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libcriu: add single pre-dump support

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In contrast to the CLI it is not possible to do a single pre-dump via
RPC and thus libcriu. In cr-service.c pre-dump always goes into a
pre-dump loop followed by a final dump. runc already works around this
to only do a single pre-dump by killing the CRIU process waiting for the
message for the final dump.

Trying to implement pre-dump in crun via libcriu it is not as easy to
work around CRIU's pre-dump loop expectations as with runc that directly
talks to CRIU via RPC.

We know that LXC/LXD also does single pre-dumps using the CLI and runc
also only does single pre-dumps by misusing the pre-dump loop interface.

With this commit it is possible to trigger a single pre-dump via RPC and
libcriu without misusing the interface provided via cr-service.c. So
this commit basically updates CRIU to the existing use cases.

The existing pre-dump loop still sounds like a very good idea, but so
far most tools have decided to implement the pre-dump loop themselves.

With this change we can implement pre-dump in crun to match what is
currently implemented in runc.

Signed-off-by: Adrian Reber <areber@redhat.com>
This commit is contained in:
Adrian Reber 2021-12-03 14:32:33 +00:00 committed by Andrei Vagin
parent 119a798856
commit 51a1adbc03
4 changed files with 30 additions and 8 deletions
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13
criu/cr-service.c
View File

@ -169,11 +169,11 @@ int send_criu_dump_resp(int socket_fd, bool success, bool restored)
return send_criu_msg(socket_fd, &msg);
}
static int send_criu_pre_dump_resp(int socket_fd, bool success)
static int send_criu_pre_dump_resp(int socket_fd, bool success, bool single)
{
CriuResp msg = CRIU_RESP__INIT;
msg.type = CRIU_REQ_TYPE__PRE_DUMP;
msg.type = single ? CRIU_REQ_TYPE__SINGLE_PRE_DUMP : CRIU_REQ_TYPE__PRE_DUMP;
msg.success = success;
set_resp_err(&msg);
@ -845,7 +845,7 @@ out:
return send_criu_msg(sk, &resp);
}
static int pre_dump_using_req(int sk, CriuOpts *req)
static int pre_dump_using_req(int sk, CriuOpts *req, bool single)
{
int pid, status;
bool success = false;
@ -886,7 +886,7 @@ static int pre_dump_using_req(int sk, CriuOpts *req)
success = true;
out:
if (send_criu_pre_dump_resp(sk, success) == -1) {
if (send_criu_pre_dump_resp(sk, success, single) == -1) {
pr_perror("Can't send pre-dump resp");
success = false;
}
@ -899,7 +899,7 @@ static int pre_dump_loop(int sk, CriuReq *msg)
int ret;
do {
ret = pre_dump_using_req(sk, msg->opts);
ret = pre_dump_using_req(sk, msg->opts, false);
if (ret < 0)
return ret;
@ -1271,6 +1271,9 @@ more:
case CRIU_REQ_TYPE__VERSION:
ret = handle_version(sk, msg);
break;
case CRIU_REQ_TYPE__SINGLE_PRE_DUMP:
ret = pre_dump_using_req(sk, msg->opts, true);
break;
default:
send_criu_err(sk, "Invalid req");

2
images/rpc.proto
View File

@ -172,6 +172,8 @@ enum criu_req_type {
WAIT_PID = 11;
PAGE_SERVER_CHLD = 12;
SINGLE_PRE_DUMP = 13;
}
/*

21
lib/c/criu.c
View File

@ -1527,7 +1527,7 @@ int criu_check(void)
return criu_local_check(global_opts);
}
int criu_local_dump(criu_opts *opts)
static int dump(bool pre_dump, criu_opts *opts)
{
int ret = -1;
CriuReq req = CRIU_REQ__INIT;
@ -1535,7 +1535,7 @@ int criu_local_dump(criu_opts *opts)
saved_errno = 0;
req.type = CRIU_REQ_TYPE__DUMP;
req.type = pre_dump ? CRIU_REQ_TYPE__SINGLE_PRE_DUMP : CRIU_REQ_TYPE__DUMP;
req.opts = opts->rpc;
ret = send_req_and_recv_resp(opts, &req, &resp);
@ -1543,7 +1543,7 @@ int criu_local_dump(criu_opts *opts)
goto exit;
if (resp->success) {
if (resp->dump->has_restored && resp->dump->restored)
if (!pre_dump && resp->dump->has_restored && resp->dump->restored)
ret = 1;
else
ret = 0;
@ -1561,11 +1561,26 @@ exit:
return ret;
}
int criu_local_dump(criu_opts *opts)
{
return dump(false, opts);
}
int criu_dump(void)
{
return criu_local_dump(global_opts);
}
int criu_local_pre_dump(criu_opts *opts)
{
return dump(true, opts);
}
int criu_pre_dump(void)
{
return criu_local_pre_dump(global_opts);
}
int criu_local_dump_iters(criu_opts *opts, int (*more)(criu_predump_info pi))
{
int ret = -1, fd = -1, uret;

2
lib/c/criu.h
View File

@ -161,6 +161,7 @@ int criu_get_orphan_pts_master_fd(void);
*/
int criu_check(void);
int criu_dump(void);
int criu_pre_dump(void);
int criu_restore(void);
int criu_restore_child(void);
@ -279,6 +280,7 @@ void criu_local_set_notify_cb(criu_opts *opts, int (*cb)(char *action, criu_noti
int criu_local_check(criu_opts *opts);
int criu_local_dump(criu_opts *opts);
int criu_local_pre_dump(criu_opts *opts);
int criu_local_restore(criu_opts *opts);
int criu_local_restore_child(criu_opts *opts);
int criu_local_dump_iters(criu_opts *opts, int (*more)(criu_predump_info pi));