Add 'no_partitions' feature

The 'no_partitions' feature serves as a trigger for kpartx for not
creating any partitions on that device. This is required if eg
the device is used as a system disk for VM guests.

Signed-off-by: Hannes Reinecke <hare@suse.de>

4 files changed, 81 insertions, 4 deletions

diff --git a/kpartx/devmapper.c b/kpartx/devmapper.c
index cb7e8a7..4adb8ee 100644
--- a/kpartx/devmapper.c
+++ b/kpartx/devmapper.c
@@ -12,6 +12,7 @@
 
 #define UUID_PREFIX "part%d-"
 #define MAX_PREFIX_LEN 8
+#define PARAMS_SIZE 1024
 
 #ifndef LIBDM_API_COOKIE
 static inline int dm_task_set_cookie(struct dm_task *dmt, uint32_t *c, int a)
@@ -278,3 +279,62 @@ out:
 	return r;
 }
 
+int
+dm_get_map(int major, int minor, char * outparams)
+{
+	int r = 1;
+	struct dm_task *dmt;
+	void *next = NULL;
+	uint64_t start, length;
+	char *target_type = NULL;
+	char *params = NULL;
+
+	if (!(dmt = dm_task_create(DM_DEVICE_TABLE)))
+		return 1;
+
+	dm_task_set_major(dmt, major);
+	dm_task_set_minor(dmt, minor);
+	dm_task_no_open_count(dmt);
+
+	if (!dm_task_run(dmt))
+		goto out;
+
+	/* Fetch 1st target */
+	next = dm_get_next_target(dmt, next, &start, &length,
+				  &target_type, &params);
+
+	if (snprintf(outparams, PARAMS_SIZE, "%s", params) <= PARAMS_SIZE)
+		r = 0;
+out:
+	dm_task_destroy(dmt);
+	return r;
+}
+
+#define FEATURE_NO_PART "no_partitions"
+
+int
+dm_no_partitions(int major, int minor)
+{
+	char params[PARAMS_SIZE], *ptr;
+	int i, num_features;
+
+	if (dm_get_map(major, minor, params))
+		return 0;
+
+	ptr = params;
+	num_features = strtoul(params, &ptr, 10);
+	if ((ptr == params) || num_features == 0) {
+		/* No features found, return success */
+		return 0;
+	}
+	for (i = 0; (i < num_features); i++) {
+		if (!ptr || ptr > params + strlen(params))
+			break;
+		/* Skip whitespaces */
+		while(ptr && *ptr == ' ') ptr++;
+		if (!strncmp(ptr, FEATURE_NO_PART, strlen(FEATURE_NO_PART)))
+			return 1;
+		ptr = strchr(ptr, ' ');
+	}
+	return 0;
+}
diff --git a/kpartx/devmapper.h b/kpartx/devmapper.h
index 6226129..8e350a0 100644
--- a/kpartx/devmapper.h
+++ b/kpartx/devmapper.h
@@ -11,3 +11,4 @@ char * dm_mapname(int major, int minor);
 dev_t dm_get_first_dep(char *devname);
 char * dm_mapuuid(int major, int minor);
 int dm_devn (char * mapname, int *major, int *minor);
+int dm_no_partitions(int major, int minor);
diff --git a/kpartx/kpartx.c b/kpartx/kpartx.c
index b70c463..5007ce2 100644
--- a/kpartx/kpartx.c
+++ b/kpartx/kpartx.c
@@ -336,6 +336,11 @@ main(int argc, char **argv){
 
 	if (!mapname)
 		mapname = device + off;
+	else if (dm_no_partitions((unsigned int)MAJOR(buf.st_rdev),
+				  (unsigned int)MINOR(buf.st_rdev))) {
+		/* Feature 'no_partitions' is set, return */
+		return 0;
+	}
 
 	fd = open(device, O_RDONLY);
 
diff --git a/multipath/multipath.conf.5 b/multipath/multipath.conf.5
index 27e1b53..8edaccd 100644
--- a/multipath/multipath.conf.5
+++ b/multipath/multipath.conf.5
@@ -167,13 +167,24 @@ Default value is \fBnone\fR.
 .RE
 .TP
 .B features
-Specify any device-mapper features to be used. The most common of
-these features is
-.I "1 queue_if_no_path" 
-Note that this can also be set via the
+Specify any device-mapper features to be used. Syntax is
+.I num list
+where
+.I num
+is the number of features in
+.I list.
+Possible values for the feature list are
+.RS
+.TP 12
+.B queue_if_no_path
+Queue IO if no path is active; identical to the
 .I no_path_retry
 keyword.
 .TP
+.B no_partitions
+Disable automatic partitions generation via kpartx.
+.RE
+.TP
 .B path_checker
 The default method used to determine the paths' state. Possible values
 are