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ipc/msg: increase MSGMNI, remove scaling

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SysV can be abused to allocate locked kernel memory.  For most systems, a
small limit doesn't make sense, see the discussion with regards to SHMMAX.

Therefore: increase MSGMNI to the maximum supported.

And: If we ignore the risk of locking too much memory, then an automatic
scaling of MSGMNI doesn't make sense.  Therefore the logic can be removed.

The code preserves auto_msgmni to avoid breaking any user space applications
that expect that the value exists.

Notes:
1) If an administrator must limit the memory allocations, then he can set
MSGMNI as necessary.

Or he can disable sysv entirely (as e.g. done by Android).

2) MSGMAX and MSGMNB are intentionally not increased, as these values are used
to control latency vs. throughput:
If MSGMNB is large, then msgsnd() just returns and more messages can be queued
before a task switch to a task that calls msgrcv() is forced.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Rafael Aquini <aquini@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Manfred Spraul 2014-12-12 16:58:17 -08:00 • committed by Linus Torvalds
commit 0050ee059f
9 changed files with 45 additions and 298 deletions
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20
include/linux/ipc_namespace.h
View file

@ -7,15 +7,6 @@
#include <linux/notifier.h>
#include <linux/nsproxy.h>
/*
* ipc namespace events
*/
#define IPCNS_MEMCHANGED 0x00000001 /* Notify lowmem size changed */
#define IPCNS_CREATED 0x00000002 /* Notify new ipc namespace created */
#define IPCNS_REMOVED 0x00000003 /* Notify ipc namespace removed */
#define IPCNS_CALLBACK_PRI 0
struct user_namespace;
struct ipc_ids {
@ -38,7 +29,6 @@ struct ipc_namespace {
unsigned int msg_ctlmni;
atomic_t msg_bytes;
atomic_t msg_hdrs;
int auto_msgmni;
size_t shm_ctlmax;
size_t shm_ctlall;
@ -77,18 +67,8 @@ extern atomic_t nr_ipc_ns;
extern spinlock_t mq_lock;
#ifdef CONFIG_SYSVIPC
extern int register_ipcns_notifier(struct ipc_namespace *);
extern int cond_register_ipcns_notifier(struct ipc_namespace *);
extern void unregister_ipcns_notifier(struct ipc_namespace *);
extern int ipcns_notify(unsigned long);
extern void shm_destroy_orphaned(struct ipc_namespace *ns);
#else /* CONFIG_SYSVIPC */
static inline int register_ipcns_notifier(struct ipc_namespace *ns)
{ return 0; }
static inline int cond_register_ipcns_notifier(struct ipc_namespace *ns)
{ return 0; }
static inline void unregister_ipcns_notifier(struct ipc_namespace *ns) { }
static inline int ipcns_notify(unsigned long l) { return 0; }
static inline void shm_destroy_orphaned(struct ipc_namespace *ns) {}
#endif /* CONFIG_SYSVIPC */