Commit a9327cac added seperate read
and write statistics of in_flight requests. And exported the number
of read and write requests in progress seperately through sysfs.

But  Corrado Zoccolo <czoccolo@gmail.com> reported getting strange
output from "iostat -kx 2". Global values for service time and
utilization were garbage. For interval values, utilization was always
100%, and service time is higher than normal.

So this was reverted by commit 0f78ab98

The problem was in part_round_stats_single(), I missed the following:
        if (now == part->stamp)
                return;

-       if (part->in_flight) {
+       if (part_in_flight(part)) {
                __part_stat_add(cpu, part, time_in_queue,
                                part_in_flight(part) * (now - part->stamp));
                __part_stat_add(cpu, part, io_ticks, (now - part->stamp));

With this chunk included, the reported regression gets fixed.
Signed-off-by: NNikanth Karthikesan <knikanth@suse.de>

--
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

It was briefly introduced to allow CFQ to to delayed scheduling,
but we ended up removing that feature again. So lets kill the
function and export, and just switch CFQ back to the normal work
schedule since it is now passing in a '0' delay from all call
sites.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

The RR service tree is indexed by a key that is relative to current jiffies.
This can cause problems on jiffies wraparound.

The patch fixes it using time_before comparison, and changing
the add_front path to use a relative number, too.
Signed-off-by: NCorrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

cfq uses rq->start_time as the fifo indicator, but that field may
get modified prior to cfq doing it's fifo list adjustment when
a request gets merged with another request. This can cause the
fifo list to become unordered.
Reported-by: NCorrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

This reverts commit a9327cac.

Corrado Zoccolo <czoccolo@gmail.com> reports:

"with 2.6.32-rc1 I started getting the following strange output from
"iostat -kx 2":
Linux 2.6.31bisect (et2) 	04/10/2009 	_i686_	(2 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
          10,70    0,00    3,16   15,75    0,00   70,38

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
avgrq-sz avgqu-sz   await  svctm  %util
sda              18,22     0,00    0,67    0,01    14,77     0,02
43,94     0,01   10,53 39043915,03 2629219,87
sdb              60,89     9,68   50,79    3,04  1724,43    50,52
65,95     0,70   13,06 488437,47 2629219,87

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           2,72    0,00    0,74    0,00    0,00   96,53

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
avgrq-sz avgqu-sz   await  svctm  %util
sda               0,00     0,00    0,00    0,00     0,00     0,00
0,00     0,00    0,00   0,00 100,00
sdb               0,00     0,00    0,00    0,00     0,00     0,00
0,00     0,00    0,00   0,00 100,00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           6,68    0,00    0,99    0,00    0,00   92,33

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
avgrq-sz avgqu-sz   await  svctm  %util
sda               0,00     0,00    0,00    0,00     0,00     0,00
0,00     0,00    0,00   0,00 100,00
sdb               0,00     0,00    0,00    0,00     0,00     0,00
0,00     0,00    0,00   0,00 100,00

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           4,40    0,00    0,73    1,47    0,00   93,40

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
avgrq-sz avgqu-sz   await  svctm  %util
sda               0,00     0,00    0,00    0,00     0,00     0,00
0,00     0,00    0,00   0,00 100,00
sdb               0,00     4,00    0,00    3,00     0,00    28,00
18,67     0,06   19,50 333,33 100,00

Global values for service time and utilization are garbage. For
interval values, utilization is always 100%, and service time is
higher than normal.

I bisected it down to:
[a9327cac] Seperate read and write
statistics of in_flight requests
and verified that reverting just that commit indeed solves the issue
on 2.6.32-rc1."

So until this is debugged, revert the bad commit.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

We cannot delay for the first dispatch of the async queue if it
hasn't dispatched at all, since that could present a local user
DoS attack vector using an app that just did slow timed sync reads
while filling memory.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Not all users of the topology information want to use libblkid.  Provide
the topology information through bdev ioctls.

Also clarify sector size comments for existing BLK ioctls.
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

We should use the sysfs modified slice sync value, in case it differs
from the default.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Don't think that's necessarily a perfect description of what this
option fiddles with, but it's probably better than 'desktop'.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

This slowly ramps up the async queue depth based on the time
passed since the sync IO, and doesn't allow async at all until
a sync slice period has passed.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

o Do not allow more than max_dispatch requests from an async queue, if some
  sync request has finished recently. This is in the hope that sync activity
  is still going on in the system and we might receive a sync request soon.
  Most likely from a sync queue which finished a request and we did not enable
  idling on it.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

This is basically identical to what Vivek Goyal posted, but combined
into one and labelled 'desktop' instead of 'fairness'. The goal
is to continue to improve on the latency side of things as it relates
to interactiveness, keeping the questionable bits under this sysfs
tunable so it would be easy for throughput-only people to turn off.

Apart from adding the interactive sysfs knob, it also adds the
behavioural change of allowing slice idling even if the hardware
does tagged command queuing.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Since 2.6.31 now has request-based device-mapper, it's useful to have
a tracepoint for request-remapping as well as bio-remapping.
This patch adds a tracepoint for request-remapping, trace_block_rq_remap().
Signed-off-by: NKiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: NJun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: Alasdair G Kergon <agk@redhat.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Currently we set the bio size to the byte equivalent of the blocks to
be trimmed when submitting the initial DISCARD ioctl.  That means it
is subject to the max_hw_sectors limitation of the HBA which is
much lower than the size of a DISCARD request we can support.
Add a separate max_discard_sectors tunable to limit the size for discard
requests.

We limit the max discard request size in bytes to 32bit as that is the
limit for bio->bi_size.  This could be much larger if we had a way to pass
that information through the block layer.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

prepare_discard_fn() was being called in a place where memory allocation
was effectively impossible.  This makes it inappropriate for all but
the most trivial translations of Linux's DISCARD operation to the block
command set.  Additionally adding a payload there makes the ownership
of the bio backing unclear as it's now allocated by the device driver
and not the submitter as usual.

It is replaced with QUEUE_FLAG_DISCARD which is used to indicate whether
the queue supports discard operations or not.  blkdev_issue_discard now
allocates a one-page, sector-length payload which is the right thing
for the common ATA and SCSI implementations.

The mtd implementation of prepare_discard_fn() is replaced with simply
checking for the request being a discard.

Largely based on a previous patch from Matthew Wilcox <matthew@wil.cx>
which did the prepare_discard_fn but not the different payload allocation
yet.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Add missing blk_trace_remove_sysfs to be in pair with blk_trace_init_sysfs
introduced in commit 1d54ad6d.
Release kobject also in case the request_fn is NULL.

Problem was noticed via kmemleak backtrace when some sysfs entries were
note properly destroyed during  device removal:

unreferenced object 0xffff88001aa76640 (size 80):
  comm "lvcreate", pid 2120, jiffies 4294885144
  hex dump (first 32 bytes):
    01 00 00 00 00 00 00 00 f0 65 a7 1a 00 88 ff ff  .........e......
    90 66 a7 1a 00 88 ff ff 86 1d 53 81 ff ff ff ff  .f........S.....
  backtrace:
    [<ffffffff813f9cc6>] kmemleak_alloc+0x26/0x60
    [<ffffffff8111d693>] kmem_cache_alloc+0x133/0x1c0
    [<ffffffff81195891>] sysfs_new_dirent+0x41/0x120
    [<ffffffff81194b0c>] sysfs_add_file_mode+0x3c/0xb0
    [<ffffffff81197c81>] internal_create_group+0xc1/0x1a0
    [<ffffffff81197d93>] sysfs_create_group+0x13/0x20
    [<ffffffff810d8004>] blk_trace_init_sysfs+0x14/0x20
    [<ffffffff8123f45c>] blk_register_queue+0x3c/0xf0
    [<ffffffff812447e4>] add_disk+0x94/0x160
    [<ffffffffa00d8b08>] dm_create+0x598/0x6e0 [dm_mod]
    [<ffffffffa00de951>] dev_create+0x51/0x350 [dm_mod]
    [<ffffffffa00de823>] ctl_ioctl+0x1a3/0x240 [dm_mod]
    [<ffffffffa00de8f2>] dm_compat_ctl_ioctl+0x12/0x20 [dm_mod]
    [<ffffffff81177bfd>] compat_sys_ioctl+0xcd/0x4f0
    [<ffffffff81036ed8>] sysenter_dispatch+0x7/0x2c
    [<ffffffffffffffff>] 0xffffffffffffffff
Signed-off-by: NZdenek Kabelac <zkabelac@redhat.com>
Reviewed-by: NLi Zefan <lizf@cn.fujitsu.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Stacking devices do not have an inherent max_hw_sector limit.  Set the
default to INT_MAX so we are bounded only by capabilities of the
underlying storage.
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

The topology changes unintentionally caused SAFE_MAX_SECTORS to be set
for stacking devices.  Set the default limit to BLK_DEF_MAX_SECTORS and
provide SAFE_MAX_SECTORS in blk_queue_make_request() for legacy hw
drivers that depend on the old behavior.
Acked-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

This allows subsytems to provide devtmpfs with non-default permissions
for the device node. Instead of the default mode of 0600, null, zero,
random, urandom, full, tty, ptmx now have a mode of 0666, which allows
non-privileged processes to access standard device nodes in case no
other userspace process applies the expected permissions.

This also fixes a wrong assignment in pktcdvd and a checkpatch.pl complain.
Signed-off-by: NKay Sievers <kay.sievers@vrfy.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Let attribute group vectors be declared "const".  We'd
like to let most attribute metadata live in read-only
sections... this is a start.
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

blk_ioctl_discard duplicates large amounts of code from blkdev_issue_discard,
the only difference between the two is that blkdev_issue_discard needs to
send a barrier discard request and blk_ioctl_discard a non-barrier one,
and blk_ioctl_discard needs to wait on the request.  To facilitates this
add a flags argument to blkdev_issue_discard to control both aspects of the
behaviour.  This will be very useful later on for using the waiting
funcitonality for other callers.

Based on an earlier patch from Matthew Wilcox <matthew@wil.cx>.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Stacked devices do not. For now, just error out with -EINVAL. Later
we could make the limit apply on stacked devices too, for throttling
reasons.

This fixes

5a54cd13353bb3b88887604e2c980aa01e314309

and should go into 2.6.31 stable as well.

Cc: stable@kernel.org
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Implement blk_limits_io_opt() and make blk_queue_io_opt() a wrapper
around it. DM needs this to avoid poking at the queue_limits directly.
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

This patch addresses http://bugzilla.kernel.org/show_bug.cgi?id=13401, a
regression introduced in 2.6.30.

From the bug report:
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Currently, there is a single in_flight counter measuring the number of
requests in the request_queue. But some monitoring tools would like to
know how many read requests and write requests are in progress. Split the
current in_flight counter into two seperate counters for read and write.

This information is exported as a sysfs attribute, as changing the
currently available stat files would break the existing tools.
Signed-off-by: NNikanth Karthikesan <knikanth@suse.de>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

If BIO is discarded or cross over end of device,
BIO queueing trial doesn't occur.

Actually the trace was called just before make_request at first:
[PATCH] Block queue IO tracing support (blktrace) as of 2006-03-23
      2056a782

And then 2 patches added some checks between them:
[PATCH] md: check bio address after mapping through partitions
        5ddfe969,
[BLOCK] Don't allow empty barriers to be passed down to
queues that don't grok them
        51fd77bd

It breaks original goal.
Let's trace it only when it happens.
Signed-off-by: NMinchan Kim <minchan.kim@gmail.com>
Acked-by: NWu Fengguang <fengguang.wu@intel.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

The blktrace tools can show process id when cfq dispatched a request,
using cfq_log_cfqq() instead of cfq_log().
Signed-off-by: NShan Wei <shanwei@cn.fujitsu.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

It's not currently used, as pointed out by
Gui Jianfeng <guijianfeng@cn.fujitsu.com>. We already check the
wait_request flag to allow an idling queue priority allocation access,
so we don't need this extra flag.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

We already have interrupts disabled at that point, so use the
__raise_softirq_irqoff() variant.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

It's not exported, I doubt we'll have a reason to change this...
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Note sure why they happened in the first place, probably some bad
terminal setting.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

This borrows some code from NAPI and implements a polled completion
mode for block devices. The idea is the same as NAPI - instead of
doing the command completion when the irq occurs, schedule a dedicated
softirq in the hopes that we will complete more IO when the iopoll
handler is invoked. Devices have a budget of commands assigned, and will
stay in polled mode as long as they continue to consume their budget
from the iopoll softirq handler. If they do not, the device is set back
to interrupt completion mode.

This patch holds the core bits for blk-iopoll, device driver support
sold separately.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Instead of just checking whether this device uses block layer
tagging, we can improve the detection by looking at the maximum
queue depth it has reached. If that crosses 4, then deem it a
queuing device.

This is important on high IOPS devices, since plugging hurts
the performance there (it can be as much as 10-15% of the sys
time).
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Get rid of any functions that test for these bits and make callers
use bio_rw_flagged() directly. Then it is at least directly apparent
what variable and flag they check.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Whenever a block device changes it's read-only attribute
notify the userspace about it.
Signed-off-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NNikanth Karthikesan <knikanth@suse.de>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

o Get rid of busy_rt_queues infrastructure. Looks like it is redundant.

o Once an RT queue gets request it will preempt any of the BE or IDLE queues
  immediately. Otherwise this queue will be put on service tree and scheduler
  will anyway select this queue before any of the BE or IDLE queue. Hence
  looks like there is no need to keep track of how many busy RT queues are
  currently on service tree.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

To lessen the impact of async IO on sync IO, let the device drain of
any async IO in progress when switching to a sync cfqq that has idling
enabled.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Update scsi_io_completion() such that it only fails requests till the
next error boundary and retry the leftover.  This enables block layer
to merge requests with different failfast settings and still behave
correctly on errors.  Allow merge of requests of different failfast
settings.

As SCSI is currently the only subsystem which follows failfast status,
there's no need to worry about other block drivers for now.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Niel Lambrechts <niel.lambrechts@gmail.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Failfast has characteristics from other attributes.  When issuing,
executing and successuflly completing requests, failfast doesn't make
any difference.  It only affects how a request is handled on failure.
Allowing requests with different failfast settings to be merged cause
normal IOs to fail prematurely while not allowing has performance
penalties as failfast is used for read aheads which are likely to be
located near in-flight or to-be-issued normal IOs.

This patch introduces the concept of 'mixed merge'.  A request is a
mixed merge if it is merge of segments which require different
handling on failure.  Currently the only mixable attributes are
failfast ones (or lack thereof).

When a bio with different failfast settings is added to an existing
request or requests of different failfast settings are merged, the
merged request is marked mixed.  Each bio carries failfast settings
and the request always tracks failfast state of the first bio.  When
the request fails, blk_rq_err_bytes() can be used to determine how
many bytes can be safely failed without crossing into an area which
requires further retrials.

This allows request merging regardless of failfast settings while
keeping the failure handling correct.

This patch only implements mixed merge but doesn't enable it.  The
next one will update SCSI to make use of mixed merge.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Niel Lambrechts <niel.lambrechts@gmail.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>