filesystem: Linux again diverges from the pack.

As we are aiming to suport the other OS, we will treat
Linux as the exception as with memory use.

Linux uses /proc/mounts for all this however BSD/macOS use a
single struct and system call. The argument might be the
expense of the syscall, but for our purposes and sanity use
the greatest common demoninator again. Sorry Linux...

Seems procfs isn't going to scale very well in the future, am
not looking forward to what they use next...

src/bin/system/filesystems.c

@@ -34,6 +34,9 @@ typedef struct {
    const char   *name;
 } _magic;
 
+/* These values are reliable though some variants may be ambiguous. We use
+ * these superblock constants to detect unusual file systems such as ZFS.
+ */
 static _magic _magique[] = {
    { .magic = 0xdf5,      .name = "adfs" },
    { .magic = 0xadff,     .name = "affs" },
@@ -101,7 +104,7 @@ static _magic _magique[] = {
    { .magic = 0x5a4f4653, .name = "zonefs" },
    { .magic = 0x15013346, .name = "udf" },
    { .magic = 0x2fc12fc1, .name = "zfs" },
-   { .magic = 0x482b,     .name = "hfs+" },
+   { .magic = 0x482b,     .name = "hfsplus" },
 };
 
 unsigned int
@@ -128,6 +131,41 @@ filesystem_name_by_id(unsigned int id)
    return NULL;
 }
 
+#if defined(__linux__)
+static char *
+filesystem_type_name(const char *mountpoint)
+{
+   FILE *f;
+   char *mount, *res, *type, *end;
+   char buf[4096];
+
+   res = NULL;
+
+   f = fopen("/proc/mounts", "r");
+   if (!f) return NULL;
+
+   while ((fgets(buf, sizeof(buf), f)) != NULL)
+     {
+        mount = strchr(buf, ' ') + 1;
+        if (!mount) continue;
+        type = strchr(mount, ' ');
+        if (!type) continue;
+        end = type;
+        *end = '\0';
+        if (strcmp(mount, mountpoint))
+          continue;
+        type++;
+        end = strchr(type, ' ');
+        if (!end) continue;
+        res = strndup(type, end - type);
+        break;
+     }
+   fclose(f);
+   return res;
+}
+
+#endif
+
 Filesystem_Info *
 filesystem_info_get(const char *path)
 {
@@ -145,7 +183,9 @@ filesystem_info_get(const char *path)
    fs->mount = strdup(mountpoint);
    fs->path  = strdup(path);
    fs->type  = stats.f_type;
-#if !defined(__linux__)
+#if defined(__linux__)
+   fs->type_name = filesystem_type_name(fs->mount);
+#else
    fs->type_name = strdup(stats.f_fstypename);
 #endif
    fs->usage.total = stats.f_bsize * stats.f_blocks;