Merge branch 'akpm' (patches from Andrew)

Merge more updates from Andrew Morton:

 - the rest of MM

 - procfs updates

 - various misc things

 - more y2038 fixes

 - get_maintainer updates

 - lib/ updates

 - checkpatch updates

 - various epoll updates

 - autofs updates

 - hfsplus

 - some reiserfs work

 - fatfs updates

 - signal.c cleanups

 - ipc/ updates

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (166 commits)
  ipc/util.c: update return value of ipc_getref from int to bool
  ipc/util.c: further variable name cleanups
  ipc: simplify ipc initialization
  ipc: get rid of ids->tables_initialized hack
  lib/rhashtable: guarantee initial hashtable allocation
  lib/rhashtable: simplify bucket_table_alloc()
  ipc: drop ipc_lock()
  ipc/util.c: correct comment in ipc_obtain_object_check
  ipc: rename ipcctl_pre_down_nolock()
  ipc/util.c: use ipc_rcu_putref() for failues in ipc_addid()
  ipc: reorganize initialization of kern_ipc_perm.seq
  ipc: compute kern_ipc_perm.id under the ipc lock
  init/Kconfig: remove EXPERT from CHECKPOINT_RESTORE
  fs/sysv/inode.c: use ktime_get_real_seconds() for superblock stamp
  adfs: use timespec64 for time conversion
  kernel/sysctl.c: fix typos in comments
  drivers/rapidio/devices/rio_mport_cdev.c: remove redundant pointer md
  fork: don't copy inconsistent signal handler state to child
  signal: make get_signal() return bool
  signal: make sigkill_pending() return bool
  ...

6 files changed, 198 insertions, 210 deletions

diff --git a/ipc/msg.c b/ipc/msg.c
index 203281198079..883642cf2b27 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -163,7 +163,7 @@ static int newque(struct ipc_namespace *ns, struct ipc_params *params)
 	/* ipc_addid() locks msq upon success. */
 	retval = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
 	if (retval < 0) {
-		call_rcu(&msq->q_perm.rcu, msg_rcu_free);
+		ipc_rcu_putref(&msq->q_perm, msg_rcu_free);
 		return retval;
 	}
 
@@ -386,7 +386,7 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
 	down_write(&msg_ids(ns).rwsem);
 	rcu_read_lock();
 
-	ipcp = ipcctl_pre_down_nolock(ns, &msg_ids(ns), msqid, cmd,
+	ipcp = ipcctl_obtain_check(ns, &msg_ids(ns), msqid, cmd,
 				      &msqid64->msg_perm, msqid64->msg_qbytes);
 	if (IS_ERR(ipcp)) {
 		err = PTR_ERR(ipcp);
@@ -456,7 +456,7 @@ static int msgctl_info(struct ipc_namespace *ns, int msqid,
 			 int cmd, struct msginfo *msginfo)
 {
 	int err;
-	int max_id;
+	int max_idx;
 
 	/*
 	 * We must not return kernel stack data.
@@ -483,16 +483,15 @@ static int msgctl_info(struct ipc_namespace *ns, int msqid,
 		msginfo->msgpool = MSGPOOL;
 		msginfo->msgtql = MSGTQL;
 	}
-	max_id = ipc_get_maxid(&msg_ids(ns));
+	max_idx = ipc_get_maxidx(&msg_ids(ns));
 	up_read(&msg_ids(ns).rwsem);
-	return (max_id < 0) ? 0 : max_id;
+	return (max_idx < 0) ? 0 : max_idx;
 }
 
 static int msgctl_stat(struct ipc_namespace *ns, int msqid,
 			 int cmd, struct msqid64_ds *p)
 {
 	struct msg_queue *msq;
-	int id = 0;
 	int err;
 
 	memset(p, 0, sizeof(*p));
@@ -504,7 +503,6 @@ static int msgctl_stat(struct ipc_namespace *ns, int msqid,
 			err = PTR_ERR(msq);
 			goto out_unlock;
 		}
-		id = msq->q_perm.id;
 	} else { /* IPC_STAT */
 		msq = msq_obtain_object_check(ns, msqid);
 		if (IS_ERR(msq)) {
@@ -549,10 +547,21 @@ static int msgctl_stat(struct ipc_namespace *ns, int msqid,
 	p->msg_lspid  = pid_vnr(msq->q_lspid);
 	p->msg_lrpid  = pid_vnr(msq->q_lrpid);
 
-	ipc_unlock_object(&msq->q_perm);
-	rcu_read_unlock();
-	return id;
+	if (cmd == IPC_STAT) {
+		/*
+		 * As defined in SUS:
+		 * Return 0 on success
+		 */
+		err = 0;
+	} else {
+		/*
+		 * MSG_STAT and MSG_STAT_ANY (both Linux specific)
+		 * Return the full id, including the sequence number
+		 */
+		err = msq->q_perm.id;
+	}
 
+	ipc_unlock_object(&msq->q_perm);
 out_unlock:
 	rcu_read_unlock();
 	return err;
@@ -1229,7 +1238,7 @@ COMPAT_SYSCALL_DEFINE5(msgrcv, int, msqid, compat_uptr_t, msgp,
 }
 #endif
 
-int msg_init_ns(struct ipc_namespace *ns)
+void msg_init_ns(struct ipc_namespace *ns)
 {
 	ns->msg_ctlmax = MSGMAX;
 	ns->msg_ctlmnb = MSGMNB;
@@ -1237,7 +1246,7 @@ int msg_init_ns(struct ipc_namespace *ns)
 
 	atomic_set(&ns->msg_bytes, 0);
 	atomic_set(&ns->msg_hdrs, 0);
-	return ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
+	ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
 }
 
 #ifdef CONFIG_IPC_NS
@@ -1278,12 +1287,11 @@ static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
 }
 #endif
 
-int __init msg_init(void)
+void __init msg_init(void)
 {
-	const int err = msg_init_ns(&init_ipc_ns);
+	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);
-	return err;
 }
diff --git a/ipc/namespace.c b/ipc/namespace.c
index f59a89966f92..21607791d62c 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -55,28 +55,16 @@ static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
 	ns->user_ns = get_user_ns(user_ns);
 	ns->ucounts = ucounts;
 
-	err = sem_init_ns(ns);
+	err = mq_init_ns(ns);
 	if (err)
 		goto fail_put;
-	err = msg_init_ns(ns);
-	if (err)
-		goto fail_destroy_sem;
-	err = shm_init_ns(ns);
-	if (err)
-		goto fail_destroy_msg;
 
-	err = mq_init_ns(ns);
-	if (err)
-		goto fail_destroy_shm;
+	sem_init_ns(ns);
+	msg_init_ns(ns);
+	shm_init_ns(ns);
 
 	return ns;
 
-fail_destroy_shm:
-	shm_exit_ns(ns);
-fail_destroy_msg:
-	msg_exit_ns(ns);
-fail_destroy_sem:
-	sem_exit_ns(ns);
 fail_put:
 	put_user_ns(ns->user_ns);
 	ns_free_inum(&ns->ns);
diff --git a/ipc/sem.c b/ipc/sem.c
index 00ef2f743a62..26f8e37fcdcb 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -221,14 +221,14 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
 #define sc_semopm	sem_ctls[2]
 #define sc_semmni	sem_ctls[3]
 
-int sem_init_ns(struct ipc_namespace *ns)
+void sem_init_ns(struct ipc_namespace *ns)
 {
 	ns->sc_semmsl = SEMMSL;
 	ns->sc_semmns = SEMMNS;
 	ns->sc_semopm = SEMOPM;
 	ns->sc_semmni = SEMMNI;
 	ns->used_sems = 0;
-	return ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
+	ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
 }
 
 #ifdef CONFIG_IPC_NS
@@ -240,14 +240,12 @@ void sem_exit_ns(struct ipc_namespace *ns)
 }
 #endif
 
-int __init sem_init(void)
+void __init sem_init(void)
 {
-	const int err = sem_init_ns(&init_ipc_ns);
-
+	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);
-	return err;
 }
 
 /**
@@ -557,7 +555,7 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
 	/* ipc_addid() locks sma upon success. */
 	retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
 	if (retval < 0) {
-		call_rcu(&sma->sem_perm.rcu, sem_rcu_free);
+		ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
 		return retval;
 	}
 	ns->used_sems += nsems;
@@ -1223,7 +1221,6 @@ static int semctl_stat(struct ipc_namespace *ns, int semid,
 {
 	struct sem_array *sma;
 	time64_t semotime;
-	int id = 0;
 	int err;
 
 	memset(semid64, 0, sizeof(*semid64));
@@ -1235,7 +1232,6 @@ static int semctl_stat(struct ipc_namespace *ns, int semid,
 			err = PTR_ERR(sma);
 			goto out_unlock;
 		}
-		id = sma->sem_perm.id;
 	} else { /* IPC_STAT */
 		sma = sem_obtain_object_check(ns, semid);
 		if (IS_ERR(sma)) {
@@ -1275,10 +1271,20 @@ static int semctl_stat(struct ipc_namespace *ns, int semid,
 #endif
 	semid64->sem_nsems = sma->sem_nsems;
 
+	if (cmd == IPC_STAT) {
+		/*
+		 * As defined in SUS:
+		 * Return 0 on success
+		 */
+		err = 0;
+	} else {
+		/*
+		 * SEM_STAT and SEM_STAT_ANY (both Linux specific)
+		 * Return the full id, including the sequence number
+		 */
+		err = sma->sem_perm.id;
+	}
 	ipc_unlock_object(&sma->sem_perm);
-	rcu_read_unlock();
-	return id;
-
 out_unlock:
 	rcu_read_unlock();
 	return err;
@@ -1288,7 +1294,7 @@ static int semctl_info(struct ipc_namespace *ns, int semid,
 			 int cmd, void __user *p)
 {
 	struct seminfo seminfo;
-	int max_id;
+	int max_idx;
 	int err;
 
 	err = security_sem_semctl(NULL, cmd);
@@ -1312,11 +1318,11 @@ static int semctl_info(struct ipc_namespace *ns, int semid,
 		seminfo.semusz = SEMUSZ;
 		seminfo.semaem = SEMAEM;
 	}
-	max_id = ipc_get_maxid(&sem_ids(ns));
+	max_idx = ipc_get_maxidx(&sem_ids(ns));
 	up_read(&sem_ids(ns).rwsem);
 	if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
 		return -EFAULT;
-	return (max_id < 0) ? 0 : max_id;
+	return (max_idx < 0) ? 0 : max_idx;
 }
 
 static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
@@ -1588,7 +1594,7 @@ static int semctl_down(struct ipc_namespace *ns, int semid,
 	down_write(&sem_ids(ns).rwsem);
 	rcu_read_lock();
 
-	ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd,
+	ipcp = ipcctl_obtain_check(ns, &sem_ids(ns), semid, cmd,
 				      &semid64->sem_perm, 0);
 	if (IS_ERR(ipcp)) {
 		err = PTR_ERR(ipcp);
diff --git a/ipc/shm.c b/ipc/shm.c
index b204feb38274..b0eb3757ab89 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -96,14 +96,14 @@ static void shm_destroy(struct ipc_namespace *ns, struct shmid_kernel *shp);
 static int sysvipc_shm_proc_show(struct seq_file *s, void *it);
 #endif
 
-int shm_init_ns(struct ipc_namespace *ns)
+void shm_init_ns(struct ipc_namespace *ns)
 {
 	ns->shm_ctlmax = SHMMAX;
 	ns->shm_ctlall = SHMALL;
 	ns->shm_ctlmni = SHMMNI;
 	ns->shm_rmid_forced = 0;
 	ns->shm_tot = 0;
-	return ipc_init_ids(&shm_ids(ns));
+	ipc_init_ids(&shm_ids(ns));
 }
 
 /*
@@ -136,9 +136,8 @@ void shm_exit_ns(struct ipc_namespace *ns)
 
 static int __init ipc_ns_init(void)
 {
-	const int err = shm_init_ns(&init_ipc_ns);
-	WARN(err, "ipc: sysv shm_init_ns failed: %d\n", err);
-	return err;
+	shm_init_ns(&init_ipc_ns);
+	return 0;
 }
 
 pure_initcall(ipc_ns_init);
@@ -180,16 +179,33 @@ static inline struct shmid_kernel *shm_obtain_object_check(struct ipc_namespace
  */
 static inline struct shmid_kernel *shm_lock(struct ipc_namespace *ns, int id)
 {
-	struct kern_ipc_perm *ipcp = ipc_lock(&shm_ids(ns), id);
+	struct kern_ipc_perm *ipcp;
+
+	rcu_read_lock();
+	ipcp = ipc_obtain_object_idr(&shm_ids(ns), id);
+	if (IS_ERR(ipcp))
+		goto err;
 
+	ipc_lock_object(ipcp);
+	/*
+	 * ipc_rmid() may have already freed the ID while ipc_lock_object()
+	 * was spinning: here verify that the structure is still valid.
+	 * Upon races with RMID, return -EIDRM, thus indicating that
+	 * the ID points to a removed identifier.
+	 */
+	if (ipc_valid_object(ipcp)) {
+		/* return a locked ipc object upon success */
+		return container_of(ipcp, struct shmid_kernel, shm_perm);
+	}
+
+	ipc_unlock_object(ipcp);
+err:
+	rcu_read_unlock();
 	/*
 	 * Callers of shm_lock() must validate the status of the returned ipc
-	 * object pointer (as returned by ipc_lock()), and error out as
-	 * appropriate.
+	 * object pointer and error out as appropriate.
 	 */
-	if (IS_ERR(ipcp))
-		return (void *)ipcp;
-	return container_of(ipcp, struct shmid_kernel, shm_perm);
+	return (void *)ipcp;
 }
 
 static inline void shm_lock_by_ptr(struct shmid_kernel *ipcp)
@@ -684,6 +700,8 @@ no_id:
 	if (is_file_hugepages(file) && shp->mlock_user)
 		user_shm_unlock(size, shp->mlock_user);
 	fput(file);
+	ipc_rcu_putref(&shp->shm_perm, shm_rcu_free);
+	return error;
 no_file:
 	call_rcu(&shp->shm_perm.rcu, shm_rcu_free);
 	return error;
@@ -879,7 +897,7 @@ static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd,
 	down_write(&shm_ids(ns).rwsem);
 	rcu_read_lock();
 
-	ipcp = ipcctl_pre_down_nolock(ns, &shm_ids(ns), shmid, cmd,
+	ipcp = ipcctl_obtain_check(ns, &shm_ids(ns), shmid, cmd,
 				      &shmid64->shm_perm, 0);
 	if (IS_ERR(ipcp)) {
 		err = PTR_ERR(ipcp);
@@ -930,7 +948,7 @@ static int shmctl_ipc_info(struct ipc_namespace *ns,
 		shminfo->shmall = ns->shm_ctlall;
 		shminfo->shmmin = SHMMIN;
 		down_read(&shm_ids(ns).rwsem);
-		err = ipc_get_maxid(&shm_ids(ns));
+		err = ipc_get_maxidx(&shm_ids(ns));
 		up_read(&shm_ids(ns).rwsem);
 		if (err < 0)
 			err = 0;
@@ -950,7 +968,7 @@ static int shmctl_shm_info(struct ipc_namespace *ns,
 		shm_info->shm_tot = ns->shm_tot;
 		shm_info->swap_attempts = 0;
 		shm_info->swap_successes = 0;
-		err = ipc_get_maxid(&shm_ids(ns));
+		err = ipc_get_maxidx(&shm_ids(ns));
 		up_read(&shm_ids(ns).rwsem);
 		if (err < 0)
 			err = 0;
@@ -962,7 +980,6 @@ static int shmctl_stat(struct ipc_namespace *ns, int shmid,
 			int cmd, struct shmid64_ds *tbuf)
 {
 	struct shmid_kernel *shp;
-	int id = 0;
 	int err;
 
 	memset(tbuf, 0, sizeof(*tbuf));
@@ -974,7 +991,6 @@ static int shmctl_stat(struct ipc_namespace *ns, int shmid,
 			err = PTR_ERR(shp);
 			goto out_unlock;
 		}
-		id = shp->shm_perm.id;
 	} else { /* IPC_STAT */
 		shp = shm_obtain_object_check(ns, shmid);
 		if (IS_ERR(shp)) {
@@ -1024,10 +1040,21 @@ static int shmctl_stat(struct ipc_namespace *ns, int shmid,
 	tbuf->shm_lpid	= pid_vnr(shp->shm_lprid);
 	tbuf->shm_nattch = shp->shm_nattch;
 
-	ipc_unlock_object(&shp->shm_perm);
-	rcu_read_unlock();
-	return id;
+	if (cmd == IPC_STAT) {
+		/*
+		 * As defined in SUS:
+		 * Return 0 on success
+		 */
+		err = 0;
+	} else {
+		/*
+		 * SHM_STAT and SHM_STAT_ANY (both Linux specific)
+		 * Return the full id, including the sequence number
+		 */
+		err = shp->shm_perm.id;
+	}
 
+	ipc_unlock_object(&shp->shm_perm);
 out_unlock:
 	rcu_read_unlock();
 	return err;
diff --git a/ipc/util.c b/ipc/util.c
index fdffff41f65b..0af05752969f 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -88,16 +88,12 @@ struct ipc_proc_iface {
  */
 static int __init ipc_init(void)
 {
-	int err_sem, err_msg;
-
 	proc_mkdir("sysvipc", NULL);
-	err_sem = sem_init();
-	WARN(err_sem, "ipc: sysv sem_init failed: %d\n", err_sem);
-	err_msg = msg_init();
-	WARN(err_msg, "ipc: sysv msg_init failed: %d\n", err_msg);
+	sem_init();
+	msg_init();
 	shm_init();
 
-	return err_msg ? err_msg : err_sem;
+	return 0;
 }
 device_initcall(ipc_init);
 
@@ -116,22 +112,17 @@ static const struct rhashtable_params ipc_kht_params = {
  * Set up the sequence range to use for the ipc identifier range (limited
  * below IPCMNI) then initialise the keys hashtable and ids idr.
  */
-int ipc_init_ids(struct ipc_ids *ids)
+void ipc_init_ids(struct ipc_ids *ids)
 {
-	int err;
 	ids->in_use = 0;
 	ids->seq = 0;
 	init_rwsem(&ids->rwsem);
-	err = rhashtable_init(&ids->key_ht, &ipc_kht_params);
-	if (err)
-		return err;
+	rhashtable_init(&ids->key_ht, &ipc_kht_params);
 	idr_init(&ids->ipcs_idr);
-	ids->tables_initialized = true;
-	ids->max_id = -1;
+	ids->max_idx = -1;
 #ifdef CONFIG_CHECKPOINT_RESTORE
 	ids->next_id = -1;
 #endif
-	return 0;
 }
 
 #ifdef CONFIG_PROC_FS
@@ -179,61 +170,66 @@ void __init ipc_init_proc_interface(const char *path, const char *header,
  */
 static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
 {
-	struct kern_ipc_perm *ipcp = NULL;
+	struct kern_ipc_perm *ipcp;
 
-	if (likely(ids->tables_initialized))
-		ipcp = rhashtable_lookup_fast(&ids->key_ht, &key,
+	ipcp = rhashtable_lookup_fast(&ids->key_ht, &key,
 					      ipc_kht_params);
+	if (!ipcp)
+		return NULL;
 
-	if (ipcp) {
-		rcu_read_lock();
-		ipc_lock_object(ipcp);
-		return ipcp;
-	}
-
-	return NULL;
+	rcu_read_lock();
+	ipc_lock_object(ipcp);
+	return ipcp;
 }
 
-#ifdef CONFIG_CHECKPOINT_RESTORE
 /*
- * Specify desired id for next allocated IPC object.
+ * Insert new IPC object into idr tree, and set sequence number and id
+ * in the correct order.
+ * Especially:
+ * - the sequence number must be set before inserting the object into the idr,
+ *   because the sequence number is accessed without a lock.
+ * - the id can/must be set after inserting the object into the idr.
+ *   All accesses must be done after getting kern_ipc_perm.lock.
+ *
+ * The caller must own kern_ipc_perm.lock.of the new object.
+ * On error, the function returns a (negative) error code.
  */
-#define ipc_idr_alloc(ids, new)						\
-	idr_alloc(&(ids)->ipcs_idr, (new),				\
-		  (ids)->next_id < 0 ? 0 : ipcid_to_idx((ids)->next_id),\
-		  0, GFP_NOWAIT)
-
-static inline int ipc_buildid(int id, struct ipc_ids *ids,
-			      struct kern_ipc_perm *new)
+static inline int ipc_idr_alloc(struct ipc_ids *ids, struct kern_ipc_perm *new)
 {
-	if (ids->next_id < 0) { /* default, behave as !CHECKPOINT_RESTORE */
+	int idx, next_id = -1;
+
+#ifdef CONFIG_CHECKPOINT_RESTORE
+	next_id = ids->next_id;
+	ids->next_id = -1;
+#endif
+
+	/*
+	 * As soon as a new object is inserted into the idr,
+	 * ipc_obtain_object_idr() or ipc_obtain_object_check() can find it,
+	 * and the lockless preparations for ipc operations can start.
+	 * This means especially: permission checks, audit calls, allocation
+	 * of undo structures, ...
+	 *
+	 * Thus the object must be fully initialized, and if something fails,
+	 * then the full tear-down sequence must be followed.
+	 * (i.e.: set new->deleted, reduce refcount, call_rcu())
+	 */
+
+	if (next_id < 0) { /* !CHECKPOINT_RESTORE or next_id is unset */
 		new->seq = ids->seq++;
 		if (ids->seq > IPCID_SEQ_MAX)
 			ids->seq = 0;
+		idx = idr_alloc(&ids->ipcs_idr, new, 0, 0, GFP_NOWAIT);
 	} else {
-		new->seq = ipcid_to_seqx(ids->next_id);
-		ids->next_id = -1;
+		new->seq = ipcid_to_seqx(next_id);
+		idx = idr_alloc(&ids->ipcs_idr, new, ipcid_to_idx(next_id),
+				0, GFP_NOWAIT);
 	}
-
-	return SEQ_MULTIPLIER * new->seq + id;
+	if (idx >= 0)
+		new->id = SEQ_MULTIPLIER * new->seq + idx;
+	return idx;
 }
 
-#else
-#define ipc_idr_alloc(ids, new)					\
-	idr_alloc(&(ids)->ipcs_idr, (new), 0, 0, GFP_NOWAIT)
-
-static inline int ipc_buildid(int id, struct ipc_ids *ids,
-			      struct kern_ipc_perm *new)
-{
-	new->seq = ids->seq++;
-	if (ids->seq > IPCID_SEQ_MAX)
-		ids->seq = 0;
-
-	return SEQ_MULTIPLIER * new->seq + id;
-}
-
-#endif /* CONFIG_CHECKPOINT_RESTORE */
-
 /**
  * ipc_addid - add an ipc identifier
  * @ids: ipc identifier set
@@ -241,9 +237,11 @@ static inline int ipc_buildid(int id, struct ipc_ids *ids,
  * @limit: limit for the number of used ids
  *
  * Add an entry 'new' to the ipc ids idr. The permissions object is
- * initialised and the first free entry is set up and the id assigned
+ * initialised and the first free entry is set up and the index assigned
  * is returned. The 'new' entry is returned in a locked state on success.
+ *
  * On failure the entry is not locked and a negative err-code is returned.
+ * The caller must use ipc_rcu_putref() to free the identifier.
  *
  * Called with writer ipc_ids.rwsem held.
  */
@@ -251,19 +249,20 @@ int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit)
 {
 	kuid_t euid;
 	kgid_t egid;
-	int id, err;
+	int idx, err;
+
+	/* 1) Initialize the refcount so that ipc_rcu_putref works */
+	refcount_set(&new->refcount, 1);
 
 	if (limit > IPCMNI)
 		limit = IPCMNI;
 
-	if (!ids->tables_initialized || ids->in_use >= limit)
+	if (ids->in_use >= limit)
 		return -ENOSPC;
 
 	idr_preload(GFP_KERNEL);
 
-	refcount_set(&new->refcount, 1);
 	spin_lock_init(&new->lock);
-	new->deleted = false;
 	rcu_read_lock();
 	spin_lock(&new->lock);
 
@@ -271,30 +270,30 @@ int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit)
 	new->cuid = new->uid = euid;
 	new->gid = new->cgid = egid;
 
-	id = ipc_idr_alloc(ids, new);
+	new->deleted = false;
+
+	idx = ipc_idr_alloc(ids, new);
 	idr_preload_end();
 
-	if (id >= 0 && new->key != IPC_PRIVATE) {
+	if (idx >= 0 && new->key != IPC_PRIVATE) {
 		err = rhashtable_insert_fast(&ids->key_ht, &new->khtnode,
 					     ipc_kht_params);
 		if (err < 0) {
-			idr_remove(&ids->ipcs_idr, id);
-			id = err;
+			idr_remove(&ids->ipcs_idr, idx);
+			idx = err;
 		}
 	}
-	if (id < 0) {
+	if (idx < 0) {
+		new->deleted = true;
 		spin_unlock(&new->lock);
 		rcu_read_unlock();
-		return id;
+		return idx;
 	}
 
 	ids->in_use++;
-	if (id > ids->max_id)
-		ids->max_id = id;
-
-	new->id = ipc_buildid(id, ids, new);
-
-	return id;
+	if (idx > ids->max_idx)
+		ids->max_idx = idx;
+	return idx;
 }
 
 /**
@@ -432,20 +431,20 @@ static void ipc_kht_remove(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
  */
 void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 {
-	int lid = ipcid_to_idx(ipcp->id);
+	int idx = ipcid_to_idx(ipcp->id);
 
-	idr_remove(&ids->ipcs_idr, lid);
+	idr_remove(&ids->ipcs_idr, idx);
 	ipc_kht_remove(ids, ipcp);
 	ids->in_use--;
 	ipcp->deleted = true;
 
-	if (unlikely(lid == ids->max_id)) {
+	if (unlikely(idx == ids->max_idx)) {
 		do {
-			lid--;
-			if (lid == -1)
+			idx--;
+			if (idx == -1)
 				break;
-		} while (!idr_find(&ids->ipcs_idr, lid));
-		ids->max_id = lid;
+		} while (!idr_find(&ids->ipcs_idr, idx));
+		ids->max_idx = idx;
 	}
 }
 
@@ -463,7 +462,7 @@ void ipc_set_key_private(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 	ipcp->key = IPC_PRIVATE;
 }
 
-int ipc_rcu_getref(struct kern_ipc_perm *ptr)
+bool ipc_rcu_getref(struct kern_ipc_perm *ptr)
 {
 	return refcount_inc_not_zero(&ptr->refcount);
 }
@@ -565,12 +564,9 @@ void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out)
 struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id)
 {
 	struct kern_ipc_perm *out;
-	int lid = ipcid_to_idx(id);
-
-	if (unlikely(!ids->tables_initialized))
-		return ERR_PTR(-EINVAL);
+	int idx = ipcid_to_idx(id);
 
-	out = idr_find(&ids->ipcs_idr, lid);
+	out = idr_find(&ids->ipcs_idr, idx);
 	if (!out)
 		return ERR_PTR(-EINVAL);
 
@@ -578,48 +574,12 @@ struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id)
 }
 
 /**
- * ipc_lock - lock an ipc structure without rwsem held
- * @ids: ipc identifier set
- * @id: ipc id to look for
- *
- * Look for an id in the ipc ids idr and lock the associated ipc object.
- *
- * The ipc object is locked on successful exit.
- */
-struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
-{
-	struct kern_ipc_perm *out;
-
-	rcu_read_lock();
-	out = ipc_obtain_object_idr(ids, id);
-	if (IS_ERR(out))
-		goto err;
-
-	spin_lock(&out->lock);
-
-	/*
-	 * ipc_rmid() may have already freed the ID while ipc_lock()
-	 * was spinning: here verify that the structure is still valid.
-	 * Upon races with RMID, return -EIDRM, thus indicating that
-	 * the ID points to a removed identifier.
-	 */
-	if (ipc_valid_object(out))
-		return out;
-
-	spin_unlock(&out->lock);
-	out = ERR_PTR(-EIDRM);
-err:
-	rcu_read_unlock();
-	return out;
-}
-
-/**
  * ipc_obtain_object_check
  * @ids: ipc identifier set
  * @id: ipc id to look for
  *
- * Similar to ipc_obtain_object_idr() but also checks
- * the ipc object reference counter.
+ * Similar to ipc_obtain_object_idr() but also checks the ipc object
+ * sequence number.
  *
  * Call inside the RCU critical section.
  * The ipc object is *not* locked on exit.
@@ -677,7 +637,7 @@ int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
 }
 
 /**
- * ipcctl_pre_down_nolock - retrieve an ipc and check permissions for some IPC_XXX cmd
+ * ipcctl_obtain_check - retrieve an ipc object and check permissions
  * @ns:  ipc namespace
  * @ids:  the table of ids where to look for the ipc
  * @id:   the id of the ipc to retrieve
@@ -687,16 +647,16 @@ int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
  *
  * This function does some common audit and permissions check for some IPC_XXX
  * cmd and is called from semctl_down, shmctl_down and msgctl_down.
- * It must be called without any lock held and:
  *
- *   - retrieves the ipc with the given id in the given table.
+ * It:
+ *   - retrieves the ipc object with the given id in the given table.
  *   - performs some audit and permission check, depending on the given cmd
  *   - returns a pointer to the ipc object or otherwise, the corresponding
  *     error.
  *
  * Call holding the both the rwsem and the rcu read lock.
  */
-struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
+struct kern_ipc_perm *ipcctl_obtain_check(struct ipc_namespace *ns,
 					struct ipc_ids *ids, int id, int cmd,
 					struct ipc64_perm *perm, int extra_perm)
 {
diff --git a/ipc/util.h b/ipc/util.h
index 0aba3230d007..0a159f69b3bb 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -18,8 +18,8 @@
 #define IPCMNI 32768  /* <= MAX_INT limit for ipc arrays (including sysctl changes) */
 #define SEQ_MULTIPLIER	(IPCMNI)
 
-int sem_init(void);
-int msg_init(void);
+void sem_init(void);
+void msg_init(void);
 void shm_init(void);
 
 struct ipc_namespace;
@@ -34,17 +34,17 @@ static inline void mq_put_mnt(struct ipc_namespace *ns) { }
 #endif
 
 #ifdef CONFIG_SYSVIPC
-int sem_init_ns(struct ipc_namespace *ns);
-int msg_init_ns(struct ipc_namespace *ns);
-int shm_init_ns(struct ipc_namespace *ns);
+void sem_init_ns(struct ipc_namespace *ns);
+void msg_init_ns(struct ipc_namespace *ns);
+void shm_init_ns(struct ipc_namespace *ns);
 
 void sem_exit_ns(struct ipc_namespace *ns);
 void msg_exit_ns(struct ipc_namespace *ns);
 void shm_exit_ns(struct ipc_namespace *ns);
 #else
-static inline int sem_init_ns(struct ipc_namespace *ns) { return 0; }
-static inline int msg_init_ns(struct ipc_namespace *ns) { return 0; }
-static inline int shm_init_ns(struct ipc_namespace *ns) { return 0; }
+static inline void sem_init_ns(struct ipc_namespace *ns) { }
+static inline void msg_init_ns(struct ipc_namespace *ns) { }
+static inline void shm_init_ns(struct ipc_namespace *ns) { }
 
 static inline void sem_exit_ns(struct ipc_namespace *ns) { }
 static inline void msg_exit_ns(struct ipc_namespace *ns) { }
@@ -83,7 +83,7 @@ struct ipc_ops {
 struct seq_file;
 struct ipc_ids;
 
-int ipc_init_ids(struct ipc_ids *);
+void ipc_init_ids(struct ipc_ids *ids);
 #ifdef CONFIG_PROC_FS
 void __init ipc_init_proc_interface(const char *path, const char *header,
 		int ids, int (*show)(struct seq_file *, void *));
@@ -113,12 +113,12 @@ void ipc_set_key_private(struct ipc_ids *, struct kern_ipc_perm *);
 int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flg);
 
 /**
- * ipc_get_maxid - get the last assigned id
+ * ipc_get_maxidx - get the highest assigned index
  * @ids: ipc identifier set
  *
  * Called with ipc_ids.rwsem held for reading.
  */
-static inline int ipc_get_maxid(struct ipc_ids *ids)
+static inline int ipc_get_maxidx(struct ipc_ids *ids)
 {
 	if (ids->in_use == 0)
 		return -1;
@@ -126,7 +126,7 @@ static inline int ipc_get_maxid(struct ipc_ids *ids)
 	if (ids->in_use == IPCMNI)
 		return IPCMNI - 1;
 
-	return ids->max_id;
+	return ids->max_idx;
 }
 
 /*
@@ -138,17 +138,16 @@ static inline int ipc_get_maxid(struct ipc_ids *ids)
  * refcount is initialized by ipc_addid(), before that point call_rcu()
  * must be used.
  */
-int ipc_rcu_getref(struct kern_ipc_perm *ptr);
+bool ipc_rcu_getref(struct kern_ipc_perm *ptr);
 void ipc_rcu_putref(struct kern_ipc_perm *ptr,
 			void (*func)(struct rcu_head *head));
 
-struct kern_ipc_perm *ipc_lock(struct ipc_ids *, int);
 struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id);
 
 void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out);
 void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out);
 int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out);
-struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
+struct kern_ipc_perm *ipcctl_obtain_check(struct ipc_namespace *ns,
 					     struct ipc_ids *ids, int id, int cmd,
 					     struct ipc64_perm *perm, int extra_perm);
 
@@ -173,9 +172,9 @@ extern struct msg_msg *load_msg(const void __user *src, size_t len);
 extern struct msg_msg *copy_msg(struct msg_msg *src, struct msg_msg *dst);
 extern int store_msg(void __user *dest, struct msg_msg *msg, size_t len);
 
-static inline int ipc_checkid(struct kern_ipc_perm *ipcp, int uid)
+static inline int ipc_checkid(struct kern_ipc_perm *ipcp, int id)
 {
-	return uid / SEQ_MULTIPLIER != ipcp->seq;
+	return ipcid_to_seqx(id) != ipcp->seq;
 }
 
 static inline void ipc_lock_object(struct kern_ipc_perm *perm)