android_kernel_motorola_sm6225/ipc
Eric B Munson 6bfde05bf5 hugetlbfs: allow the creation of files suitable for MAP_PRIVATE on the vfs internal mount
This patchset adds a flag to mmap that allows the user to request that an
anonymous mapping be backed with huge pages.  This mapping will borrow
functionality from the huge page shm code to create a file on the kernel
internal mount and use it to approximate an anonymous mapping.  The
MAP_HUGETLB flag is a modifier to MAP_ANONYMOUS and will not work without
both flags being preset.

A new flag is necessary because there is no other way to hook into huge
pages without creating a file on a hugetlbfs mount which wouldn't be
MAP_ANONYMOUS.

To userspace, this mapping will behave just like an anonymous mapping
because the file is not accessible outside of the kernel.

This patchset is meant to simplify the programming model.  Presently there
is a large chunk of boiler platecode, contained in libhugetlbfs, required
to create private, hugepage backed mappings.  This patch set would allow
use of hugepages without linking to libhugetlbfs or having hugetblfs
mounted.

Unification of the VM code would provide these same benefits, but it has
been resisted each time that it has been suggested for several reasons: it
would break PAGE_SIZE assumptions across the kernel, it makes page-table
abstractions really expensive, and it does not provide any benefit on
architectures that do not support huge pages, incurring fast path
penalties without providing any benefit on these architectures.

This patch:

There are two means of creating mappings backed by huge pages:

        1. mmap() a file created on hugetlbfs
        2. Use shm which creates a file on an internal mount which essentially
           maps it MAP_SHARED

The internal mount is only used for shared mappings but there is very
little that stops it being used for private mappings. This patch extends
hugetlbfs_file_setup() to deal with the creation of files that will be
mapped MAP_PRIVATE on the internal hugetlbfs mount. This extended API is
used in a subsequent patch to implement the MAP_HUGETLB mmap() flag.

Signed-off-by: Eric Munson <ebmunson@us.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Adam Litke <agl@us.ibm.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-09-22 07:17:41 -07:00
..
compat.c fix logic error in ipc compat semctl() 2007-07-06 10:23:43 -07:00
compat_mq.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ipc_sysctl.c proc_sysctl: use CONFIG_PROC_SYSCTL around ipc and utsname proc_handlers 2009-04-02 19:05:01 -07:00
ipcns_notifier.c ipc: do not use a negative value to re-enable msgmni automatic recomputing 2008-07-25 10:53:42 -07:00
Makefile namespaces: mqueue namespace: adapt sysctl 2009-04-07 08:31:09 -07:00
mq_sysctl.c namespaces: move get_mq() inside #ifdef CONFIG_SYSCTL 2009-04-13 15:04:29 -07:00
mqueue.c const: mark remaining super_operations const 2009-09-22 07:17:24 -07:00
msg.c [CVE-2009-0029] System call wrappers part 24 2009-01-14 14:15:28 +01:00
msgutil.c namespaces: ipc namespaces: implement support for posix msqueues 2009-04-07 08:31:09 -07:00
namespace.c ipcns: make free_ipc_ns() static 2009-06-18 13:03:56 -07:00
sem.c rculist: use list_entry_rcu in places where it's appropriate 2009-04-15 12:05:25 +02:00
shm.c hugetlbfs: allow the creation of files suitable for MAP_PRIVATE on the vfs internal mount 2009-09-22 07:17:41 -07:00
util.c namespaces: mqueue ns: move mqueue_mnt into struct ipc_namespace 2009-04-07 08:31:09 -07:00
util.h ipc: unbreak 32-bit shmctl/semctl/msgctl 2009-06-21 12:48:43 -07:00