[PATCH 5/6] libxl: introduce libxl__alloc_vdev

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

Introduce libxl__alloc_vdev: find a spare virtual block device in the
domain passed as argument.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
 tools/libxl/libxl.c |   60 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 60 insertions(+), 0 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index fe63fd5..fa7898a 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -1228,6 +1228,13 @@ int libxl_vncviewer_exec(libxl_ctx *ctx, uint32_t domid, int autopass)
 
 /******************************************************************************/
 
+static int libxl__append_disk_list_of_type(libxl__gc *gc,
+                                           uint32_t domid,
+                                           xs_transaction_t t,
+                                           const char *type,
+                                           libxl_device_disk **disks,
+                                           int *ndisks);
+
 int libxl__device_disk_setdefault(libxl__gc *gc, libxl_device_disk *disk)
 {
     int rc;
@@ -1278,6 +1285,59 @@ static int libxl__device_from_disk(libxl__gc *gc, uint32_t domid,
     return 0;
 }
 
+static int libxl__vdev_to_index(libxl__gc *gc, char *vdev)
+{
+    if (vdev == NULL)
+        return 0;
+    if (strlen(vdev) > 4 || strlen(vdev) < 4)
+        return 0;
+    /* assume xvdz is the last one available */
+    if (vdev[3] >= 'z')
+        return -1;
+    return vdev[3] - 'a';
+}
+
+static char* libxl__index_to_vdev(libxl__gc *gc, int idx)
+{
+    if (idx < 0)
+        return NULL;
+    return libxl__sprintf(gc, "xvd%c", 'a' + idx);
+}
+
+static char * libxl__alloc_vdev(libxl__gc *gc, uint32_t domid, xs_transaction_t t,
+        libxl_device_disk *disk)
+{
+    int rc = 0;
+    libxl_device_disk *disks = NULL;
+    int num = 0, idx = -1, max_idx = -1, i = 0;
+
+    rc = libxl__append_disk_list_of_type(gc, domid, t, "vbd", &disks, &num);
+    if (rc) goto out;
+
+    rc = libxl__append_disk_list_of_type(gc, domid, t, "tap", &disks, &num);
+    if (rc) goto out;
+
+    rc = libxl__append_disk_list_of_type(gc, domid, t, "qdisk", &disks, &num);
+    if (rc) goto out;
+
+    for (i = 0; i < num; i++) {
+        idx = libxl__vdev_to_index(gc, disks[i].vdev);
+        if (idx < 0) {
+            max_idx = -1;
+            goto out;
+        }
+        if (idx > max_idx)
+            max_idx = idx;
+    }
+    max_idx++;
+out:
+    while (disks && num) {
+        num--;
+        libxl_device_disk_dispose(&disks[num]);
+    }
+    free(disks);
+    return libxl__index_to_vdev(gc, max_idx);
+}
 
 static int libxl__device_disk_add_t(libxl__gc *gc, uint32_t domid, xs_transaction_t t,
         libxl_device_disk *disk)
-- 
1.7.2.5