virDevMapperGetTargetsImpl: Check for dm major properly

In v6.4.0-rc1~143 I've introduced a check that is supposed to
return from the function early, if given path is not a dm target.
While the idea is still valid, the implementation had a flaw.
It calls stat() over given path and the uses major(sb.st_dev) to
learn the major of the device. This is then passed to
dm_is_dm_major() which returns true or false depending whether
the device is under devmapper's control or not.

The problem with this approach is in how the major of the device
is obtained - paths managed by devmapper are special files and
thus we want to be using st_rdev instead of st_dev to obtain the
major number. Well, that's what virIsDevMapperDevice() does
already so might as well us that.

Fixes: 01626c66
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1839992Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NJiri Denemark <jdenemar@redhat.com>

src/util/virdevmapper.c

@@ -64,7 +64,6 @@ virDevMapperGetTargetsImpl(const char *path,
                            char ***devPaths_ret,
                            unsigned int ttl)
 {
-    struct stat sb;
     struct dm_task *dmt = NULL;
     struct dm_deps *deps;
     struct dm_info info;
@@ -83,13 +82,7 @@ virDevMapperGetTargetsImpl(const char *path,
         return ret;
     }
 
-    if (stat(path, &sb) < 0) {
-        if (errno == ENOENT)
-            return 0;
-        return -1;
-    }
-
-    if (!dm_is_dm_major(major(sb.st_dev)))
+    if (!virIsDevMapperDevice(path))
         return 0;
 
     if (!(dmt = dm_task_create(DM_DEVICE_DEPS))) {