ipc/mqueue: cleanup definition names and locations

ipc/mqueue: cleanup definition names and locations

We had a customer come up with a problem while trying to upgrade from our
2.6.18 kernel to our 2.6.32 kernel.  In diagnosing their problem, it was
determined that when commit b231cca4 ("message queues: increase range
limits") changed the msg size max from INT_MAX to 8192*128, that's what
broke their setup.

While fixing this problem, testing showed that if you increase the max
values of a msg queue, then attempt to create one without an attr struct
passed in to the open call, it could fail because it sets the queue size
to the max of both the msg size and queue size.  If these are large
enough, they over run the default RLIMIT_MSGQUEUE.  This change was also
introduced in the b231cca4 ("message queues: increase range limits")
commit.

We then found that the msg queue limits were not all being enforced on
CAP_SYS_RESOURCE apps.

Finally, we found that commit 9cf18e1d ("ipc: HARD_MSGMAX should be higher
not lower on 64bit") fiddled with HARD_MSGMAX without realizing that the
reason it was set to what it was, was to avoid trying to kmalloc a chunk
larger than 128K.

So this series of patches cleans up the various defines, takes us back to
having a larger HARD_MSGSIZEMAX, goes back to using a separate define for
the case where a user doesn't pass in an attr struct in case the maxes
have been raised too large for RLIMIT_MSGQUEUE, enforces the maximums on
CAP_SYS_RESOURCE apps, uses vmalloc instead of kmalloc when the msg
pointer array is too large, and documents all of this so it shouldn't
happen again.

This patch:

The various defines for minimums and maximums of the sysctl controllable
mqueue values are scattered amongst different files and named
inconsistently.  Move them all into ipc_namespace.h and make them have
consistent names.  Additionally, make the number of queues per namespace
also have a minimum and maximum and use the same sysctl function as the
other two settable variables.

Signed-off-by: Doug Ledford <dledford@redhat.com>
Cc: Amerigo Wang <amwang@redhat.com>
Cc: Serge E. Hallyn <serue@us.ibm.com>
Cc: Joe Korty <joe.korty@ccur.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: <stable@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>