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Commit a2606241 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Alasdair G Kergon
Browse files

dm ioctl: allow message to return data 



This patch introduces enhanced message support that allows the
device-mapper core to recognise messages that are common to all devices,
and for messages to return data to userspace.

Core messages are processed by the function "message_for_md".  If the
device mapper doesn't support the message, it is passed to the target
driver.

If the message returns data, the kernel sets the flag
DM_MESSAGE_OUT_FLAG.

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 02cde50b

drivers/md/dm-ioctl.c

+35 −1
Original line number Diff line number Diff line
@@ -1414,6 +1414,22 @@ static int table_status(struct dm_ioctl *param, size_t param_size) 
	return 0;

}



static bool buffer_test_overflow(char *result, unsigned maxlen)

{

	return !maxlen || strlen(result) + 1 >= maxlen;

}



/*

 * Process device-mapper dependent messages.

 * Returns a number <= 1 if message was processed by device mapper.

 * Returns 2 if message should be delivered to the target.

 */

static int message_for_md(struct mapped_device *md, unsigned argc, char **argv,

			  char *result, unsigned maxlen)

{

	return 2;

}



/*

 * Pass a message to the target that's at the supplied device offset.

 */
@@ -1425,6 +1441,8 @@ static int target_message(struct dm_ioctl *param, size_t param_size) 
	struct dm_table *table;

	struct dm_target *ti;

	struct dm_target_msg *tmsg = (void *) param + param->data_start;

	size_t maxlen;

	char *result = get_result_buffer(param, param_size, &maxlen);



	md = find_device(param);

	if (!md)
@@ -1448,6 +1466,10 @@ static int target_message(struct dm_ioctl *param, size_t param_size) 
		goto out_argv;

	}



	r = message_for_md(md, argc, argv, result, maxlen);

	if (r <= 1)

		goto out_argv;



	table = dm_get_live_table(md);

	if (!table)

		goto out_argv;
@@ -1473,7 +1495,18 @@ static int target_message(struct dm_ioctl *param, size_t param_size) 
 out_argv:

	kfree(argv);

 out:

	param->data_size = 0;

	if (r >= 0)

		__dev_status(md, param);



	if (r == 1) {

		param->flags |= DM_DATA_OUT_FLAG;

		if (buffer_test_overflow(result, maxlen))

			param->flags |= DM_BUFFER_FULL_FLAG;

		else

			param->data_size = param->data_start + strlen(result) + 1;

		r = 0;

	}



	dm_put(md);

	return r;

}
@@ -1653,6 +1686,7 @@ static int validate_params(uint cmd, struct dm_ioctl *param) 
	param->flags &= ~DM_BUFFER_FULL_FLAG;

	param->flags &= ~DM_UEVENT_GENERATED_FLAG;

	param->flags &= ~DM_SECURE_DATA_FLAG;

	param->flags &= ~DM_DATA_OUT_FLAG;



	/* Ignores parameters */

	if (cmd == DM_REMOVE_ALL_CMD ||

include/uapi/linux/dm-ioctl.h

+5 −0
Original line number Diff line number Diff line
@@ -336,4 +336,9 @@ enum { 
 */

#define DM_SECURE_DATA_FLAG		(1 << 15) /* In */



/*

 * If set, a message generated output data.

 */

#define DM_DATA_OUT_FLAG		(1 << 16) /* Out */



#endif				/* _LINUX_DM_IOCTL_H */