[Libguestfs] [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.
---
v2v/output_null.ml | 60 +++++++++++++++++++++++++++++++++++++---------
1 file changed, 49 insertions(+), 11 deletions(-)
diff --git a/v2v/output_null.ml b/v2v/output_null.ml
index b93d53dc5..5a5473c0d 100644
--- a/v2v/output_null.ml
+++ b/v2v/output_null.ml
@@ -42,7 +42,37 @@ open Utils
* size instead.
*)
+let qemu_supports_null_co_device () =
+ (* We actually attempt to convert a raw file to the null-co device. *)
+ 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.
+ *)
+ 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 +81,27 @@ 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 qemu_supports_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
--
2.17.0