ipc: re-enable msgmni automatic recomputing msgmni if set to negative
The enhancement as asked for by Yasunori: if msgmni is set to a negative
value, register it back into the ipcns notifier chain.
A new interface has been added to the notification mechanism:
notifier_chain_cond_register() registers a notifier block only if not already
registered. With that new interface we avoid taking care of the states
changes in procfs.
Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Mingming Cao <cmm@us.ibm.com>
Cc: Pierre Peiffer <pierre.peiffer@bull.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index c3b1da9..ea6c18a 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -52,6 +52,7 @@
#define INIT_IPC_NS(ns) .ns = &init_ipc_ns,
extern int register_ipcns_notifier(struct ipc_namespace *);
+extern int cond_register_ipcns_notifier(struct ipc_namespace *);
extern int unregister_ipcns_notifier(struct ipc_namespace *);
extern int ipcns_notify(unsigned long);
diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index 20dfed5..0ff6224 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -121,6 +121,10 @@
extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
struct notifier_block *nb);
+extern int blocking_notifier_chain_cond_register(
+ struct blocking_notifier_head *nh,
+ struct notifier_block *nb);
+
extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
struct notifier_block *nb);
extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index d12ff5c..d349746 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -15,6 +15,8 @@
#include <linux/sysctl.h>
#include <linux/uaccess.h>
#include <linux/ipc_namespace.h>
+#include <linux/msg.h>
+#include "util.h"
static void *get_ipc(ctl_table *table)
{
@@ -24,6 +26,27 @@
return which;
}
+/*
+ * Routine that is called when a tunable has successfully been changed by
+ * hand and it has a callback routine registered on the ipc namespace notifier
+ * chain: we don't want such tunables to be recomputed anymore upon memory
+ * add/remove or ipc namespace creation/removal.
+ * They can come back to a recomputable state by being set to a <0 value.
+ */
+static void tunable_set_callback(int val)
+{
+ if (val >= 0)
+ unregister_ipcns_notifier(current->nsproxy->ipc_ns);
+ else {
+ /*
+ * Re-enable automatic recomputing only if not already
+ * enabled.
+ */
+ recompute_msgmni(current->nsproxy->ipc_ns);
+ cond_register_ipcns_notifier(current->nsproxy->ipc_ns);
+ }
+}
+
#ifdef CONFIG_PROC_FS
static int proc_ipc_dointvec(ctl_table *table, int write, struct file *filp,
void __user *buffer, size_t *lenp, loff_t *ppos)
@@ -38,17 +61,17 @@
static int proc_ipc_callback_dointvec(ctl_table *table, int write,
struct file *filp, void __user *buffer, size_t *lenp, loff_t *ppos)
{
+ struct ctl_table ipc_table;
size_t lenp_bef = *lenp;
int rc;
- rc = proc_ipc_dointvec(table, write, filp, buffer, lenp, ppos);
+ memcpy(&ipc_table, table, sizeof(ipc_table));
+ ipc_table.data = get_ipc(table);
+
+ rc = proc_dointvec(&ipc_table, write, filp, buffer, lenp, ppos);
if (write && !rc && lenp_bef == *lenp)
- /*
- * Tunable has successfully been changed from userland:
- * disable its automatic recomputing.
- */
- unregister_ipcns_notifier(current->nsproxy->ipc_ns);
+ tunable_set_callback(*((int *)(ipc_table.data)));
return rc;
}
@@ -119,12 +142,14 @@
rc = sysctl_ipc_data(table, name, nlen, oldval, oldlenp, newval,
newlen);
- if (newval && newlen && rc > 0)
+ if (newval && newlen && rc > 0) {
/*
- * Tunable has successfully been changed from userland:
- * disable its automatic recomputing.
+ * Tunable has successfully been changed from userland
*/
- unregister_ipcns_notifier(current->nsproxy->ipc_ns);
+ int *data = get_ipc(table);
+
+ tunable_set_callback(*data);
+ }
return rc;
}
diff --git a/ipc/ipcns_notifier.c b/ipc/ipcns_notifier.c
index c797460..70ff091 100644
--- a/ipc/ipcns_notifier.c
+++ b/ipc/ipcns_notifier.c
@@ -61,6 +61,15 @@
return blocking_notifier_chain_register(&ipcns_chain, &ns->ipcns_nb);
}
+int cond_register_ipcns_notifier(struct ipc_namespace *ns)
+{
+ memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
+ ns->ipcns_nb.notifier_call = ipcns_callback;
+ ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
+ return blocking_notifier_chain_cond_register(&ipcns_chain,
+ &ns->ipcns_nb);
+}
+
int unregister_ipcns_notifier(struct ipc_namespace *ns)
{
return blocking_notifier_chain_unregister(&ipcns_chain,
diff --git a/kernel/notifier.c b/kernel/notifier.c
index 643360d..823be115 100644
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -31,6 +31,21 @@
return 0;
}
+static int notifier_chain_cond_register(struct notifier_block **nl,
+ struct notifier_block *n)
+{
+ while ((*nl) != NULL) {
+ if ((*nl) == n)
+ return 0;
+ if (n->priority > (*nl)->priority)
+ break;
+ nl = &((*nl)->next);
+ }
+ n->next = *nl;
+ rcu_assign_pointer(*nl, n);
+ return 0;
+}
+
static int notifier_chain_unregister(struct notifier_block **nl,
struct notifier_block *n)
{
@@ -205,6 +220,29 @@
EXPORT_SYMBOL_GPL(blocking_notifier_chain_register);
/**
+ * blocking_notifier_chain_cond_register - Cond add notifier to a blocking notifier chain
+ * @nh: Pointer to head of the blocking notifier chain
+ * @n: New entry in notifier chain
+ *
+ * Adds a notifier to a blocking notifier chain, only if not already
+ * present in the chain.
+ * Must be called in process context.
+ *
+ * Currently always returns zero.
+ */
+int blocking_notifier_chain_cond_register(struct blocking_notifier_head *nh,
+ struct notifier_block *n)
+{
+ int ret;
+
+ down_write(&nh->rwsem);
+ ret = notifier_chain_cond_register(&nh->head, n);
+ up_write(&nh->rwsem);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(blocking_notifier_chain_cond_register);
+
+/**
* blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain
* @nh: Pointer to head of the blocking notifier chain
* @n: Entry to remove from notifier chain