Fix these sparse warings:
fs/binfmt_elf.c:1749:29: warning: symbol 'tmp' shadows an earlier one
fs/binfmt_elf.c:1734:28: originally declared here
fs/binfmt_elf.c:2009:26: warning: symbol 'vma' shadows an earlier one
fs/binfmt_elf.c:1892:24: originally declared here

[akpm@linux-foundation.org: chose better variable name]
Signed-off-by: NWANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch does simplify fill_elf_header function by setting
to zero the whole elf header first. So we fillup the fields
we really need only.

before:
   text    data     bss     dec     hex filename
  11735      80       0   11815    2e27 fs/binfmt_elf.o

after:
   text    data     bss     dec     hex filename
  11710      80       0   11790    2e0e fs/binfmt_elf.o

viola, 25 bytes of text is freed
Signed-off-by: NCyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NCyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

A void returning function returned the return value of another void
returning function...

Spotted by sparse.
Signed-off-by: NAdrian Bunk <bunk@kernel.org>
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Make the needlessly global ipmi_alloc_recv_msg() static.
Signed-off-by: NAdrian Bunk <bunk@kernel.org>
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NRobert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

IPMI code theoretically allows ->write_proc users, but nobody uses this thus
far.
Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Acked-by: NCorey Minyard <minyard@acm.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Kbuild system handles this automatically.
Signed-off-by: NDenis Cheng <crquan@gmail.com>
Cc: Corey Minyard <minyard@acm.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Lots of style fixes for the miscellaneous IPMI files.  No functional
changes.  Basically fixes everything reported by checkpatch and fixes the
comment style.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Lots of style fixes for the IPMI system interface driver.  No functional
changes.  Basically fixes everything reported by checkpatch and fixes the
comment style.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Cc: Rocky Craig <rocky.craig@hp.com>
Cc: Hannes Schulz <schulz@schwaar.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Lots of style fixes for the base IPMI driver.  No functional changes.
Basically fixes everything reported by checkpatch and fixes the comment
style.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Convert the #defines for statistics into an enum in the IPMI system interface
and remove the unused timeout_restart statistic.  And comment what these
statistics mean.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Atomics are faster and neater than locked counters.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Convert the #defines for statistics into an enum in the IPMI message
handler.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Atomics are a lot more efficient and neat than using a lock.
Signed-off-by: NKonstantin Baydarov <kbaidarov@ru.mvista.com>
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Enough bug fixes and changes that we need a new driver version.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Don't print out that the event queue is full on every event, only
print something out when it becomes full or becomes not full.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch prevents deadlocks in IPMI panic handler caused by msg_lock
in smi_info structure and waiting_msgs_lock in ipmi_smi structure.

[cminyard@mvista.com: remove unnecessary memory barriers]
Signed-off-by: NKonstantin Baydarov <kbaidarov@ru.mvista.com>
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The "run_to_completion" mode was somewhat broken.  Locks need to be avoided in
run_to_completion mode, and it shouldn't be used by normal users, just
internally for panic situations.

This patch removes locks in run_to_completion mode and removes the user call
for setting the mode.  The only user was the poweroff code, but it was easily
converted to use the polling interface.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Hold handling of ATTN until the upper layer has reported that it is
ready.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Cc: Patrick Schoeller <Patrick.Schoeller@hp.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

CLONE_NEWIPC|CLONE_SYSVSEM interaction isn't handled properly.  This can cause
a kernel memory corruption.  CLONE_NEWIPC must detach from the existing undo
lists.

Fix, part 3: refuse clone(CLONE_SYSVSEM|CLONE_NEWIPC).

With unshare, specifying CLONE_SYSVSEM means unshare the sysvsem.  So it seems
reasonable that CLONE_NEWIPC without CLONE_SYSVSEM would just imply
CLONE_SYSVSEM.

However with clone, specifying CLONE_SYSVSEM means *share* the sysvsem.  So
calling clone(CLONE_SYSVSEM|CLONE_NEWIPC) is explicitly asking for something
we can't allow.  So return -EINVAL in that case.

[akpm@linux-foundation.org: cleanups]
Signed-off-by: NSerge E. Hallyn <serue@us.ibm.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Acked-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: Pierre Peiffer <peifferp@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

sys_unshare(CLONE_NEWIPC) doesn't handle the undo lists properly, this can
cause a kernel memory corruption.  CLONE_NEWIPC must detach from the existing
undo lists.

Fix, part 2: perform an implicit CLONE_SYSVSEM in CLONE_NEWIPC.  CLONE_NEWIPC
creates a new IPC namespace, the task cannot access the existing semaphore
arrays after the unshare syscall.  Thus the task can/must detach from the
existing undo list entries, too.

This fixes the kernel corruption, because it makes it impossible that
undo records from two different namespaces are in sysvsem.undo_list.
Signed-off-by: NManfred Spraul <manfred@colorfullife.com>
Signed-off-by: NSerge E. Hallyn <serue@us.ibm.com>
Acked-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: Pierre Peiffer <peifferp@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

sys_unshare(CLONE_NEWIPC) doesn't handle the undo lists properly, this can
cause a kernel memory corruption.  CLONE_NEWIPC must detach from the existing
undo lists.

Fix, part 1: add support for sys_unshare(CLONE_SYSVSEM)

The original reason to not support it was the potential (inevitable?)
confusion due to the fact that sys_unshare(CLONE_SYSVSEM) has the
inverse meaning of clone(CLONE_SYSVSEM).

Our two most reasonable options then appear to be (1) fully support
CLONE_SYSVSEM, or (2) continue to refuse explicit CLONE_SYSVSEM,
but always do it anyway on unshare(CLONE_SYSVSEM).  This patch does
(1).

Changelog:
	Apr 16: SEH: switch to Manfred's alternative patch which
		removes the unshare_semundo() function which
		always refused CLONE_SYSVSEM.
Signed-off-by: NManfred Spraul <manfred@colorfullife.com>
Signed-off-by: NSerge E. Hallyn <serue@us.ibm.com>
Acked-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: Pierre Peiffer <peifferp@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add definitions of USHORT_MAX and others into kernel.  ipc uses it and slub
implementation might also use it.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NZhang Yanmin <yanmin.zhang@intel.com>
Reviewed-by: NChristoph Lameter <clameter@sgi.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Cc: "Pierre Peiffer" <peifferp@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

semctl_down(), msgctl_down() and shmctl_down() are used to handle the same set
of commands for each kind of IPC.  They all start to do the same job (they
retrieve the ipc and do some permission checks) before handling the commands
on their own.

This patch proposes to consolidate this by moving these same pieces of code
into one common function called ipcctl_pre_down().

It simplifies a little these xxxctl_down() functions and increases a little
the maintainability.
Signed-off-by: NPierre Peiffer <pierre.peiffer@bull.net>
Acked-by: NSerge Hallyn <serue@us.ibm.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The IPC_SET command performs the same permission setting for all IPCs.  This
patch introduces a common ipc_update_perm() function to update these
permissions and makes use of it for all IPCs.
Signed-off-by: NPierre Peiffer <pierre.peiffer@bull.net>
Acked-by: NSerge Hallyn <serue@us.ibm.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

All IPCs make use of an intermetiate *_setbuf structure to handle the IPC_SET
command.  This is not really needed and, moreover, it complicates a little bit
the code.

This patch gets rid of the use of it and uses directly the semid64_ds/
msgid64_ds/shmid64_ds structure.

In addition of removing one struture declaration, it also simplifies and
improves a little bit the common 64-bits path.
Signed-off-by: NPierre Peiffer <pierre.peiffer@bull.net>
Acked-by: NSerge Hallyn <serue@us.ibm.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

semctl_down() takes one unused parameter: semnum.  This patch proposes to get
rid of it.
Signed-off-by: NPierre Peiffer <pierre.peiffer@bull.net>
Acked-by: NSerge Hallyn <serue@us.ibm.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

semctl_down is called with the rwmutex (the one which protects the list of
ipcs) taken in write mode.

This patch moves this rwmutex taken in write-mode inside semctl_down.

This has the advantages of reducing a little bit the window during which this
rwmutex is taken, clarifying sys_semctl, and finally of having a coherent
behaviour with [shm|msg]ctl_down
Signed-off-by: NPierre Peiffer <pierre.peiffer@bull.net>
Acked-by: NSerge Hallyn <serue@us.ibm.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently, sys_msgctl is not easy to read.

This patch tries to improve that by introducing the msgctl_down function to
handle all commands requiring the rwmutex to be taken in write mode (ie
IPC_SET and IPC_RMID for now).  It is the equivalent function of semctl_down
for message queues.

This greatly changes the readability of sys_msgctl and also harmonizes the way
these commands are handled among all IPCs.
Signed-off-by: NPierre Peiffer <pierre.peiffer@bull.net>
Acked-by: NSerge Hallyn <serue@us.ibm.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently, the way the different commands are handled in sys_shmctl introduces
some duplicated code.

This patch introduces the shmctl_down function to handle all the commands
requiring the rwmutex to be taken in write mode (ie IPC_SET and IPC_RMID for
now).  It is the equivalent function of semctl_down for shared memory.

This removes some duplicated code for handling these both commands and
harmonizes the way they are handled among all IPCs.
Signed-off-by: NPierre Peiffer <pierre.peiffer@bull.net>
Acked-by: NSerge Hallyn <serue@us.ibm.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Trivial patch which adds some small locking functions and makes use of them to
factorize some part of the code and to make it cleaner.
Signed-off-by: NPierre Peiffer <pierre.peiffer@bull.net>
Acked-by: NSerge Hallyn <serue@us.ibm.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

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: NNadia 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: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Make msgmni not recomputed anymore upon ipc namespace creation / removal or
memory add/remove, as soon as it has been set from userland.

As soon as msgmni is explicitly set via procfs or sysctl(), the associated
callback routine is unregistered from the ipc namespace notifier chain.
Signed-off-by: NNadia 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: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Introduce a notification mechanism that aims at recomputing msgmni each time
an ipc namespace is created or removed.

The ipc namespace notifier chain already defined for memory hotplug management
is used for that purpose too.

Each time a new ipc namespace is allocated or an existing ipc namespace is
removed, the ipcns notifier chain is notified.  The callback routine for each
registered ipc namespace is then activated in order to recompute msgmni for
that namespace.
Signed-off-by: NNadia 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: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Make the memory hotplug chain's mutex held for a shorter time: when memory is
offlined or onlined a work item is added to the global workqueue.  When the
work item is run, it notifies the ipcns notifier chain with the
IPCNS_MEMCHANGED event.
Signed-off-by: NNadia 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: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Introduce the registration of a callback routine that recomputes msg_ctlmni
upon memory add / remove.

A single notifier block is registered in the hotplug memory chain for all the
ipc namespaces.

Since the ipc namespaces are not linked together, they have their own
notification chain: one notifier_block is defined per ipc namespace.

Each time an ipc namespace is created (removed) it registers (unregisters) its
notifier block in (from) the ipcns chain.  The callback routine registered in
the memory chain invokes the ipcns notifier chain with the IPCNS_LOWMEM event.
 Each callback routine registered in the ipcns namespace, in turn, recomputes
msgmni for the owning namespace.
Signed-off-by: NNadia 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: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This is a trivial patch that defines the priority of slab_memory_callback in
the callback chain as a constant.  This is to prepare for next patch in the
series.
Signed-off-by: NNadia 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: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Since all the namespaces see the same amount of memory (the total one) this
patch introduces a new variable that counts the ipc namespaces and divides
msg_ctlmni by this counter.
Signed-off-by: NNadia 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: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

On large systems we'd like to allow a larger number of message queues.  In
some cases up to 32K.  However simply setting MSGMNI to a larger value may
cause problems for smaller systems.

The first patch of this series introduces a default maximum number of message
queue ids that scales with the amount of lowmem.

Since msgmni is per namespace and there is no amount of memory dedicated to
each namespace so far, the second patch of this series scales msgmni to the
number of ipc namespaces too.

Since msgmni depends on the amount of memory, it becomes necessary to
recompute it upon memory add/remove.  In the 4th patch, memory hotplug
management is added: a notifier block is registered into the memory hotplug
notifier chain for the ipc subsystem.  Since the ipc namespaces are not linked
together, they have their own notification chain: one notifier_block is
defined per ipc namespace.  Each time an ipc namespace is created (removed) it
registers (unregisters) its notifier block in (from) the ipcns chain.  The
callback routine registered in the memory chain invokes the ipcns notifier
chain with the IPCNS_MEMCHANGE event.  Each callback routine registered in the
ipcns namespace, in turn, recomputes msgmni for the owning namespace.

The 5th patch makes it possible to keep the memory hotplug notifier chain's
lock for a lesser amount of time: instead of directly notifying the ipcns
notifier chain upon memory add/remove, a work item is added to the global
workqueue.  When activated, this work item is the one who notifies the ipcns
notifier chain.

Since msgmni depends on the number of ipc namespaces, it becomes necessary to
recompute it upon ipc namespace creation / removal.  The 6th patch uses the
ipc namespace notifier chain for that purpose: that chain is notified each
time an ipc namespace is created or removed.  This makes it possible to
recompute msgmni for all the namespaces each time one of them is created or
removed.

When msgmni is explicitely set from userspace, we should avoid recomputing it
upon memory add/remove or ipcns creation/removal.  This is what the 7th patch
does: it simply unregisters the ipcns callback routine as soon as msgmni has
been changed from procfs or sysctl().

Even if msgmni is set by hand, it should be possible to make it back
automatically recomputed upon memory add/remove or ipcns creation/removal.
This what is achieved in patch 8: if set to a negative value, msgmni is added
back to the ipcns notifier chain, making it automatically recomputed again.

This patch:

Compute msg_ctlmni to make it scale with the amount of lowmem.  msg_ctlmni is
now set to make the message queues occupy 1/32 of the available lowmem.

Some cleaning has also been done for the MSGPOOL constant: the msgctl man page
says it's not used, but it also defines it as a size in bytes (the code
expresses it in Kbytes).
Signed-off-by: NNadia 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: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>