fix jiffy calculations in calibrate_delay_direct to handle overflow

Fixes a hang when booting as dom0 under Xen, when jiffies can be
quite large by the time the kernel init gets this far.

Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>
[jbeulich@novell.com: !time_after() -> time_before_eq() as suggested by Jiri Slaby]
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
calibrate: extract fall-back calculation into own helper

The motivation for this patch series is that currently our OMAP calibrates
itself using the trial-and-error binary chop fallback that some other
architectures no longer need to perform.  This is a lengthy process,
taking 0.2s in an environment where boot time is of great interest.

Patch 2/4 has two optimisations.  Firstly, it replaces the initial
repeated- doubling to find the relevant power of 2 with a tight loop that
just does as much as it can in a jiffy.  Secondly, it doesn't binary chop
over an entire power of 2 range, it choses a much smaller range based on
how much it squeezed in, and failed to squeeze in, during the first stage.
 Both are significant optimisations, and bring our calibration down from
23 jiffies to 5, and, in the process, often arrive at a more accurate lpj
value.

The 'bands' and 'sub-logarithmic' growth may look over-engineered, but
they only cost a small level of inaccuracy in the initial guess (for all
architectures) in order to avoid the very large inaccuracies that appeared
during testing (on x86_64 architectures, and presumably others with less
metronomic operation).  Note that due to the existence of the TSC and
other timers, the x86_64 will not typically use this fallback routine, but
I wanted to code defensively, able to cope with all kinds of processor
behaviours and kernel command line options.

Patch 3/4 is an additional trap for the nightmare scenario where the
initial estimate is very inaccurate, possibly due to things like SMIs.
It simply retries with a larger bound.

Stephen said:

I tried this patch set out on an MSM7630.
:
: Before:
:
: Calibrating delay loop... 681.57 BogoMIPS (lpj=3407872)
:
: After:
:
: Calibrating delay loop... 680.75 BogoMIPS (lpj=3403776)
:
: But the really good news is calibration time dropped from ~247ms to ~56ms.
:  Sadly we won't be able to benefit from this should my udelay patches make
: it into ARM because we would be using calibrate_delay_direct() instead (at
: least on machines who choose to).  Can we somehow reapply the logic behind
: this to calibrate_delay_direct()?  That would be even better, but this is
: definitely a boot time improvement.
:
: Or maybe we could just replace calibrate_delay_direct() with this fallback
: calculation?  If __delay() is a thin wrapper around read_current_timer()
: it should work just as well (plus patch 3 makes it handle SMIs).  I'll try
: that out.

This patch:

... so that it can be modified more clinically.

This is almost entirely cosmetic. The only change to the operation
is that the global variable is only set once after the estimation is
completed, rather than taking on all the intermediate values. However,
there are no readers of that variable, so this change is unimportant.

Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Tested-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
calibrate: home in on correct lpj value more quickly

Binary chop with a jiffy-resync on each step to find an upper bound is
slow, so just race in a tight-ish loop to find an underestimate.

If done with lots of individual steps, sometimes several hundreds of
iterations would be required, which would impose a significant overhead,
and make the initial estimate very low.  By taking slowly increasing steps
there will be less overhead.

E.g.  an x86_64 2.67GHz could have fitted in 613 individual small delays,
but in reality should have been able to fit in a single delay 644 times
longer, so underestimated by 31 steps.  To reach the equivalent of 644
small delays with the accelerating scheme now requires about 130
iterations, so has <1/4th of the overhead, and can therefore be expected
to underestimate by only 7 steps.

As now we have a better initial estimate we can binary chop over a smaller
range.  With the loop overhead in the initial estimate kept low, and the
step sizes moderate, we won't have under-estimated by much, so chose as
tight a range as we can.

Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Tested-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
calibrate: retry with wider bounds when converge seems to fail

Systems with unmaskable interrupts such as SMIs may massively
underestimate loops_per_jiffy, and fail to converge anywhere near the real
value.  A case seen on x86_64 was an initial estimate of 256<<12, which
converged to 511<<12 where the real value should have been over 630<<12.
This admitedly requires bypassing the TSC calibration (lpj_fine), and a
failure to settle in the direct calibration too, but is physically
possible.  This failure does not depend on my previous calibration
optimisation, but by luck is easy to fix with the optimisation in place
with a trivial retry loop.

In the context of the optimised converging method, as we can no longer
trust the starting estimate, enlarge the search bounds exponentially so
that the number of retries is logarithmically bounded.

[akpm@linux-foundation.org: mention x86_64 SMIs in comment]
Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Tested-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
init/calibrate.c: fix for critical bogoMIPS intermittent calculation failure

A fix to the TSC (Time Stamp Counter) based bogoMIPS calculation used on
secondary CPUs which has two faults:

1: Not handling wrapping of the lower 32 bits of the TSC counter on
   32bit kernel - perhaps TSC is not reset by a warm reset?

2: TSC and Jiffies are no incrementing together properly.  Either
   jiffies increment too quickly or Time Stamp Counter isn't incremented
   in during an SMI but the real time clock is and jiffies are
   incremented.

Case 1 can result in a factor of 16 too large a value which makes udelay()
values too small and can cause mysterious driver errors.  Case 2 appears
to give smaller 10-15% errors after averaging but enough to cause
occasional failures on my own board

I have tested this code on my own branch and attach patch suitable for
current kernel code.  See below for examples of the failures and how the
fix handles these situations now.

I reported this issue earlier here:
     Intermittent problem with BogoMIPs calculation on Intel AP CPUs -
http://marc.info/?l=linux-kernel&m=129947246316875&w=4

I suspect this issue has been seen by others but as it is intermittent and
bogoMIPS for secondary CPUs are no longer printed out it might have been
difficult to identify this as the cause.  Perhaps these unresolved issues,
although quite old, might be relevant as possibly this fault has been
around for a while.  In particular Case 1 may only be relevant to 32bit
kernels on newer HW (most people run 64bit kernels?).  Case 2 is less
dramatic since the earlier fix in this area and also intermittent.

   Re: bogomips discrepancy on Intel Core2 Quad CPU -
http://marc.info/?l=linux-kernel&m=118929277524298&w=4
   slow system and bogus bogomips  -
http://marc.info/?l=linux-kernel&m=116791286716107&w=4
   Re: Re: [RFC-PATCH] clocksource: update lpj if clocksource has -
http://marc.info/?l=linux-kernel&m=128952775819467&w=4

This issue is masked a little by commit feae3203d711db0a ("timers, init:
Limit the number of per cpu calibration bootup messages") which only
prints out the first bogoMIPS value making it much harder to notice other
values differing.  Perhaps it should be changed to only suppress them when
they are similar values?

Here are some outputs showing faults occurring and the new code handling
them properly.  See my earlier message for examples of the original
failure.

    Case 1:   A Time Stamp Counter wrap:
...
Calibrating delay loop (skipped), value calculated using timer
frequency.. 6332.70 BogoMIPS (lpj=31663540)
....
calibrate_delay_direct() timer_rate_max=31666493
timer_rate_min=31666151 pre_start=4170369255 pre_end=4202035539
calibrate_delay_direct() timer_rate_max=2425955274
timer_rate_min=2425954941 pre_start=4265368533 pre_end=2396356387
calibrate_delay_direct() ignoring timer_rate as we had a TSC wrap
around start=4265368581 >=post_end=2396356511
calibrate_delay_direct() timer_rate_max=31666274
timer_rate_min=31665942 pre_start=2440373374 pre_end=2472039515
calibrate_delay_direct() timer_rate_max=31666492
timer_rate_min=31666160 pre_start=2535372139 pre_end=2567038422
calibrate_delay_direct() timer_rate_max=31666455
timer_rate_min=31666207 pre_start=2630371084 pre_end=2662037415
Calibrating delay using timer specific routine.. 6333.28 BogoMIPS (lpj=31666428)
Total of 2 processors activated (12665.99 BogoMIPS).
....

    Case 2:  Some thing (presumably the SMM interrupt?) causing the
very low increase in TSC counter for the DELAY_CALIBRATION_TICKS
increase in jiffies
...
Calibrating delay loop (skipped), value calculated using timer
frequency.. 6333.25 BogoMIPS (lpj=31666270)
...
calibrate_delay_direct() timer_rate_max=31666483
timer_rate_min=31666074 pre_start=4199536526 pre_end=4231202809
calibrate_delay_direct() timer_rate_max=864348 timer_rate_min=864016
pre_start=2405343672 pre_end=2406207897
calibrate_delay_direct() timer_rate_max=31666483
timer_rate_min=31666179 pre_start=2469540464 pre_end=2501206823
calibrate_delay_direct() timer_rate_max=31666511
timer_rate_min=31666122 pre_start=2564539400 pre_end=2596205712
calibrate_delay_direct() timer_rate_max=31666084
timer_rate_min=31665685 pre_start=2659538782 pre_end=2691204657
calibrate_delay_direct() dropping min bogoMips estimate 1 = 864348
Calibrating delay using timer specific routine.. 6333.27 BogoMIPS (lpj=31666390)
Total of 2 processors activated (12666.53 BogoMIPS).
...

After 70 boots I saw 2 variations <1% slip through

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix straggly printk mess]
Signed-off-by: Andrew Worsley <amworsley@gmail.com>
Reviewed-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
init/calibrate.c: remove annoying printk

Remove calibrate_delay_direct()'s KERN_DEBUG printk related to bogomips
calculation as it appears when booting every core on setups with
'ignore_loglevel' which dmesg people scan for possible issues.  As the
message doesn't show very useful information to the widest audience of
kernel boot message gazers, it should be removed.

Introduced by commit d2b463135f84 ("init/calibrate.c: fix for critical
bogoMIPS intermittent calculation failure").

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Cc: Andrew Worsley <amworsley@gmail.com>
Cc: Phil Carmody <ext-phil.2.carmody@nokia.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix CPU spinlock lockups on secondary CPU bringup

Secondary CPU bringup typically calls calibrate_delay() during its
initialization.  However, calibrate_delay() modifies a global variable
(loops_per_jiffy) used for udelay() and __delay().

A side effect of 71c696b1 ("calibrate: extract fall-back calculation
into own helper") introduced in the 2.6.39 merge window means that we
end up with a substantial period where loops_per_jiffy is zero.  This
causes the spinlock debugging code to malfunction:

	u64 loops = loops_per_jiffy * HZ;
	for (;;) {
		for (i = 0; i < loops; i++) {
			if (arch_spin_trylock(&lock->raw_lock))
				return;
			__delay(1);
		}
		...
	}

by never calling arch_spin_trylock() - resulting in the CPU locking
up in an infinite loop inside __spin_lock_debug().

Work around this by only writing to loops_per_jiffy only once we have
completed all the calibration decisions.

Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: <stable@kernel.org> (2.6.39-stable)
--
Better solutions (such as omitting the calibration for secondary CPUs,
or arranging for calibrate_delay() to return the LPJ value and leave
it to the caller to decide where to store it) are a possibility, but
would be much more invasive into each architecture.

I think this is the best solution for -rc and stable, but it should be
revisited for the next merge window.

 init/calibrate.c |   14 ++++++++------
 1 files changed, 8 insertions(+), 6 deletions(-)
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
cpufreq: interactive: add suspend/resume logic

If the display of the phone is off, it won't need
high frequencies probably, so we can limit it to the
lowest possible frequency. After resume (display on)
we can simply restore the old frequency which was used
before.

This should not only increase battery life a bit, but
also can improve performance in some workloads.

Also some tunables were slightly adjusted.

Change-Id: I27a18c23238001f398a8eb7c01597b2f070e578a
Signed-off-by: Blechd0se <alex.christ@hotmail.de>
init: mark __user address space on string literals

When calling syscall service routines in kernel, some of arguments should
be user pointers but were missing __user markup on string literals.  Add
it.  Removes some sparse warnings.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Cc: Phillip Lougher <phillip@lougher.demon.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
userns: add a user_namespace as creator/owner of uts_namespace

The expected course of development for user namespaces targeted
capabilities is laid out at https://wiki.ubuntu.com/UserNamespace.

Goals:

- Make it safe for an unprivileged user to unshare namespaces.  They
  will be privileged with respect to the new namespace, but this should
  only include resources which the unprivileged user already owns.

- Provide separate limits and accounting for userids in different
  namespaces.

Status:

  Currently (as of 2.6.38) you can clone with the CLONE_NEWUSER flag to
  get a new user namespace if you have the CAP_SYS_ADMIN, CAP_SETUID, and
  CAP_SETGID capabilities.  What this gets you is a whole new set of
  userids, meaning that user 500 will have a different 'struct user' in
  your namespace than in other namespaces.  So any accounting information
  stored in struct user will be unique to your namespace.

  However, throughout the kernel there are checks which

  - simply check for a capability.  Since root in a child namespace
    has all capabilities, this means that a child namespace is not
    constrained.

  - simply compare uid1 == uid2.  Since these are the integer uids,
    uid 500 in namespace 1 will be said to be equal to uid 500 in
    namespace 2.

  As a result, the lxc implementation at lxc.sf.net does not use user
  namespaces.  This is actually helpful because it leaves us free to
  develop user namespaces in such a way that, for some time, user
  namespaces may be unuseful.

Bugs aside, this patchset is supposed to not at all affect systems which
are not actively using user namespaces, and only restrict what tasks in
child user namespace can do.  They begin to limit privilege to a user
namespace, so that root in a container cannot kill or ptrace tasks in the
parent user namespace, and can only get world access rights to files.
Since all files currently belong to the initila user namespace, that means
that child user namespaces can only get world access rights to *all*
files.  While this temporarily makes user namespaces bad for system
containers, it starts to get useful for some sandboxing.

I've run the 'runltplite.sh' with and without this patchset and found no
difference.

This patch:

copy_process() handles CLONE_NEWUSER before the rest of the namespaces.
So in the case of clone(CLONE_NEWUSER|CLONE_NEWUTS) the new uts namespace
will have the new user namespace as its owner.  That is what we want,
since we want root in that new userns to be able to have privilege over
it.

Changelog:
	Feb 15: don't set uts_ns->user_ns if we didn't create
		a new uts_ns.
	Feb 23: Move extern init_user_ns declaration from
		init/version.c to utsname.h.

Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Daniel Lezcano <daniel.lezcano@free.fr>
Acked-by: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
swap_info: private to swapfile.c

The swap_info_struct is mostly private to mm/swapfile.c, with only
one other in-tree user: get_swap_bio().  Adjust its interface to
map_swap_page(), so that we can then remove get_swap_info_struct().

But there is a popular user out-of-tree, TuxOnIce: so leave the
declaration of swap_info_struct in linux/swap.h.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Nigel Cunningham <ncunningham@crca.org.au>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Conflicts:
	mm/page_io.c
	mm/swapfile.c
swap_info: change to array of pointers

The swap_info_struct is only 76 or 104 bytes, but it does seem wrong
to reserve an array of about 30 of them in bss, when most people will
want only one.  Change swap_info[] to an array of pointers.

That does need a "type" field in the structure: pack it as a char with
next type and short prio (aha, char is unsigned by default on PowerPC).
Use the (admittedly peculiar) name "type" throughout for this index.

/proc/swaps does not take swap_lock: I wouldn't want it to, but do take
care with barriers when adding a new item to the array (never removed).

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Conflicts:
	mm/swapfile.c
swap_info: include first_swap_extent

Make better use of the space by folding first swap_extent into its
swap_info_struct, instead of just the list_head: swap partitions need
only that one, and for others it's used as a circular list anyway.

[jirislaby@gmail.com: fix crash on double swapon]
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
swap_info: miscellaneous minor cleanups

Move CONFIG_HIBERNATION's swapdev_block() into the main CONFIG_HIBERNATION
block, remove extraneous whitespace and return, fix typo in a comment.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
swap_info: SWAP_HAS_CACHE cleanups

Though swap_count() is useful, I'm finding that swap_has_cache() and
encode_swapmap() obscure what happens in the swap_map entry, just at
those points where I need to understand it.  Remove them, and pass
more usable "usage" values to scan_swap_map(), swap_entry_free() and
__swap_duplicate(), instead of the SWAP_MAP and SWAP_CACHE enum.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Conflicts:
	mm/swapfile.c
swap_info: swap_map of chars not shorts

Halve the vmalloc'ed swap_map array from unsigned shorts to unsigned
chars: it's still very unusual to reach a swap count of 126, and the
next patch allows it to be extended indefinitely.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
swap_info: swap count continuations

Swap is duplicated (reference count incremented by one) whenever the same
swap page is inserted into another mm (when forking finds a swap entry in
place of a pte, or when reclaim unmaps a pte to insert the swap entry).

swap_info_struct's vmalloc'ed swap_map is the array of these reference
counts: but what happens when the unsigned short (or unsigned char since
the preceding patch) is full? (and its high bit is kept for a cache flag)

We then lose track of it, never freeing, leaving it in use until swapoff:
at which point we _hope_ that a single pass will have found all instances,
assume there are no more, and will lose user data if we're wrong.

Swapping of KSM pages has not yet been enabled; but it is implemented,
and makes it very easy for a user to overflow the maximum swap count:
possible with ordinary process pages, but unlikely, even when pid_max
has been raised from PID_MAX_DEFAULT.

This patch implements swap count continuations: when the count overflows,
a continuation page is allocated and linked to the original vmalloc'ed
map page, and this used to hold the continuation counts for that entry
and its neighbours.  These continuation pages are seldom referenced:
the common paths all work on the original swap_map, only referring to
a continuation page when the low "digit" of a count is incremented or
decremented through SWAP_MAP_MAX.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
swap_info: note SWAP_MAP_SHMEM

While we're fiddling with the swap_map values, let's assign a particular
value to shmem/tmpfs swap pages: their swap counts are never incremented,
and it helps swapoff's try_to_unuse() a little if it can immediately
distinguish those pages from process pages.

Since we've no use for SWAP_MAP_BAD | COUNT_CONTINUED,
we might as well use that 0xbf value for SWAP_MAP_SHMEM.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
swap: rework map_swap_page() again

Seems that page_io.c doesn't really need to know that page_private(page)
is the swp_entry 'val'.  Rework map_swap_page() to do what its name says
and map a page to a page offset in the swap space.

The only other caller of map_swap_page() is internal to mm/swapfile.c and
it does want to map a swap entry to the 'sector'.  So rename
map_swap_page() to map_swap_entry(), make it 'static' and and implement
map_swap_page() as a wrapper around that.

Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
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>
mm: define PAGE_MAPPING_FLAGS

At present we define PageAnon(page) by the low PAGE_MAPPING_ANON bit set
in page->mapping, with the higher bits a pointer to the anon_vma; and have
defined PageKsm(page) as that with NULL anon_vma.

But KSM swapping will need to store a pointer there: so in preparation for
that, now define PAGE_MAPPING_FLAGS as the low two bits, including
PAGE_MAPPING_KSM (always set along with PAGE_MAPPING_ANON, until some
other use for the bit emerges).

Declare page_rmapping(page) to return the pointer part of page->mapping,
and page_anon_vma(page) to return the anon_vma pointer when that's what it
is.  Use these in a few appropriate places: notably, unuse_vma() has been
testing page->mapping, but is better to be testing page_anon_vma() (cases
may be added in which flag bits are set without any pointer).

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>