Recognise cd-rom devices in devsparts.c

Also:
* Un-duplicate device detection code by creating a common mapping function.
* Add some more comments.

daemon/devsparts.c

@@ -29,14 +29,19 @@
 #include "daemon.h"
 #include "actions.h"
 
-char **
-do_list_devices (void)
+typedef int (*block_dev_func_t)(const char *dev,
+                                char ***r, int *size, int *alloc);
+
+/* Execute a given function for each discovered block device */
+static char**
+foreach_block_device (block_dev_func_t func)
 {
   char **r = NULL;
   int size = 0, alloc = 0;
+
   DIR *dir;
   struct dirent *d;
-  char buf[256];
+  int err = 0;
 
   dir = opendir ("/sys/block");
   if (!dir) {
@@ -44,121 +49,140 @@ do_list_devices (void)
     return NULL;
   }
 
+  errno = 0;
   while ((d = readdir (dir)) != NULL) {
     if (strncmp (d->d_name, "sd", 2) == 0 ||
         strncmp (d->d_name, "hd", 2) == 0 ||
-        strncmp (d->d_name, "vd", 2) == 0) {
-      snprintf (buf, sizeof buf, "/dev/%s", d->d_name);
+        strncmp (d->d_name, "vd", 2) == 0 ||
+        strncmp (d->d_name, "sr", 2) == 0) {
+      char dev_path[256];
+      snprintf (dev_path, sizeof dev_path, "/dev/%s", d->d_name);
 
       /* RHBZ#514505: Some versions of qemu <= 0.10 add a
        * CD-ROM device even though we didn't request it.  Try to
        * detect this by seeing if the device contains media.
        */
-      int fd = open (buf, O_RDONLY);
+      int fd = open (dev_path, O_RDONLY);
       if (fd == -1) {
-        perror (buf);
+        perror (dev_path);
         continue;
       }
       close (fd);
 
-      if (add_string (&r, &size, &alloc, buf) == -1) {
-        closedir (dir);
-        return NULL;
+      /* Call the map function for this device */
+      if((*func)(d->d_name, &r, &size, &alloc) != 0) {
+        err = 1;
+        break;
       }
     }
   }
 
-  if (add_string (&r, &size, &alloc, NULL) == -1) {
-    closedir (dir);
+  /* Check readdir didn't fail */
+  if(0 != errno) {
+    reply_with_perror ("readdir: /sys/block");
+    free_stringslen(r, size);
     return NULL;
   }
 
+  /* Close the directory handle */
   if (closedir (dir) == -1) {
     reply_with_perror ("closedir: /sys/block");
-    free_strings (r);
+    free_stringslen(r, size);
+    return NULL;
+  }
+
+  /* Free the result list on error */
+  if(err) {
+    free_stringslen(r, size);
+    return NULL;
+  }
+
+  /* Sort the devices */
+  sort_strings (r, size);
+
+  /* NULL terminate the list */
+  if (add_string (&r, &size, &alloc, NULL) == -1) {
     return NULL;
   }
 
-  sort_strings (r, size-1);
   return r;
 }
 
+/* Add a device to the list of devices */
+static int
+add_device(const char *device,
+           char ***const r, int *const size, int *const alloc)
+{
+  char dev_path[256];
+  snprintf (dev_path, sizeof dev_path, "/dev/%s", device);
+
+  if (add_string (r, size, alloc, dev_path) == -1) {
+    return -1;
+  }
+
+  return 0;
+}
+
+char **
+do_list_devices (void)
+{
+  return foreach_block_device(add_device);
+}
+
+static int
+add_partitions(const char *device,
+               char ***const r, int *const size, int *const alloc)
+{
+  char devdir[256];
+
+  /* Open the device's directory under /sys/block */
+  snprintf (devdir, sizeof devdir, "/sys/block/%s", device);
+
+  DIR *dir = opendir (devdir);
+  if (!dir) {
+    reply_with_perror ("opendir: %s", devdir);
+    free_stringslen (*r, *size);
+    return -1;
+  }
+
+  /* Look in /sys/block/<device>/ for entries starting with <device>
+   * e.g. /sys/block/sda/sda1
+   */
+  errno = 0;
+  struct dirent *d;
+  while ((d = readdir (dir)) != NULL) {
+    if (strncmp (d->d_name, device, strlen (device)) == 0) {
+      char part[256];
+      snprintf (part, sizeof part, "/dev/%s", d->d_name);
+
+      if (add_string (r, size, alloc, part) == -1) {
+        closedir (dir);
+        return -1;
+      }
+    }
+  }
+
+  /* Check if readdir failed */
+  if(0 != errno) {
+      reply_with_perror ("readdir: %s", devdir);
+      free_stringslen(*r, *size);
+      return -1;
+  }
+
+  /* Close the directory handle */
+  if (closedir (dir) == -1) {
+    reply_with_perror ("closedir: /sys/block/%s", device);
+    free_stringslen (*r, *size);
+    return -1;
+  }
+
+  return 0;
+}
+
 char **
 do_list_partitions (void)
 {
-  char **r = NULL;
-  int size = 0, alloc = 0;
-  DIR *dir, *dir2;
-  struct dirent *d;
-  char buf[256], devname[256];
-
-  dir = opendir ("/sys/block");
-  if (!dir) {
-    reply_with_perror ("opendir: /sys/block");
-    return NULL;
-  }
-
-  while ((d = readdir (dir)) != NULL) {
-    if (strncmp (d->d_name, "sd", 2) == 0 ||
-        strncmp (d->d_name, "hd", 2) == 0 ||
-        strncmp (d->d_name, "vd", 2) == 0) {
-      snprintf (buf, sizeof buf, "/dev/%s", d->d_name);
-
-      /* RHBZ#514505: Some versions of qemu <= 0.10 add a
-       * CD-ROM device even though we didn't request it.  Try to
-       * detect this by seeing if the device contains media.
-       */
-      int fd = open (buf, O_RDONLY);
-      if (fd == -1) {
-        perror (buf);
-        continue;
-      }
-      close (fd);
-
-      strncpy (devname, d->d_name, sizeof devname);
-      devname[sizeof devname - 1] = '\0';
-
-      snprintf (buf, sizeof buf, "/sys/block/%s", devname);
-
-      dir2 = opendir (buf);
-      if (!dir2) {
-        reply_with_perror ("opendir: %s", buf);
-        free_stringslen (r, size);
-        return NULL;
-      }
-      while ((d = readdir (dir2)) != NULL) {
-        if (strncmp (d->d_name, devname, strlen (devname)) == 0) {
-          snprintf (buf, sizeof buf, "/dev/%s", d->d_name);
-
-          if (add_string (&r, &size, &alloc, buf) == -1) {
-            closedir (dir2);
-            closedir (dir);
-            return NULL;
-          }
-        }
-      }
-
-      if (closedir (dir2) == -1) {
-        reply_with_perror ("closedir: /sys/block/%s", devname);
-        free_stringslen (r, size);
-        return NULL;
-      }
-    }
-  }
-
-  if (add_string (&r, &size, &alloc, NULL) == -1) {
-    closedir (dir);
-    return NULL;
-  }
-
-  if (closedir (dir) == -1) {
-    reply_with_perror ("closedir: /sys/block");
-    free_strings (r);
-    return NULL;
-  }
-
-  sort_strings (r, size-1);
-  return r;
+  return foreach_block_device(add_partitions);
 }
 
 int