lib/procutils: improve proc_is_procfs(), add test

* add delay between attempts
* zeroize errno and check for EAGAIN (like in other code)
* add small test program
   ./test_procutils --is-procfs [<dir>]

Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/lib/procutils.c b/lib/procutils.c
index 4436f38fa402dc87abd0d1a1e8889d7a9f586642..bf689ab63947ee84981d6b5d28e2c655fc56608d 100644 (file)
--- a/lib/procutils.c
+++ b/lib/procutils.c
@@ -245,13 +245,17 @@ int proc_is_procfs(int fd)
        int ret;
 
        do {
+               errno = 0;
                ret = fstatfs(fd, &st);
-       } while (ret == -1 && errno == EINTR);
 
-       if (ret == 0)
-               return st.f_type == STATFS_PROC_MAGIC;
-       else
-               return 0;
+               if (ret < 0) {
+                       if (errno != EINTR && errno != EAGAIN)
+                               return 0;
+                       xusleep(250000);
+               }
+       } while (ret != 0);
+
+       return st.f_type == STATFS_PROC_MAGIC;
 }
 
 #ifdef TEST_PROGRAM_PROCUTILS
@@ -302,10 +306,28 @@ static int test_processes(int argc, char *argv[])
        return EXIT_SUCCESS;
 }
 
+static int test_isprocfs(int argc, char *argv[])
+{
+       const char *name = argc > 1 ? argv[1] : "/proc";
+       int fd = open(name, O_RDONLY);
+       int is = 0;
+
+       if (fd >= 0) {
+               is = proc_is_procfs(fd);
+               close(fd);
+       } else
+               err(EXIT_FAILURE, "cannot open %s", name);
+
+       printf("%s: %s procfs\n", name, is ? "is" : "is NOT");
+       return is ? EXIT_SUCCESS : EXIT_FAILURE;
+}
+
+
 int main(int argc, char *argv[])
 {
        if (argc < 2) {
                fprintf(stderr, "usage: %1$s --tasks <pid>\n"
+                               "       %1$s --is-procfs [<dir>]\n"
                                "       %1$s --processes [---name <name>] [--uid <uid>]\n",
                                program_invocation_short_name);
                return EXIT_FAILURE;
@@ -315,6 +337,8 @@ int main(int argc, char *argv[])
                return test_tasks(argc - 1, argv + 1);
        if (strcmp(argv[1], "--processes") == 0)
                return test_processes(argc - 1, argv + 1);
+       if (strcmp(argv[1], "--is-procfs") == 0)
+               return test_isprocfs(argc - 1, argv + 1);
 
        return EXIT_FAILURE;
 }