1  /*
       2   * device-mapper (dm) topology
       3   * -- this is fallback for old systems where the topology information is not
       4   *    exported by sysfs
       5   *
       6   * Copyright (C) 2009 Karel Zak <kzak@redhat.com>
       7   *
       8   * This file may be redistributed under the terms of the
       9   * GNU Lesser General Public License.
      10   *
      11   */
      12  #include <errno.h>
      13  #include <fcntl.h>
      14  #include <stdint.h>
      15  #include <stdio.h>
      16  #include <stdlib.h>
      17  #include <string.h>
      18  #include <sys/stat.h>
      19  #include <sys/types.h>
      20  #include <unistd.h>
      21  
      22  #include "topology.h"
      23  
      24  static int is_dm_device(dev_t devno)
      25  {
      26  	return blkid_driver_has_major("device-mapper", major(devno));
      27  }
      28  
      29  static int probe_dm_tp(blkid_probe pr,
      30  		const struct blkid_idmag *mag __attribute__((__unused__)))
      31  {
      32  	const char * const paths[] = {
      33  		"/usr/local/sbin/dmsetup",
      34  		"/usr/sbin/dmsetup",
      35  		"/sbin/dmsetup"
      36  	};
      37  	int dmpipe[] = { -1, -1 }, stripes = 0, stripesize = 0;
      38  	const char *cmd = NULL;
      39  	FILE *stream = NULL;
      40  	long long  offset = 0, size = 0;
      41  	size_t i;
      42  	dev_t devno = blkid_probe_get_devno(pr);
      43  
      44  	if (!devno)
      45  		goto nothing;		/* probably not a block device */
      46  	if (!is_dm_device(devno))
      47  		goto nothing;
      48  
      49  	for (i = 0; i < ARRAY_SIZE(paths); i++) {
      50  		struct stat sb;
      51  		if (stat(paths[i], &sb) == 0) {
      52  			cmd = paths[i];
      53  			break;
      54  		}
      55  	}
      56  
      57  	if (!cmd)
      58  		goto nothing;
      59  	if (pipe(dmpipe) < 0) {
      60  		DBG(LOWPROBE, ul_debug("Failed to open pipe: errno=%d", errno));
      61  		goto nothing;
      62  	}
      63  
      64  	switch (fork()) {
      65  	case 0:
      66  	{
      67  		const char *dmargv[7];
      68  	        char maj[16], min[16];
      69  
      70  		/* Plumbing */
      71  		close(dmpipe[0]);
      72  
      73  		if (dmpipe[1] != STDOUT_FILENO)
      74  			dup2(dmpipe[1], STDOUT_FILENO);
      75  
      76  		if (drop_permissions() != 0)
      77  			 exit(1);
      78  
      79  		snprintf(maj, sizeof(maj), "%d", major(devno));
      80  		snprintf(min, sizeof(min), "%d", minor(devno));
      81  
      82  		dmargv[0] = cmd;
      83  		dmargv[1] = "table";
      84  		dmargv[2] = "-j";
      85  		dmargv[3] = maj;
      86  		dmargv[4] = "-m";
      87  		dmargv[5] = min;
      88  		dmargv[6] = NULL;
      89  
      90  		execv(dmargv[0], (char * const *) dmargv);
      91  
      92  		DBG(LOWPROBE, ul_debug("Failed to execute %s: errno=%d", cmd, errno));
      93  		exit(1);
      94  	}
      95  	case -1:
      96  		DBG(LOWPROBE, ul_debug("Failed to forking: errno=%d", errno));
      97  		goto nothing;
      98  	default:
      99  		break;
     100  	}
     101  
     102  	stream = fdopen(dmpipe[0], "r" UL_CLOEXECSTR);
     103  	if (!stream)
     104  		goto nothing;
     105  
     106  	if (dmpipe[1] != -1) {
     107  		close(dmpipe[1]);
     108  	}
     109  
     110  	if (fscanf(stream, "%lld %lld striped %d %d ",
     111  			&offset, &size, &stripes, &stripesize) != 0)
     112  		goto nothing;
     113  
     114  	blkid_topology_set_minimum_io_size(pr, stripesize << 9);
     115  	blkid_topology_set_optimal_io_size(pr, (stripes * stripesize) << 9);
     116  
     117  	fclose(stream);
     118  	return 0;
     119  
     120  nothing:
     121  	if (stream)
     122  		fclose(stream);
     123  	else if (dmpipe[0] != -1)
     124  		close(dmpipe[0]);
     125  	return 1;
     126  }
     127  
     128  const struct blkid_idinfo dm_tp_idinfo =
     129  {
     130  	.name		= "dm",
     131  	.probefunc	= probe_dm_tp,
     132  	.magics		= BLKID_NONE_MAGIC
     133  };
     134