ext4: speed up truncate/unlink by not using bforget() unless needed

Do not iterate over data blocks scanning for bh's to forget as they're
never exist. This improves time taken by unlink / truncate syscall.
Tested by continuously truncating file that is being written by dd.
Another test is rm -rf of linux tree while tar unpacks it. With
ordered data mode condition unlikely(!tbh) was always met in
ext4_free_blocks. With journal data mode tbh was found only few times,
so optimisation is also possible.

Unlinking fallocated 60G file after doing sync && echo 3 >
/proc/sys/vm/drop_caches && time rm --help

X86 before (linux 3.6-rc4):
# time rm -f test1
real    0m2.710s
user    0m0.000s
sys     0m1.530s

X86 after:
# time rm -f test1
real    0m0.644s
user    0m0.003s
sys     0m0.060s

MIPS before (linux 2.6.37):
# time rm -f test1
real    0m 4.93s
user    0m 0.00s
sys     0m 4.61s

MIPS after:
# time rm -f test1
real    0m 0.16s
user    0m 0.00s
sys     0m 0.06s

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrey Sidorov <qrxd43@motorola.com>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
kthread: squash https://github.com/torvalds/linux/commit/9a2e03d8ed518a61154f18d83d6466628e519f94 and https://github.com/torvalds/linux/commit/46f3d976213452350f9d10b0c2780c2681f7075b

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
kthread: Implement park/unpark facility

To avoid the full teardown/setup of per cpu kthreads in the case of
cpu hot(un)plug, provide a facility which allows to put the kthread
into a park position and unpark it when the cpu comes online again.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120716103948.236618824@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
smp: patches from mainline 3.5 to hopefully help with hotplug
efficiency

Thomas Gleixner's generic-idle patches:

smp: Add task_struct argument to __cpu_up()
Preparatory patch to make the idle thread allocation for secondary
cpus generic.
http://git.kernel.org/?p=linux/kernel/git/tip/tip.git;a=commit;h=8239c25f47d2b318156993b15f33900a86ea5e17

smp: Add generic smpboot facility
Start a new file, which will hold SMP and CPU hotplug related generic
infrastructure.
http://git.kernel.org/?p=linux/kernel/git/tip/tip.git;a=commit;h=38498a67aa2cf8c80754b8d304bfacc10bc582b5

smp: Provide generic idle thread allocation
All SMP architectures have magic to fork the idle task and to store it
for reusage when cpu hotplug is enabled. Provide a generic
infrastructure for it.
Create/reinit the idle thread for the cpu which is brought up in the
generic code and hand the thread pointer to the architecture code via
__cpu_up().
Note, that fork_idle() is called via a workqueue, because this
guarantees that the idle thread does not get a reference to a user
space VM. This can happen when the boot process did not bring up all
possible cpus and a later cpu_up() is initiated via the sysfs
interface. In that case fork_idle() would be called in the context of
the user space task and take a reference on the user space VM.
http://git.kernel.org/?p=linux/kernel/git/tip/tip.git;a=commit;h=29d5e0476e1c4a513859e7858845ad172f560389

arm: Use generic idle thread allocation
http://git.kernel.org/?p=linux/kernel/git/tip/tip.git;a=commit;h=84ec6d5796e095e2f8698bd2b5d33849ed26d9e2
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>

Conflicts:
	arch/arm/Kconfig
smp, idle: Allocate idle thread for each possible cpu during boot

percpu areas are already allocated during boot for each possible cpu.
percpu idle threads can be considered as an extension of the percpu areas,
and allocate them for each possible cpu during boot.

This will eliminate the need for workqueue based idle thread allocation.
In future we can move the idle thread area into the percpu area too.

[ tglx: Moved the loop into smpboot.c and added an error check when
  the init code failed to allocate an idle thread for a cpu which
  should be onlined ]

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: venki@google.com
Link: http://lkml.kernel.org/r/1334966930.28674.245.camel@sbsiddha-desk.sc.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
smpboot, idle: Optimize calls to smp_processor_id() in idle_threads_init()

While trying to initialize idle threads for all cpus, idle_threads_init()
calls smp_processor_id() in a loop, which is unnecessary. The intent
is to initialize idle threads for all non-boot cpus. So just use a variable
to note the boot cpu and use it in the loop.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: suresh.b.siddha@intel.com
Cc: venki@google.com
Cc: nikunj@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/20120524151055.2549.64309.stgit@srivatsabhat.in.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
smpboot, idle: Fix comment mismatch over idle_threads_init()

The comment over idle_threads_init() really talks about the functionality
of idle_init(). Move that comment to idle_init(), and add a suitable
comment over idle_threads_init().

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: suresh.b.siddha@intel.com
Cc: venki@google.com
Cc: nikunj@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/20120524151100.2549.66501.stgit@srivatsabhat.in.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
smpboot: Provide infrastructure for percpu hotplug threads

Provide a generic interface for setting up and tearing down percpu
threads.

On registration the threads for already online cpus are created and
started. On deregistration (modules) the threads are stoppped.

During hotplug operations the threads are created, started, parked and
unparked. The datastructure for registration provides a pointer to
percpu storage space and optional setup, cleanup, park, unpark
functions. These functions are called when the thread state changes.

Each implementation has to provide a function which is queried and
returns whether the thread should run and the thread function itself.

The core code handles all state transitions and avoids duplicated code
in the call sites.

[ paulmck: Preemption leak fix ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20120716103948.352501068@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
hotplug: Fix UP bug in smpboot hotplug code

Because kernel subsystems need their per-CPU kthreads on UP systems as
well as on SMP systems, the smpboot hotplug kthread functions must be
provided in UP builds as well as in SMP builds.  This commit therefore
adds smpboot.c to UP builds and excludes irrelevant code via #ifdef.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
smpboot: Allow selfparking per cpu threads

The stop machine threads are still killed when a cpu goes offline. The
reason is that the thread is used to bring the cpu down, so it can't
be parked along with the other per cpu threads.

Allow a per cpu thread to be excluded from automatic parking, so it
can park itself once it's done

Add a create callback function as well.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Arjan van de Veen <arjan@infradead.org>
Cc: Paul Turner <pjt@google.com>
Cc: Richard Weinberger <rw@linutronix.de>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130131120741.553993267@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
stop_machine: Store task reference in a separate per cpu variable

To allow the stopper thread being managed by the smpboot thread
infrastructure separate out the task storage from the stopper data
structure.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Arjan van de Veen <arjan@infradead.org>
Cc: Paul Turner <pjt@google.com>
Cc: Richard Weinberger <rw@linutronix.de>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130131120741.626690384@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
stop_machine: Use smpboot threads

Use the smpboot thread infrastructure. Mark the stopper thread
selfparking and park it after it has finished the take_cpu_down()
work.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Arjan van de Veen <arjan@infradead.org>
Cc: Paul Turner <pjt@google.com>
Cc: Richard Weinberger <rw@linutronix.de>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130131120741.686315164@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
stop_machine: Mark per cpu stopper enabled early

commit 14e568e78 (stop_machine: Use smpboot threads) introduced the
following regression:

Before this commit the stopper enabled bit was set in the online
notifier.

CPU0				CPU1
cpu_up
				cpu online
hotplug_notifier(ONLINE)
  stopper(CPU1)->enabled = true;
...
stop_machine()

The conversion to smpboot threads moved the enablement to the wakeup
path of the parked thread. The majority of users seem to have the
following working order:

CPU0				CPU1
cpu_up
				cpu online
unpark_threads()
  wakeup(stopper[CPU1])
....
				stopper thread runs
				  stopper(CPU1)->enabled = true;
stop_machine()

But Konrad and Sander have observed:

CPU0				CPU1
cpu_up
				cpu online
unpark_threads()
  wakeup(stopper[CPU1])
....
stop_machine()
				stopper thread runs
				  stopper(CPU1)->enabled = true;

Now the stop machinery kicks CPU0 into the stop loop, where it gets
stuck forever because the queue code saw stopper(CPU1)->enabled ==
false, so CPU0 waits for CPU1 to enter stomp_machine, but the CPU1
stopper work got discarded due to enabled == false.

Add a pre_unpark function to the smpboot thread descriptor and call it
before waking the thread.

This fixes the problem at hand, but the stop_machine code should be
more robust. The stopper->enabled flag smells fishy at best.

Thanks to Konrad for going through a loop of debug patches and
providing the information to decode this issue.

Reported-and-tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reported-and-tested-by: Sander Eikelenboom <linux@eikelenboom.it>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1302261843240.22263@ionos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
kthread: Prevent unpark race which puts threads on the wrong cpu

The smpboot threads rely on the park/unpark mechanism which binds per
cpu threads on a particular core. Though the functionality is racy:

CPU0	       	 	CPU1  	     	    CPU2
unpark(T)				    wake_up_process(T)
  clear(SHOULD_PARK)	T runs
			leave parkme() due to !SHOULD_PARK
  bind_to(CPU2)		BUG_ON(wrong CPU)

We cannot let the tasks move themself to the target CPU as one of
those tasks is actually the migration thread itself, which requires
that it starts running on the target cpu right away.

The solution to this problem is to prevent wakeups in park mode which
are not from unpark(). That way we can guarantee that the association
of the task to the target cpu is working correctly.

Add a new task state (TASK_PARKED) which prevents other wakeups and
use this state explicitly for the unpark wakeup.

Peter noticed: Also, since the task state is visible to userspace and
all the parked tasks are still in the PID space, its a good hint in ps
and friends that these tasks aren't really there for the moment.

The migration thread has another related issue.

CPU0	      	     	 CPU1
Bring up CPU2
create_thread(T)
park(T)
 wait_for_completion()
			 parkme()
			 complete()
sched_set_stop_task()
			 schedule(TASK_PARKED)

The sched_set_stop_task() call is issued while the task is on the
runqueue of CPU1 and that confuses the hell out of the stop_task class
on that cpu. So we need the same synchronizaion before
sched_set_stop_task().

Reported-by: Dave Jones <davej@redhat.com>
Reported-and-tested-by: Dave Hansen <dave@sr71.net>
Reported-and-tested-by: Borislav Petkov <bp@alien8.de>
Acked-by: Peter Ziljstra <peterz@infradead.org>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: dhillf@gmail.com
Cc: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1304091635430.21884@ionos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
cpufreq: Optimize cpufreq_frequency_table_verify()

cpufreq_frequency_table_verify() is rewritten here to make it more logical
and efficient.
 - merge multiple lines for variable declarations together.
 - quit early if any frequency between min/max is found.
 - don't call cpufreq_verify_within_limits() in case any valid freq is
   found as it is of no use.
 - rename the count variable as found and change its type to boolean.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
cpufreq: Fix policy getting stuck when user & kernel min/max don't overlap

Every __cpufreq_set_policy starts with checking the new policy min/max has
some overlap with the current policy min/max. This works out fine until we
end up with the policy min/max being set to a range that doesn't overlap
with the user policy min/max. Once we get into this situation, the check at
the start of __cpufreq_set_policy fails and prevents us from getting out of
this state.

This only happens when one of the CPUFREQ_ADJUST/CPUFREQ_INCOMPATIBLE
notifiers called inside __cpufreq_set_policy pick a min/max outside the
range of user policy min/max.

The real intent of the check at the start of __cpufreq_set_policy is to
make sure userspace can't set user policy min > user policy max. Since
__cpufreq_set_policy always gets called only with current user policy
min/max except when the actual user space policy min/max is changed, we can
fix the issue by simply checking the new policy min/max against current
user policy min/max.

Change-Id: Iaac805825e64d7985c41fb9052bd96baacdf3d6f
Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
CPU hotplug, debug: detect imbalance between get_online_cpus() and put_online_cpus()

The synchronization between CPU hotplug readers and writers is achieved
by means of refcounting, safeguarded by the cpu_hotplug.lock.

get_online_cpus() increments the refcount, whereas put_online_cpus()
decrements it.  If we ever hit an imbalance between the two, we end up
compromising the guarantees of the hotplug synchronization i.e, for
example, an extra call to put_online_cpus() can end up allowing a
hotplug reader to execute concurrently with a hotplug writer.

So, add a WARN_ON() in put_online_cpus() to detect such cases where the
refcount can go negative, and also attempt to fix it up, so that we can
continue to run.

Change-Id: I144efeaa5899a2e8a3cddd21f010679cbaaa2459
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-commit: 075663d19885eb3738fd2d7dbdb8947e12563b68
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Osvaldo Banuelos <osvaldob@codeaurora.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>