list_entry() and hlist_entry() are both simply aliases for
container_of(), but since io_context.cic_list.first is an hlist_node one
should at least use the correct alias.
Signed-off-by: NPaul Bolle <pebolle@tiscali.nl>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

queue_fail can only be reached if cic is NULL, so its check for cic must
be bogus.
Signed-off-by: NPaul Bolle <pebolle@tiscali.nl>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Fix comment typo and remove unnecessary semicolon at macro
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

We need them in SCSI to fix a bug, but currently they are not
exported to modules. Export them.
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Add cgroup subsystem callbacks for per-thread attachment in atomic contexts

Add can_attach_task(), pre_attach(), and attach_task() as new callbacks
for cgroups's subsystem interface.  Unlike can_attach and attach, these
are for per-thread operations, to be called potentially many times when
attaching an entire threadgroup.

Also, the old "bool threadgroup" interface is removed, as replaced by
this.  All subsystems are modified for the new interface - of note is
cpuset, which requires from/to nodemasks for attach to be globally scoped
(though per-cpuset would work too) to persist from its pre_attach to
attach_task and attach.

This is a pre-patch for cgroup-procs-writable.patch.
Signed-off-by: NBen Blum <bblum@andrew.cmu.edu>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Reviewed-by: NPaul Menage <menage@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

sector is never read inside the function.
Signed-off-by: NLuca Tettamanti <kronos.it@gmail.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

9fd097b1 (block: unexport DISK_EVENT_MEDIA_CHANGE for legacy/fringe
drivers) removed DISK_EVENT_MEDIA_CHANGE from legacy/fringe block
drivers which have inadequate ->check_events().  Combined with earlier
change 7c88a168 (block: don't propagate unlisted DISK_EVENTs to
userland), this enables using ->check_events() for internal processing
while avoiding enabling in-kernel block event polling which can lead
to infinite event loop.

Unfortunately, this made many drivers including floppy without any bit
set in disk->events and ->async_events in which case disk_add_events()
simply skipped allocation of disk->ev, which disables whole event
handling.  As ->check_events() is still used during open processing
for revalidation, this can lead to open failure.

This patch always allocates disk->ev if ->check_events is implemented.
In the long term, it would make sense to simply include the event
structure inline into genhd as it's now used by virtually all block
devices.
Signed-off-by: NTejun Heo <tj@kernel.org>
Reported-by: NOndrej Zary <linux@rainbow-software.org>
Reported-by: NAlex Villacis Lasso <avillaci@ceibo.fiec.espol.edu.ec>
Cc: stable@kernel.org
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

When struct cfq_data allocation fails, cic_index need to be freed.
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

The 'group_changed' variable is initialized to 0 and never changed, so
checking the variable is meaningless.

It is a leftover from 0bbfeb83 ("cfq-iosched: Always provide group
iosolation."). Let's get rid of it.
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Cc: Justin TerAvest <teravest@google.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Reduce the number of bit operations in cfq_choose_req() on average
(and worst) cases.
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Simplify the calculation in cfq_prio_to_maxrq(), plus replace CFQ_PRIO_LISTS to
IOPRIO_BE_NR since they are the same and IOPRIO_BE_NR looks more reasonable in
this context IMHO.
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

If we don't explicitly initialize it to zero, CFQ might think that
cgroup of ioc has changed and it generates lots of unnecessary calls
to call_for_each_cic(changed_cgroup). Fix it.

cfq_get_io_context()
  cfq_ioc_set_cgroup()
     call_for_each_cic(ioc, changed_cgroup)
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Commit 73c10101 ("block: initial patch for on-stack per-task plugging")
removed calls to elv_bio_merged() when @bio merged with @req. Re-add them.

This in turn will update merged stats in associated group. That
should be safe as long as request has got reference to the blkio_group.
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Cc: Divyesh Shah <dpshah@google.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Make BLKIO_STAT_MERGED per cpu hence gettring rid of need of taking
blkg->stats_lock.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

We allocated per cpu stats struct for root group but did not free it.
Fix it.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

We don't need them anymore, so kill:

- REQ_ON_PLUG checks in various places
- !rq_mergeable() check in plug merging
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Currently we take a queue lock on each bio to check if there are any
throttling rules associated with the group and also update the stats.
Now access the group under rcu and update the stats without taking
the queue lock. Queue lock is taken only if there are throttling rules
associated with the group.

So the common case of root group when there are no rules, save
unnecessary pounding of request queue lock.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Now dispatch stats update is lock free. But reset of these stats still
takes blkg->stats_lock and is dependent on that. As stats are per cpu,
we should be able to just reset the stats on each cpu without any locks.
(Atleast for 64bit arch).

On 32bit arch there is a small race where 64bit updates are not atomic.
The result of this race can be that in the presence of other writers,
one might not get 0 value after reset of a stat and might see something
intermediate

One can write more complicated code to cover this race like sending IPI
to other cpus to reset stats and for offline cpus, reset these directly.

Right not I am not taking that path because reset_update is more of a
debug feature and it can happen only on 32bit arch and possibility of
it happening is small. Will fix it if it becomes a real problem. For
the time being going for code simplicity.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Some of the stats are 64bit and updation will be non atomic on 32bit
architecture. Use sequence counters on 32bit arch to make reading
of stats safe.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Currently we take blkg_stat lock for even updating the stats. So even if
a group has no throttling rules (common case for root group), we end
up taking blkg_lock, for updating the stats.

Make dispatch stats per cpu so that these can be updated without taking
blkg lock.

If cpu goes offline, these stats simply disappear. No protection has
been provided for that yet. Do we really need anything for that?
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Soon we will allow accessing a throtl_grp under rcu_read_lock(). Hence
start freeing up throtl_grp after one rcu grace period.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Use same helper function for root group as we use with dynamically
allocated groups to add it to various lists.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

A helper function for the code which is used at 2-3 places. Makes reading
code little easier.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Currently, we allocate root throtl_grp statically. But as we will be
introducing per cpu stat pointers and that will be allocated
dynamically even for root group, we might as well make whole root
throtl_grp allocation dynamic and treat it in same manner as other
groups.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Currently, all the cfq_group or throtl_group allocations happen while
we are holding ->queue_lock and sleeping is not allowed.

Soon, we will move to per cpu stats and also need to allocate the
per group stats. As one can not call alloc_percpu() from atomic
context as it can sleep, we need to drop ->queue_lock, allocate the
group, retake the lock and continue processing.

In throttling code, I check the queue DEAD flag again to make sure
that driver did not call blk_cleanup_queue() in the mean time.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

blkg->key = cfqd is an rcu protected pointer and hence we used to do
call_rcu(cfqd->rcu_head) to free up cfqd after one rcu grace period.

The problem here is that even though cfqd is around, there are no
gurantees that associated request queue (td->queue) or q->queue_lock
is still around. A driver might have called blk_cleanup_queue() and
release the lock.

It might happen that after freeing up the lock we call
blkg->key->queue->queue_ock and crash. This is possible in following
path.

blkiocg_destroy()
 blkio_unlink_group_fn()
  cfq_unlink_blkio_group()

Hence, wait for an rcu peirod if there are groups which have not
been unlinked from blkcg->blkg_list. That way, if there are any groups
which are taking cfq_unlink_blkio_group() path, can safely take queue
lock.

This is how we have taken care of race in throttling logic also.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Nobody seems to be using cfq_find_alloc_cfqg() function parameter "create".
Get rid of that.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

cgroup unaccounted_time file is created only if CONFIG_DEBUG_BLK_CGROUP=y.
there are some fields which are out side this config option. Fix that.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Group initialization code seems to be at two places. root group
initialization in blk_throtl_init() and dynamically allocated group
in throtl_find_alloc_tg(). Create a common function and use at both
the places.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

blk_cleanup_queue() calls elevator_exit() and after this, we can't
touch the elevator without oopsing.  __elv_next_request() must check
for this state because in the refcounted queue model, we can still
call it after blk_cleanup_queue() has been called.

This was reported as causing an oops attributable to scsi.
Signed-off-by: NJames Bottomley <James.Bottomley@suse.de>
Cc: stable@kernel.org
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Let's check a scenario:
1. blk_delay_queue(q, SCSI_QUEUE_DELAY);
2. blk_run_queue_async();
the second one will became a noop, because q->delay_work already has
WORK_STRUCT_PENDING_BIT set, so the delayed work will still run after
SCSI_QUEUE_DELAY. But blk_run_queue_async actually hopes the delayed
work runs immediately.

Fix this by doing a cancel on potentially pending delayed work
before queuing an immediate run of the workqueue.
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

In some cases we would end up stacking discard_zeroes_data incorrectly.
Fix this by enabling the feature by default for stacking drivers and
clearing it for low-level drivers. Incorporating a device that does not
support dzd will then cause the feature to be disabled in the stacking
driver.

Also ensure that the maximum discard value does not overflow when
exported in sysfs and return 0 in the alignment and dzd fields for
devices that don't support discard.
Reported-by: NLukas Czerner <lczerner@redhat.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Acked-by: NMike Snitzer <snitzer@redhat.com>
Cc: stable@kernel.org
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Currentlly we first map the task to cgroup and then cgroup to
blkio_cgroup. There is a more direct way to get to blkio_cgroup
from task using task_subsys_state(). Use that.

The real reason for the fix is that it also avoids a race in generic
cgroup code. During remount/umount rebind_subsystems() is called and
it can do following with and rcu protection.

cgrp->subsys[i] = NULL;

That means if somebody got hold of cgroup under rcu and then it tried
to do cgroup->subsys[] to get to blkio_cgroup, it would get NULL which
is wrong. I was running into this race condition with ltp running on a
upstream derived kernel and that lead to crash.

So ideally we should also fix cgroup generic code to wait for rcu
grace period before setting pointer to NULL. Li Zefan is not very keen
on introducing synchronize_wait() as he thinks it will slow
down moun/remount/umount operations.

So for the time being atleast fix the kernel crash by taking a more
direct route to blkio_cgroup.

One tester had reported a crash while running LTP on a derived kernel
and with this fix crash is no more seen while the test has been
running for over 6 days.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Reviewed-by: NLi Zefan <lizf@cn.fujitsu.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Currently we return -EOPNOTSUPP in blkdev_issue_discard() if any of the
bio fails due to underlying device not supporting discard request.
However, if the device is for example dm device composed of devices
which some of them support discard and some of them does not, it is ok
for some bios to fail with EOPNOTSUPP, but it does not mean that discard
is not supported at all.

This commit removes the check for bios failed with EOPNOTSUPP and change
blkdev_issue_discard() to return operation not supported if and only if
the device does not actually supports it, not just part of the device as
some bios might indicate.

This change also fixes problem with BLKDISCARD ioctl() which now works
correctly on such dm devices.
Signed-off-by: NLukas Czerner <lczerner@redhat.com>
CC: Jens Axboe <jaxboe@fusionio.com>
CC: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

In blkdev_issue_zeroout() we are submitting regular WRITE bios, so we do
not need to check for -EOPNOTSUPP specifically in case of error. Also
there is no need to have label submit: because there is no way to jump
out from the while cycle without an error and we really want to exit,
rather than try again. And also remove the check for (sz == 0) since at
that point sz can never be zero.
Signed-off-by: NLukas Czerner <lczerner@redhat.com>
Reviewed-by: NJeff Moyer <jmoyer@redhat.com>
CC: Dmitry Monakhov <dmonakhov@openvz.org>
CC: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Currently we are waiting for every submitted REQ_DISCARD bio separately,
but it can have unwanted consequences of repeatedly flushing the queue,
so we rather submit bios in batches and wait for the entire batch, hence
narrowing the window of other ios going in.

Use bio_batch_end_io() and struct bio_batch for that purpose, the same
is used by blkdev_issue_zeroout(). Also change bio_batch_end_io() so we
always set !BIO_UPTODATE in the case of error and remove the check for
bb, since we are the only user of this function and we always set this.

Remove bio_get()/bio_put() from the blkdev_issue_discard() since
bio_alloc() and bio_batch_end_io() is doing the same thing, hence it is
not needed anymore.

I have done simple dd testing with surprising results. The script I have
used is:

for i in $(seq 10); do
        echo $i
        dd if=/dev/sdb1 of=/dev/sdc1 bs=4k &
        sleep 5
done
/usr/bin/time -f %e ./blkdiscard /dev/sdc1

Running time of BLKDISCARD on the whole device:
with patch              without patch
0.95                    15.58

So we can see that in this artificial test the kernel with the patch
applied is approx 16x faster in discarding the device.
Signed-off-by: NLukas Czerner <lczerner@redhat.com>
CC: Dmitry Monakhov <dmonakhov@openvz.org>
CC: Jens Axboe <jaxboe@fusionio.com>
CC: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

In some drives, flush requests are non-queueable. When flush request is
running, normal read/write requests can't run. If block layer dispatches
such request, driver can't handle it and requeue it.  Tejun suggested we
can hold the queue when flush is running. This can avoid unnecessary
requeue.  Also this can improve performance. For example, we have
request flush1, write1, flush 2. flush1 is dispatched, then queue is
hold, write1 isn't inserted to queue. After flush1 is finished, flush2
will be dispatched. Since disk cache is already clean, flush2 will be
finished very soon, so looks like flush2 is folded to flush1.

In my test, the queue holding completely solves a regression introduced by
commit 53d63e6b:

    block: make the flush insertion use the tail of the dispatch list

    It's not a preempt type request, in fact we have to insert it
    behind requests that do specify INSERT_FRONT.

which causes about 20% regression running a sysbench fileio
workload.

Stable: 2.6.39 only

Cc: stable@kernel.org
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

flush request isn't queueable in some drives. Add a flag to let driver
notify block layer about this. We can optimize flush performance with the
knowledge.

Stable: 2.6.39 only

Cc: stable@kernel.org
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

After the anticipatory scheduler was dropped, there was no need to
special-case the request_module string. As such, drop the redundant
sprintf and stack variable.
Signed-off-by: NKees Cook <kees.cook@canonical.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

unplug is replaced with blk_run_queue now in blk_execute_rq_nowait,
so change the comment accordingly.
Signed-off-by: NTao Ma <boyu.mt@taobao.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>