Use built-in rules for device aliases: block/ < dm- < disk/ < mapper/ < other.

diff --git a/WHATS_NEW_DM b/WHATS_NEW_DM
index 4104eae2d47ef46bf134c99e590df121cf2eef40..69acfb3d593ca4628791395bb3e643293a11ab00 100644 (file)
--- a/WHATS_NEW_DM
+++ b/WHATS_NEW_DM
@@ -1,5 +1,6 @@
 Version 1.02.54 - 
 ================================
+  Use built-in rule for device aliases: block/ < dm- < disk/ < mapper/ < other.
   Wait for node creation before displaying debug info in dmsetup.
   Fix return status 0 for "dmsetup info -c -o help".
   Add check for kernel semaphore support and disable udev_sync if not available.

diff --git a/lib/device/dev-cache.c b/lib/device/dev-cache.c
index f6c8a467e8b9c91d93e2cb813571a6362f4fa563..f28968fa99fe0d386c5a85caeccf7d51a200b68f 100644 (file)
--- a/lib/device/dev-cache.c
+++ b/lib/device/dev-cache.c
@@ -147,6 +147,71 @@ void dev_set_preferred_name(struct str_list *sl, struct device *dev)
        dm_list_add_h(&dev->aliases, &sl->list);
 }
 
+/*
+ * Check whether path0 or path1 contains the subpath. The path that
+ * *does not* contain the subpath wins (return 0 or 1). If both paths
+ * contain the subpath, return -1. If none of them contains the subpath,
+ * return -2.
+ */
+static int _builtin_preference(const char *path0, const char *path1,
+                              size_t skip_prefix_count, const char *subpath)
+{
+       size_t subpath_len;
+       int r0, r1;
+
+       subpath_len = strlen(subpath);
+
+       r0 = !strncmp(path0 + skip_prefix_count, subpath, subpath_len);
+       r1 = !strncmp(path1 + skip_prefix_count, subpath, subpath_len);
+
+       if (!r0 && r1)
+               /* path0 does not have the subpath - it wins */
+               return 0;
+       else if (r0 && !r1)
+               /* path1 does not have the subpath - it wins */
+               return 1;
+       else if (r0 && r1)
+               /* both of them have the subpath */
+               return -1;
+
+       /* no path has the subpath */
+       return -2;
+}
+
+static int _apply_builtin_path_preference_rules(const char *path0, const char *path1)
+{
+       size_t devdir_len;
+       int r;
+
+       devdir_len = strlen(_cache.dev_dir);
+
+       if (!strncmp(path0, _cache.dev_dir, devdir_len) &&
+           !strncmp(path1, _cache.dev_dir, devdir_len)) {
+               /*
+                * We're trying to achieve the ordering:
+                *      /dev/block/ < /dev/dm-* < /dev/disk/ < /dev/mapper/ < anything else
+                */
+
+               /* Prefer any other path over /dev/block/ path. */
+               if ((r = _builtin_preference(path0, path1, devdir_len, "block/")) >= -1)
+                       return r;
+
+               /* Prefer any other path over /dev/dm-* path. */
+               if ((r = _builtin_preference(path0, path1, devdir_len, "dm-")) >= -1)
+                       return r;
+
+               /* Prefer any other path over /dev/disk/ path. */
+               if ((r = _builtin_preference(path0, path1, devdir_len, "disk/")) >= -1)
+                       return r;
+
+               /* Prefer any other path over /dev/mapper/ path. */
+               if ((r = _builtin_preference(path0, path1, 0, dm_dir())) >= -1)
+                       return r;
+       }
+
+       return -1;
+}
+
 /* Return 1 if we prefer path1 else return 0 */
 static int _compare_paths(const char *path0, const char *path1)
 {
@@ -156,7 +221,7 @@ static int _compare_paths(const char *path0, const char *path1)
        char p0[PATH_MAX], p1[PATH_MAX];
        char *s0, *s1;
        struct stat stat0, stat1;
-       size_t devdir_len;
+       int r;
 
        /*
         * FIXME Better to compare patterns one-at-a-time against all names.
@@ -177,22 +242,9 @@ static int _compare_paths(const char *path0, const char *path1)
                }
        }
 
-       /*
-        * Built-in rules.
-        */
-
-       /*
-        * Anything beats /dev/block.
-        */
-       devdir_len = strlen(_cache.dev_dir);
-       if (!strncmp(path0, _cache.dev_dir, devdir_len) &&
-           !strncmp(path1, _cache.dev_dir, devdir_len)) {
-               if (!strncmp(path0 + devdir_len, "block/", 6)) {
-                       if (strncmp(path1 + devdir_len, "block/", 6))
-                               return 1;
-               } else if (!strncmp(path1 + devdir_len, "block/", 6))
-                       return 0;
-       }
+       /* Apply built-in preference rules first. */
+       if ((r = _apply_builtin_path_preference_rules(path0, path1)) >= 0)
+               return r;
 
        /* Return the path with fewer slashes */
        for (p = path0; p++; p = (const char *) strchr(p, '/'))