daemon: Fix order of devices in guestfs_list_devices when > 26 disks.

Sort the device names correctly, not just treating them as
strings.  As a result, /dev/sdz < /dev/sdaa.

daemon/daemon.h

@@ -79,6 +79,9 @@ extern void sort_strings (char **argv, size_t len);
 extern void free_strings (char **argv);
 extern void free_stringslen (char **argv, size_t len);
 
+extern void sort_device_names (char **argv, size_t len);
+extern int compare_device_names (const char *a, const char *b);
+
 extern char **split_lines (char *str);
 
 #define command(out,err,name,...) commandf((out),(err),0,(name),__VA_ARGS__)

daemon/devsparts.c

@@ -1,5 +1,5 @@
 /* libguestfs - the guestfsd daemon
- * Copyright (C) 2009 Red Hat Inc.
+ * Copyright (C) 2009-2012 Red Hat Inc.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -106,7 +106,7 @@ foreach_block_device (block_dev_func_t func)
 
   /* Sort the devices. */
   if (r.size > 0)
-    sort_strings (r.argv, r.size);
+    sort_device_names (r.argv, r.size);
 
   /* NULL terminate the list */
   if (end_stringsbuf (&r) == -1) {

daemon/guestfsd.c

@@ -40,6 +40,7 @@
 #include <arpa/inet.h>
 #include <netinet/in.h>
 #include <errno.h>
+#include <assert.h>
 
 #ifdef HAVE_PRINTF_H
 # include <printf.h>
@@ -514,6 +515,69 @@ free_stringslen (char **argv, size_t len)
   free (argv);
 }
 
+/* Compare device names (including partition numbers if present).
+ * https://rwmj.wordpress.com/2011/01/09/how-are-linux-drives-named-beyond-drive-26-devsdz/
+ */
+int
+compare_device_names (const char *a, const char *b)
+{
+  size_t a_devlen, b_devlen;
+  int r;
+  int a_partnum, b_partnum;
+
+  /* Skip /dev/ prefix if present. */
+  if (STRPREFIX (a, "/dev/"))
+    a += 5;
+  if (STRPREFIX (b, "/dev/"))
+    b += 5;
+
+  /* Skip sd/hd/vd. */
+  assert (a[1] == 'd');
+  a += 2;
+  assert (b[1] == 'd');
+  b += 2;
+
+  /* Get device name part, that is, just 'a', 'ab' etc. */
+  a_devlen = strcspn (a, "0123456789");
+  b_devlen = strcspn (b, "0123456789");
+
+  /* If device name part is longer, it is always greater, eg.
+   * "/dev/sdz" < "/dev/sdaa".
+   */
+  if (a_devlen != b_devlen)
+    return a_devlen - b_devlen;
+
+  /* Device name parts are the same length, so do a regular compare. */
+  r = strncmp (a, b, a_devlen);
+  if (r != 0)
+    return r;
+
+  /* Compare partitions numbers. */
+  a += a_devlen;
+  b += a_devlen;
+
+  r = sscanf (a, "%d", &a_partnum);
+  assert (r == 1);
+  r = sscanf (b, "%d", &b_partnum);
+  assert (r == 1);
+
+  return a_partnum - b_partnum;
+}
+
+static int
+compare_device_names_vp (const void *vp1, const void *vp2)
+{
+  char * const *p1 = (char * const *) vp1;
+  char * const *p2 = (char * const *) vp2;
+  return compare_device_names (*p1, *p2);
+}
+
+void
+sort_device_names (char **argv, size_t len)
+{
+  qsort (argv, len, sizeof (char *), compare_device_names_vp);
+}
+
 /* Easy ways to run external commands.  For full documentation, see
  * 'commandrvf' below.
  */