Re: [Libguestfs] [PATCH 4/5] v2v: ova: don't extract files from OVA if it's not needed

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(a)redhat.com&gt; ---

v2v/input_ova.ml | 113 +++++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 98 insertions(+), 15 deletions(-) diff --git a/v2v/input_ova.ml b/v2v/input_ova.ml index f76fe82..60dbaf1 100644 --- a/v2v/input_ova.ml +++ b/v2v/input_ova.ml @@ -39,17 +39,20 @@ 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; path ] 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 +70,19 @@ object tmpfile in + (* Untar only ovf and manifest from the archive *) + let untar_partial file outdir = + let cmd1 = [ "tar"; "-tf" ; file ] in + let cmd2 = [ "grep"; "\\.\\(ovf\\|mf\\)$" ] in + let cmd3 = [ "xargs"; "tar"; "-xf" ; file; "-C"; outdir ] in + if shell_command ((stringify_args cmd1) ^ " | " ^ (stringify_args cmd2) ^ " | " ^ (stringify_args cmd3)) <> 0 then

+ error (f_"error unpacking %s, see earlier error messages") ova in + match detect_file_type ova with | `Tar -> (* Normal ovas are tar file (not compressed). *) - untar ova tmpdir; - tmpdir + untar_partial ova tmpdir; + tmpdir, true | `Zip -> (* However, although not permitted by the spec, people ship * zip files as ova too. @@ -81,7 +92,7 @@ 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 +105,7 @@ 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 +146,49 @@ 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 cmd1 = [ "tar"; "tRvf"; tar ] in + let cmd2 = [ "awk"; sprintf + "$8 == \"%s\" {print substr($2, 1, index($2, \":\")-1), $5}" + filename ] + in

+ let lines = + external_command ((stringify_args cmd1) ^ " | " ^ (stringify_args cmd2)) + in + if (List.length lines < 1) then

+ raise Not_found + else + let soffset, ssize = String.split " " (List.hd lines) in + let offset = + try Int64.of_string soffset + with Failure _ -> + error (f_"Invalid offset returned by `tar`: %s") soffset + in + let size = + try Int64.of_string ssize + with Failure _ -> + error (f_"Invalid size returend by `tar': %s") ssize

+ in + (* 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 + 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)