[CRIU] [PATCH 1/2] ipc/sysctl: c/r fs.mqueue.msg_default fs.mqueue.msgsize_default

[Pavel Tikhomirov]

we already have 3/5 fs.mqueue.xxx sysctls so why not have all:

/proc/sys/fs/mqueue/msg_default is  a read/write  file for
setting/getting the default number of messages in a queue value
if attr parameter of mq_open(2) is NULL. If it exceed msg_max,
the default value is initialized msg_max.

/proc/sys/fs/mqueue/msgsize_default is a read/write file for
setting/getting the default message size value if attr parameter
of mq_open(2) is NULL. If it exceed msgsize_max, the default
value is initialized msgsize_max.

*We have these sysctls writable in VZ7 CT.
https://jira.sw.ru/browse/PSBM-48397

Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
 criu/ipc_ns.c        | 13 ++++++++++++-
 images/ipc-var.proto |  2 ++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/criu/ipc_ns.c b/criu/ipc_ns.c
index 19dfb72..002b39a 100644
--- a/criu/ipc_ns.c
+++ b/criu/ipc_ns.c
@@ -309,6 +309,8 @@ static int ipc_sysctl_req(IpcVarEntry *e, int op)
 		{ "fs/mqueue/queues_max",	&e->mq_queues_max,	CTL_U32 },
 		{ "fs/mqueue/msg_max",		&e->mq_msg_max,		CTL_U32 },
 		{ "fs/mqueue/msgsize_max",	&e->mq_msgsize_max,	CTL_U32 },
+		{ "fs/mqueue/msg_default",	&e->mq_msg_default,	CTL_U32 },
+		{ "fs/mqueue/msgsize_default",	&e->mq_msgsize_default,	CTL_U32 },
 	};
 
 	int ret;
@@ -322,7 +324,14 @@ static int ipc_sysctl_req(IpcVarEntry *e, int op)
 		return 0;
 	}
 
-	return sysctl_op(req_mq, ARRAY_SIZE(req_mq), op, CLONE_NEWIPC);
+	if (access("/proc/sys/fs/mqueue/msg_default", F_OK)) {
+		/* In case the kernel is < v3.5 */
+		pr_info("Mqueue msg_default and msgsize_default sysctls are missing\n");
+		e->has_mq_msg_default = e->has_mq_msgsize_default = false;
+	}
+
+	return sysctl_op(req_mq, ARRAY_SIZE(req_mq) - (e->has_mq_msg_default ? 0 : 2),
+	                 op, CLONE_NEWIPC);
 }
 
 /*
@@ -416,6 +425,8 @@ static int dump_ipc_var(struct cr_img *img)
 	var.sem_ctls	= xmalloc(pb_repeated_size(&var, sem_ctls));
 	if (!var.sem_ctls)
 		goto err;
+	var.has_mq_msg_default = true;
+	var.has_mq_msgsize_default = true;
 
 	ret = ipc_sysctl_req(&var, CTL_READ);
 	if (ret < 0) {
diff --git a/images/ipc-var.proto b/images/ipc-var.proto
index 4acda69..153b167 100644
--- a/images/ipc-var.proto
+++ b/images/ipc-var.proto
@@ -11,4 +11,6 @@ message ipc_var_entry {
 	required uint32			mq_queues_max		= 10;
 	required uint32			mq_msg_max		= 11;
 	required uint32			mq_msgsize_max		= 12;
+	optional uint32			mq_msg_default		= 13;
+	optional uint32			mq_msgsize_default	= 14;
 }
-- 
2.5.5