libblkid: Give a priority bonus to "leaf" devicemapper devices

Give a boost to dm devices which are not used to build other dm
devices, since "leaf" devices are generally more likely to be
interesting as devices to mount.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/lib/blkid/devname.c b/lib/blkid/devname.c
index 48a1dcc..2b3855b 100644 (file)
--- a/lib/blkid/devname.c
+++ b/lib/blkid/devname.c
@@ -25,6 +25,7 @@
 #if HAVE_SYS_TYPES_H
 #include <sys/types.h>
 #endif
+#include <dirent.h>
 #if HAVE_SYS_STAT_H
 #include <sys/stat.h>
 #endif
@@ -117,6 +118,38 @@ blkid_dev blkid_get_dev(blkid_cache cache, const char *devname, int flags)
 /* Directories where we will try to search for device names */
 static const char *dirlist[] = { "/dev", "/devfs", "/devices", NULL };
 
+static int is_dm_leaf(const char *devname)
+{
+       struct dirent   *de, *d_de;
+       DIR             *dir, *d_dir;
+       char            path[256];
+       int             ret = 1;
+
+       if ((dir = opendir("/sys/block")) == NULL)
+               return 0;
+       while ((de = readdir(dir)) != NULL) {
+               if (!strcmp(de->d_name, ".") || !strcmp(de->d_name, "..") ||
+                   !strcmp(de->d_name, devname) ||
+                   strncmp(de->d_name, "dm-", 3) ||
+                   strlen(de->d_name) > sizeof(path)-32)
+                       continue;
+               sprintf(path, "/sys/block/%s/slaves", de->d_name);
+               if ((d_dir = opendir(path)) == NULL)
+                       continue;
+               while ((d_de = readdir(d_dir)) != NULL) {
+                       if (!strcmp(d_de->d_name, devname)) {
+                               ret = 0;
+                               break;
+                       }
+               }
+               closedir(d_dir);
+               if (!ret)
+                       break;
+       }
+       closedir(dir);
+       return ret;
+}
+
 /*
  * Probe a single block device to add to the device cache.
  */
@@ -180,9 +213,11 @@ set_pri:
        if (dev) {
                if (pri)
                        dev->bid_pri = pri;
-               else if (!strncmp(dev->bid_name, "/dev/mapper/", 11))
+               else if (!strncmp(dev->bid_name, "/dev/mapper/", 11)) {
                        dev->bid_pri = BLKID_PRI_DM;
-               else if (!strncmp(ptname, "md", 2))
+                       if (is_dm_leaf(ptname))
+                               dev->bid_pri += 5;
+               } else if (!strncmp(ptname, "md", 2))
                        dev->bid_pri = BLKID_PRI_MD;
        }
        return;
@@ -198,7 +233,6 @@ set_pri:
  * safe thing to do?)
  */
 #ifdef VG_DIR
-#include <dirent.h>
 static dev_t lvm_get_devno(const char *lvm_device)
 {
        FILE *lvf;