libblkid: add DM topology support (for old kernels)

Signed-off-by: Karel Zak <kzak@redhat.com>

4 files changed, 148 insertions, 2 deletions

diff --git a/shlibs/blkid/src/topology/Makefile.am b/shlibs/blkid/src/topology/Makefile.am
index 7464d2a8f..06927b287 100644
--- a/shlibs/blkid/src/topology/Makefile.am
+++ b/shlibs/blkid/src/topology/Makefile.am
@@ -7,4 +7,5 @@ noinst_LTLIBRARIES = libblkid_topology.la
 libblkid_topology_la_SOURCES =	topology.c \
 				topology.h \
 				sysfs.c \
-				md.c
+				md.c \
+				dm.c
diff --git a/shlibs/blkid/src/topology/dm.c b/shlibs/blkid/src/topology/dm.c
new file mode 100644
index 000000000..138c9f4be
--- /dev/null
+++ b/shlibs/blkid/src/topology/dm.c
@@ -0,0 +1,143 @@
+/*
+ * device-mapper (dm) topology
+ * -- this is fallback for old systems where the toplogy information are not
+ *    exported by sysfs
+ *
+ * Copyright (C) 2009 Karel Zak <kzak@redhat.com>
+ *
+ * This file may be redistributed under the terms of the
+ * GNU Lesser General Public License.
+ *
+ */
+#include <errno.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "topology.h"
+
+
+static int is_dm_device(dev_t devno)
+{
+	if (blkid_driver_has_major("device-mapper", major(devno)))
+		return 1;
+	return 0;
+}
+
+static int probe_dm_tp(blkid_probe pr, const struct blkid_idmag *mag)
+{
+	const char *paths[] = {
+		"/usr/local/sbin/dmsetup",
+		"/usr/sbin/dmsetup",
+		"/sbin/dmsetup"
+	};
+	int i, dmpipe[] = { -1, -1 }, stripes, stripesize;
+	char *cmd = NULL;
+	FILE *stream;
+	long long  offset, size;
+	dev_t devno = blkid_probe_get_devno(pr);
+
+	if (!devno)
+		goto nothing;		/* probably not a block device */
+	if (!is_dm_device(devno))
+		goto nothing;
+
+	for (i = 0; i < ARRAY_SIZE(paths); i++) {
+		struct stat sb;
+		if (stat(paths[i], &sb) == 0) {
+			cmd = (char *) paths[i];
+			break;
+		}
+	}
+
+	if (!cmd)
+		goto nothing;
+	if (pipe(dmpipe) < 0) {
+		DBG(DEBUG_LOWPROBE,
+			printf("Failed to open pipe: errno=%d", errno));
+		goto nothing;
+	}
+
+	switch (fork()) {
+	case 0:
+	{
+		char *dmargv[7], maj[16], min[16];
+
+		/* Plumbing */
+		close(dmpipe[0]);
+
+		if (dmpipe[1] != STDOUT_FILENO)
+			dup2(dmpipe[1], STDOUT_FILENO);
+
+		/* The libblkid library could linked with setuid programs */
+		if (setgid(getgid()) < 0)
+			 exit(1);
+		if (setuid(getuid()) < 0)
+			 exit(1);
+
+		snprintf(maj, sizeof(maj), "%d", major(devno));
+		snprintf(min, sizeof(min), "%d", minor(devno));
+
+		dmargv[0] = cmd;
+		dmargv[1] = "table";
+		dmargv[2] = "-j";
+		dmargv[3] = maj;
+		dmargv[4] = "-m";
+		dmargv[5] = min;
+		dmargv[6] = NULL;
+
+		execv(dmargv[0], dmargv);
+
+		DBG(DEBUG_LOWPROBE,
+			printf("Failed to execute %s: errno=%d", cmd, errno));
+		exit(1);
+	}
+	case -1:
+		DBG(DEBUG_LOWPROBE,
+			printf("Failed to forking: errno=%d", errno));
+		goto nothing;
+	default:
+		break;
+	}
+
+	close(dmpipe[1]);
+	dmpipe[1] = -1;
+
+	stream = fdopen(dmpipe[0], "r");
+	if (!stream)
+		goto nothing;
+
+	i = fscanf(stream, "%lld %lld striped %d %d ",
+			&offset, &size, &stripes, &stripesize);
+	fclose(stream);
+	dmpipe[0] = -1;
+
+	if (i != 4)
+		goto nothing;
+
+	blkid_topology_set_minimum_io_size(pr, stripesize << 9);
+	blkid_topology_set_optimal_io_size(pr, (stripes * stripesize) << 9);
+
+	return 0;
+
+nothing:
+	if (dmpipe[0] != -1)
+		close(dmpipe[0]);
+	if (dmpipe[1] != -1)
+		close(dmpipe[1]);
+	return 1;
+}
+
+const struct blkid_idinfo dm_tp_idinfo =
+{
+	.name		= "dm",
+	.probefunc	= probe_dm_tp,
+	.magics		= BLKID_NONE_MAGIC
+};
+
diff --git a/shlibs/blkid/src/topology/topology.c b/shlibs/blkid/src/topology/topology.c
index adb59f129..d6132a8f3 100644
--- a/shlibs/blkid/src/topology/topology.c
+++ b/shlibs/blkid/src/topology/topology.c
@@ -60,7 +60,8 @@ struct blkid_struct_topology {
 static const struct blkid_idinfo *idinfos[] =
 {
 	&sysfs_tp_idinfo,
-	&md_tp_idinfo
+	&md_tp_idinfo,
+	&dm_tp_idinfo
 };
 
 
diff --git a/shlibs/blkid/src/topology/topology.h b/shlibs/blkid/src/topology/topology.h
index ecebb3304..8cfcaf980 100644
--- a/shlibs/blkid/src/topology/topology.h
+++ b/shlibs/blkid/src/topology/topology.h
@@ -12,6 +12,7 @@ extern int blkid_topology_set_optimal_io_size(blkid_probe pr, unsigned long val)
  */
 extern const struct blkid_idinfo sysfs_tp_idinfo;
 extern const struct blkid_idinfo md_tp_idinfo;
+extern const struct blkid_idinfo dm_tp_idinfo;
 
 #endif /* BLKID_TOPOLOGY_H */