[Libguestfs] [v2v PATCH] RHV outputs: limit copied disk count to 23
Richard W.M. Jones
rjones at redhat.com
Fri Jun 17 09:33:30 UTC 2022
On Fri, Jun 17, 2022 at 11:32:36AM +0200, Laszlo Ersek wrote:
> On 06/17/22 11:17, Richard W.M. Jones wrote:
> > On Fri, Jun 17, 2022 at 11:08:52AM +0200, Laszlo Ersek wrote:
> >> We currently support virtio-blk (commonly) or IDE (unusually) for exposing
> >> disks to the converted guest; refer to "guestcaps.gcaps_block_bus" in
> >> "lib/create_ovf.ml". When using virtio-blk (i.e., in the common case), RHV
> >> can deal with at most 23 disks, as it plugs each virtio-blk device in a
> >> separate slot on the PCI(e) root bus; and the other slots are reserved for
> >> various purposes. When a domain has too many disks, the problem only
> >> becomes apparent once the copying finishes and an import is attempted.
> >> Modify the RHV outputs to fail relatively early when a domain has more
> >> than 23 disks that need to be copied.
> >>
> >> Notes:
> >>
> >> - With IDE, the theoretical limit may even be as low as 4. However, in the
> >> "Output_module.setup" function, we don't have access to
> >> "guestcaps.gcaps_block_bus", and in practice the IDE limitation has not
> >> caused surprises. So for now stick with 23, assuming virtio-blk.
> >> Modifying the "Output_module.setup" parameter list just for this seems
> >> overkill.
> >>
> >> - We could move the new check to an even earlier step, namely
> >> "Output_module.parse_options", due to the v2v directory deliberately
> >> existing (and having been populated with input sockets) at that time.
> >> However, even discounting the fact that "parse_options" is not a good
> >> name for including this kind of step, "parse_options" does not have
> >> access to the v2v directory name, and modifying the signature just for
> >> this is (again) overkill.
> >>
> >> - By adding the check to "Output_module.setup", we waste *some* effort
> >> (namely, the conversion occurs between "parse_options" and "setup"),
> >> but: (a) the "rhv-disk-uuid" count check (against the disk count) is
> >> already being done in the rhv-upload module's "setup" function, (b) in
> >> practice the slowest step ought to be the copying, and placing the new
> >> check in "setup" is early enough to prevent that.
> >>
> >> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2051564
> >> Signed-off-by: Laszlo Ersek <lersek at redhat.com>
> >> ---
> >>
> >> Notes:
> >> This patch can be tested easily by replacing 23 with 0 in all three
> >> affected output modules -- then the following test cases all fail in
> >> "make check":
> >>
> >> FAIL: test-v2v-o-rhv.sh
> >> FAIL: test-v2v-o-vdsm-options.sh
> >> FAIL: test-v2v-o-rhv-upload.sh
> >>
> >> > [ 11.3] Setting up the destination: -o rhv
> >> > virt-v2v: error: this output module doesn't support copying more than 0 disks
> >>
> >> > [ 9.0] Setting up the destination: -o vdsm
> >> > virt-v2v: error: this output module doesn't support copying more than 0 disks
> >>
> >> > [ 11.2] Setting up the destination: -o rhv-upload -oc https://example.com/ovirt-engine/api -os Storage
> >> > virt-v2v: error: this output module doesn't support copying more than 0 disks
> >>
> >> output/output.mli | 7 +++++++
> >> output/output.ml | 5 +++++
> >> output/output_rhv.ml | 1 +
> >> output/output_rhv_upload.ml | 1 +
> >> output/output_vdsm.ml | 1 +
> >> 5 files changed, 15 insertions(+)
> >>
> >> diff --git a/output/output.mli b/output/output.mli
> >> index 533a0c51d31c..2dec8ccdc690 100644
> >> --- a/output/output.mli
> >> +++ b/output/output.mli
> >> @@ -76,6 +76,13 @@ val get_disks : string -> (int * int64) list
> >> (** Examines the v2v directory and opens each input socket (in0 etc),
> >> returning a list of input disk index and size. *)
> >>
> >> +val bail_if_disk_count_gt : string -> int -> unit
> >> +(** This function lets an output module enforce a maximum disk count.
> >> + [bail_if_disk_count_gt dir n] checks whether the domain has more than [n]
> >> + disks that need to be copied, by examining the existence of input NBD socket
> >> + "in[n]" in the v2v directory [dir]. If the socket exists, [error] is
> >> + called. *)
> >
> > We've commonly called these types of functions "error_if_..." or
> > "error_unless_..." (you'll find many examples in the existing code).
> > Could be better to rename it that way for consistency.
> >
> >> val output_to_local_file : ?changeuid:((unit -> unit) -> unit) ->
> >> Types.output_allocation ->
> >> string -> string -> int64 -> string ->
> >> diff --git a/output/output.ml b/output/output.ml
> >> index 10e685c46926..0c4b437997d4 100644
> >> --- a/output/output.ml
> >> +++ b/output/output.ml
> >> @@ -64,6 +64,11 @@ let get_disks dir =
> >> in
> >> loop [] 0
> >>
> >> +let bail_if_disk_count_gt dir n =
> >> + let socket = sprintf "%s/in%d" dir n in
> >> + if Sys.file_exists socket then
> >> + error (f_"this output module doesn't support copying more than %d disks") n
> >> +
> >> let output_to_local_file ?(changeuid = fun f -> f ())
> >> output_alloc output_format filename size socket =
> >> (* Check nbdkit is installed and has the required plugin. *)
> >> diff --git a/output/output_rhv.ml b/output/output_rhv.ml
> >> index 119207fdc065..a0c0be270755 100644
> >> --- a/output/output_rhv.ml
> >> +++ b/output/output_rhv.ml
> >> @@ -56,6 +56,7 @@ module RHV = struct
> >> (options.output_alloc, options.output_format, output_name, output_storage)
> >>
> >> let rec setup dir options source =
> >> + bail_if_disk_count_gt dir 23;
> >> let disks = get_disks dir in
> >> let output_alloc, output_format, output_name, output_storage = options in
> >>
> >> diff --git a/output/output_rhv_upload.ml b/output/output_rhv_upload.ml
> >> index 828996b36261..6a9abf4eecdf 100644
> >> --- a/output/output_rhv_upload.ml
> >> +++ b/output/output_rhv_upload.ml
> >> @@ -133,6 +133,7 @@ after their uploads (if you do, you must supply one for each disk):
> >> else PCRE.matches (Lazy.force rex_uuid) uuid
> >>
> >> let rec setup dir options source =
> >> + bail_if_disk_count_gt dir 23;
> >> let disks = get_disks dir in
> >> let output_conn, output_format,
> >> output_password, output_name, output_storage,
> >> diff --git a/output/output_vdsm.ml b/output/output_vdsm.ml
> >> index a1e8c2465810..02a2b5817fbc 100644
> >> --- a/output/output_vdsm.ml
> >> +++ b/output/output_vdsm.ml
> >> @@ -119,6 +119,7 @@ For each disk you must supply one of each of these options:
> >> compat, ovf_flavour)
> >>
> >> let setup dir options source =
> >> + bail_if_disk_count_gt dir 23;
> >> let disks = get_disks dir in
> >> let output_alloc, output_format,
> >> output_name, output_storage,
> >> --
> >> 2.19.1.3.g30247aa5d201
> >
> > Looks fine, although I'd prefer the function to be renamed.
>
> Yes I will, consistency is important!
With the function renamed for consistency:
Reviewed-by: Richard W.M. Jones <rjones at redhat.com>
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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