test: fix test-mount-util when handling duplicate mounts on the same location

The test was written so far under the assumption that if two mounts are
placed onto the same location the "upper" mount is listed later in
/proc/self/mountinfo. This appears not to be guaranteed however, as
running the tests in a normal nspawn shows.

This patch fixes that: it reverses the hashmap of mounts we build:
instead of keying by path, we key by mnt_id, and if we notice that
path_get_mnt_id() doesn't match what a line in /proc/self/mountinfo
says, we use the returned ID to check if maybe another line agrees.

Fixes: #7431

1 files changed, 18 insertions, 21 deletions

diff --git a/src/test/test-mount-util.c b/src/test/test-mount-util.c
index 5a93da1c0d..9582d6ceec 100644
--- a/src/test/test-mount-util.c
+++ b/src/test/test-mount-util.c
@@ -27,6 +27,7 @@
 #include "hashmap.h"
 #include "log.h"
 #include "mount-util.h"
+#include "path-util.h"
 #include "string-util.h"
 
 static void test_mount_propagation_flags(const char *name, int ret, unsigned long expected) {
@@ -51,16 +52,15 @@ static void test_mnt_id(void) {
         _cleanup_fclose_ FILE *f = NULL;
         Hashmap *h;
         Iterator i;
-        char *k;
-        void *p;
+        char *p;
+        void *k;
         int r;
 
         assert_se(f = fopen("/proc/self/mountinfo", "re"));
-        assert_se(h = hashmap_new(&string_hash_ops));
+        assert_se(h = hashmap_new(&trivial_hash_ops));
 
         for (;;) {
                 _cleanup_free_ char *line = NULL, *path = NULL;
-                void *old_key;
                 int mnt_id;
 
                 r = read_line(f, LONG_LINE_MAX, &line);
@@ -70,38 +70,35 @@ static void test_mnt_id(void) {
 
                 assert_se(sscanf(line, "%i %*s %*s %*s %ms", &mnt_id, &path) == 2);
 
-                /* Add all mount points and their ids to a hashtable, so that we filter out mount points that are
-                 * overmounted. For those we only care for the "upper" mount, since that's the only one
-                 * path_get_mnt_id() can determine. */
-
-                if (hashmap_remove2(h, path, &old_key))
-                        free(old_key);
-
-                assert_se(hashmap_put(h, path, INT_TO_PTR(mnt_id)) >= 0);
+                assert_se(hashmap_put(h, INT_TO_PTR(mnt_id), path) >= 0);
                 path = NULL;
         }
 
         HASHMAP_FOREACH_KEY(p, k, h, i) {
-                int mnt_id = PTR_TO_INT(p), mnt_id2;
+                int mnt_id = PTR_TO_INT(k), mnt_id2;
 
-                r = path_get_mnt_id(k, &mnt_id2);
+                r = path_get_mnt_id(p, &mnt_id2);
                 if (r == -EOPNOTSUPP) { /* kernel or file system too old? */
-                        log_debug("%s doesn't support mount IDs\n", k);
+                        log_debug("%s doesn't support mount IDs\n", p);
                         continue;
                 }
                 if (IN_SET(r, -EACCES, -EPERM)) {
-                        log_debug("Can't access %s\n", k);
+                        log_debug("Can't access %s\n", p);
                         continue;
                 }
 
-                log_debug("mnt id of %s is %i\n", k, mnt_id2);
+                log_debug("mnt id of %s is %i\n", p, mnt_id2);
+
+                if (mnt_id == mnt_id2)
+                        continue;
 
-                assert_se(r >= 0);
-                assert_se(mnt_id == mnt_id2);
+                /* The ids don't match? If so, then there are two mounts on the same path, let's check if that's really
+                 * the case */
+                assert_se(path_equal_ptr(hashmap_get(h, INT_TO_PTR(mnt_id2)), p));
         }
 
-        while ((k = hashmap_steal_first_key(h)))
-                free(k);
+        while ((p = hashmap_steal_first(h)))
+                free(p);
 
         hashmap_free(h);
 }