Re: [PATCH] xfstests 311: test fsync with dm flakey

[Zach Brown <zab@xxxxxxxxxx>]

> +static void drop_all_caches()
> +{
> +     int value = 3;
> +     int fd;
> +
> +     if ((fd = open("/proc/sys/vm/drop_caches", O_WRONLY)) < 0) {
> +             fprintf(stderr, "Error opening drop caches: %d\n", errno);
> +             return;
> +     }
> +
> +     write(fd, &value, sizeof(int));
> +     close(fd);
> +}

fwiw drop_caches takes an ascii string, not a native int:

  open("/proc/sys/vm/drop_caches", O_WRONLY) = 3
  write(3, "\3\0\0\0", 4)                 = -1 EINVAL (Invalid argument)

--- test.c.busted       2013-04-22 15:22:57.593575545 -0700
+++ test.c      2013-04-22 15:29:25.358072087 -0700
@@ -7,7 +7,7 @@
 
 static void drop_all_caches()
 {
-       int value = 3;
+       char value[] = "3\n";
        int fd;
 
        if ((fd = open("/proc/sys/vm/drop_caches", O_WRONLY)) < 0) {
@@ -15,7 +15,7 @@
                return;
        }
 
-       write(fd, &value, sizeof(int));
+       write(fd, value, sizeof(value) - 1);
        close(fd);
 }
 
  open("/proc/sys/vm/drop_caches", O_WRONLY) = 3
  write(3, "3\n", 2)                      = 2

and all this makes me think that the write() return should probably have
been checked :).

- z