Re: [Libguestfs] [PATCH v3 02/13] v2v: factor out overlay creation

Iterating over source disks and creating temporary overlays for easy rollback fits nicely into a separate function. In addition, determining their size doesn't need to wait until the guestfs is launched: the size can be obtained via disk_virtual_size() method. Signed-off-by: Roman Kagan <rkagan(a)virtuozzo.com&gt; --- v2v/v2v.ml | 91 +++++++++++++++++++++++++++++--------------------------------- 1 file changed, 42 insertions(+), 49 deletions(-) diff --git a/v2v/v2v.ml b/v2v/v2v.ml index 564c5da..155eb83 100644 --- a/v2v/v2v.ml +++ b/v2v/v2v.ml @@ -57,40 +57,7 @@ let rec main () = let source = open_source input print_source in let source = amend_source source output_name network_map in - - (* Create a qcow2 v3 overlay to protect the source image(s). There - * is a specific reason to use the newer qcow2 variant: Because the - * L2 table can store zero clusters efficiently, and because - * discarded blocks are stored as zero clusters, this should allow us - * to fstrim/blkdiscard and avoid copying significant parts of the - * data over the wire. - *) - message (f_"Creating an overlay to protect the source from being modified"); - let overlay_dir = (new Guestfs.guestfs ())#get_cachedir () in - let overlays = - List.map ( - fun ({ s_qemu_uri = qemu_uri; s_format = format } as source) -> - let overlay_file = - Filename.temp_file ~temp_dir:overlay_dir "v2vovl" ".qcow2" in - unlink_on_exit overlay_file; - - let options = - "compat=1.1" ^ - (match format with None -> "" - | Some fmt -> ",backing_fmt=" ^ fmt) in - let cmd = - sprintf "qemu-img create -q -f qcow2 -b %s -o %s %s" - (quote qemu_uri) (quote options) overlay_file in - if verbose () then printf "%s\n%!" cmd; - if Sys.command cmd <> 0 then - error (f_"qemu-img command failed, see earlier errors"); - - (* Sanity check created overlay (see below). *) - if not ((new G.guestfs ())#disk_has_backing_file overlay_file) then - error (f_"internal error: qemu-img did not create overlay with backing file"); - - overlay_file, source - ) source.s_disks in + let overlays = create_overlays source.s_disks in (* Open the guestfs handle. *) message (f_"Opening the overlay"); @@ -100,7 +67,7 @@ let rec main () = if verbose () then g#set_verbose true; g#set_network true; List.iter ( - fun (overlay_file, _) -> + fun ({ov_overlay_file = overlay_file}) -> g#add_drive_opts overlay_file ~format:"qcow2" ~cachemode:"unsafe" ~discard:"besteffort" ~copyonread:true @@ -108,20 +75,6 @@ let rec main () = g#launch (); - (* Create the list of overlays structs. Query each disk for its - * virtual size, and fill in a few other fields. - *) - let overlays = - mapi ( - fun i (overlay_file, source) -> - let sd = "sd" ^ drive_name i in - let dev = "/dev/" ^ sd in - let vsize = g#blockdev_getsize64 dev in - - { ov_overlay_file = overlay_file; ov_sd = sd; - ov_virtual_size = vsize; ov_source = source } - ) overlays in - (* Work out where we will write the final output. Do this early * just so we can display errors to the user before doing too much * work. @@ -385,6 +338,7 @@ let rec main () = (* Save overlays if --debug-overlays option was used. *) if debug_overlays then ( + let overlay_dir = (new Guestfs.guestfs ())#get_cachedir () in List.iter ( fun ov -> let saved_filename = @@ -460,6 +414,45 @@ and amend_source source output_name network_map = { source with s_nics = nics } +and create_overlays src_disks = + (* Create a qcow2 v3 overlay to protect the source image(s). There + * is a specific reason to use the newer qcow2 variant: Because the + * L2 table can store zero clusters efficiently, and because + * discarded blocks are stored as zero clusters, this should allow us + * to fstrim/blkdiscard and avoid copying significant parts of the + * data over the wire. + *) + message (f_"Creating an overlay to protect the source from being modified"); + let overlay_dir = (new Guestfs.guestfs ())#get_cachedir () in + List.mapi ( + fun i ({ s_qemu_uri = qemu_uri; s_format = format } as source) -> + let overlay_file = + Filename.temp_file ~temp_dir:overlay_dir "v2vovl" ".qcow2" in + unlink_on_exit overlay_file; + + let options = + "compat=1.1" ^ + (match format with None -> "" + | Some fmt -> ",backing_fmt=" ^ fmt) in + let cmd = + sprintf "qemu-img create -q -f qcow2 -b %s -o %s %s" + (quote qemu_uri) (quote options) overlay_file in + if verbose () then printf "%s\n%!" cmd; + if Sys.command cmd <> 0 then + error (f_"qemu-img command failed, see earlier errors"); + + (* Sanity check created overlay (see below). *) + if not ((new G.guestfs ())#disk_has_backing_file overlay_file) then + error (f_"internal error: qemu-img did not create overlay with backing file"); + + let sd = "sd" ^ drive_name i in + + let vsize = (new G.guestfs ())#disk_virtual_size overlay_file in + + { ov_overlay_file = overlay_file; ov_sd = sd; + ov_virtual_size = vsize; ov_source = source } + ) src_disks + and inspect_source g root_choice = let roots = g#inspect_os () in let roots = Array.to_list roots in