[Xen-devel] [PATCH 04 of 16 RFC] blktap3: change libxl__blktap_devpath prototype to return an error code

[Thanos Makatos <thanos.makatos@xxxxxxxxxx>]

Make libxl__blktap_devpath return an error code instead of the device, since 
there is no device in dom0 any more. Amend the libxl code that uses this 
functions accordingly.

diff -r 80e0bc67dcda -r bcb5a6182868 tools/libxl/libxl.c
--- a/tools/libxl/libxl.c       Wed Oct 24 17:24:53 2012 +0100
+++ b/tools/libxl/libxl.c       Wed Oct 24 17:25:02 2012 +0100
@@ -1844,13 +1844,14 @@ static void device_disk_add(libxl__egc *
                 break;
 
             case LIBXL_DISK_BACKEND_TAP:
-                dev = libxl__blktap_devpath(gc, disk->pdev_path, disk->format);
-                if (!dev) {
-                    LOG(ERROR, "failed to get blktap devpath for %p\n",
-                        disk->pdev_path);
+                rc = libxl__blktap_devpath(gc, disk->pdev_path, disk->format);
+                if (rc) {
+                    LOG(ERROR, "failed to get blktap devpath for %s: %s\n",
+                        disk->pdev_path, strerror(rc));
                     rc = ERROR_FAIL;
                     goto out;
                 }
+                dev = NULL;
                 flexarray_append(back, "tapdisk-params");
                 flexarray_append(back, libxl__sprintf(gc, "%s:%s",
                     libxl__device_disk_string_of_format(disk->format),
@@ -2277,8 +2278,13 @@ void libxl__device_disk_local_initiate_a
                 dev = disk->pdev_path;
                 break;
             case LIBXL_DISK_FORMAT_VHD:
-                dev = libxl__blktap_devpath(gc, disk->pdev_path,
-                                            disk->format);
+                rc = libxl__blktap_devpath(gc, disk->pdev_path, disk->format);
+                if (!rc) {
+                    LIBXL__LOG(ctx, LIBXL__LOG_ERROR,
+                           "error getting tapdisk: %s", strerror(rc));
+                    rc = ERROR_FAIL;
+                    goto out;
+                }
                 break;
             case LIBXL_DISK_FORMAT_QCOW:
             case LIBXL_DISK_FORMAT_QCOW2:
diff -r 80e0bc67dcda -r bcb5a6182868 tools/libxl/libxl_blktap3.c
--- a/tools/libxl/libxl_blktap3.c       Wed Oct 24 17:24:53 2012 +0100
+++ b/tools/libxl/libxl_blktap3.c       Wed Oct 24 17:25:02 2012 +0100
@@ -5,9 +5,9 @@ int libxl__blktap_enabled(libxl__gc *gc)
     return 1;
 }
 
-char *libxl__blktap_devpath(libxl__gc *gc, const char *disk,
+int libxl__blktap_devpath(libxl__gc *gc, const char *disk,
     libxl_disk_format format) {
-    return NULL;
+    return -ENOSYS;
 }
 
 int libxl__device_destroy_tapdisk(libxl__gc *gc, const char *be_path) {
diff -r 80e0bc67dcda -r bcb5a6182868 tools/libxl/libxl_internal.h
--- a/tools/libxl/libxl_internal.h      Wed Oct 24 17:24:53 2012 +0100
+++ b/tools/libxl/libxl_internal.h      Wed Oct 24 17:25:02 2012 +0100
@@ -1344,10 +1344,9 @@ struct libxl__cpuid_policy {
 /* libxl__blktap_devpath:
  *    Argument: path and disk image as specified in config file.
  *      The type specifies whether this is aio, qcow, qcow2, etc.
- *    returns device path xenstore wants to have. returns NULL
- *      if no device corresponds to the disk.
+ *    returns 0 on success, an error code otherwise 
  */
-_hidden char *libxl__blktap_devpath(libxl__gc *gc,
+_hidden int libxl__blktap_devpath(libxl__gc *gc,
                                     const char *disk,
                                     libxl_disk_format format);
 

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