Cedric Le Goater wrote:
> Pierre Peiffer wrote:
>> Each ipc_namespace contains a table of 3 pointers to struct ipc_ids (3 for
>> msg, sem and shm, structure used to store all ipcs)
>> These 'struct ipc_ids' are dynamically allocated for each icp_namespace as
>> the ipc_namespace itself (for the init namespace, they are initialized with
>> pointers to static variables instead)
>>
>> It is so for historical reason: in fact, before the use of idr to store the
>> ipcs, the ipcs were stored in tables of variable length, depending of the
>> maximum number of ipc allowed.
>> Now, these 'struct ipc_ids' have a fixed size. As they are allocated in any
>> cases for each new ipc_namespace, there is no gain of memory in having them
>> allocated separately of the struct ipc_namespace.
>>
>> This patch proposes to make this table static in the struct ipc_namespace.
>> Thus, we can allocate all in once and get rid of all the code needed to
>> allocate and free these ipc_ids separately.
> 
> It looks safe and saves quite a lot of line.
> 
> Pavel, what do you think of it ? 

Looks sane, good catch, Pierre.

But I'd find out whether these three ipc_ids intersect any 
cache-line. In other words I'd mark the struct ipc_ids as
____cacheline_aligned and checked for any differences.

> Acked-by: Cedric Le Goater <clg@fr.ibm.com>
> 
> Thanks,

Thanks,
Pavel

> C.
> 
> 
>> Signed-off-by: Pierre Peiffer <pierre.peiffer@bull.net>
>> ---
>>  include/linux/ipc_namespace.h |   13 +++++++++++--
>>  ipc/msg.c                     |   26 ++++----------------------
>>  ipc/namespace.c               |   25 ++++---------------------
>>  ipc/sem.c                     |   26 ++++----------------------
>>  ipc/shm.c                     |   26 ++++----------------------
>>  ipc/util.c                    |    6 +++---
>>  ipc/util.h                    |   16 ++++------------
>>  7 files changed, 34 insertions(+), 104 deletions(-)
>>
>> Index: b/include/linux/ipc_namespace.h
>> ===================================================================
>> --- a/include/linux/ipc_namespace.h
>> +++ b/include/linux/ipc_namespace.h
>> @@ -2,11 +2,20 @@
>>  #define __IPC_NAMESPACE_H__
>>  
>>  #include <linux/err.h>
>> +#include <linux/idr.h>
>> +#include <linux/rwsem.h>
>> +
>> +struct ipc_ids {
>> +	int in_use;
>> +	unsigned short seq;
>> +	unsigned short seq_max;
>> +	struct rw_semaphore rw_mutex;
>> +	struct idr ipcs_idr;
>> +};
>>  
>> -struct ipc_ids;
>>  struct ipc_namespace {
>>  	struct kref	kref;
>> -	struct ipc_ids	*ids[3];
>> +	struct ipc_ids	ids[3];
>>  
>>  	int		sem_ctls[4];
>>  	int		used_sems;
>> Index: b/ipc/msg.c
>> ===================================================================
>> --- a/ipc/msg.c
>> +++ b/ipc/msg.c
>> @@ -67,9 +67,7 @@ struct msg_sender {
>>  #define SEARCH_NOTEQUAL		3
>>  #define SEARCH_LESSEQUAL	4
>>  
>> -static struct ipc_ids init_msg_ids;
>> -
>> -#define msg_ids(ns)	(*((ns)->ids[IPC_MSG_IDS]))
>> +#define msg_ids(ns)	((ns)->ids[IPC_MSG_IDS])
>>  
>>  #define msg_unlock(msq)		ipc_unlock(&(msq)->q_perm)
>>  #define msg_buildid(id, seq)	ipc_buildid(id, seq)
>> @@ -80,30 +78,17 @@ static int newque(struct ipc_namespace *
>>  static int sysvipc_msg_proc_show(struct seq_file *s, void *it);
>>  #endif
>>  
>> -static void __msg_init_ns(struct ipc_namespace *ns, struct ipc_ids *ids)
>> +void msg_init_ns(struct ipc_namespace *ns)
>>  {
>> -	ns->ids[IPC_MSG_IDS] = ids;
>>  	ns->msg_ctlmax = MSGMAX;
>>  	ns->msg_ctlmnb = MSGMNB;
>>  	ns->msg_ctlmni = MSGMNI;
>>  	atomic_set(&ns->msg_bytes, 0);
>>  	atomic_set(&ns->msg_hdrs, 0);
>> -	ipc_init_ids(ids);
>> +	ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
>>  }
>>  
>>  #ifdef CONFIG_IPC_NS
>> -int msg_init_ns(struct ipc_namespace *ns)
>> -{
>> -	struct ipc_ids *ids;
>> -
>> -	ids = kmalloc(sizeof(struct ipc_ids), GFP_KERNEL);
>> -	if (ids == NULL)
>> -		return -ENOMEM;
>> -
>> -	__msg_init_ns(ns, ids);
>> -	return 0;
>> -}
>> -
>>  void msg_exit_ns(struct ipc_namespace *ns)
>>  {
>>  	struct msg_queue *msq;
>> @@ -126,15 +111,12 @@ void msg_exit_ns(struct ipc_namespace *n
>>  	}
>>  
>>  	up_write(&msg_ids(ns).rw_mutex);
>> -
>> -	kfree(ns->ids[IPC_MSG_IDS]);
>> -	ns->ids[IPC_MSG_IDS] = NULL;
>>  }
>>  #endif
>>  
>>  void __init msg_init(void)
>>  {
>> -	__msg_init_ns(&init_ipc_ns, &init_msg_ids);
>> +	msg_init_ns(&init_ipc_ns);
>>  	ipc_init_proc_interface("sysvipc/msg",
>>  				"       key      msqid perms      cbytes       qnum lspid lrpid   uid   gid  cuid  cgid      stime      rtime      ctime\n",
>>  				IPC_MSG_IDS, sysvipc_msg_proc_show);
>> Index: b/ipc/namespace.c
>> ===================================================================
>> --- a/ipc/namespace.c
>> +++ b/ipc/namespace.c
>> @@ -14,35 +14,18 @@
>>  
>>  static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
>>  {
>> -	int err;
>>  	struct ipc_namespace *ns;
>>  
>> -	err = -ENOMEM;
>>  	ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
>>  	if (ns == NULL)
>> -		goto err_mem;
>> +		return ERR_PTR(-ENOMEM);
>>  
>> -	err = sem_init_ns(ns);
>> -	if (err)
>> -		goto err_sem;
>> -	err = msg_init_ns(ns);
>> -	if (err)
>> -		goto err_msg;
>> -	err = shm_init_ns(ns);
>> -	if (err)
>> -		goto err_shm;
>> +	sem_init_ns(ns);
>> +	msg_init_ns(ns);
>> +	shm_init_ns(ns);
>>  
>>  	kref_init(&ns->kref);
>>  	return ns;
>> -
>> -err_shm:
>> -	msg_exit_ns(ns);
>> -err_msg:
>> -	sem_exit_ns(ns);
>> -err_sem:
>> -	kfree(ns);
>> -err_mem:
>> -	return ERR_PTR(err);
>>  }
>>  
>>  struct ipc_namespace *copy_ipcs(unsigned long flags, struct ipc_namespace *ns)
>> Index: b/ipc/sem.c
>> ===================================================================
>> --- a/ipc/sem.c
>> +++ b/ipc/sem.c
>> @@ -87,14 +87,12 @@
>>  #include <asm/uaccess.h>
>>  #include "util.h"
>>  
>> -#define sem_ids(ns)	(*((ns)->ids[IPC_SEM_IDS]))
>> +#define sem_ids(ns)	((ns)->ids[IPC_SEM_IDS])
>>  
>>  #define sem_unlock(sma)		ipc_unlock(&(sma)->sem_perm)
>>  #define sem_checkid(sma, semid)	ipc_checkid(&sma->sem_perm, semid)
>>  #define sem_buildid(id, seq)	ipc_buildid(id, seq)
>>  
>> -static struct ipc_ids init_sem_ids;
>> -
>>  static int newary(struct ipc_namespace *, struct ipc_params *);
>>  static void freeary(struct ipc_namespace *, struct sem_array *);
>>  #ifdef CONFIG_PROC_FS
>> @@ -118,30 +116,17 @@ static int sysvipc_sem_proc_show(struct 
>>  #define sc_semopm	sem_ctls[2]
>>  #define sc_semmni	sem_ctls[3]
>>  
>> -static void __sem_init_ns(struct ipc_namespace *ns, struct ipc_ids *ids)
>> +void sem_init_ns(struct ipc_namespace *ns)
>>  {
>> -	ns->ids[IPC_SEM_IDS] = ids;
>>  	ns->sc_semmsl = SEMMSL;
>>  	ns->sc_semmns = SEMMNS;
>>  	ns->sc_semopm = SEMOPM;
>>  	ns->sc_semmni = SEMMNI;
>>  	ns->used_sems = 0;
>> -	ipc_init_ids(ids);
>> +	ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
>>  }
>>  
>>  #ifdef CONFIG_IPC_NS
>> -int sem_init_ns(struct ipc_namespace *ns)
>> -{
>> -	struct ipc_ids *ids;
>> -
>> -	ids = kmalloc(sizeof(struct ipc_ids), GFP_KERNEL);
>> -	if (ids == NULL)
>> -		return -ENOMEM;
>> -
>> -	__sem_init_ns(ns, ids);
>> -	return 0;
>> -}
>> -
>>  void sem_exit_ns(struct ipc_namespace *ns)
>>  {
>>  	struct sem_array *sma;
>> @@ -163,15 +148,12 @@ void sem_exit_ns(struct ipc_namespace *n
>>  		total++;
>>  	}
>>  	up_write(&sem_ids(ns).rw_mutex);
>> -
>> -	kfree(ns->ids[IPC_SEM_IDS]);
>> -	ns->ids[IPC_SEM_IDS] = NULL;
>>  }
>>  #endif
>>  
>>  void __init sem_init (void)
>>  {
>> -	__sem_init_ns(&init_ipc_ns, &init_sem_ids);
>> +	sem_init_ns(&init_ipc_ns);
>>  	ipc_init_proc_interface("sysvipc/sem",
>>  				"       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n",
>>  				IPC_SEM_IDS, sysvipc_sem_proc_show);
>> Index: b/ipc/util.c
>> ===================================================================
>> --- a/ipc/util.c
>> +++ b/ipc/util.c
>> @@ -782,7 +782,7 @@ static void *sysvipc_proc_next(struct se
>>  	if (ipc && ipc != SEQ_START_TOKEN)
>>  		ipc_unlock(ipc);
>>  
>> -	return sysvipc_find_ipc(iter->ns->ids[iface->ids], *pos, pos);
>> +	return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
>>  }
>>  
>>  /*
>> @@ -795,7 +795,7 @@ static void *sysvipc_proc_start(struct s
>>  	struct ipc_proc_iface *iface = iter->iface;
>>  	struct ip