[Libguestfs] [PATCH v2 4/5] v2v: ova: don't extract files from OVA if it's not needed
Tomáš Golembiovský
tgolembi at redhat.com
Sat Nov 12 15:37:52 UTC 2016
We don't have to always extract all files from the OVA archive. The OVA,
as defined in the standard, is plain tar. We can work directly over the
tar archive if we use correct 'offset' and 'size' options when defining
the backing file for QEMU.
This leads to improvements in speed and puts much lower requirement on
available disk space.
Signed-off-by: Tomáš Golembiovský <tgolembi at redhat.com>
---
v2v/input_ova.ml | 177 +++++++++++++++++++++++++++++++++++++++++++++++--------
1 file changed, 154 insertions(+), 23 deletions(-)
diff --git a/v2v/input_ova.ml b/v2v/input_ova.ml
index f76fe82..7a3e27b 100644
--- a/v2v/input_ova.ml
+++ b/v2v/input_ova.ml
@@ -39,17 +39,23 @@ object
method source () =
- let untar ?(format = "") file outdir =
- let cmd = [ "tar"; sprintf "-x%sf" format; file; "-C"; outdir ] in
+ (* Untar part or all files from tar archive. If [path] is specified it is
+ * a path in the tar archive.
+ *)
+ let untar ?(format = "") ?(path) file outdir =
+ let cmd =
+ [ "tar"; sprintf "-x%sf" format; file; "-C"; outdir ]
+ @ (match path with None -> [] | Some p -> [p])
+ in
if run_command cmd <> 0 then
error (f_"error unpacking %s, see earlier error messages") ova in
(* Extract ova file. *)
- let exploded =
+ let exploded, partial =
(* The spec allows a directory to be specified as an ova. This
* is also pretty convenient.
*)
- if is_directory ova then ova
+ if is_directory ova then ova, false
else (
let uncompress_head zcat file =
let cmd = sprintf "%s %s" zcat (quote file) in
@@ -67,11 +73,53 @@ object
tmpfile in
+ (* Untar only ovf and manifest from the archive *)
+ let untar_partial file outdir =
+ let files =
+ external_command (sprintf "tar -tf %s" (Filename.quote file)) in
+ List.iter (fun f ->
+ if Filename.check_suffix f ".ovf" ||
+ Filename.check_suffix f ".mf" then
+ untar ~path:f file outdir
+ ) files in
+
+ let qemu_img_version () =
+ let cmd = "qemu-img --version" in
+ let lines = external_command cmd in
+ match lines with
+ | [] -> error ("'qemu-img --version' returned no output")
+ | line :: _ ->
+ let rex = Str.regexp "qemu-img version \\([0-9]+\\)\\.\\([0-9]+\\)" in
+ if Str.string_match rex line 0 then (
+ try
+ int_of_string (Str.matched_group 1 line),
+ int_of_string (Str.matched_group 2 line)
+ with Failure _ ->
+ warning (f_"warning: failed to read qemu-img version! Line: %S")
+ line;
+ 0, 9
+ ) else (
+ warning (f_"warning: failed to read qemu-img version! Line: %S")
+ line;
+ 0, 9
+ )
+ in
+
match detect_file_type ova with
| `Tar ->
(* Normal ovas are tar file (not compressed). *)
- untar ova tmpdir;
- tmpdir
+ let qmajor, qminor = qemu_img_version () in
+ if qmajor > 2 || (qmajor == 2 && qminor >= 8) then (
+ (* If QEMU is recent enough we don't have to extract everything. We
+ * can access disks inside the tar archive.
+ *)
+ untar_partial ova tmpdir;
+ tmpdir, true
+ ) else (
+ untar ova tmpdir;
+ tmpdir, false
+ )
+
| `Zip ->
(* However, although not permitted by the spec, people ship
* zip files as ova too.
@@ -81,7 +129,7 @@ object
[ "-j"; "-d"; tmpdir; ova ] in
if run_command cmd <> 0 then
error (f_"error unpacking %s, see earlier error messages") ova;
- tmpdir
+ tmpdir, false
| (`GZip|`XZ) as format ->
let zcat, tar_fmt =
match format with
@@ -94,7 +142,7 @@ object
(match tmpfiletype with
| `Tar ->
untar ~format:tar_fmt ova tmpdir;
- tmpdir
+ tmpdir, false
| `Zip | `GZip | `XZ | `Unknown ->
error (f_"%s: unsupported file format\n\nFormats which we currently understand for '-i ova' are: tar (uncompressed, compress with gzip or xz), zip") ova
)
@@ -135,6 +183,59 @@ object
loop [dir]
in
+ (* Find file in [tar] archive and return at which byte it starts and how
+ * long it is.
+ *)
+ let find_file_in_tar tar filename =
+ let lines = external_command (stringify_args [ "tar"; "tRvf"; tar ]) in
+ let rec loop lines =
+ match lines with
+ | [] -> raise Not_found
+ | line :: lines -> (
+ (* Lines have the form:
+ * block <offset>: <perms> <owner>/<group> <size> <mdate> <mtime> <file>
+ *)
+ let rex = Str.regexp "^block \\([0-9]+\\): \\([^ \\t]+\\) \\([^ \\t]+\\) +\\([^ \\t]+\\) \\([^ \\t]+\\) \\([^ \\t]+\\) \\(.+\\)$" in
+ if Str.string_match rex line 0 then (
+ let offset = Str.matched_group 1 line in
+ let size = Str.matched_group 4 line in
+ let fname = Str.matched_group 7 line in
+
+ let offset =
+ try Int64.of_string offset
+ with Failure _ ->
+ error (f_"invalid offset returned by tar: %S") offset in
+
+ let size =
+ try Int64.of_string size
+ with Failure _ ->
+ error (f_"invalid size returned by tar: %S") size in
+
+ if fname = filename then
+ (* Note: Offset is actualy block number and there is a single
+ * block with tar header at the beginning of the file. So skip
+ * the header and convert the block number to bytes before
+ * returning.
+ *)
+ (offset +^ 1L) *^ 512L, size
+ else loop lines
+ ) else
+ error (f_"failed to parse line returned by tar: %S") line
+ )
+ in
+ loop lines
+ in
+
+ let subfolder folder parent =
+ if String.is_prefix folder (parent // "") then
+ let len = String.length parent in
+ String.sub folder (len+1) (String.length folder-len-1)
+ else if folder = parent then
+ ""
+ else
+ assert false
+ in
+
(* Search for the ovf file. *)
let ovf = find_files exploded ".ovf" in
let ovf =
@@ -152,6 +253,7 @@ object
fun mf ->
debug "processing manifest %s" mf;
let mf_folder = Filename.dirname mf in
+ let mf_subfolder = subfolder mf_folder exploded in
let chan = open_in mf in
let rec loop () =
let line = input_line chan in
@@ -160,7 +262,11 @@ object
let disk = Str.matched_group 2 line in
let expected = Str.matched_group 3 line in
let csum = Checksums.of_string mode expected in
- try Checksums.verify_checksum csum (mf_folder // disk)
+ try
+ if partial then
+ Checksums.verify_checksum csum ~tar:ova (mf_subfolder // disk)
+ else
+ Checksums.verify_checksum csum (mf_folder // disk)
with Checksums.Mismatched_checksum (_, actual) ->
error (f_"checksum of disk %s does not match manifest %s (actual %s(%s) = %s, expected %s(%s) = %s)")
disk mf mode disk actual mode disk expected;
@@ -283,25 +389,50 @@ object
| Some "gzip" -> true
| Some s -> error (f_"unsupported comprression in OVF: %s") s in
- let filename = if compressed then (
- let new_filename = tmpdir // String.random8 () ^ ".vmdk" in
- let cmd =
- sprintf "zcat %s > %s" (quote ovf_folder // filename) (quote new_filename) in
- if shell_command cmd <> 0 then
- error (f_"error uncompressing %s, see earlier error messages")
- filename;
- new_filename
- )
- else
- ovf_folder // filename
+ let filename, partial =
+ if compressed then (
+ if partial then
+ untar ~path:((subfolder ovf_folder exploded) // filename)
+ ova tmpdir;
+ let new_filename = tmpdir // String.random8 () ^ ".vmdk" in
+ let cmd =
+ sprintf "zcat %s > %s" (quote ovf_folder // filename) (quote new_filename) in
+ if shell_command cmd <> 0 then
+ error (f_"error uncompressing %s, see earlier error messages")
+ filename;
+ new_filename, false
+ )
+ else if partial then
+ (subfolder ovf_folder exploded) // filename, partial
+ else
+ ovf_folder // filename, partial
in
- (* Does the file exist and is it readable? *)
- Unix.access filename [Unix.R_OK];
+ let qemu_uri =
+ if not partial then (
+ (* Does the file exist and is it readable? *)
+ Unix.access filename [Unix.R_OK];
+ filename
+ )
+ else (
+ let offset, size =
+ try find_file_in_tar ova filename
+ with Not_found ->
+ error (f_"file '%s' not found in the ova") filename
+ in
+ (* QEMU requires size aligned to 512 bytes. This is safe because
+ * tar also works with 512 byte blocks.
+ *)
+ let size = roundup64 size 512L in
+ sprintf
+ "json:{ \"file\": { \"driver\":\"raw\", \"offset\":\"%Ld\", \"size\":\"%Ld\", \"file\": { \"filename\":\"%s\" } } }"
+ offset size ova
+ )
+ in
let disk = {
s_disk_id = i;
- s_qemu_uri = filename;
+ s_qemu_uri = qemu_uri;
s_format = Some "vmdk";
s_controller = controller;
} in
--
2.10.1
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