On Tue, Jun 5, 2012 at 3:20 AM, Florian Achleitner
<florian.achleitner.2.6.31@xxxxxxxxx> wrote:
> On invocation of a helper a new pipe is opened.
> To close the other end after fork, the prexec_cb feature
> of the run_command api is used.
> If the helper is not used with fast-import later the pipe
> is unused.
> The FD is passed to the remote-helper via it's environment,
> helpers that don't use fast-import can simply ignore it.
> fast-import has an argv for that.
>
> Signed-off-by: Florian Achleitner <florian.achleitner.2.6.31@xxxxxxxxx>
> ---
> transport-helper.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
> vcs-svn/svndump.c | 9 ++++++++-
> 2 files changed, 56 insertions(+), 1 deletion(-)
>
> diff --git a/transport-helper.c b/transport-helper.c
> index 61c928f..b438040 100644
> --- a/transport-helper.c
> +++ b/transport-helper.c
> @@ -17,6 +17,7 @@ struct helper_data {
> const char *name;
> struct child_process *helper;
> FILE *out;
> + int fast_import_backchannel_pipe[2];
> unsigned fetch : 1,
> import : 1,
> export : 1,
> @@ -98,19 +99,30 @@ static void do_take_over(struct transport *transport)
> free(data);
> }
>
> +static int fd_to_close;
> +void close_fd_prexec_cb(void)
> +{
> + if(debug)
> + fprintf(stderr, "close_fd_prexec_cb closing %d\n", fd_to_close);
> + close(fd_to_close);
> +}
> +
> static struct child_process *get_helper(struct transport *transport)
> {
> struct helper_data *data = transport->data;
> struct strbuf buf = STRBUF_INIT;
> + struct strbuf envbuf = STRBUF_INIT;
> struct child_process *helper;
> const char **refspecs = NULL;
> int refspec_nr = 0;
> int refspec_alloc = 0;
> int duped;
> int code;
> + int err;
> char git_dir_buf[sizeof(GIT_DIR_ENVIRONMENT) + PATH_MAX + 1];
> const char *helper_env[] = {
> git_dir_buf,
> + NULL, /* placeholder */
> NULL
> };
>
> @@ -133,6 +145,24 @@ static struct child_process *get_helper(struct transport *transport)
> snprintf(git_dir_buf, sizeof(git_dir_buf), "%s=%s", GIT_DIR_ENVIRONMENT, get_git_dir());
> helper->env = helper_env;
>
> +
> + /* create an additional pipe from fast-import to the helper */
> + err = pipe(data->fast_import_backchannel_pipe);
> + if(err)
> + die("cannot create fast_import_backchannel_pipe: %s", strerror(errno));
> +
> + if(debug)
> + fprintf(stderr, "Remote helper created fast_import_backchannel_pipe { %d, %d }\n",
> + data->fast_import_backchannel_pipe[0], data->fast_import_backchannel_pipe[1]);
> +
> + strbuf_addf(&envbuf, "GIT_REPORT_FILENO=%d", data->fast_import_backchannel_pipe[0]);
> + helper_env[1] = strbuf_detach(&envbuf, NULL);
> +
> + /* after the fork, we need to close the write end in the helper */
> + fd_to_close = data->fast_import_backchannel_pipe[1];
> + /* the prexec callback is run just before exec */
> + helper->preexec_cb = close_fd_prexec_cb;
> +
> code = start_command(helper);
> if (code < 0 && errno == ENOENT)
> die("Unable to find remote helper for '%s'", data->name);
> @@ -141,6 +171,7 @@ static struct child_process *get_helper(struct transport *transport)
>
> data->helper = helper;
> data->no_disconnect_req = 0;
> + free((void*)helper_env[1]);
>
> /*
> * Open the output as FILE* so strbuf_getline() can be used.
> @@ -237,6 +268,10 @@ static int disconnect_helper(struct transport *transport)
> xwrite(data->helper->in, "\n", 1);
> sigchain_pop(SIGPIPE);
> }
> + /* close the pipe, it is still open if it wasn't used for fast-import. */
> + close(data->fast_import_backchannel_pipe[0]);
> + close(data->fast_import_backchannel_pipe[1]);
> +
> close(data->helper->in);
> close(data->helper->out);
> fclose(data->out);
> @@ -376,13 +411,20 @@ static int fetch_with_fetch(struct transport *transport,
> static int get_importer(struct transport *transport, struct child_process *fastimport)
> {
> struct child_process *helper = get_helper(transport);
> + struct helper_data *data = transport->data;
> + struct strbuf buf = STRBUF_INIT;
> memset(fastimport, 0, sizeof(*fastimport));
> fastimport->in = helper->out;
> fastimport->argv = xcalloc(5, sizeof(*fastimport->argv));
> fastimport->argv[0] = "fast-import";
> fastimport->argv[1] = "--quiet";
> + strbuf_addf(&buf, "--cat-blob-fd=%d", data->fast_import_backchannel_pipe[1]);
> + fastimport->argv[2] = strbuf_detach(&buf, NULL);
>
> fastimport->git_cmd = 1;
> +
> + fd_to_close = data->fast_import_backchannel_pipe[0];
> + fastimport->preexec_cb = close_fd_prexec_cb;
> return start_command(fastimport);
> }
>
> @@ -427,6 +469,11 @@ static int fetch_with_import(struct transport *transport,
> if (get_importer(transport, &fastimport))
> die("Couldn't run fast-import");
>
> +
> + /* in the parent process we close both pipe ends. */
> + close(data->fast_import_backchannel_pipe[0]);
> + close(data->fast_import_backchannel_pipe[1]);
> +
> for (i = 0; i < nr_heads; i++) {
> posn = to_fetch[i];
> if (posn->status & REF_STATUS_UPTODATE)
> @@ -441,6 +488,7 @@ static int fetch_with_import(struct transport *transport,
>
> if (finish_command(&fastimport))
> die("Error while running fast-import");
> + free((void*)fastimport.argv[2]);
> free(fastimport.argv);
> fastimport.argv = NULL;
>
> diff --git a/vcs-svn/svndump.c b/vcs-svn/svndump.c
> index 2f0089f..b1fe03f 100644
> --- a/vcs-svn/svndump.c
> +++ b/vcs-svn/svndump.c
> @@ -467,7 +467,14 @@ void svndump_read(const char *url)
>
> static void init()
> {
> - fast_export_init(REPORT_FILENO);
> + int report_fd;
> + char* back_fd_env = getenv("GIT_REPORT_FILENO");
> + if(!back_fd_env || sscanf(back_fd_env, "%d", &report_fd) != 1) {
> + warning("Cannot get cat-blob fd from environment, using default!");
> + report_fd = REPORT_FILENO;
> + }
> +
> + fast_export_init(report_fd);
> strbuf_init(&dump_ctx.uuid, 4096);
> strbuf_init(&dump_ctx.url, 4096);
> strbuf_init(&rev_ctx.log, 4096);
> --
> 1.7.9.5
+cc Sverre Rabbelier and Jeff King, as they have been active in
transport-helper.c.
--
David Barr
--
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