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9eefe520c8
This patch proposes an alternative to the "magical positive-versus-negative number trick" Andrew complained about last week in http://lkml.org/lkml/2008/6/24/418. This had been introduced with the patches that scale msgmni to the amount of lowmem. With these patches, msgmni has a registered notification routine that recomputes msgmni value upon memory add/remove or ipc namespace creation/ removal. When msgmni is changed from user space (i.e. value written to the proc file), that notification routine is unregistered, and the way to make it registered back is to write a negative value into the proc file. This is the "magical positive-versus-negative number trick". To fix this, a new proc file is introduced: /proc/sys/kernel/auto_msgmni. This file acts as ON/OFF for msgmni automatic recomputing. With this patch, the process is the following: 1) kernel boots in "automatic recomputing mode" /proc/sys/kernel/msgmni contains the value that has been computed (depends on lowmem) /proc/sys/kernel/automatic_msgmni contains "1" 2) echo <val> > /proc/sys/kernel/msgmni . sets msg_ctlmni to <val> . de-activates automatic recomputing (i.e. if, say, some memory is added msgmni won't be recomputed anymore) . /proc/sys/kernel/automatic_msgmni now contains "0" 3) echo "0" > /proc/sys/kernel/automatic_msgmni . de-activates msgmni automatic recomputing this has the same effect as 2) except that msg_ctlmni's value stays blocked at its current value) 3) echo "1" > /proc/sys/kernel/automatic_msgmni . recomputes msgmni's value based on the current available memory size and number of ipc namespaces . re-activates automatic recomputing for msgmni. Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net> Cc: Solofo Ramangalahy <Solofo.Ramangalahy@bull.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
102 lines
2.2 KiB
C
102 lines
2.2 KiB
C
#ifndef __IPC_NAMESPACE_H__
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#define __IPC_NAMESPACE_H__
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#include <linux/err.h>
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#include <linux/idr.h>
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#include <linux/rwsem.h>
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#include <linux/notifier.h>
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/*
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* ipc namespace events
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*/
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#define IPCNS_MEMCHANGED 0x00000001 /* Notify lowmem size changed */
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#define IPCNS_CREATED 0x00000002 /* Notify new ipc namespace created */
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#define IPCNS_REMOVED 0x00000003 /* Notify ipc namespace removed */
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#define IPCNS_CALLBACK_PRI 0
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struct ipc_ids {
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int in_use;
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unsigned short seq;
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unsigned short seq_max;
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struct rw_semaphore rw_mutex;
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struct idr ipcs_idr;
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};
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struct ipc_namespace {
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struct kref kref;
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struct ipc_ids ids[3];
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int sem_ctls[4];
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int used_sems;
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int msg_ctlmax;
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int msg_ctlmnb;
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int msg_ctlmni;
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atomic_t msg_bytes;
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atomic_t msg_hdrs;
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int auto_msgmni;
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size_t shm_ctlmax;
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size_t shm_ctlall;
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int shm_ctlmni;
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int shm_tot;
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struct notifier_block ipcns_nb;
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};
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extern struct ipc_namespace init_ipc_ns;
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extern atomic_t nr_ipc_ns;
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#ifdef CONFIG_SYSVIPC
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#define INIT_IPC_NS(ns) .ns = &init_ipc_ns,
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extern int register_ipcns_notifier(struct ipc_namespace *);
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extern int cond_register_ipcns_notifier(struct ipc_namespace *);
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extern void unregister_ipcns_notifier(struct ipc_namespace *);
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extern int ipcns_notify(unsigned long);
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#else /* CONFIG_SYSVIPC */
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#define INIT_IPC_NS(ns)
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#endif /* CONFIG_SYSVIPC */
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#if defined(CONFIG_SYSVIPC) && defined(CONFIG_IPC_NS)
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extern void free_ipc_ns(struct kref *kref);
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extern struct ipc_namespace *copy_ipcs(unsigned long flags,
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struct ipc_namespace *ns);
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extern void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
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void (*free)(struct ipc_namespace *,
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struct kern_ipc_perm *));
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static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
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{
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if (ns)
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kref_get(&ns->kref);
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return ns;
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}
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static inline void put_ipc_ns(struct ipc_namespace *ns)
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{
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kref_put(&ns->kref, free_ipc_ns);
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}
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#else
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static inline struct ipc_namespace *copy_ipcs(unsigned long flags,
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struct ipc_namespace *ns)
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{
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if (flags & CLONE_NEWIPC)
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return ERR_PTR(-EINVAL);
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return ns;
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}
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static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
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{
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return ns;
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}
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static inline void put_ipc_ns(struct ipc_namespace *ns)
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{
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}
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#endif
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#endif
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