From 62dce61f73b9f0ea9e75a65713a21f4f8368381e Mon Sep 17 00:00:00 2001

From: Pino Toscano <ptoscano@redhat.com>

Date: Mon, 21 May 2018 17:19:25 +0200

Subject: [PATCH] v2v: -o null: support older qemu-img (RHBZ#1580309)

Commit 4699c7b6e126e07c95b67fb95df58aed87a680dd converted the null

output to use the null-co qemu driver with a JSON URL syntax --

especially the latter is only available in newer versions of qemu.

Even if this output mode is mostly for testing, check at runtime whether

the null-co + JSON way is possible, falling back to the creation of

thrown-away temporary files as before.

(cherry picked from commit 1b6a2b221d04e455bdd31cff09015f74487882c1)

---

 v2v/output_null.ml | 66 ++++++++++++++++++++++++++++++++++++++--------

 1 file changed, 55 insertions(+), 11 deletions(-)

diff --git a/v2v/output_null.ml b/v2v/output_null.ml

index b93d53dc5..228c0b631 100644

--- a/v2v/output_null.ml

+++ b/v2v/output_null.ml

@@ -40,9 +40,45 @@ open Utils

  * too small, so we have to set the size.  We could set it to

  * match the input size but it's easier to set it to some huge

  * size instead.

+ *

+ * In case neither the null-co driver nor the JSON syntax for URLs

+ * is supported, fall back by writing the disks to a temporary

+ * directory removed at exit.

  *)

+let can_use_qemu_null_co_device () =

+  (* We actually attempt to convert a raw file to the null-co device

+   * using a JSON URL.

+   *)

+  let tmp = Filename.temp_file "v2vqemunullcotst" ".img" in

+  Unix.truncate tmp 1024;

+

+  let json = [

+    "file.driver", JSON.String "null-co";

+    "file.size", JSON.String "1E";

+  ] in

+

+  let cmd =

+    sprintf "qemu-img convert -n -f raw -O raw %s json:%s >/dev/null%s"

+            (quote tmp)

+            (quote (JSON.string_of_doc ~fmt:JSON.Compact json))

+            (if verbose () then "" else " 2>&1") in

+  debug "%s" cmd;

+  let r = 0 = Sys.command cmd in

+  Unix.unlink tmp;

+  debug "qemu-img supports the null-co device: %b" r;

+  r

+

 class output_null =

+  (* Create a temporary directory which is always deleted at exit,

+   * so we can put the drives there in case qemu does not support

+   * the null-co device w/ a JSON URL.

+   *)

+  let tmpdir =

+    let base_dir = (open_guestfs ())#get_cachedir () in

+    let t = Mkdtemp.temp_dir ~base_dir "null." in

+    rmdir_on_exit t;

+    t in

 object

   inherit output

@@ -51,19 +87,27 @@ object

   method supported_firmware = [ TargetBIOS; TargetUEFI ]

   method prepare_targets source targets =

-    let json_params = [

-      "file.driver", JSON.String "null-co";

-      "file.size", JSON.String "1E";

-    ] in

-    let target_file = TargetURI ("json:" ^ JSON.string_of_doc json_params) in

+    if can_use_qemu_null_co_device () then (

+      let json_params = [

+        "file.driver", JSON.String "null-co";

+        "file.size", JSON.String "1E";

+      ] in

+      let target_file = TargetURI ("json:" ^ JSON.string_of_doc json_params) in

-    (* While it's not intended that output drivers can set the

-     * target_format field (thus overriding the -of option), in

-     * this special case of -o null it is reasonable.

-     *)

-    let target_format = "raw" in

+      (* While it's not intended that output drivers can set the

+       * target_format field (thus overriding the -of option), in

+       * this special case of -o null it is reasonable.

+       *)

+      let target_format = "raw" in

-    List.map (fun t -> { t with target_file; target_format }) targets

+      List.map (fun t -> { t with target_file; target_format }) targets

+    ) else (

+      List.map (

+        fun t ->

+          let target_file = tmpdir // t.target_overlay.ov_sd in

+          { t with target_file = TargetFile target_file }

+      ) targets

+    )

   method create_metadata _ _ _ _ _ _ = ()

 end

-- 

2.17.1