Allow Xen tmem shim to be built/loaded as a module.  Xen self-ballooning
and frontswap-selfshrinking are now also "lazily" initialized when the
Xen tmem shim is loaded as a module, unless explicitly disabled by
module parameters.

Note runtime dependency disallows loading if cleancache/frontswap lazy
initialization patches are not present.

If built-in (not built as a module), the original mechanism of enabling
via a kernel boot parameter is retained, but this should be considered
deprecated.

Note that module unload is explicitly not yet supported.

[v1: Removed the [CLEANCACHE|FRONTSWAP]_HAS_LAZY_INIT ifdef]
[v2: Squashed the xen/tmem: Remove the subsys call patch in]
[akpm@linux-foundation.org: fix build (disable_frontswap_selfshrinking undeclared)]
Signed-off-by: NDan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: NBob Liu <lliubbo@gmail.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Andor Daam <andor.daam@googlemail.com>
Cc: Florian Schmaus <fschmaus@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Stefan Hengelein <ilendir@googlemail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

It will be useful to be able to access global memory commitment from
device drivers.  On the Hyper-V platform, the host has a policy engine to
balance the available physical memory amongst all competing virtual
machines hosted on a given node.  This policy engine is driven by a number
of metrics including the memory commitment reported by the guests.  The
balloon driver for Linux on Hyper-V will use this function to retrieve
guest memory commitment.  This function is also used in Xen self
ballooning code.

[akpm@linux-foundation.org: coding-style tweak]
Signed-off-by: NK. Y. Srinivasan <kys@microsoft.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NDan Magenheimer <dan.magenheimer@oracle.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Currently, the memory target in the Xen selfballooning driver is mainly
driven by the value of "Committed_AS".  However, there are cases in
which it is desirable to assign additional memory to be available for
the kernel, e.g. for local caches (which are not covered by cleancache),
e.g. dcache and inode caches.

This adds an additional tunable in the selfballooning driver (accessible
via sysfs) which allows the user to specify an additional constant
amount of memory to be reserved by the selfballoning driver for the
local domain.
Signed-off-by: NJana Saout <jana@saout.de>
Acked-by: NDan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

The functions these get passed to have been taking pointers to const
since at least 2.6.16.
Signed-off-by: NJan Beulich <jbeulich@suse.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

This adds the needed include file for xen-selfballoon.c to fix the build
error reported by Stephen Rothwell.
Reported-by: NStephen Rothwell <sfr@canb.auug.org.au>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

After all sysdev classes are ported to regular driver core entities, the
sysdev implementation will be entirely removed from the kernel.

Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: NKay Sievers <kay.sievers@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

The balloon driver's "current_pages" is very different from
totalram_pages.  Self-ballooning needs to be driven by
the latter.  Also, Committed_AS doesn't account for pages
used by the kernel so:
1) Add totalreserve_pages to Committed_AS for the normal target.
2) Enforce a floor for when there are little or no user-space threads
   using memory (e.g. single-user mode) to avoid OOMs.  The floor
   function includes a "min_usable_mb" tuneable in case we discover
   later that the floor function is still too aggressive in some
   workloads, though likely it will not be needed.

Changes since version 4:
- change floor calculation so that it is not as aggressive; this version
  uses a piecewise linear function similar to minimum_target in the 2.6.18
  balloon driver, but modified to add to totalreserve_pages instead of
  subtract from max_pfn, the 2.6.18 version causes OOMs on recent kernels
  because the kernel has expanded over time
- change safety_margin to min_usable_mb and comment on its use
- since committed_as does NOT include kernel space (and other reserved
  pages), totalreserve_pages is now added to committed_as.  The result is
  less aggressive self-ballooning, but theoretically more appropriate.
Changes since version 3:
- missing include causes compile problem when CONFIG_FRONTSWAP is disabled
- add comments after includes
Changes since version 2:
- missing include causes compile problem only on 32-bit
Changes since version 1:
- tuneable safety margin added

[v5: avi.miller@oracle.com: still too aggressive, seeing some OOMs]
[v4: konrad.wilk@oracle.com: fix compile when CONFIG_FRONTSWAP is disabled]
[v3: guru.anbalagane@oracle.com: fix 32-bit compile]
[v2: konrad.wilk@oracle.com: make safety margin tuneable]
Signed-off-by: NDan Magenheimer <dan.magenheimer@oracle.com>
[v1: Altered description and added an extra include]
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Fix build errors (found when CONFIG_SYSFS is not enabled):

  drivers/xen/xen-selfballoon.c:446: warning: data definition has no type or storage class
  drivers/xen/xen-selfballoon.c:446: warning: type defaults to 'int' in declaration of 'EXPORT_SYMBOL'
  drivers/xen/xen-selfballoon.c:446: warning: parameter names (without types) in function declaration
  drivers/xen/xen-selfballoon.c:485: error: expected declaration specifiers or '...' before string constant
  drivers/xen/xen-selfballoon.c:485: warning: data definition has no type or storage class
  drivers/xen/xen-selfballoon.c:485: warning: type defaults to 'int' in declaration of 'MODULE_LICENSE'
  drivers/xen/xen-selfballoon.c:485: warning: function declaration isn't a prototype
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Acked-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fix build errors (found when CONFIG_SYSFS is not enabled):

drivers/xen/xen-selfballoon.c:446: warning: data definition has no type or storage class
drivers/xen/xen-selfballoon.c:446: warning: type defaults to 'int' in declaration of 'EXPORT_SYMBOL'
drivers/xen/xen-selfballoon.c:446: warning: parameter names (without types) in function declaration
drivers/xen/xen-selfballoon.c:485: error: expected declaration specifiers or '...' before string constant
drivers/xen/xen-selfballoon.c:485: warning: data definition has no type or storage class
drivers/xen/xen-selfballoon.c:485: warning: type defaults to 'int' in declaration of 'MODULE_LICENSE'
drivers/xen/xen-selfballoon.c:485: warning: function declaration isn't a prototype
Signed-off-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

With a specific enough .config file compile errors show
for missing workqueue declarations.
Reported-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

With a specific enough .config file compile errors show
for missing workqueue declarations.
Reported-by: NRandy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

This patch introduces two in-kernel drivers for Xen transcendent memory
("tmem") functionality that complement cleancache and frontswap.  Both
use control theory to dynamically adjust and optimize memory utilization.
Selfballooning controls the in-kernel Xen balloon driver, targeting a goal
value (vm_committed_as), thus pushing less frequently used clean
page cache pages (through the cleancache code) into Xen tmem where
Xen can balance needs across all VMs residing on the physical machine.
Frontswap-selfshrinking controls the number of pages in frontswap,
driving it towards zero (effectively doing a partial swapoff) when
in-kernel memory pressure subsides, freeing up RAM for other VMs.

More detail is provided in the header comment of xen-selfballooning.c.
Signed-off-by: NDan Magenheimer <dan.magenheimer@oracle.com>

[v8: konrad.wilk@oracle.com: set default enablement depending on frontswap]
[v7: konrad.wilk@oracle.com: fix capitalization and punctuation in comments]
[v6: fix frontswap-selfshrinking initialization]
[v6: konrad.wilk@oracle.com: fix init pr_infos; add comments about swap]
[v5: konrad.wilk@oracle.com: add NULL to attr list; move inits up to decls]
[v4: dkiper@net-space.pl: use strict_strtoul plus a few syntactic nits]
[v3: konrad.wilk@oracle.com: fix potential divides-by-zero]
[v3: konrad.wilk@oracle.com: add many more comments, fix nits]
[v2: rebased to linux-3.0-rc1]
[v2: Ian.Campbell@citrix.com: reorganize as new file (xen-selfballoon.c)]
[v2: dkiper@net-space.pl: proper access to vm_committed_as]
[v2: dkiper@net-space.pl: accounting fixes]
Cc: Jan Beulich <JBeulich@novell.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: <xen-devel@lists.xensource.com>