !(cmd->se_cmd_flags & SCF_SCSI_DATA_CDB);



	/*

	 * Determine is the TCM fabric module has already allocated physical
@@ -2326,7 +2342,6 @@ transport_generic_new_cmd(struct se_cmd *cmd) 
	 */

	if (!(cmd->se_cmd_flags & SCF_PASSTHROUGH_SG_TO_MEM_NOALLOC) &&

	    cmd->data_length) {

		bool zero_flag = !(cmd->se_cmd_flags & SCF_SCSI_DATA_CDB);



		if ((cmd->se_cmd_flags & SCF_BIDI) ||

		    (cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE)) {
@@ -2357,6 +2372,20 @@ transport_generic_new_cmd(struct se_cmd *cmd) 
				       cmd->data_length, zero_flag);

		if (ret < 0)

			return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

	} else if ((cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE) &&

		    cmd->data_length) {

		/*

		 * Special case for COMPARE_AND_WRITE with fabrics

		 * using SCF_PASSTHROUGH_SG_TO_MEM_NOALLOC.

		 */

		u32 caw_length = cmd->t_task_nolb *

				 cmd->se_dev->dev_attrib.block_size;



		ret = target_alloc_sgl(&cmd->t_bidi_data_sg,

				       &cmd->t_bidi_data_nents,

				       caw_length, zero_flag);

		if (ret < 0)

			return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

	}

	/*

	 * If this command is not a write we can execute it right here,

include/target/target_core_base.h

+1 −1
Original line number Diff line number Diff line
@@ -523,7 +523,7 @@ struct se_cmd { 
	sense_reason_t		(*execute_cmd)(struct se_cmd *);

	sense_reason_t		(*execute_rw)(struct se_cmd *, struct scatterlist *,

					      u32, enum dma_data_direction);

	sense_reason_t (*transport_complete_callback)(struct se_cmd *);

	sense_reason_t (*transport_complete_callback)(struct se_cmd *, bool);



	unsigned char		*t_task_cdb;

	unsigned char		__t_task_cdb[TCM_MAX_COMMAND_SIZE];