libxl: refactor DISK_BACKEND_PHY handling in libxl_device_disk_add

A step on the path to sharing this code with the tail-end of the
DISK_BACKEND_TAP case.

I made the result of libxl__blktap_devpath non-const to achieve
this. The existing caller calls libxl__strdup on the result but since
the function is an internal one and the result is already garbage
collected I think this is unnecessary and we can just use the
non-const result directly.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

4 files changed, 35 insertions, 31 deletions

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 80660dccb7..853a612f7f 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -949,6 +949,7 @@ int libxl_device_disk_add(libxl_ctx *ctx, uint32_t domid, libxl_device_disk *dis
     libxl__gc gc = LIBXL_INIT_GC(ctx);
     flexarray_t *front;
     flexarray_t *back;
+    char *dev;
     char *backend_type;
     int devid;
     libxl__device device;
@@ -997,36 +998,39 @@ int libxl_device_disk_add(libxl_ctx *ctx, uint32_t domid, libxl_device_disk *dis
         disk->backend == DISK_BACKEND_QDISK;
 
     switch (disk->backend) {
-        case DISK_BACKEND_PHY: 
-            libxl__device_physdisk_major_minor(disk->pdev_path, &major, &minor);
+        case DISK_BACKEND_PHY:
+            dev = disk->pdev_path;
+
+            libxl__device_physdisk_major_minor(dev, &major, &minor);
             flexarray_append(back, "physical-device");
             flexarray_append(back, libxl__sprintf(&gc, "%x:%x", major, minor));
 
             flexarray_append(back, "params");
-            flexarray_append(back, disk->pdev_path);
+            flexarray_append(back, dev);
 
             device.backend_kind = DEVICE_VBD;
             break;
         case DISK_BACKEND_TAP:
-            {
-                const char *dev = libxl__blktap_devpath(&gc,
-                                               disk->pdev_path, disk->format);
-                if (!dev) {
-                    rc = ERROR_FAIL;
-                    goto out_free;
-                }
-                flexarray_append(back, "tapdisk-params");
-                flexarray_append(back, libxl__sprintf(&gc, "%s:%s",
-                    libxl__device_disk_string_of_format(disk->format),
-                    disk->pdev_path));
-                flexarray_append(back, "params");
-                flexarray_append(back, libxl__strdup(&gc, dev));
-                backend_type = "phy";
-                libxl__device_physdisk_major_minor(dev, &major, &minor);
-                flexarray_append(back, "physical-device");
-                flexarray_append(back, libxl__sprintf(&gc, "%x:%x", major, minor));
-                device.backend_kind = DEVICE_VBD;
+            dev = libxl__blktap_devpath(&gc, disk->pdev_path, disk->format);
+            if (!dev) {
+                rc = ERROR_FAIL;
+                goto out_free;
             }
+            flexarray_append(back, "tapdisk-params");
+            flexarray_append(back, libxl__sprintf(&gc, "%s:%s",
+                libxl__device_disk_string_of_format(disk->format),
+                disk->pdev_path));
+
+            flexarray_append(back, "params");
+            flexarray_append(back, dev);
+
+            backend_type = "phy";
+
+            libxl__device_physdisk_major_minor(dev, &major, &minor);
+            flexarray_append(back, "physical-device");
+            flexarray_append(back, libxl__sprintf(&gc, "%x:%x", major, minor));
+
+            device.backend_kind = DEVICE_VBD;
             break;
         case DISK_BACKEND_QDISK:
             flexarray_append(back, "params");
@@ -1110,7 +1114,7 @@ int libxl_device_disk_del(libxl_ctx *ctx, uint32_t domid,
 char * libxl_device_disk_local_attach(libxl_ctx *ctx, libxl_device_disk *disk)
 {
     libxl__gc gc = LIBXL_INIT_GC(ctx);
-    const char *dev = NULL;
+    char *dev = NULL;
     char *ret = NULL;
 
     switch (disk->backend) {
diff --git a/tools/libxl/libxl_blktap2.c b/tools/libxl/libxl_blktap2.c
index b238a0a7ca..7c165fcc9a 100644
--- a/tools/libxl/libxl_blktap2.c
+++ b/tools/libxl/libxl_blktap2.c
@@ -24,9 +24,9 @@ int libxl__blktap_enabled(libxl__gc *gc)
     return !tap_ctl_check(&msg);
 }
 
-const char *libxl__blktap_devpath(libxl__gc *gc,
-                                 const char *disk,
-                                 libxl_disk_format format)
+char *libxl__blktap_devpath(libxl__gc *gc,
+                            const char *disk,
+                            libxl_disk_format format)
 {
     const char *type;
     char *params, *devname = NULL;
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 539191e3cc..9fd0f58e08 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -325,9 +325,9 @@ _hidden int libxl__blktap_enabled(libxl__gc *gc);
  *    returns device path xenstore wants to have. returns NULL
  *      if no device corresponds to the disk.
  */
-_hidden const char *libxl__blktap_devpath(libxl__gc *gc,
-                                 const char *disk,
-                                 libxl_disk_format format);
+_hidden char *libxl__blktap_devpath(libxl__gc *gc,
+                                    const char *disk,
+                                    libxl_disk_format format);
 
 _hidden char *libxl__uuid2string(libxl__gc *gc, const libxl_uuid uuid);
 
diff --git a/tools/libxl/libxl_noblktap2.c b/tools/libxl/libxl_noblktap2.c
index 95fee973ed..a66346a286 100644
--- a/tools/libxl/libxl_noblktap2.c
+++ b/tools/libxl/libxl_noblktap2.c
@@ -21,9 +21,9 @@ int libxl__blktap_enabled(libxl__gc *gc)
     return 0;
 }
 
-const char *libxl__blktap_devpath(libxl__gc *gc,
-                                 const char *disk,
-                                 libxl_disk_format format)
+char *libxl__blktap_devpath(libxl__gc *gc,
+                            const char *disk,
+                            libxl_disk_format format)
 {
     return NULL;
 }