[Libguestfs] [virt-v2v PATCH 1/3] lib/nbdkit: add the "Nbdkit.with_connect_unix" helper function

Connecting to an NBD server temporarily, for a "one-shot" operation, is quite similar to "Std_utils.with_open_in" and "Std_utils.with_open_out", as there are cleanup operations regardless of whether the "one-shot" operation completes successfully or throws an exception. Introduce the "Nbdkit.with_connect_unix" function, which takes a Unix domain socket pathname, a list of metadata contexts to request from the NBD server, and calls a function with the live NBD server connection. Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2027598 Signed-off-by: Laszlo Ersek <lersek(a)redhat.com&gt; --- lib/Makefile.am | 2 +- lib/nbdkit.mli | 10 ++++++++++ lib/nbdkit.ml | 12 ++++++++++++ 3 files changed, 23 insertions(+), 1 deletion(-) diff --git a/lib/Makefile.am b/lib/Makefile.am index c274b9ecf6c7..1fab25b326f5 100644 --- a/lib/Makefile.am +++ b/lib/Makefile.am @@ -80,7 +80,7 @@ BOBJECTS = config.cmo $(SOURCES_ML:.ml=.cmo) XOBJECTS = $(BOBJECTS:.cmo=.cmx) OCAMLPACKAGES = \ - -package str,unix \ + -package str,unix,nbd \ -I $(builddir) \ -I $(top_builddir)/common/mlgettext \ -I $(top_builddir)/common/mlpcre \ diff --git a/lib/nbdkit.mli b/lib/nbdkit.mli index ae19295186ed..825755e61dbe 100644 --- a/lib/nbdkit.mli +++ b/lib/nbdkit.mli @@ -107,3 +107,13 @@ val run_unix : ?socket:string -> cmd -> string * int The --exit-with-parent, --foreground, --pidfile, --newstyle and --unix flags are added automatically. Other flags are set as in the {!cmd} struct. *) + +val with_connect_unix : socket:string -> + meta_contexts:string list -> + f:(NBD.t -> 'a) -> + 'a +(** [with_connect_unix socket meta_contexts f] calls function [f] with the NBD + server at Unix domain socket [socket] connected, and the metadata contexts + in [meta_contexts] requested (each of which is not necessarily supported by + the server though). The connection is torn down either on normal return or + if the function [f] throws an exception. *) diff --git a/lib/nbdkit.ml b/lib/nbdkit.ml index 8d0bfdf9cff1..43e0fc5c728a 100644 --- a/lib/nbdkit.ml +++ b/lib/nbdkit.ml @@ -217,3 +217,15 @@ If the messages above are not sufficient to diagnose the problem then add the chmod socket 0o777; socket, pid + +let with_connect_unix ~socket ~meta_contexts ~f = + let nbd = NBD.create () in + protect + ~f:(fun () -> + List.iter (NBD.add_meta_context nbd) meta_contexts; + NBD.connect_unix nbd socket; + protect + ~f:(fun () -> f nbd) + ~finally:(fun () -> NBD.shutdown nbd) + ) + ~finally:(fun () -> NBD.close nbd) -- 2.19.1.3.g30247aa5d201