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Re: [dm-devel] Re: [PATCH] dm-add-ioband.patch



On Fri, Apr 03, 2009 at 06:53:42PM +0900, Ryo Tsuruta wrote:
> Hi Alasdair,
> 
> The patches I posted to this ML are still not reflected to the dm
> quilt tree and rejected when applying to the kernel, so I've attached
> the dm-add-ioband.patch and could you please replace the patch in the
> tree? The patch includes some changes which are reflected some
> Lindent's output and some points you suggested before.
> 
> I would appreciate it if you could take a look and review this patch
> and advice me about merging dm-ioband to upstream.

Do we have any agreement on what io bandwith controller we want to
merge?  Personally I don't think a dm target is a good idea, this seem
like something we want to tie into the block layer directly, especially
when using cfq so that it gets integrated into the scheduling decisions.

> 
> Thanks,
> Ryo Tsuruta
> 
> Signed-off-by: Ryo Tsuruta <ryov valinux co jp>
> Signed-off-by: Hirokazu Takahashi <taka valinux co jp>
> 
> ---
>  Documentation/device-mapper/ioband.txt |  976 ++++++++++++++++++++++++
>  drivers/md/Kconfig                     |   13 
>  drivers/md/Makefile                    |    2 
>  drivers/md/dm-ioband-ctl.c             | 1312 +++++++++++++++++++++++++++++++++
>  drivers/md/dm-ioband-policy.c          |  457 +++++++++++
>  drivers/md/dm-ioband-type.c            |   77 +
>  drivers/md/dm-ioband.h                 |  186 ++++
>  7 files changed, 3023 insertions(+)
> 
> Index: linux-2.6.29/Documentation/device-mapper/ioband.txt
> ===================================================================
> --- /dev/null
> +++ linux-2.6.29/Documentation/device-mapper/ioband.txt
> @@ -0,0 +1,976 @@
> +                     Block I/O bandwidth control: dm-ioband
> +
> +            -------------------------------------------------------
> +
> +   Table of Contents
> +
> +   [1]What's dm-ioband all about?
> +
> +   [2]Differences from the CFQ I/O scheduler
> +
> +   [3]How dm-ioband works.
> +
> +   [4]Setup and Installation
> +
> +   [5]Getting started
> +
> +   [6]Command Reference
> +
> +   [7]Examples
> +
> +What's dm-ioband all about?
> +
> +     dm-ioband is an I/O bandwidth controller implemented as a device-mapper
> +   driver. Several jobs using the same block device have to share the
> +   bandwidth of the device. dm-ioband gives bandwidth to each job according
> +   to its weight, which each job can set its own value to.
> +
> +     A job is a group of processes with the same pid or pgrp or uid or a
> +   virtual machine such as KVM or Xen. A job can also be a cgroup by applying
> +   the bio-cgroup patch, which can be found at
> +   [8]http://people.valinux.co.jp/~ryov/bio-cgroup/.
> +
> +     +------+ +------+ +------+   +------+ +------+ +------+
> +     |cgroup| |cgroup| | the  |   | pid  | | pid  | | the  |  jobs
> +     |  A   | |  B   | |others|   |  X   | |  Y   | |others|
> +     +--|---+ +--|---+ +--|---+   +--|---+ +--|---+ +--|---+
> +     +--V----+---V---+----V---+   +--V----+---V---+----V---+
> +     | group | group | default|   | group | group | default|  ioband groups
> +     |       |       |  group |   |       |       |  group |
> +     +-------+-------+--------+   +-------+-------+--------+
> +     |        ioband1         |   |       ioband2          |  ioband devices
> +     +-----------|------------+   +-----------|------------+
> +     +-----------V--------------+-------------V------------+
> +     |                          |                          |
> +     |          sdb1            |           sdb2           |  block devices
> +     +--------------------------+--------------------------+
> +
> +
> +   --------------------------------------------------------------------------
> +
> +Differences from the CFQ I/O scheduler
> +
> +     Dm-ioband is flexible to configure the bandwidth settings.
> +
> +     Dm-ioband can work with any type of I/O scheduler such as the NOOP
> +   scheduler, which is often chosen for high-end storages, since it is
> +   implemented outside the I/O scheduling layer. It allows both of partition
> +   based bandwidth control and job --- a group of processes --- based
> +   control. In addition, it can set different configuration on each block
> +   device to control its bandwidth.
> +
> +     Meanwhile the current implementation of the CFQ scheduler has 8 IO
> +   priority levels and all jobs whose processes have the same IO priority
> +   share the bandwidth assigned to this level between them. And IO priority
> +   is an attribute of a process, so that it equally effects to all block
> +   devices.
> +
> +   --------------------------------------------------------------------------
> +
> +How dm-ioband works.
> +
> +     Every ioband device has one ioband group, which by default is called the
> +   default group.
> +
> +     Ioband devices can also have extra ioband groups in them. Each ioband
> +   group has a job to support and a weight. Proportional to the weight,
> +   dm-ioband gives tokens to the group.
> +
> +     A group passes on I/O requests that its job issues to the underlying
> +   layer so long as it has tokens left, while requests are blocked if there
> +   aren't any tokens left in the group. Tokens are refilled once all of
> +   groups that have requests on a given underlying block device use up their
> +   tokens.
> +
> +     There are two policies for token consumption. One is that a token is
> +   consumed for each I/O request. The other is that a token is consumed for
> +   each I/O sector, for example, one I/O request which consists of
> +   4Kbytes(512bytes * 8 sectors) read consumes 8 tokens. A user can choose
> +   either policy.
> +
> +     With this approach, a job running on an ioband group with large weight
> +   is guaranteed a wide I/O bandwidth.
> +
> +   --------------------------------------------------------------------------
> +
> +Setup and Installation
> +
> +     Build a kernel with these options enabled:
> +
> +     CONFIG_MD
> +     CONFIG_BLK_DEV_DM
> +     CONFIG_DM_IOBAND
> +
> +
> +     If compiled as module, use modprobe to load dm-ioband.
> +
> +     # make modules
> +     # make modules_install
> +     # depmod -a
> +     # modprobe dm-ioband
> +
> +
> +     "dmsetup targets" command shows all available device-mapper targets.
> +   "ioband" and the version number are displayed when dm-ioband has been
> +   loaded.
> +
> +     # dmsetup targets | grep ioband
> +     ioband           v1.10.2
> +
> +
> +   --------------------------------------------------------------------------
> +
> +Getting started
> +
> +     The following is a brief description how to control the I/O bandwidth of
> +   disks. In this description, we'll take one disk with two partitions as an
> +   example target.
> +
> +   --------------------------------------------------------------------------
> +
> +  Create and map ioband devices
> +
> +     Create two ioband devices "ioband1" and "ioband2". "ioband1" is mapped
> +   to "/dev/sda1" and has a weight of 40. "ioband2" is mapped to "/dev/sda2"
> +   and has a weight of 10. "ioband1" can use 80% --- 40/(40+10)*100 --- of
> +   the bandwidth of "/dev/sda" while "ioband2" can use 20%.
> +
> +    # echo "0 $(blockdev --getsize /dev/sda1) ioband /dev/sda1 1 0 0 none" \
> +        "weight 0 :40" | dmsetup create ioband1
> +    # echo "0 $(blockdev --getsize /dev/sda2) ioband /dev/sda2 1 0 0 none" \
> +        "weight 0 :10" | dmsetup create ioband2
> +
> +
> +     If the commands are successful then the device files
> +   "/dev/mapper/ioband1" and "/dev/mapper/ioband2" will have been created.
> +
> +   --------------------------------------------------------------------------
> +
> +  Additional bandwidth control
> +
> +     In this example two extra ioband groups are created on "ioband1."
> +
> +     First, set the ioband group type as user. Next, create two ioband groups
> +   that have id 1000 and 2000. Then, give weights of 30 and 20 to the ioband
> +   groups respectively.
> +
> +    # dmsetup message ioband1 0 type user
> +    # dmsetup message ioband1 0 attach 1000
> +    # dmsetup message ioband1 0 attach 2000
> +    # dmsetup message ioband1 0 weight 1000:30
> +    # dmsetup message ioband1 0 weight 2000:20
> +
> +
> +     Now the processes owned by uid 1000 can use 30% --- 30/(30+20+40+10)*100
> +   --- of the bandwidth of "/dev/sda" when the processes issue I/O requests
> +   through "ioband1." The processes owned by uid 2000 can use 20% of the
> +   bandwidth likewise.
> +
> +   Table 1. Weight assignments
> +
> +   +----------------------------------------------------------------+
> +   | ioband device |          ioband group          | ioband weight |
> +   |---------------+--------------------------------+---------------|
> +   | ioband1       | user id 1000                   | 30            |
> +   |---------------+--------------------------------+---------------|
> +   | ioband1       | user id 2000                   | 20            |
> +   |---------------+--------------------------------+---------------|
> +   | ioband1       | default group(the other users) | 40            |
> +   |---------------+--------------------------------+---------------|
> +   | ioband2       | default group                  | 10            |
> +   +----------------------------------------------------------------+
> +
> +   --------------------------------------------------------------------------
> +
> +  Remove the ioband devices
> +
> +     Remove the ioband devices when no longer used.
> +
> +     # dmsetup remove ioband1
> +     # dmsetup remove ioband2
> +
> +
> +   --------------------------------------------------------------------------
> +
> +Command Reference
> +
> +  Create an ioband device
> +
> +   SYNOPSIS
> +
> +           dmsetup create IOBAND_DEVICE
> +
> +   DESCRIPTION
> +
> +             Create an ioband device with the given name IOBAND_DEVICE.
> +           Generally, dmsetup reads a table from standard input. Each line of
> +           the table specifies a single target and is of the form:
> +
> +             start_sector num_sectors "ioband" device_file ioband_device_id \
> +                 io_throttle io_limit ioband_group_type policy token_base \
> +                 :weight [ioband_group_id:weight...]
> +
> +
> +                start_sector, num_sectors
> +
> +                          The sector range of the underlying device where
> +                        dm-ioband maps.
> +
> +                ioband
> +
> +                          Specify the string "ioband" as a target type.
> +
> +                device_file
> +
> +                          Underlying device name.
> +
> +                ioband_device_id
> +
> +                          The ID number for an ioband device. The same ID
> +                        must be set among the ioband devices that share the
> +                        same bandwidth. This is useful for grouping disk
> +                        drives partitioned from one disk drive such as RAID
> +                        drive or LVM logical striped volume.
> +
> +                io_throttle
> +
> +                          Dm-ioband starts to control the bandwidth when the
> +                        number of BIOs in progress exceeds this value. If 0
> +                        is specified, the default value is used. This setting
> +                        applies all ioband devices which has the same ioband
> +                        device ID as you specified by "ioband_device_id."
> +
> +                io_limit
> +
> +                          Dm-ioband blocks all I/O requests for IOBAND_DEVICE
> +                        when the number of BIOs in progress exceeds this
> +                        value. If 0 is specified, the default value is used.
> +                        This setting applies all ioband devices which has the
> +                        same ioband device ID as you specified by
> +                        "ioband_device_id."
> +
> +                ioband_group_type
> +
> +                          Specify how to evaluate the ioband group ID. The
> +                        type must be one of "none", "user", "gid", "pid" or
> +                        "pgrp." The type "cgroup" is enabled by applying the
> +                        bio-cgroup patch. Specify "none" if you don't need
> +                        any ioband groups other than the default ioband
> +                        group.
> +
> +                policy
> +
> +                          Specify a bandwidth control policy. A user can
> +                        choose either policy "weight" or "weight-iosize."
> +                        This setting applies all ioband devices which has the
> +                        same ioband device ID as you specified by
> +                        "ioband_device_id."
> +
> +                             weight
> +
> +                                       This policy controls bandwidth
> +                                     according to the proportional to the
> +                                     weight of each ioband group based on the
> +                                     number of I/O requests.
> +
> +                             weight-iosize
> +
> +                                       This policy controls bandwidth
> +                                     according to the proportional to the
> +                                     weight of each ioband group based on the
> +                                     number of I/O sectors.
> +
> +                token_base
> +
> +                          The number of tokens which specified by token_base
> +                        will be distributed to all ioband groups according to
> +                        the proportional to the weight of each ioband group.
> +                        If 0 is specified, the default value is used. This
> +                        setting applies all ioband devices which has the same
> +                        ioband device ID as you specified by
> +                        "ioband_device_id."
> +
> +                ioband_group_id:weight
> +
> +                          Set the weight of the ioband group specified by
> +                        ioband_group_id. If ioband_group_id is omitted, the
> +                        weight is assigned to the default ioband group.
> +
> +   EXAMPLE
> +
> +             Create an ioband device with the following parameters:
> +
> +              *   Starting sector = "0"
> +
> +              *   The number of sectors = "$(blockdev --getsize /dev/sda1)"
> +
> +              *   Target type = "ioband"
> +
> +              *   Underlying device name = "/dev/sda1"
> +
> +              *   Ioband device ID = "128"
> +
> +              *   I/O throttle = "10"
> +
> +              *   I/O limit = "400"
> +
> +              *   Ioband group type = "user"
> +
> +              *   Bandwidth control policy = "weight"
> +
> +              *   Token base = "2048"
> +
> +              *   Weight for the default ioband group = "100"
> +
> +              *   Weight for the ioband group 1000 = "80"
> +
> +              *   Weight for the ioband group 2000 = "20"
> +
> +              *   Ioband device name = "ioband1"
> +
> +             # echo "0 $(blockdev --getsize /dev/sda1) ioband" \
> +               "/dev/sda1 128 10 400 user weight 2048 :100 1000:80 2000:20" \
> +               | dmsetup create ioband1
> +
> +
> +             Create two device groups (ID=1,2). The bandwidths of these
> +           device groups will be individually controlled.
> +
> +             # echo "0 $(blockdev --getsize /dev/sda1) ioband /dev/sda1 1" \
> +               "0 0 none weight 0 :80" | dmsetup create ioband1
> +             # echo "0 $(blockdev --getsize /dev/sda2) ioband /dev/sda2 1" \
> +               "0 0 none weight 0 :20" | dmsetup create ioband2
> +             # echo "0 $(blockdev --getsize /dev/sdb3) ioband /dev/sdb3 2" \
> +               "0 0 none weight 0 :60" | dmsetup create ioband3
> +             # echo "0 $(blockdev --getsize /dev/sdb4) ioband /dev/sdb4 2" \
> +               "0 0 none weight 0 :40" | dmsetup create ioband4
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Remove the ioband device
> +
> +   SYNOPSIS
> +
> +           dmsetup remove IOBAND_DEVICE
> +
> +   DESCRIPTION
> +
> +             Remove the specified ioband device IOBAND_DEVICE. All the band
> +           groups attached to the ioband device are also removed
> +           automatically.
> +
> +   EXAMPLE
> +
> +             Remove ioband device "ioband1."
> +
> +             # dmsetup remove ioband1
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Set an ioband group type
> +
> +   SYNOPSIS
> +
> +           dmsetup message IOBAND_DEVICE 0 type TYPE
> +
> +   DESCRIPTION
> +
> +             Set an ioband group type of IOBAND_DEVICE. TYPE must be one of
> +           "none", "user", "gid", "pid" or "pgrp." The type "cgroup" is
> +           enabled by applying the bio-cgroup patch. Once the type is set,
> +           new ioband groups can be created on IOBAND_DEVICE.
> +
> +   EXAMPLE
> +
> +             Set the ioband group type of ioband device "ioband1" to "user."
> +
> +             # dmsetup message ioband1 0 type user
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Create an ioband group
> +
> +   SYNOPSIS
> +
> +           dmsetup message IOBAND_DEVICE 0 attach ID
> +
> +   DESCRIPTION
> +
> +             Create an ioband group and attach it to IOBAND_DEVICE. ID
> +           specifies user-id, group-id, process-id or process-group-id
> +           depending the ioband group type of IOBAND_DEVICE.
> +
> +   EXAMPLE
> +
> +             Create an ioband group which consists of all processes with
> +           user-id 1000 and attach it to ioband device "ioband1."
> +
> +             # dmsetup message ioband1 0 type user
> +             # dmsetup message ioband1 0 attach 1000
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Detach the ioband group
> +
> +   SYNOPSIS
> +
> +           dmsetup message IOBAND_DEVICE 0 detach ID
> +
> +   DESCRIPTION
> +
> +             Detach the ioband group specified by ID from ioband device
> +           IOBAND_DEVICE.
> +
> +   EXAMPLE
> +
> +             Detach the ioband group with ID "2000" from ioband device
> +           "ioband2."
> +
> +             # dmsetup message ioband2 0 detach 1000
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Set bandwidth control policy
> +
> +   SYNOPSIS
> +
> +           dmsetup message IOBAND_DEVICE 0 policy policy
> +
> +   DESCRIPTION
> +
> +             Set a bandwidth control policy. A user can choose either policy
> +           "weight" or "weight-iosize." This setting applies all ioband
> +           devices which has the same ioband device ID as IOBAND_DEVICE.
> +
> +                weight
> +
> +                          This policy controls bandwidth according to the
> +                        proportional to the weight of each ioband group based
> +                        on the number of I/O requests.
> +
> +                weight-iosize
> +
> +                          This policy controls bandwidth according to the
> +                        proportional to the weight of each ioband group based
> +                        on the number of I/O sectors.
> +
> +   EXAMPLE
> +
> +             Set bandwidth control policy of ioband devices which have the
> +           same ioband device ID as "ioband1" to "weight-iosize."
> +
> +             # dmsetup message ioband1 0 policy weight-iosize
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Set the weight of an ioband group
> +
> +   SYNOPSIS
> +
> +           dmsetup message IOBAND_DEVICE 0 weight VAL
> +
> +           dmsetup message IOBAND_DEVICE 0 weight ID:VAL
> +
> +   DESCRIPTION
> +
> +             Set the weight of the ioband group specified by ID. Set the
> +           weight of the default ioband group of IOBAND_DEVICE if ID isn't
> +           specified.
> +
> +             The following example means that "ioband1" can use 80% ---
> +           40/(40+10)*100 --- of the bandwidth of the underlying block device
> +           while "ioband2" can use 20%.
> +
> +             # dmsetup message ioband1 0 weight 40
> +             # dmsetup message ioband2 0 weight 10
> +
> +
> +             The following lines have the same effect as the above:
> +
> +             # dmsetup message ioband1 0 weight 4
> +             # dmsetup message ioband2 0 weight 1
> +
> +
> +             VAL must be an integer larger than 0. The default value, which
> +           is assigned to newly created ioband groups, is 100.
> +
> +   EXAMPLE
> +
> +             Set the weight of the default ioband group of "ioband1" to 40.
> +
> +             # dmsetup message ioband1 0 weight 40
> +
> +
> +             Set the weight of the ioband group of "ioband1" with ID "1000"
> +           to 10.
> +
> +             # dmsetup message ioband1 0 weight 1000:10
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Set the number of tokens
> +
> +   SYNOPSIS
> +
> +           dmsetup message IOBAND_DEVICE 0 token VAL
> +
> +   DESCRIPTION
> +
> +             The number of tokens will be distributed to all ioband groups
> +           according to the proportional to the weight of each ioband group.
> +           If 0 is specified, the default value is used. This setting applies
> +           all ioband devices which has the same ioband device ID as
> +           IOBAND_DEVICE
> +
> +   EXAMPLE
> +
> +             Set the number of tokens to 256.
> +
> +             # dmsetup message ioband1 0 token 256
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Set a limit of how many tokens are carried over
> +
> +   SYNOPSIS
> +
> +           dmsetup message IOBAND_DEVICE 0 carryover VAL
> +
> +   DESCRIPTION
> +
> +             When dm-ioband tries to refill an ioband group with tokens after
> +           another ioband group is already refilled several times, dm-ioband
> +           determines the number of tokens to refill by multiplying the
> +           number of tokens refilled once by the smaller of how many times
> +           the other group is already refilled or this limit. If 0 is
> +           specified, the default value is used. This setting applies all
> +           ioband devices which has the same ioband device ID as
> +           IOBAND_DEVICE.
> +
> +   EXAMPLE
> +
> +             Set a limit for "ioband1" to 2.
> +
> +             # dmsetup message ioband1 0 carryover 2
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Set I/O throttling
> +
> +   SYNOPSIS
> +
> +           dmsetup message IOBAND_DEVICE 0 io_throttle VAL
> +
> +   DESCRIPTION
> +
> +             Dm-ioband starts to control the bandwidth when the number of
> +           BIOs in progress exceeds this value. If 0 is specified, the
> +           default value is used. This setting applies all ioband devices
> +           which has the same ioband device ID as IOBAND_DEVICE.
> +
> +   EXAMPLE
> +
> +             Set the I/O throttling value of "ioband1" to 16.
> +
> +             # dmsetup message ioband1 0 io_throttle 16
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Set I/O limiting
> +
> +   SYNOPSIS
> +
> +           dmsetup message IOBAND_DEVICE 0 io_limit VAL
> +
> +   DESCRIPTION
> +
> +             Dm-ioband blocks all I/O requests for IOBAND_DEVICE when the
> +           number of BIOs in progress exceeds this value. If 0 is specified,
> +           the default value is used. This setting applies all ioband devices
> +           which has the same ioband device ID as IOBAND_DEVICE.
> +
> +   EXAMPLE
> +
> +             Set the I/O limiting value of "ioband1" to 128.
> +
> +             # dmsetup message ioband1 0 io_limit 128
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Display settings
> +
> +   SYNOPSIS
> +
> +           dmsetup table --target ioband
> +
> +   DESCRIPTION
> +
> +             Display the current table for the ioband device in a format. See
> +           "dmsetup create" command for information on the table format.
> +
> +   EXAMPLE
> +
> +             The following output shows the current table of "ioband1."
> +
> +             # dmsetup table --target ioband
> +             ioband: 0 32129937 ioband1 8:29 128 10 400 user weight \
> +               2048 :100 1000:80 2000:20
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Display Statistics
> +
> +   SYNOPSIS
> +
> +           dmsetup status --target ioband
> +
> +   DESCRIPTION
> +
> +             Display the statistics of all the ioband devices whose target
> +           type is "ioband."
> +
> +             The output format is as below. the first five columns shows:
> +
> +              *   ioband device name
> +
> +              *   logical start sector of the device (must be 0)
> +
> +              *   device size in sectors
> +
> +              *   target type (must be "ioband")
> +
> +              *   device group ID
> +
> +             The remaining columns show the statistics of each ioband group
> +           on the band device. Each group uses seven columns for its
> +           statistics.
> +
> +              *   ioband group ID (-1 means default)
> +
> +              *   total read requests
> +
> +              *   delayed read requests
> +
> +              *   total read sectors
> +
> +              *   total write requests
> +
> +              *   delayed write requests
> +
> +              *   total write sectors
> +
> +   EXAMPLE
> +
> +             The following output shows the statistics of two ioband devices.
> +           Ioband2 only has the default ioband group and ioband1 has three
> +           (default, 1001, 1002) ioband groups.
> +
> +             # dmsetup status
> +             ioband2: 0 44371467 ioband 128 -1 143 90 424 122 78 352
> +             ioband1: 0 44371467 ioband 128 -1 223 172 408 211 136 600 1001 \
> +             166 107 472 139 95 352 1002 211 146 520 210 147 504
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Reset status counter
> +
> +   SYNOPSIS
> +
> +           dmsetup message IOBAND_DEVICE 0 reset
> +
> +   DESCRIPTION
> +
> +             Reset the statistics of ioband device IOBAND_DEVICE.
> +
> +   EXAMPLE
> +
> +             Reset the statistics of "ioband1."
> +
> +             # dmsetup message ioband1 0 reset
> +
> +
> +   --------------------------------------------------------------------------
> +
> +Examples
> +
> +  Example #1: Bandwidth control on Partitions
> +
> +     This example describes how to control the bandwidth with disk
> +   partitions. The following diagram illustrates the configuration of this
> +   example. You may want to run a database on /dev/mapper/ioband1 and web
> +   applications on /dev/mapper/ioband2.
> +
> +                 /mnt1                        /mnt2            mount points
> +                   |                              |
> +     +-------------V------------+ +-------------V------------+
> +     |   /dev/mapper/ioband1    | |   /dev/mapper/ioband2    | ioband devices
> +     +--------------------------+ +--------------------------+
> +     |       default group      | |       default group      | ioband groups
> +     |           (80)           | |           (40)           |    (weight)
> +     +-------------|------------+ +-------------|------------+
> +                   |                            |
> +     +-------------V-------------+--------------V------------+
> +     |         /dev/sda1         |          /dev/sda2        | partitions
> +     +---------------------------+---------------------------+
> +
> +
> +     To setup the above configuration, follow these steps:
> +
> +    1.   Create ioband devices with the same device group ID and assign
> +       weights of 80 and 40 to the default ioband groups respectively.
> +
> +         # echo "0 $(blockdev --getsize /dev/sda1) ioband /dev/sda1 1 0 0" \
> +             "none weight 0 :80" | dmsetup create ioband1
> +         # echo "0 $(blockdev --getsize /dev/sda2) ioband /dev/sda2 1 0 0" \
> +             "none weight 0 :40" | dmsetup create ioband2
> +
> +
> +    2.   Create filesystems on the ioband devices and mount them.
> +
> +         # mkfs.ext3 /dev/mapper/ioband1
> +         # mount /dev/mapper/ioband1 /mnt1
> +
> +         # mkfs.ext3 /dev/mapper/ioband2
> +         # mount /dev/mapper/ioband2 /mnt2
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Example #2: Bandwidth control on Logical Volumes
> +
> +     This example is similar to the example #1 but it uses LVM logical
> +   volumes instead of disk partitions. This example shows how to configure
> +   ioband devices on two striped logical volumes.
> +
> +                 /mnt1                        /mnt2            mount points
> +                   |                            |
> +     +-------------V------------+ +-------------V------------+
> +     |   /dev/mapper/ioband1    | |   /dev/mapper/ioband2    | ioband devices
> +     +--------------------------+ +--------------------------+
> +     |       default group      | |       default group      | ioband groups
> +     |           (80)           | |           (40)           |    (weight)
> +     +-------------|------------+ +-------------|------------+
> +                   |                            |
> +     +-------------V------------+ +-------------V------------+
> +     |      /dev/mapper/lv0     | |     /dev/mapper/lv1      | striped logical
> +     |                          | |                          | volumes
> +     +-------------------------------------------------------+
> +     |                          vg0                          | volume group
> +     +-------------|----------------------------|------------+
> +                   |                            |
> +     +-------------V------------+ +-------------V------------+
> +     |         /dev/sdb         | |         /dev/sdc         | physical disks
> +     +--------------------------+ +--------------------------+
> +
> +
> +     To setup the above configuration, follow these steps:
> +
> +    1.   Initialize the partitions for use by LVM.
> +
> +         # pvcreate /dev/sdb
> +         # pvcreate /dev/sdc
> +
> +
> +    2.   Create a new volume group named "vg0" with /dev/sdb and /dev/sdc.
> +
> +         # vgcreate vg0 /dev/sdb /dev/sdc
> +
> +
> +    3.   Create two logical volumes in "vg0." The volumes have to be striped.
> +
> +         # lvcreate -n lv0 -i 2 -I 64 vg0 -L 1024M
> +         # lvcreate -n lv1 -i 2 -I 64 vg0 -L 1024M
> +
> +
> +         The rest is the same as the example #1.
> +
> +    4.   Create ioband devices corresponding to each logical volume and
> +       assign weights of 80 and 40 to the default ioband groups respectively.
> +
> +         # echo "0 $(blockdev --getsize /dev/mapper/vg0-lv0)" \
> +            "ioband /dev/mapper/vg0-lv0 1 0 0 none weight 0 :80" | \
> +            dmsetup create ioband1
> +         # echo "0 $(blockdev --getsize /dev/mapper/vg0-lv1)" \
> +            "ioband /dev/mapper/vg0-lv1 1 0 0 none weight 0 :40" | \
> +            dmsetup create ioband2
> +
> +
> +    5.   Create filesystems on the ioband devices and mount them.
> +
> +         # mkfs.ext3 /dev/mapper/ioband1
> +         # mount /dev/mapper/ioband1 /mnt1
> +
> +         # mkfs.ext3 /dev/mapper/ioband2
> +         # mount /dev/mapper/ioband2 /mnt2
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Example #3: Bandwidth control on processes
> +
> +     This example describes how to control the bandwidth with groups of
> +   processes. You may also want to run an additional application on the same
> +   machine described in the example #1. This example shows how to add a new
> +   ioband group for this application.
> +
> +                 /mnt1                        /mnt2            mount points
> +                   |                            |
> +     +-------------V------------+ +-------------V------------+
> +     |   /dev/mapper/ioband1    | |   /dev/mapper/ioband2    | ioband devices
> +     +-------------+------------+ +-------------+------------+
> +     |          default         | |  user=1000  |   default  | ioband groups
> +     |           (80)           | |     (20)    |    (40)    |   (weight)
> +     +-------------+------------+ +-------------+------------+
> +                   |                            |
> +     +-------------V-------------+--------------V------------+
> +     |         /dev/sda1         |          /dev/sda2        | partitions
> +     +---------------------------+---------------------------+
> +
> +
> +     The following shows to set up a new ioband group on the machine that is
> +   already configured as the example #1. The application will have a weight
> +   of 20 and run with user-id 1000 on /dev/mapper/ioband2.
> +
> +    1.   Set the type of ioband2 to "user."
> +
> +         # dmsetup message ioband2 0 type user.
> +
> +
> +    2.   Create a new ioband group on ioband2.
> +
> +         # dmsetup message ioband2 0 attach 1000
> +
> +
> +    3.   Assign weight of 10 to this newly created ioband group.
> +
> +         # dmsetup message ioband2 0 weight 1000:20
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Example #4: Bandwidth control for Xen virtual block devices
> +
> +     This example describes how to control the bandwidth for Xen virtual
> +   block devices. The following diagram illustrates the configuration of this
> +   example.
> +
> +           Virtual Machine 1            Virtual Machine 2      virtual machines
> +                   |                            |
> +     +-------------V------------+ +-------------V------------+
> +     |         /dev/xvda1       | |         /dev/xvda1       | virtual block
> +     +-------------|------------+ +-------------|------------+    devices
> +                   |                            |
> +     +-------------V------------+ +-------------V------------+
> +     |   /dev/mapper/ioband1    | |   /dev/mapper/ioband2    | ioband devices
> +     +--------------------------+ +--------------------------+
> +     |       default group      | |       default group      | ioband groups
> +     |           (80)           | |           (40)           |    (weight)
> +     +-------------|------------+ +-------------|------------+
> +                   |                            |
> +     +-------------V-------------+--------------V------------+
> +     |         /dev/sda1         |          /dev/sda2        | partitions
> +     +---------------------------+---------------------------+
> +
> +
> +     The followings shows how to map ioband device "ioband1" and "ioband2" to
> +   virtual block device "/dev/xvda1 on Virtual Machine 1" and "/dev/xvda1 on
> +   Virtual Machine 2" respectively on the machine configured as the example
> +   #1. Add the following lines to the configuration files that are referenced
> +   when creating "Virtual Machine 1" and "Virtual Machine 2."
> +
> +       For "Virtual Machine 1"
> +       disk = [ 'phy:/dev/mapper/ioband1,xvda,w' ]
> +
> +       For "Virtual Machine 2"
> +       disk = [ 'phy:/dev/mapper/ioband2,xvda,w' ]
> +
> +
> +   --------------------------------------------------------------------------
> +
> +  Example #5: Bandwidth control for Xen blktap devices
> +
> +     This example describes how to control the bandwidth for Xen virtual
> +   block devices when Xen blktap devices are used. The following diagram
> +   illustrates the configuration of this example.
> +
> +           Virtual Machine 1            Virtual Machine 2      virtual machines
> +                   |                            |
> +     +-------------V------------+ +-------------V------------+
> +     |         /dev/xvda1       | |         /dev/xvda1       | virtual block
> +     +-------------|------------+ +-------------|------------+    devices
> +                   |                            |
> +     +-------------V----------------------------V------------+
> +     |                  /dev/mapper/ioband1                  | ioband device
> +     +---------------------------+---------------------------+
> +     |       default group       |        default group      | ioband groups
> +     |           (80)            |            (40)           |    (weight)
> +     +-------------|-------------+--------------|------------+
> +                   |                            |
> +     +-------------|----------------------------|------------+
> +     |  +----------V----------+      +----------V---------+  |
> +     |  |       vm1.img       |      |       vm2.img      |  | disk image files
> +     |  +---------------------+      +--------------------+  |
> +     |                        /vmdisk                        | mount point
> +     +---------------------------|---------------------------+
> +                                 |
> +     +---------------------------V---------------------------+
> +     |                       /dev/sda1                       | partition
> +     +-------------------------------------------------------+
> +
> +
> +     To setup the above configuration, follow these steps:
> +
> +    1.   Create an ioband device.
> +
> +         # echo "0 $(blockdev --getsize /dev/sda1) ioband /dev/sda1" \
> +             "1 0 0 none weight 0 :100" | dmsetup create ioband1
> +
> +
> +    2.   Add the following lines to the configuration files that are
> +       referenced when creating "Virtual Machine 1" and "Virtual Machine 2."
> +       Disk image files "/vmdisk/vm1.img" and "/vmdisk/vm2.img" will be used.
> +
> +         For "Virtual Machine 1"
> +         disk = [ 'tap:aio:/vmdisk/vm1.img,xvda,w', ]
> +
> +         For "Virtual Machine 1"
> +         disk = [ 'tap:aio:/vmdisk/vm2.img,xvda,w', ]
> +
> +
> +    3.   Run the virtual machines.
> +
> +         # xm create vm1
> +         # xm create vm2
> +
> +
> +    4.   Find out the process IDs of the daemons which control the blktap
> +       devices.
> +
> +         # lsof /vmdisk/disk[12].img
> +         COMMAND   PID USER   FD   TYPE DEVICE       SIZE  NODE NAME
> +         tapdisk 15011 root   11u   REG  253,0 2147483648 48961 /vmdisk/vm1.img
> +         tapdisk 15276 root   13u   REG  253,0 2147483648 48962 /vmdisk/vm2.img
> +
> +
> +    5.   Create new ioband groups of pid 15011 and pid 15276, which are
> +       process IDs of the tapdisks, and assign weight of 80 and 40 to the
> +       groups respectively.
> +
> +         # dmsetup message ioband1 0 type pid
> +         # dmsetup message ioband1 0 attach 15011
> +         # dmsetup message ioband1 0 weight 15011:80
> +         # dmsetup message ioband1 0 attach 15276
> +         # dmsetup message ioband1 0 weight 15276:40
> Index: linux-2.6.29/drivers/md/Kconfig
> ===================================================================
> --- linux-2.6.29.orig/drivers/md/Kconfig
> +++ linux-2.6.29/drivers/md/Kconfig
> @@ -289,4 +289,17 @@ config DM_UEVENT
>  	---help---
>  	Generate udev events for DM events.
>  
> +config DM_IOBAND
> +	tristate "I/O bandwidth control (EXPERIMENTAL)"
> +	depends on BLK_DEV_DM && EXPERIMENTAL
> +	---help---
> +	This device-mapper target allows to define how the
> +	available bandwidth of a storage device should be
> +	shared between processes, cgroups, the partitions or the LUNs.
> +
> +	Information on how to use dm-ioband is available in:
> +	   <file:Documentation/device-mapper/ioband.txt>.
> +
> +	If unsure, say N.
> +
>  endif # MD
> Index: linux-2.6.29/drivers/md/Makefile
> ===================================================================
> --- linux-2.6.29.orig/drivers/md/Makefile
> +++ linux-2.6.29/drivers/md/Makefile
> @@ -8,6 +8,7 @@ dm-multipath-objs := dm-path-selector.o 
>  dm-snapshot-objs := dm-snap.o dm-exception-store.o dm-snap-transient.o \
>  		    dm-snap-persistent.o
>  dm-mirror-objs	:= dm-raid1.o
> +dm-ioband-objs	:= dm-ioband-ctl.o dm-ioband-policy.o dm-ioband-type.o
>  md-mod-objs     := md.o bitmap.o
>  raid456-objs	:= raid5.o raid6algos.o raid6recov.o raid6tables.o \
>  		   raid6int1.o raid6int2.o raid6int4.o \
> @@ -37,6 +38,7 @@ obj-$(CONFIG_DM_MULTIPATH)	+= dm-multipa
>  obj-$(CONFIG_DM_SNAPSHOT)	+= dm-snapshot.o
>  obj-$(CONFIG_DM_MIRROR)		+= dm-mirror.o dm-log.o dm-region-hash.o
>  obj-$(CONFIG_DM_ZERO)		+= dm-zero.o
> +obj-$(CONFIG_DM_IOBAND)		+= dm-ioband.o
>  
>  quiet_cmd_unroll = UNROLL  $@
>        cmd_unroll = $(PERL) $(srctree)/$(src)/unroll.pl $(UNROLL) \
> Index: linux-2.6.29/drivers/md/dm-ioband-ctl.c
> ===================================================================
> --- /dev/null
> +++ linux-2.6.29/drivers/md/dm-ioband-ctl.c
> @@ -0,0 +1,1312 @@
> +/*
> + * Copyright (C) 2008 VA Linux Systems Japan K.K.
> + * Authors: Hirokazu Takahashi <taka valinux co jp>
> + *          Ryo Tsuruta <ryov valinux co jp>
> + *
> + *  I/O bandwidth control
> + *
> + * This file is released under the GPL.
> + */
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/bio.h>
> +#include <linux/slab.h>
> +#include <linux/workqueue.h>
> +#include <linux/raid/md.h>
> +#include <linux/rbtree.h>
> +#include "dm.h"
> +#include "dm-bio-list.h"
> +#include "dm-ioband.h"
> +
> +#define POLICY_PARAM_START 6
> +#define POLICY_PARAM_DELIM "=:,"
> +
> +static LIST_HEAD(ioband_device_list);
> +/* to protect ioband_device_list */
> +static DEFINE_SPINLOCK(ioband_devicelist_lock);
> +
> +static void suspend_ioband_device(struct ioband_device *, unsigned long, int);
> +static void resume_ioband_device(struct ioband_device *);
> +static void ioband_conduct(struct work_struct *);
> +static void ioband_hold_bio(struct ioband_group *, struct bio *);
> +static struct bio *ioband_pop_bio(struct ioband_group *);
> +static int ioband_set_param(struct ioband_group *, char *, char *);
> +static int ioband_group_attach(struct ioband_group *, int, char *);
> +static int ioband_group_type_select(struct ioband_group *, char *);
> +
> +static void do_nothing(void) {}
> +
> +static int policy_init(struct ioband_device *dp, char *name,
> +		       int argc, char **argv)
> +{
> +	struct policy_type *p;
> +	struct ioband_group *gp;
> +	unsigned long flags;
> +	int r;
> +
> +	for (p = dm_ioband_policy_type; p->p_name; p++) {
> +		if (!strcmp(name, p->p_name))
> +			break;
> +	}
> +	if (!p->p_name)
> +		return -EINVAL;
> +
> +	spin_lock_irqsave(&dp->g_lock, flags);
> +	if (dp->g_policy == p) {
> +		/* do nothing if the same policy is already set */
> +		spin_unlock_irqrestore(&dp->g_lock, flags);
> +		return 0;
> +	}
> +
> +	suspend_ioband_device(dp, flags, 1);
> +	list_for_each_entry(gp, &dp->g_groups, c_list)
> +		dp->g_group_dtr(gp);
> +
> +	/* switch to the new policy */
> +	dp->g_policy = p;
> +	r = p->p_policy_init(dp, argc, argv);
> +	if (!r) {
> +		if (!dp->g_hold_bio)
> +			dp->g_hold_bio = ioband_hold_bio;
> +		if (!dp->g_pop_bio)
> +			dp->g_pop_bio = ioband_pop_bio;
> +
> +		list_for_each_entry(gp, &dp->g_groups, c_list)
> +			dp->g_group_ctr(gp, NULL);
> +	}
> +	resume_ioband_device(dp);
> +	spin_unlock_irqrestore(&dp->g_lock, flags);
> +	return r;
> +}
> +
> +static struct ioband_device *alloc_ioband_device(char *name,
> +						 int io_throttle, int io_limit)
> +{
> +	struct ioband_device *dp, *new_dp;
> +	unsigned long flags;
> +
> +	new_dp = kzalloc(sizeof(struct ioband_device), GFP_KERNEL);
> +	if (!new_dp)
> +		return NULL;
> +
> +	/*
> +	 * Prepare its own workqueue as generic_make_request() may
> +	 * potentially block the workqueue when submitting BIOs.
> +	 */
> +	new_dp->g_ioband_wq = create_workqueue("kioband");
> +	if (!new_dp->g_ioband_wq) {
> +		kfree(new_dp);
> +		return NULL;
> +	}
> +
> +	spin_lock_irqsave(&ioband_devicelist_lock, flags);
> +	list_for_each_entry(dp, &ioband_device_list, g_list) {
> +		if (!strcmp(dp->g_name, name)) {
> +			dp->g_ref++;
> +			spin_unlock_irqrestore(&ioband_devicelist_lock, flags);
> +			destroy_workqueue(new_dp->g_ioband_wq);
> +			kfree(new_dp);
> +			return dp;
> +		}
> +	}
> +
> +	INIT_DELAYED_WORK(&new_dp->g_conductor, ioband_conduct);
> +	INIT_LIST_HEAD(&new_dp->g_groups);
> +	INIT_LIST_HEAD(&new_dp->g_list);
> +	spin_lock_init(&new_dp->g_lock);
> +	mutex_init(&new_dp->g_lock_device);
> +	bio_list_init(&new_dp->g_urgent_bios);
> +	new_dp->g_io_throttle = io_throttle;
> +	new_dp->g_io_limit[READ] = io_limit;
> +	new_dp->g_io_limit[WRITE] = io_limit;
> +	new_dp->g_issued[READ] = 0;
> +	new_dp->g_issued[WRITE] = 0;
> +	new_dp->g_blocked = 0;
> +	new_dp->g_ref = 1;
> +	new_dp->g_flags = 0;
> +	strlcpy(new_dp->g_name, name, sizeof(new_dp->g_name));
> +	new_dp->g_policy = NULL;
> +	new_dp->g_hold_bio = NULL;
> +	new_dp->g_pop_bio = NULL;
> +	init_waitqueue_head(&new_dp->g_waitq);
> +	init_waitqueue_head(&new_dp->g_waitq_suspend);
> +	init_waitqueue_head(&new_dp->g_waitq_flush);
> +	list_add_tail(&new_dp->g_list, &ioband_device_list);
> +
> +	spin_unlock_irqrestore(&ioband_devicelist_lock, flags);
> +	return new_dp;
> +}
> +
> +static void release_ioband_device(struct ioband_device *dp)
> +{
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&ioband_devicelist_lock, flags);
> +	dp->g_ref--;
> +	if (dp->g_ref > 0) {
> +		spin_unlock_irqrestore(&ioband_devicelist_lock, flags);
> +		return;
> +	}
> +	list_del(&dp->g_list);
> +	spin_unlock_irqrestore(&ioband_devicelist_lock, flags);
> +	destroy_workqueue(dp->g_ioband_wq);
> +	kfree(dp);
> +}
> +
> +static int is_ioband_device_flushed(struct ioband_device *dp,
> +				    int wait_completion)
> +{
> +	struct ioband_group *gp;
> +
> +	if (wait_completion && dp->g_issued[READ] + dp->g_issued[WRITE] > 0)
> +		return 0;
> +	if (dp->g_blocked || waitqueue_active(&dp->g_waitq))
> +		return 0;
> +	list_for_each_entry(gp, &dp->g_groups, c_list)
> +		if (waitqueue_active(&gp->c_waitq))
> +			return 0;
> +	return 1;
> +}
> +
> +static void suspend_ioband_device(struct ioband_device *dp,
> +				  unsigned long flags, int wait_completion)
> +{
> +	struct ioband_group *gp;
> +
> +	/* block incoming bios */
> +	set_device_suspended(dp);
> +
> +	/* wake up all blocked processes and go down all ioband groups */
> +	wake_up_all(&dp->g_waitq);
> +	list_for_each_entry(gp, &dp->g_groups, c_list) {
> +		if (!is_group_down(gp)) {
> +			set_group_down(gp);
> +			set_group_need_up(gp);
> +		}
> +		wake_up_all(&gp->c_waitq);
> +	}
> +
> +	/* flush the already mapped bios */
> +	spin_unlock_irqrestore(&dp->g_lock, flags);
> +	queue_delayed_work(dp->g_ioband_wq, &dp->g_conductor, 0);
> +	flush_workqueue(dp->g_ioband_wq);
> +
> +	/* wait for all processes to wake up and bios to release */
> +	spin_lock_irqsave(&dp->g_lock, flags);
> +	wait_event_lock_irq(dp->g_waitq_flush,
> +			    is_ioband_device_flushed(dp, wait_completion),
> +			    dp->g_lock, do_nothing());
> +}
> +
> +static void resume_ioband_device(struct ioband_device *dp)
> +{
> +	struct ioband_group *gp;
> +
> +	/* go up ioband groups */
> +	list_for_each_entry(gp, &dp->g_groups, c_list) {
> +		if (group_need_up(gp)) {
> +			clear_group_need_up(gp);
> +			clear_group_down(gp);
> +		}
> +	}
> +
> +	/* accept incoming bios */
> +	wake_up_all(&dp->g_waitq_suspend);
> +	clear_device_suspended(dp);
> +}
> +
> +static struct ioband_group *ioband_group_find(struct ioband_group *head, int id)
> +{
> +	struct rb_node *node = head->c_group_root.rb_node;
> +
> +	while (node) {
> +		struct ioband_group *p =
> +			container_of(node, struct ioband_group, c_group_node);
> +
> +		if (p->c_id == id || id == IOBAND_ID_ANY)
> +			return p;
> +		node = (id < p->c_id) ? node->rb_left : node->rb_right;
> +	}
> +	return NULL;
> +}
> +
> +static void ioband_group_add_node(struct rb_root *root, struct ioband_group *gp)
> +{
> +	struct rb_node **node = &root->rb_node, *parent = NULL;
> +	struct ioband_group *p;
> +
> +	while (*node) {
> +		p = container_of(*node, struct ioband_group, c_group_node);
> +		parent = *node;
> +		node = (gp->c_id < p->c_id) ?
> +				&(*node)->rb_left : &(*node)->rb_right;
> +	}
> +
> +	rb_link_node(&gp->c_group_node, parent, node);
> +	rb_insert_color(&gp->c_group_node, root);
> +}
> +
> +static int ioband_group_init(struct ioband_group *gp,
> +			     struct ioband_group *head,
> +			     struct ioband_device *dp, int id, char *param)
> +{
> +	unsigned long flags;
> +	int r;
> +
> +	INIT_LIST_HEAD(&gp->c_list);
> +	bio_list_init(&gp->c_blocked_bios);
> +	bio_list_init(&gp->c_prio_bios);
> +	gp->c_id = id;	/* should be verified */
> +	gp->c_blocked = 0;
> +	gp->c_prio_blocked = 0;
> +	memset(gp->c_stat, 0, sizeof(gp->c_stat));
> +	init_waitqueue_head(&gp->c_waitq);
> +	gp->c_flags = 0;
> +	gp->c_group_root = RB_ROOT;
> +	gp->c_banddev = dp;
> +
> +	spin_lock_irqsave(&dp->g_lock, flags);
> +	if (head && ioband_group_find(head, id)) {
> +		spin_unlock_irqrestore(&dp->g_lock, flags);
> +		DMWARN("ioband_group: id=%d already exists.", id);
> +		return -EEXIST;
> +	}
> +
> +	list_add_tail(&gp->c_list, &dp->g_groups);
> +
> +	r = dp->g_group_ctr(gp, param);
> +	if (r) {
> +		list_del(&gp->c_list);
> +		spin_unlock_irqrestore(&dp->g_lock, flags);
> +		return r;
> +	}
> +
> +	if (head) {
> +		ioband_group_add_node(&head->c_group_root, gp);
> +		gp->c_dev = head->c_dev;
> +		gp->c_target = head->c_target;
> +	}
> +
> +	spin_unlock_irqrestore(&dp->g_lock, flags);
> +
> +	return 0;
> +}
> +
> +static void ioband_group_release(struct ioband_group *head,
> +				 struct ioband_group *gp)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +
> +	list_del(&gp->c_list);
> +	if (head)
> +		rb_erase(&gp->c_group_node, &head->c_group_root);
> +	dp->g_group_dtr(gp);
> +	kfree(gp);
> +}
> +
> +static void ioband_group_destroy_all(struct ioband_group *gp)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +	struct ioband_group *p;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&dp->g_lock, flags);
> +	while ((p = ioband_group_find(gp, IOBAND_ID_ANY)))
> +		ioband_group_release(gp, p);
> +	ioband_group_release(NULL, gp);
> +	spin_unlock_irqrestore(&dp->g_lock, flags);
> +}
> +
> +static void ioband_group_stop_all(struct ioband_group *head, int suspend)
> +{
> +	struct ioband_device *dp = head->c_banddev;
> +	struct ioband_group *p;
> +	struct rb_node *node;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&dp->g_lock, flags);
> +	for (node = rb_first(&head->c_group_root); node; node = rb_next(node)) {
> +		p = rb_entry(node, struct ioband_group, c_group_node);
> +		set_group_down(p);
> +		if (suspend)
> +			set_group_suspended(p);
> +	}
> +	set_group_down(head);
> +	if (suspend)
> +		set_group_suspended(head);
> +	spin_unlock_irqrestore(&dp->g_lock, flags);
> +	queue_delayed_work(dp->g_ioband_wq, &dp->g_conductor, 0);
> +	flush_workqueue(dp->g_ioband_wq);
> +}
> +
> +static void ioband_group_resume_all(struct ioband_group *head)
> +{
> +	struct ioband_device *dp = head->c_banddev;
> +	struct ioband_group *p;
> +	struct rb_node *node;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&dp->g_lock, flags);
> +	for (node = rb_first(&head->c_group_root); node; node = rb_next(node)) {
> +		p = rb_entry(node, struct ioband_group, c_group_node);
> +		clear_group_down(p);
> +		clear_group_suspended(p);
> +	}
> +	clear_group_down(head);
> +	clear_group_suspended(head);
> +	spin_unlock_irqrestore(&dp->g_lock, flags);
> +}
> +
> +static int split_string(char *s, long *id, char **v)
> +{
> +	char *p, *q;
> +	int r = 0;
> +
> +	*id = IOBAND_ID_ANY;
> +	p = strsep(&s, POLICY_PARAM_DELIM);
> +	q = strsep(&s, POLICY_PARAM_DELIM);
> +	if (!q) {
> +		*v = p;
> +	} else {
> +		r = strict_strtol(p, 0, id);
> +		*v = q;
> +	}
> +	return r;
> +}
> +
> +/*
> + * Create a new band device:
> + *   parameters:  <device> <device-group-id> <io_throttle> <io_limit>
> + *     <type> <policy> <policy-param...> <group-id:group-param...>
> + */
> +static int ioband_ctr(struct dm_target *ti, unsigned argc, char **argv)
> +{
> +	struct ioband_group *gp;
> +	struct ioband_device *dp;
> +	struct dm_dev *dev;
> +	int io_throttle;
> +	int io_limit;
> +	int i, r, start;
> +	long val, id;
> +	char *param, *s;
> +
> +	if (argc < POLICY_PARAM_START) {
> +		ti->error = "Requires " __stringify(POLICY_PARAM_START)
> +							" or more arguments";
> +		return -EINVAL;
> +	}
> +
> +	if (strlen(argv[1]) > IOBAND_NAME_MAX) {
> +		ti->error = "Ioband device name is too long";
> +		return -EINVAL;
> +	}
> +
> +	r = strict_strtol(argv[2], 0, &val);
> +	if (r || val < 0 || val > SHORT_MAX) {
> +		ti->error = "Invalid io_throttle";
> +		return -EINVAL;
> +	}
> +	io_throttle = (val == 0) ? DEFAULT_IO_THROTTLE : val;
> +
> +	r = strict_strtol(argv[3], 0, &val);
> +	if (r || val < 0 || val > SHORT_MAX) {
> +		ti->error = "Invalid io_limit";
> +		return -EINVAL;
> +	}
> +	io_limit = val;
> +
> +	r = dm_get_device(ti, argv[0], 0, ti->len,
> +			  dm_table_get_mode(ti->table), &dev);
> +	if (r) {
> +		ti->error = "Device lookup failed";
> +		return r;
> +	}
> +
> +	if (io_limit == 0) {
> +		struct request_queue *q;
> +
> +		q = bdev_get_queue(dev->bdev);
> +		if (!q) {
> +			ti->error = "Can't get queue size";
> +			r = -ENXIO;
> +			goto release_dm_device;
> +		}
> +		io_limit = q->nr_requests;
> +	}
> +
> +	if (io_limit < io_throttle)
> +		io_limit = io_throttle;
> +
> +	dp = alloc_ioband_device(argv[1], io_throttle, io_limit);
> +	if (!dp) {
> +		ti->error = "Cannot create ioband device";
> +		r = -EINVAL;
> +		goto release_dm_device;
> +	}
> +
> +	mutex_lock(&dp->g_lock_device);
> +	r = policy_init(dp, argv[POLICY_PARAM_START - 1],
> +			argc - POLICY_PARAM_START, &argv[POLICY_PARAM_START]);
> +	if (r) {
> +		ti->error = "Invalid policy parameter";
> +		goto release_ioband_device;
> +	}
> +
> +	gp = kzalloc(sizeof(struct ioband_group), GFP_KERNEL);
> +	if (!gp) {
> +		ti->error = "Cannot allocate memory for ioband group";
> +		r = -ENOMEM;
> +		goto release_ioband_device;
> +	}
> +
> +	ti->private = gp;
> +	gp->c_target = ti;
> +	gp->c_dev = dev;
> +
> +	/* Find a default group parameter */
> +	for (start = POLICY_PARAM_START; start < argc; start++) {
> +		s = strpbrk(argv[start], POLICY_PARAM_DELIM);
> +		if (s == argv[start])
> +			break;
> +	}
> +	param = (start < argc) ? &argv[start][1] : NULL;
> +
> +	/* Create a default ioband group */
> +	r = ioband_group_init(gp, NULL, dp, IOBAND_ID_ANY, param);
> +	if (r) {
> +		kfree(gp);
> +		ti->error = "Cannot create default ioband group";
> +		goto release_ioband_device;
> +	}
> +
> +	r = ioband_group_type_select(gp, argv[4]);
> +	if (r) {
> +		ti->error = "Cannot set ioband group type";
> +		goto release_ioband_group;
> +	}
> +
> +	/* Create sub ioband groups */
> +	for (i = start + 1; i < argc; i++) {
> +		r = split_string(argv[i], &id, &param);
> +		if (r) {
> +			ti->error = "Invalid ioband group parameter";
> +			goto release_ioband_group;
> +		}
> +		r = ioband_group_attach(gp, id, param);
> +		if (r) {
> +			ti->error = "Cannot create ioband group";
> +			goto release_ioband_group;
> +		}
> +	}
> +	mutex_unlock(&dp->g_lock_device);
> +	return 0;
> +
> +release_ioband_group:
> +	ioband_group_destroy_all(gp);
> +release_ioband_device:
> +	mutex_unlock(&dp->g_lock_device);
> +	release_ioband_device(dp);
> +release_dm_device:
> +	dm_put_device(ti, dev);
> +	return r;
> +}
> +
> +static void ioband_dtr(struct dm_target *ti)
> +{
> +	struct ioband_group *gp = ti->private;
> +	struct ioband_device *dp = gp->c_banddev;
> +
> +	mutex_lock(&dp->g_lock_device);
> +	ioband_group_stop_all(gp, 0);
> +	cancel_delayed_work_sync(&dp->g_conductor);
> +	dm_put_device(ti, gp->c_dev);
> +	ioband_group_destroy_all(gp);
> +	mutex_unlock(&dp->g_lock_device);
> +	release_ioband_device(dp);
> +}
> +
> +static void ioband_hold_bio(struct ioband_group *gp, struct bio *bio)
> +{
> +	/* Todo: The list should be split into a read list and a write list */
> +	bio_list_add(&gp->c_blocked_bios, bio);
> +}
> +
> +static struct bio *ioband_pop_bio(struct ioband_group *gp)
> +{
> +	return bio_list_pop(&gp->c_blocked_bios);
> +}
> +
> +static int is_urgent_bio(struct bio *bio)
> +{
> +	struct page *page = bio_iovec_idx(bio, 0)->bv_page;
> +	/*
> +	 * ToDo: A new flag should be added to struct bio, which indicates
> +	 *       it contains urgent I/O requests.
> +	 */
> +	if (!PageReclaim(page))
> +		return 0;
> +	if (PageSwapCache(page))
> +		return 2;
> +	return 1;
> +}
> +
> +static inline int device_should_block(struct ioband_group *gp)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +
> +	if (is_group_down(gp))
> +		return 0;
> +	if (is_device_blocked(dp))
> +		return 1;
> +	if (dp->g_blocked >= dp->g_io_limit[READ] + dp->g_io_limit[WRITE]) {
> +		set_device_blocked(dp);
> +		return 1;
> +	}
> +	return 0;
> +}
> +
> +static inline int group_should_block(struct ioband_group *gp)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +
> +	if (is_group_down(gp))
> +		return 0;
> +	if (is_group_blocked(gp))
> +		return 1;
> +	if (dp->g_should_block(gp)) {
> +		set_group_blocked(gp);
> +		return 1;
> +	}
> +	return 0;
> +}
> +
> +static void prevent_burst_bios(struct ioband_group *gp, struct bio *bio)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +
> +	if (current->flags & PF_KTHREAD || is_urgent_bio(bio)) {
> +		/*
> +		 * Kernel threads shouldn't be blocked easily since each of
> +		 * them may handle BIOs for several groups on several
> +		 * partitions.
> +		 */
> +		wait_event_lock_irq(dp->g_waitq, !device_should_block(gp),
> +				    dp->g_lock, do_nothing());
> +	} else {
> +		wait_event_lock_irq(gp->c_waitq, !group_should_block(gp),
> +				    dp->g_lock, do_nothing());
> +	}
> +}
> +
> +static inline int should_pushback_bio(struct ioband_group *gp)
> +{
> +	return is_group_suspended(gp) && dm_noflush_suspending(gp->c_target);
> +}
> +
> +static inline int prepare_to_issue(struct ioband_group *gp, struct bio *bio)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +
> +	dp->g_issued[bio_data_dir(bio)]++;
> +	return dp->g_prepare_bio(gp, bio, 0);
> +}
> +
> +static inline int room_for_bio(struct ioband_device *dp)
> +{
> +	return dp->g_issued[READ] < dp->g_io_limit[READ]
> +		|| dp->g_issued[WRITE] < dp->g_io_limit[WRITE];
> +}
> +
> +static void hold_bio(struct ioband_group *gp, struct bio *bio)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +
> +	dp->g_blocked++;
> +	if (is_urgent_bio(bio)) {
> +		/*
> +		 * ToDo:
> +		 * When barrier mode is supported, write bios sharing the same
> +		 * file system with the currnt one would be all moved
> +		 * to g_urgent_bios list.
> +		 * You don't have to care about barrier handling if the bio
> +		 * is for swapping.
> +		 */
> +		dp->g_prepare_bio(gp, bio, IOBAND_URGENT);
> +		bio_list_add(&dp->g_urgent_bios, bio);
> +	} else {
> +		gp->c_blocked++;
> +		dp->g_hold_bio(gp, bio);
> +	}
> +}
> +
> +static inline int room_for_bio_rw(struct ioband_device *dp, int direct)
> +{
> +	return dp->g_issued[direct] < dp->g_io_limit[direct];
> +}
> +
> +static void push_prio_bio(struct ioband_group *gp, struct bio *bio, int direct)
> +{
> +	if (bio_list_empty(&gp->c_prio_bios))
> +		set_prio_queue(gp, direct);
> +	bio_list_add(&gp->c_prio_bios, bio);
> +	gp->c_prio_blocked++;
> +}
> +
> +static struct bio *pop_prio_bio(struct ioband_group *gp)
> +{
> +	struct bio *bio = bio_list_pop(&gp->c_prio_bios);
> +
> +	if (bio_list_empty(&gp->c_prio_bios))
> +		clear_prio_queue(gp);
> +
> +	if (bio)
> +		gp->c_prio_blocked--;
> +	return bio;
> +}
> +
> +static int make_issue_list(struct ioband_group *gp, struct bio *bio,
> +			   struct bio_list *issue_list,
> +			   struct bio_list *pushback_list)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +
> +	dp->g_blocked--;
> +	gp->c_blocked--;
> +	if (!gp->c_blocked && is_group_blocked(gp)) {
> +		clear_group_blocked(gp);
> +		wake_up_all(&gp->c_waitq);
> +	}
> +	if (should_pushback_bio(gp))
> +		bio_list_add(pushback_list, bio);
> +	else {
> +		int rw = bio_data_dir(bio);
> +
> +		gp->c_stat[rw].deferred++;
> +		gp->c_stat[rw].sectors += bio_sectors(bio);
> +		bio_list_add(issue_list, bio);
> +	}
> +	return prepare_to_issue(gp, bio);
> +}
> +
> +static void release_urgent_bios(struct ioband_device *dp,
> +				struct bio_list *issue_list,
> +				struct bio_list *pushback_list)
> +{
> +	struct bio *bio;
> +
> +	if (bio_list_empty(&dp->g_urgent_bios))
> +		return;
> +	while (room_for_bio_rw(dp, WRITE)) {
> +		bio = bio_list_pop(&dp->g_urgent_bios);
> +		if (!bio)
> +			return;
> +		dp->g_blocked--;
> +		dp->g_issued[bio_data_dir(bio)]++;
> +		bio_list_add(issue_list, bio);
> +	}
> +}
> +
> +static int release_prio_bios(struct ioband_group *gp,
> +			     struct bio_list *issue_list,
> +			     struct bio_list *pushback_list)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +	struct bio *bio;
> +	int direct;
> +	int ret;
> +
> +	if (bio_list_empty(&gp->c_prio_bios))
> +		return R_OK;
> +	direct = prio_queue_direct(gp);
> +	while (gp->c_prio_blocked) {
> +		if (!dp->g_can_submit(gp))
> +			return R_BLOCK;
> +		if (!room_for_bio_rw(dp, direct))
> +			return R_OK;
> +		bio = pop_prio_bio(gp);
> +		if (!bio)
> +			return R_OK;
> +		ret = make_issue_list(gp, bio, issue_list, pushback_list);
> +		if (ret)
> +			return ret;
> +	}
> +	return R_OK;
> +}
> +
> +static int release_norm_bios(struct ioband_group *gp,
> +			     struct bio_list *issue_list,
> +			     struct bio_list *pushback_list)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +	struct bio *bio;
> +	int direct;
> +	int ret;
> +
> +	while (gp->c_blocked - gp->c_prio_blocked) {
> +		if (!dp->g_can_submit(gp))
> +			return R_BLOCK;
> +		if (!room_for_bio(dp))
> +			return R_OK;
> +		bio = dp->g_pop_bio(gp);
> +		if (!bio)
> +			return R_OK;
> +
> +		direct = bio_data_dir(bio);
> +		if (!room_for_bio_rw(dp, direct)) {
> +			push_prio_bio(gp, bio, direct);
> +			continue;
> +		}
> +		ret = make_issue_list(gp, bio, issue_list, pushback_list);
> +		if (ret)
> +			return ret;
> +	}
> +	return R_OK;
> +}
> +
> +static inline int release_bios(struct ioband_group *gp,
> +			       struct bio_list *issue_list,
> +			       struct bio_list *pushback_list)
> +{
> +	int ret = release_prio_bios(gp, issue_list, pushback_list);
> +	if (ret)
> +		return ret;
> +	return release_norm_bios(gp, issue_list, pushback_list);
> +}
> +
> +static struct ioband_group *ioband_group_get(struct ioband_group *head,
> +					     struct bio *bio)
> +{
> +	struct ioband_group *gp;
> +
> +	if (!head->c_type->t_getid)
> +		return head;
> +
> +	gp = ioband_group_find(head, head->c_type->t_getid(bio));
> +
> +	if (!gp)
> +		gp = head;
> +	return gp;
> +}
> +
> +/*
> + * Start to control the bandwidth once the number of uncompleted BIOs
> + * exceeds the value of "io_throttle".
> + */
> +static int ioband_map(struct dm_target *ti, struct bio *bio,
> +		      union map_info *map_context)
> +{
> +	struct ioband_group *gp = ti->private;
> +	struct ioband_device *dp = gp->c_banddev;
> +	unsigned long flags;
> +	int direct;
> +
> +	spin_lock_irqsave(&dp->g_lock, flags);
> +
> +	/*
> +	 * The device is suspended while some of the ioband device
> +	 * configurations are being changed.
> +	 */
> +	if (is_device_suspended(dp))
> +		wait_event_lock_irq(dp->g_waitq_suspend,
> +				    !is_device_suspended(dp), dp->g_lock,
> +				    do_nothing());
> +
> +	gp = ioband_group_get(gp, bio);
> +	prevent_burst_bios(gp, bio);
> +	if (should_pushback_bio(gp)) {
> +		spin_unlock_irqrestore(&dp->g_lock, flags);
> +		return DM_MAPIO_REQUEUE;
> +	}
> +
> +	bio->bi_bdev = gp->c_dev->bdev;
> +	bio->bi_sector -= ti->begin;
> +	direct = bio_data_dir(bio);
> +
> +	if (!gp->c_blocked && room_for_bio_rw(dp, direct)) {
> +		if (dp->g_can_submit(gp)) {
> +			prepare_to_issue(gp, bio);
> +			gp->c_stat[direct].immediate++;
> +			gp->c_stat[direct].sectors += bio_sectors(bio);
> +			spin_unlock_irqrestore(&dp->g_lock, flags);
> +			return DM_MAPIO_REMAPPED;
> +		} else if (!dp->g_blocked &&
> +			   dp->g_issued[READ] + dp->g_issued[WRITE] == 0) {
> +			DMDEBUG("%s: token expired gp:%p", __func__, gp);
> +			queue_delayed_work(dp->g_ioband_wq,
> +					   &dp->g_conductor, 1);
> +		}
> +	}
> +	hold_bio(gp, bio);
> +	spin_unlock_irqrestore(&dp->g_lock, flags);
> +
> +	return DM_MAPIO_SUBMITTED;
> +}
> +
> +/*
> + * Select the best group to resubmit its BIOs.
> + */
> +static struct ioband_group *choose_best_group(struct ioband_device *dp)
> +{
> +	struct ioband_group *gp;
> +	struct ioband_group *best = NULL;
> +	int highest = 0;
> +	int pri;
> +
> +	/* Todo: The algorithm should be optimized.
> +	 *       It would be better to use rbtree.
> +	 */
> +	list_for_each_entry(gp, &dp->g_groups, c_list) {
> +		if (!gp->c_blocked || !room_for_bio(dp))
> +			continue;
> +		if (gp->c_blocked == gp->c_prio_blocked &&
> +		    !room_for_bio_rw(dp, prio_queue_direct(gp))) {
> +			continue;
> +		}
> +		pri = dp->g_can_submit(gp);
> +		if (pri > highest) {
> +			highest = pri;
> +			best = gp;
> +		}
> +	}
> +
> +	return best;
> +}
> +
> +/*
> + * This function is called right after it becomes able to resubmit BIOs.
> + * It selects the best BIOs and passes them to the underlying layer.
> + */
> +static void ioband_conduct(struct work_struct *work)
> +{
> +	struct ioband_device *dp =
> +		container_of(work, struct ioband_device, g_conductor.work);
> +	struct ioband_group *gp = NULL;
> +	struct bio *bio;
> +	unsigned long flags;
> +	struct bio_list issue_list, pushback_list;
> +
> +	bio_list_init(&issue_list);
> +	bio_list_init(&pushback_list);
> +
> +	spin_lock_irqsave(&dp->g_lock, flags);
> +	release_urgent_bios(dp, &issue_list, &pushback_list);
> +	if (dp->g_blocked) {
> +		gp = choose_best_group(dp);
> +		if (gp &&
> +		    release_bios(gp, &issue_list, &pushback_list) == R_YIELD)
> +			queue_delayed_work(dp->g_ioband_wq,
> +					   &dp->g_conductor, 0);
> +	}
> +
> +	if (is_device_blocked(dp) &&
> +	    dp->g_blocked < dp->g_io_limit[READ] + dp->g_io_limit[WRITE]) {
> +		clear_device_blocked(dp);
> +		wake_up_all(&dp->g_waitq);
> +	}
> +
> +	if (dp->g_blocked &&
> +	    room_for_bio_rw(dp, READ) && room_for_bio_rw(dp, WRITE) &&
> +	    bio_list_empty(&issue_list) && bio_list_empty(&pushback_list) &&
> +	    dp->g_restart_bios(dp)) {
> +		DMDEBUG("%s: token expired dp:%p issued(%d,%d) g_blocked(%d)",
> +			__func__, dp, dp->g_issued[READ], dp->g_issued[WRITE],
> +			dp->g_blocked);
> +		queue_delayed_work(dp->g_ioband_wq, &dp->g_conductor, 0);
> +	}
> +
> +	spin_unlock_irqrestore(&dp->g_lock, flags);
> +
> +	while ((bio = bio_list_pop(&issue_list)))
> +		generic_make_request(bio);
> +	while ((bio = bio_list_pop(&pushback_list)))
> +		bio_endio(bio, -EIO);
> +}
> +
> +static int ioband_end_io(struct dm_target *ti, struct bio *bio,
> +			 int error, union map_info *map_context)
> +{
> +	struct ioband_group *gp = ti->private;
> +	struct ioband_device *dp = gp->c_banddev;
> +	unsigned long flags;
> +	int r = error;
> +
> +	/*
> +	 *  XXX: A new error code for device mapper devices should be used
> +	 *       rather than EIO.
> +	 */
> +	if (error == -EIO && should_pushback_bio(gp)) {
> +		/* This ioband device is suspending */
> +		r = DM_ENDIO_REQUEUE;
> +	}
> +	/*
> +	 * Todo: The algorithm should be optimized to eliminate the spinlock.
> +	 */
> +	spin_lock_irqsave(&dp->g_lock, flags);
> +	dp->g_issued[bio_data_dir(bio)]--;
> +
> +	/*
> +	 * Todo: It would be better to introduce high/low water marks here
> +	 *       not to kick the workqueues so often.
> +	 */
> +	if (dp->g_blocked)
> +		queue_delayed_work(dp->g_ioband_wq, &dp->g_conductor, 0);
> +	else if (is_device_suspended(dp) &&
> +		 dp->g_issued[READ] + dp->g_issued[WRITE] == 0)
> +		wake_up_all(&dp->g_waitq_flush);
> +	spin_unlock_irqrestore(&dp->g_lock, flags);
> +	return r;
> +}
> +
> +static void ioband_presuspend(struct dm_target *ti)
> +{
> +	struct ioband_group *gp = ti->private;
> +	struct ioband_device *dp = gp->c_banddev;
> +
> +	mutex_lock(&dp->g_lock_device);
> +	ioband_group_stop_all(gp, 1);
> +	mutex_unlock(&dp->g_lock_device);
> +}
> +
> +static void ioband_resume(struct dm_target *ti)
> +{
> +	struct ioband_group *gp = ti->private;
> +	struct ioband_device *dp = gp->c_banddev;
> +
> +	mutex_lock(&dp->g_lock_device);
> +	ioband_group_resume_all(gp);
> +	mutex_unlock(&dp->g_lock_device);
> +}
> +
> +static void ioband_group_status(struct ioband_group *gp, int *szp,
> +				char *result, unsigned maxlen)
> +{
> +	struct ioband_group_stat *stat;
> +	int i, sz = *szp; /* used in DMEMIT() */
> +
> +	DMEMIT(" %d", gp->c_id);
> +	for (i = 0; i < 2; i++) {
> +		stat = &gp->c_stat[i];
> +		DMEMIT(" %lu %lu %lu",
> +		       stat->immediate + stat->deferred, stat->deferred,
> +		       stat->sectors);
> +	}
> +	*szp = sz;
> +}
> +
> +static int ioband_status(struct dm_target *ti, status_type_t type,
> +			 char *result, unsigned maxlen)
> +{
> +	struct ioband_group *gp = ti->private, *p;
> +	struct ioband_device *dp = gp->c_banddev;
> +	struct rb_node *node;
> +	int sz = 0;	/* used in DMEMIT() */
> +	unsigned long flags;
> +
> +	mutex_lock(&dp->g_lock_device);
> +
> +	switch (type) {
> +	case STATUSTYPE_INFO:
> +		spin_lock_irqsave(&dp->g_lock, flags);
> +		DMEMIT("%s", dp->g_name);
> +		ioband_group_status(gp, &sz, result, maxlen);
> +		for (node = rb_first(&gp->c_group_root); node;
> +		     node = rb_next(node)) {
> +			p = rb_entry(node, struct ioband_group, c_group_node);
> +			ioband_group_status(p, &sz, result, maxlen);
> +		}
> +		spin_unlock_irqrestore(&dp->g_lock, flags);
> +		break;
> +
> +	case STATUSTYPE_TABLE:
> +		spin_lock_irqsave(&dp->g_lock, flags);
> +		DMEMIT("%s %s %d %d %s %s",
> +		       gp->c_dev->name, dp->g_name,
> +		       dp->g_io_throttle, dp->g_io_limit[READ],
> +		       gp->c_type->t_name, dp->g_policy->p_name);
> +		dp->g_show(gp, &sz, result, maxlen);
> +		spin_unlock_irqrestore(&dp->g_lock, flags);
> +		break;
> +	}
> +
> +	mutex_unlock(&dp->g_lock_device);
> +	return 0;
> +}
> +
> +static int ioband_group_type_select(struct ioband_group *gp, char *name)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +	struct group_type *t;
> +	unsigned long flags;
> +
> +	for (t = dm_ioband_group_type; (t->t_name); t++) {
> +		if (!strcmp(name, t->t_name))
> +			break;
> +	}
> +	if (!t->t_name) {
> +		DMWARN("ioband type select: %s isn't supported.", name);
> +		return -EINVAL;
> +	}
> +	spin_lock_irqsave(&dp->g_lock, flags);
> +	if (!RB_EMPTY_ROOT(&gp->c_group_root)) {
> +		spin_unlock_irqrestore(&dp->g_lock, flags);
> +		return -EBUSY;
> +	}
> +	gp->c_type = t;
> +	spin_unlock_irqrestore(&dp->g_lock, flags);
> +
> +	return 0;
> +}
> +
> +static int ioband_set_param(struct ioband_group *gp, char *cmd, char *value)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +	char *val_str;
> +	long id;
> +	unsigned long flags;
> +	int r;
> +
> +	r = split_string(value, &id, &val_str);
> +	if (r)
> +		return r;
> +
> +	spin_lock_irqsave(&dp->g_lock, flags);
> +	if (id != IOBAND_ID_ANY) {
> +		gp = ioband_group_find(gp, id);
> +		if (!gp) {
> +			spin_unlock_irqrestore(&dp->g_lock, flags);
> +			DMWARN("ioband_set_param: id=%ld not found.", id);
> +			return -EINVAL;
> +		}
> +	}
> +	r = dp->g_set_param(gp, cmd, val_str);
> +	spin_unlock_irqrestore(&dp->g_lock, flags);
> +	return r;
> +}
> +
> +static int ioband_group_attach(struct ioband_group *gp, int id, char *param)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +	struct ioband_group *sub_gp;
> +	int r;
> +
> +	if (id < 0) {
> +		DMWARN("ioband_group_attach: invalid id:%d", id);
> +		return -EINVAL;
> +	}
> +	if (!gp->c_type->t_getid) {
> +		DMWARN("ioband_group_attach: "
> +		       "no ioband group type is specified");
> +		return -EINVAL;
> +	}
> +
> +	sub_gp = kzalloc(sizeof(struct ioband_group), GFP_KERNEL);
> +	if (!sub_gp)
> +		return -ENOMEM;
> +
> +	r = ioband_group_init(sub_gp, gp, dp, id, param);
> +	if (r < 0) {
> +		kfree(sub_gp);
> +		return r;
> +	}
> +	return 0;
> +}
> +
> +static int ioband_group_detach(struct ioband_group *gp, int id)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +	struct ioband_group *sub_gp;
> +	unsigned long flags;
> +
> +	if (id < 0) {
> +		DMWARN("ioband_group_detach: invalid id:%d", id);
> +		return -EINVAL;
> +	}
> +	spin_lock_irqsave(&dp->g_lock, flags);
> +	sub_gp = ioband_group_find(gp, id);
> +	if (!sub_gp) {
> +		spin_unlock_irqrestore(&dp->g_lock, flags);
> +		DMWARN("ioband_group_detach: invalid id:%d", id);
> +		return -EINVAL;
> +	}
> +
> +	/*
> +	 * Todo: Calling suspend_ioband_device() before releasing the
> +	 *       ioband group has a large overhead. Need improvement.
> +	 */
> +	suspend_ioband_device(dp, flags, 0);
> +	ioband_group_release(gp, sub_gp);
> +	resume_ioband_device(dp);
> +	spin_unlock_irqrestore(&dp->g_lock, flags);
> +	return 0;
> +}
> +
> +/*
> + * Message parameters:
> + *	"policy"      <name>
> + *       ex)
> + *		"policy" "weight"
> + *	"type"        "none"|"pid"|"pgrp"|"node"|"cpuset"|"cgroup"|"user"|"gid"
> + * 	"io_throttle" <value>
> + * 	"io_limit"    <value>
> + *	"attach"      <group id>
> + *	"detach"      <group id>
> + *	"any-command" <group id>:<value>
> + *       ex)
> + *		"weight" 0:<value>
> + *		"token"  24:<value>
> + */
> +static int __ioband_message(struct dm_target *ti, unsigned argc, char **argv)
> +{
> +	struct ioband_group *gp = ti->private, *p;
> +	struct ioband_device *dp = gp->c_banddev;
> +	struct rb_node *node;
> +	long val;
> +	int r = 0;
> +	unsigned long flags;
> +
> +	if (argc == 1 && !strcmp(argv[0], "reset")) {
> +		spin_lock_irqsave(&dp->g_lock, flags);
> +		memset(gp->c_stat, 0, sizeof(gp->c_stat));
> +		for (node = rb_first(&gp->c_group_root); node;
> +		     node = rb_next(node)) {
> +			p = rb_entry(node, struct ioband_group, c_group_node);
> +			memset(p->c_stat, 0, sizeof(p->c_stat));
> +		}
> +		spin_unlock_irqrestore(&dp->g_lock, flags);
> +		return 0;
> +	}
> +
> +	if (argc != 2) {
> +		DMWARN("Unrecognised band message received.");
> +		return -EINVAL;
> +	}
> +	if (!strcmp(argv[0], "io_throttle")) {
> +		r = strict_strtol(argv[1], 0, &val);
> +		if (r || val < 0 || val > SHORT_MAX)
> +			return -EINVAL;
> +		if (val == 0)
> +			val = DEFAULT_IO_THROTTLE;
> +		spin_lock_irqsave(&dp->g_lock, flags);
> +		if (val > dp->g_io_limit[READ] ||
> +		    val > dp->g_io_limit[WRITE]) {
> +			spin_unlock_irqrestore(&dp->g_lock, flags);
> +			return -EINVAL;
> +		}
> +		dp->g_io_throttle = val;
> +		spin_unlock_irqrestore(&dp->g_lock, flags);
> +		ioband_set_param(gp, argv[0], argv[1]);
> +		return 0;
> +	} else if (!strcmp(argv[0], "io_limit")) {
> +		r = strict_strtol(argv[1], 0, &val);
> +		if (r || val < 0 || val > SHORT_MAX)
> +			return -EINVAL;
> +		spin_lock_irqsave(&dp->g_lock, flags);
> +		if (val == 0) {
> +			struct request_queue *q;
> +
> +			q = bdev_get_queue(gp->c_dev->bdev);
> +			if (!q) {
> +				spin_unlock_irqrestore(&dp->g_lock, flags);
> +				return -ENXIO;
> +			}
> +			val = q->nr_requests;
> +		}
> +		if (val < dp->g_io_throttle) {
> +			spin_unlock_irqrestore(&dp->g_lock, flags);
> +			return -EINVAL;
> +		}
> +		dp->g_io_limit[READ] = dp->g_io_limit[WRITE] = val;
> +		spin_unlock_irqrestore(&dp->g_lock, flags);
> +		ioband_set_param(gp, argv[0], argv[1]);
> +		return 0;
> +	} else if (!strcmp(argv[0], "type")) {
> +		return ioband_group_type_select(gp, argv[1]);
> +	} else if (!strcmp(argv[0], "attach")) {
> +		r = strict_strtol(argv[1], 0, &val);
> +		if (r)
> +			return r;
> +		return ioband_group_attach(gp, val, NULL);
> +	} else if (!strcmp(argv[0], "detach")) {
> +		r = strict_strtol(argv[1], 0, &val);
> +		if (r)
> +			return r;
> +		return ioband_group_detach(gp, val);
> +	} else if (!strcmp(argv[0], "policy")) {
> +		r = policy_init(dp, argv[1], 0, &argv[2]);
> +		return r;
> +	} else {
> +		/* message anycommand <group-id>:<value> */
> +		r = ioband_set_param(gp, argv[0], argv[1]);
> +		if (r < 0)
> +			DMWARN("Unrecognised band message received.");
> +		return r;
> +	}
> +	return 0;
> +}
> +
> +static int ioband_message(struct dm_target *ti, unsigned argc, char **argv)
> +{
> +	struct ioband_group *gp = ti->private;
> +	struct ioband_device *dp = gp->c_banddev;
> +	int r;
> +
> +	mutex_lock(&dp->g_lock_device);
> +	r = __ioband_message(ti, argc, argv);
> +	mutex_unlock(&dp->g_lock_device);
> +	return r;
> +}
> +
> +static int ioband_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
> +			struct bio_vec *biovec, int max_size)
> +{
> +	struct ioband_group *gp = ti->private;
> +	struct request_queue *q = bdev_get_queue(gp->c_dev->bdev);
> +
> +	if (!q->merge_bvec_fn)
> +		return max_size;
> +
> +	bvm->bi_bdev = gp->c_dev->bdev;
> +	bvm->bi_sector -= ti->begin;
> +
> +	return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
> +}
> +
> +static struct target_type ioband_target = {
> +	.name	     = "ioband",
> +	.module      = THIS_MODULE,
> +	.version     = {1, 10, 2},
> +	.ctr	     = ioband_ctr,
> +	.dtr	     = ioband_dtr,
> +	.map	     = ioband_map,
> +	.end_io	     = ioband_end_io,
> +	.presuspend  = ioband_presuspend,
> +	.resume	     = ioband_resume,
> +	.status	     = ioband_status,
> +	.message     = ioband_message,
> +	.merge       = ioband_merge,
> +};
> +
> +static int __init dm_ioband_init(void)
> +{
> +	int r;
> +
> +	r = dm_register_target(&ioband_target);
> +	if (r < 0) {
> +		DMERR("register failed %d", r);
> +		return r;
> +	}
> +	return r;
> +}
> +
> +static void __exit dm_ioband_exit(void)
> +{
> +	dm_unregister_target(&ioband_target);
> +}
> +
> +module_init(dm_ioband_init);
> +module_exit(dm_ioband_exit);
> +
> +MODULE_DESCRIPTION(DM_NAME " I/O bandwidth control");
> +MODULE_AUTHOR("Hirokazu Takahashi <taka valinux co jp>, "
> +	      "Ryo Tsuruta <ryov valinux co jp");
> +MODULE_LICENSE("GPL");
> Index: linux-2.6.29/drivers/md/dm-ioband-policy.c
> ===================================================================
> --- /dev/null
> +++ linux-2.6.29/drivers/md/dm-ioband-policy.c
> @@ -0,0 +1,457 @@
> +/*
> + * Copyright (C) 2008 VA Linux Systems Japan K.K.
> + *
> + *  I/O bandwidth control
> + *
> + * This file is released under the GPL.
> + */
> +#include <linux/bio.h>
> +#include <linux/workqueue.h>
> +#include <linux/rbtree.h>
> +#include "dm.h"
> +#include "dm-bio-list.h"
> +#include "dm-ioband.h"
> +
> +/*
> + * The following functions determine when and which BIOs should
> + * be submitted to control the I/O flow.
> + * It is possible to add a new BIO scheduling policy with it.
> + */
> +
> +/*
> + * Functions for weight balancing policy based on the number of I/Os.
> + */
> +#define DEFAULT_WEIGHT		100
> +#define DEFAULT_TOKENPOOL	2048
> +#define DEFAULT_BUCKET		2
> +#define IOBAND_IOPRIO_BASE	100
> +#define TOKEN_BATCH_UNIT	20
> +#define PROCEED_THRESHOLD	8
> +#define	LOCAL_ACTIVE_RATIO	8
> +#define	GLOBAL_ACTIVE_RATIO	16
> +#define OVERCOMMIT_RATE		4
> +
> +/*
> + * Calculate the effective number of tokens this group has.
> + */
> +static int get_token(struct ioband_group *gp)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +	int token = gp->c_token;
> +	int allowance = dp->g_epoch - gp->c_my_epoch;
> +
> +	if (allowance) {
> +		if (allowance > dp->g_carryover)
> +			allowance = dp->g_carryover;
> +		token += gp->c_token_initial * allowance;
> +	}
> +	if (is_group_down(gp))
> +		token += gp->c_token_initial * dp->g_carryover * 2;
> +
> +	return token;
> +}
> +
> +/*
> + * Calculate the priority of a given group.
> + */
> +static int iopriority(struct ioband_group *gp)
> +{
> +	return get_token(gp) * IOBAND_IOPRIO_BASE / gp->c_token_initial + 1;
> +}
> +
> +/*
> + * This function is called when all the active group on the same ioband
> + * device has used up their tokens. It makes a new global epoch so that
> + * all groups on this device will get freshly assigned tokens.
> + */
> +static int make_global_epoch(struct ioband_device *dp)
> +{
> +	struct ioband_group *gp = dp->g_dominant;
> +
> +	/*
> +	 * Don't make a new epoch if the dominant group still has a lot of
> +	 * tokens, except when the I/O load is low.
> +	 */
> +	if (gp) {
> +		int iopri = iopriority(gp);
> +		if (iopri * PROCEED_THRESHOLD > IOBAND_IOPRIO_BASE &&
> +		    dp->g_issued[READ] + dp->g_issued[WRITE] >=
> +		    dp->g_io_throttle)
> +			return 0;
> +	}
> +
> +	dp->g_epoch++;
> +	DMDEBUG("make_epoch %d", dp->g_epoch);
> +
> +	/* The leftover tokens will be used in the next epoch. */
> +	dp->g_token_extra = dp->g_token_left;
> +	if (dp->g_token_extra < 0)
> +		dp->g_token_extra = 0;
> +	dp->g_token_left = dp->g_token_bucket;
> +
> +	dp->g_expired = NULL;
> +	dp->g_dominant = NULL;
> +
> +	return 1;
> +}
> +
> +/*
> + * This function is called when this group has used up its own tokens.
> + * It will check whether it's possible to make a new epoch of this group.
> + */
> +static inline int make_epoch(struct ioband_group *gp)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +	int allowance = dp->g_epoch - gp->c_my_epoch;
> +
> +	if (!allowance)
> +		return 0;
> +	if (allowance > dp->g_carryover)
> +		allowance = dp->g_carryover;
> +	gp->c_my_epoch = dp->g_epoch;
> +	return allowance;
> +}
> +
> +/*
> + * Check whether this group has tokens to issue an I/O. Return 0 if it
> + * doesn't have any, otherwise return the priority of this group.
> + */
> +static int is_token_left(struct ioband_group *gp)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +	int allowance;
> +	int delta;
> +	int extra;
> +
> +	if (gp->c_token > 0)
> +		return iopriority(gp);
> +
> +	if (is_group_down(gp)) {
> +		gp->c_token = gp->c_token_initial;
> +		return iopriority(gp);
> +	}
> +	allowance = make_epoch(gp);
> +	if (!allowance)
> +		return 0;
> +	/*
> +	 * If this group has the right to get tokens for several epochs,
> +	 * give all of them to the group here.
> +	 */
> +	delta = gp->c_token_initial * allowance;
> +	dp->g_token_left -= delta;
> +	/*
> +	 * Give some extra tokens to this group when there have left unused
> +	 * tokens on this ioband device from the previous epoch.
> +	 */
> +	extra = dp->g_token_extra * gp->c_token_initial /
> +	    (dp->g_token_bucket - dp->g_token_extra / 2);
> +	delta += extra;
> +	gp->c_token += delta;
> +	gp->c_consumed = 0;
> +
> +	if (gp == dp->g_current)
> +		dp->g_yield_mark += delta;
> +	DMDEBUG("refill token: gp:%p token:%d->%d extra(%d) allowance(%d)",
> +		gp, gp->c_token - delta, gp->c_token, extra, allowance);
> +	if (gp->c_token > 0)
> +		return iopriority(gp);
> +	DMDEBUG("refill token: yet empty gp:%p token:%d", gp, gp->c_token);
> +	return 0;
> +}
> +
> +/*
> + * Use tokens to issue an I/O. After the operation, the number of tokens left
> + * on this group may become negative value, which will be treated as debt.
> + */
> +static int consume_token(struct ioband_group *gp, int count, int flag)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +
> +	if (gp->c_consumed * LOCAL_ACTIVE_RATIO < gp->c_token_initial &&
> +	    gp->c_consumed * GLOBAL_ACTIVE_RATIO < dp->g_token_bucket) {
> +		; /* Do nothing unless this group is really active. */
> +	} else if (!dp->g_dominant ||
> +		   get_token(gp) > get_token(dp->g_dominant)) {
> +		/*
> +		 * Regard this group as the dominant group on this
> +		 * ioband device when it has larger number of tokens
> +		 * than those of the previous one.
> +		 */
> +		dp->g_dominant = gp;
> +	}
> +	if (dp->g_epoch == gp->c_my_epoch &&
> +	    gp->c_token > 0 && gp->c_token - count <= 0) {
> +		/* Remember the last group which used up its own tokens. */
> +		dp->g_expired = gp;
> +		if (dp->g_dominant == gp)
> +			dp->g_dominant = NULL;
> +	}
> +
> +	if (gp != dp->g_current) {
> +		/* This group is the current already. */
> +		dp->g_current = gp;
> +		dp->g_yield_mark =
> +		    gp->c_token - (TOKEN_BATCH_UNIT << dp->g_token_unit);
> +	}
> +	gp->c_token -= count;
> +	gp->c_consumed += count;
> +	if (gp->c_token <= dp->g_yield_mark && !(flag & IOBAND_URGENT)) {
> +		/*
> +		 * Return-value 1 means that this policy requests dm-ioband
> +		 * to give a chance to another group to be selected since
> +		 * this group has already issued enough amount of I/Os.
> +		 */
> +		dp->g_current = NULL;
> +		return R_YIELD;
> +	}
> +	/*
> +	 * Return-value 0 means that this policy allows dm-ioband to select
> +	 * this group to issue I/Os without a break.
> +	 */
> +	return R_OK;
> +}
> +
> +/*
> + * Consume one token on each I/O.
> + */
> +static int prepare_token(struct ioband_group *gp, struct bio *bio, int flag)
> +{
> +	return consume_token(gp, 1, flag);
> +}
> +
> +/*
> + * Check if this group is able to receive a new bio.
> + */
> +static int is_queue_full(struct ioband_group *gp)
> +{
> +	return gp->c_blocked >= gp->c_limit;
> +}
> +
> +static void set_weight(struct ioband_group *gp, int new)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +	struct ioband_group *p;
> +
> +	dp->g_weight_total += (new - gp->c_weight);
> +	gp->c_weight = new;
> +
> +	if (dp->g_weight_total == 0) {
> +		list_for_each_entry(p, &dp->g_groups, c_list)
> +			p->c_token = p->c_token_initial = p->c_limit = 1;
> +	} else {
> +		list_for_each_entry(p, &dp->g_groups, c_list) {
> +			p->c_token = p->c_token_initial =
> +				dp->g_token_bucket * p->c_weight /
> +				dp->g_weight_total + 1;
> +			p->c_limit = (dp->g_io_limit[READ] +
> +				dp->g_io_limit[WRITE]) * p->c_weight /
> +				dp->g_weight_total / OVERCOMMIT_RATE + 1;
> +		}
> +	}
> +}
> +
> +static void init_token_bucket(struct ioband_device *dp,
> +			      int token_bucket, int carryover)
> +{
> +	if (!token_bucket)
> +		dp->g_token_bucket =
> +			((dp->g_io_limit[READ] + dp->g_io_limit[WRITE]) *
> +			DEFAULT_BUCKET) << dp->g_token_unit;
> +	else
> +		dp->g_token_bucket = token_bucket;
> +	if (!carryover)
> +		dp->g_carryover = (DEFAULT_TOKENPOOL << dp->g_token_unit) /
> +							dp->g_token_bucket;
> +	else
> +		dp->g_carryover = carryover;
> +	if (dp->g_carryover < 1)
> +		dp->g_carryover = 1;
> +	dp->g_token_left = 0;
> +}
> +
> +static int policy_weight_param(struct ioband_group *gp, char *cmd, char *value)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +	long val;
> +	int r = 0, err;
> +
> +	err = strict_strtol(value, 0, &val);
> +	if (!strcmp(cmd, "weight")) {
> +		if (!err && 0 < val && val <= SHORT_MAX)
> +			set_weight(gp, val);
> +		else
> +			r = -EINVAL;
> +	} else if (!strcmp(cmd, "token")) {
> +		if (!err && 0 <= val && val <= INT_MAX) {
> +			init_token_bucket(dp, val, 0);
> +			set_weight(gp, gp->c_weight);
> +			dp->g_token_extra = 0;
> +		} else
> +			r = -EINVAL;
> +	} else if (!strcmp(cmd, "carryover")) {
> +		if (!err && 0 <= val && val <= INT_MAX) {
> +			init_token_bucket(dp, dp->g_token_bucket, val);
> +			set_weight(gp, gp->c_weight);
> +			dp->g_token_extra = 0;
> +		} else
> +			r = -EINVAL;
> +	} else if (!strcmp(cmd, "io_limit")) {
> +		init_token_bucket(dp, 0, 0);
> +		set_weight(gp, gp->c_weight);
> +	} else {
> +		r = -EINVAL;
> +	}
> +	return r;
> +}
> +
> +static int policy_weight_ctr(struct ioband_group *gp, char *arg)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +
> +	if (!arg)
> +		arg = __stringify(DEFAULT_WEIGHT);
> +	gp->c_my_epoch = dp->g_epoch;
> +	gp->c_weight = 0;
> +	gp->c_consumed = 0;
> +	return policy_weight_param(gp, "weight", arg);
> +}
> +
> +static void policy_weight_dtr(struct ioband_group *gp)
> +{
> +	struct ioband_device *dp = gp->c_banddev;
> +	set_weight(gp, 0);
> +	dp->g_dominant = NULL;
> +	dp->g_expired = NULL;
> +}
> +
> +static void policy_weight_show(struct ioband_group *gp, int *szp,
> +			       char *result, unsigned maxlen)
> +{
> +	struct ioband_group *p;
> +	struct ioband_device *dp = gp->c_banddev;
> +	struct rb_node *node;
> +	int sz = *szp;	/* used in DMEMIT() */
> +
> +	DMEMIT(" %d :%d", dp->g_token_bucket, gp->c_weight);
> +
> +	for (node = rb_first(&gp->c_group_root); node; node = rb_next(node)) {
> +		p = rb_entry(node, struct ioband_group, c_group_node);
> +		DMEMIT(" %d:%d", p->c_id, p->c_weight);
> +	}
> +	*szp = sz;
> +}
> +
> +/*
> + *  <Method>      <description>
> + * g_can_submit   : To determine whether a given group has the right to
> + *                  submit BIOs. The larger the return value the higher the
> + *                  priority to submit. Zero means it has no right.
> + * g_prepare_bio  : Called right before submitting each BIO.
> + * g_restart_bios : Called if this ioband device has some BIOs blocked but none
> + *                  of them can be submitted now. This method has to
> + *                  reinitialize the data to restart to submit BIOs and return
> + *                  0 or 1.
> + *                  The return value 0 means that it has become able to submit
> + *                  them now so that this ioband device will continue its work.
> + *                  The return value 1 means that it is still unable to submit
> + *                  them so that this device will stop its work. And this
> + *                  policy module has to reactivate the device when it gets
> + *                  to be able to submit BIOs.
> + * g_hold_bio     : To hold a given BIO until it is submitted.
> + *                  The default function is used when this method is undefined.
> + * g_pop_bio      : To select and get the best BIO to submit.
> + * g_group_ctr    : To initalize the policy own members of struct ioband_group.
> + * g_group_dtr    : Called when struct ioband_group is removed.
> + * g_set_param    : To update the policy own date.
> + *                  The parameters can be passed through "dmsetup message"
> + *                  command.
> + * g_should_block : Called every time this ioband device receive a BIO.
> + *                  Return 1 if a given group can't receive any more BIOs,
> + *                  otherwise return 0.
> + * g_show         : Show the configuration.
> + */
> +static int policy_weight_init(struct ioband_device *dp, int argc, char **argv)
> +{
> +	long val;
> +	int r = 0;
> +
> +	if (argc < 1)
> +		val = 0;
> +	else {
> +		r = strict_strtol(argv[0], 0, &val);
> +		if (r || val < 0 || val > INT_MAX)
> +			return -EINVAL;
> +	}
> +
> +	dp->g_can_submit = is_token_left;
> +	dp->g_prepare_bio = prepare_token;
> +	dp->g_restart_bios = make_global_epoch;
> +	dp->g_group_ctr = policy_weight_ctr;
> +	dp->g_group_dtr = policy_weight_dtr;
> +	dp->g_set_param = policy_weight_param;
> +	dp->g_should_block = is_queue_full;
> +	dp->g_show = policy_weight_show;
> +
> +	dp->g_epoch = 0;
> +	dp->g_weight_total = 0;
> +	dp->g_current = NULL;
> +	dp->g_dominant = NULL;
> +	dp->g_expired = NULL;
> +	dp->g_token_extra = 0;
> +	dp->g_token_unit = 0;
> +	init_token_bucket(dp, val, 0);
> +	dp->g_token_left = dp->g_token_bucket;
> +
> +	return 0;
> +}
> +
> +/* weight balancing policy based on the number of I/Os. --- End --- */
> +
> +/*
> + * Functions for weight balancing policy based on I/O size.
> + * It just borrows a lot of functions from the regular weight balancing policy.
> + */
> +static int w2_prepare_token(struct ioband_group *gp, struct bio *bio, int flag)
> +{
> +	/* Consume tokens depending on the size of a given bio. */
> +	return consume_token(gp, bio_sectors(bio), flag);
> +}
> +
> +static int w2_policy_weight_init(struct ioband_device *dp,
> +				 int argc, char **argv)
> +{
> +	long val;
> +	int r = 0;
> +
> +	if (argc < 1)
> +		val = 0;
> +	else {
> +		r = strict_strtol(argv[0], 0, &val);
> +		if (r || val < 0 || val > INT_MAX)
> +			return -EINVAL;
> +	}
> +
> +	r = policy_weight_init(dp, argc, argv);
> +	if (r < 0)
> +		return r;
> +
> +	dp->g_prepare_bio = w2_prepare_token;
> +	dp->g_token_unit = PAGE_SHIFT - 9;
> +	init_token_bucket(dp, val, 0);
> +	dp->g_token_left = dp->g_token_bucket;
> +	return 0;
> +}
> +
> +/* weight balancing policy based on I/O size. --- End --- */
> +
> +static int policy_default_init(struct ioband_device *dp, int argc, char **argv)
> +{
> +	return policy_weight_init(dp, argc, argv);
> +}
> +
> +struct policy_type dm_ioband_policy_type[] = {
> +	{"default", policy_default_init},
> +	{"weight", policy_weight_init},
> +	{"weight-iosize", w2_policy_weight_init},
> +	{NULL, policy_default_init}
> +};
> Index: linux-2.6.29/drivers/md/dm-ioband-type.c
> ===================================================================
> --- /dev/null
> +++ linux-2.6.29/drivers/md/dm-ioband-type.c
> @@ -0,0 +1,77 @@
> +/*
> + * Copyright (C) 2008 VA Linux Systems Japan K.K.
> + *
> + *  I/O bandwidth control
> + *
> + * This file is released under the GPL.
> + */
> +#include <linux/bio.h>
> +#include "dm.h"
> +#include "dm-bio-list.h"
> +#include "dm-ioband.h"
> +
> +/*
> + * Any I/O bandwidth can be divided into several bandwidth groups, each of which
> + * has its own unique ID. The following functions are called to determine
> + * which group a given BIO belongs to and return the ID of the group.
> + */
> +
> +/* ToDo: unsigned long value would be better for group ID */
> +
> +static int ioband_process_id(struct bio *bio)
> +{
> +	/*
> +	 * This function will work for KVM and Xen.
> +	 */
> +	return (int)current->tgid;
> +}
> +
> +static int ioband_process_group(struct bio *bio)
> +{
> +	return (int)task_pgrp_nr(current);
> +}
> +
> +static int ioband_uid(struct bio *bio)
> +{
> +	return (int)current_uid();
> +}
> +
> +static int ioband_gid(struct bio *bio)
> +{
> +	return (int)current_gid();
> +}
> +
> +static int ioband_cpuset(struct bio *bio)
> +{
> +	return 0;	/* not implemented yet */
> +}
> +
> +static int ioband_node(struct bio *bio)
> +{
> +	return 0;	/* not implemented yet */
> +}
> +
> +static int ioband_cgroup(struct bio *bio)
> +{
> +	/*
> +	 * This function should return the ID of the cgroup which
> +	 * issued "bio". The ID of the cgroup which the current
> +	 * process belongs to won't be suitable ID for this purpose,
> +	 * since some BIOs will be handled by kernel threads like aio
> +	 * or pdflush on behalf of the process requesting the BIOs.
> +	 */
> +	return 0;	/* not implemented yet */
> +}
> +
> +struct group_type dm_ioband_group_type[] = {
> +	{"none", NULL},
> +	{"pgrp", ioband_process_group},
> +	{"pid", ioband_process_id},
> +	{"node", ioband_node},
> +	{"cpuset", ioband_cpuset},
> +	{"cgroup", ioband_cgroup},
> +	{"user", ioband_uid},
> +	{"uid", ioband_uid},
> +	{"gid", ioband_gid},
> +	{NULL, NULL}
> +};
> Index: linux-2.6.29/drivers/md/dm-ioband.h
> ===================================================================
> --- /dev/null
> +++ linux-2.6.29/drivers/md/dm-ioband.h
> @@ -0,0 +1,186 @@
> +/*
> + * Copyright (C) 2008 VA Linux Systems Japan K.K.
> + *
> + *  I/O bandwidth control
> + *
> + * This file is released under the GPL.
> + */
> +
> +#include <linux/version.h>
> +#include <linux/wait.h>
> +
> +#define DM_MSG_PREFIX "ioband"
> +
> +#define DEFAULT_IO_THROTTLE	4
> +#define DEFAULT_IO_LIMIT	128
> +#define IOBAND_NAME_MAX 31
> +#define IOBAND_ID_ANY (-1)
> +
> +struct ioband_group;
> +
> +struct ioband_device {
> +	struct list_head g_groups;
> +	struct delayed_work g_conductor;
> +	struct workqueue_struct *g_ioband_wq;
> +	struct bio_list g_urgent_bios;
> +	int g_io_throttle;
> +	int g_io_limit[2];
> +	int g_issued[2];
> +	int g_blocked;
> +	spinlock_t g_lock;
> +	struct mutex g_lock_device;
> +	wait_queue_head_t g_waitq;
> +	wait_queue_head_t g_waitq_suspend;
> +	wait_queue_head_t g_waitq_flush;
> +
> +	int g_ref;
> +	struct list_head g_list;
> +	int g_flags;
> +	char g_name[IOBAND_NAME_MAX + 1];
> +	struct policy_type *g_policy;
> +
> +	/* policy dependent */
> +	int (*g_can_submit) (struct ioband_group *);
> +	int (*g_prepare_bio) (struct ioband_group *, struct bio *, int);
> +	int (*g_restart_bios) (struct ioband_device *);
> +	void (*g_hold_bio) (struct ioband_group *, struct bio *);
> +	struct bio *(*g_pop_bio) (struct ioband_group *);
> +	int (*g_group_ctr) (struct ioband_group *, char *);
> +	void (*g_group_dtr) (struct ioband_group *);
> +	int (*g_set_param) (struct ioband_group *, char *cmd, char *value);
> +	int (*g_should_block) (struct ioband_group *);
> +	void (*g_show) (struct ioband_group *, int *, char *, unsigned);
> +
> +	/* members for weight balancing policy */
> +	int g_epoch;
> +	int g_weight_total;
> +	/* the number of tokens which can be used in every epoch */
> +	int g_token_bucket;
> +	/* how many epochs tokens can be carried over */
> +	int g_carryover;
> +	/* how many tokens should be used for one page-sized I/O */
> +	int g_token_unit;
> +	/* the last group which used a token */
> +	struct ioband_group *g_current;
> +	/* give another group a chance to be scheduled when the rest
> +	   of tokens of the current group reaches this mark */
> +	int g_yield_mark;
> +	/* the latest group which used up its tokens */
> +	struct ioband_group *g_expired;
> +	/* the group which has the largest number of tokens in the
> +	   active groups */
> +	struct ioband_group *g_dominant;
> +	/* the number of unused tokens in this epoch */
> +	int g_token_left;
> +	/* left-over tokens from the previous epoch */
> +	int g_token_extra;
> +};
> +
> +struct ioband_group_stat {
> +	unsigned long sectors;
> +	unsigned long immediate;
> +	unsigned long deferred;
> +};
> +
> +struct ioband_group {
> +	struct list_head c_list;
> +	struct ioband_device *c_banddev;
> +	struct dm_dev *c_dev;
> +	struct dm_target *c_target;
> +	struct bio_list c_blocked_bios;
> +	struct bio_list c_prio_bios;
> +	struct rb_root c_group_root;
> +	struct rb_node c_group_node;
> +	int c_id;	/* should be unsigned long or unsigned long long */
> +	char c_name[IOBAND_NAME_MAX + 1];	/* rfu */
> +	int c_blocked;
> +	int c_prio_blocked;
> +	wait_queue_head_t c_waitq;
> +	int c_flags;
> +	struct ioband_group_stat c_stat[2];	/* hold rd/wr status */
> +	struct group_type *c_type;
> +
> +	/* members for weight balancing policy */
> +	int c_weight;
> +	int c_my_epoch;
> +	int c_token;
> +	int c_token_initial;
> +	int c_limit;
> +	int c_consumed;
> +
> +	/* rfu */
> +	/* struct bio_list	c_ordered_tag_bios; */
> +};
> +
> +#define IOBAND_URGENT 1
> +
> +#define DEV_BIO_BLOCKED		1
> +#define DEV_SUSPENDED		2
> +
> +#define set_device_blocked(dp)		((dp)->g_flags |= DEV_BIO_BLOCKED)
> +#define clear_device_blocked(dp)	((dp)->g_flags &= ~DEV_BIO_BLOCKED)
> +#define is_device_blocked(dp)		((dp)->g_flags & DEV_BIO_BLOCKED)
> +
> +#define set_device_suspended(dp)	((dp)->g_flags |= DEV_SUSPENDED)
> +#define clear_device_suspended(dp)	((dp)->g_flags &= ~DEV_SUSPENDED)
> +#define is_device_suspended(dp)		((dp)->g_flags & DEV_SUSPENDED)
> +
> +#define IOG_PRIO_BIO_WRITE	1
> +#define IOG_PRIO_QUEUE		2
> +#define IOG_BIO_BLOCKED		4
> +#define IOG_GOING_DOWN		8
> +#define IOG_SUSPENDED		16
> +#define IOG_NEED_UP		32
> +
> +#define R_OK		0
> +#define R_BLOCK		1
> +#define R_YIELD		2
> +
> +#define set_group_blocked(gp)		((gp)->c_flags |= IOG_BIO_BLOCKED)
> +#define clear_group_blocked(gp)		((gp)->c_flags &= ~IOG_BIO_BLOCKED)
> +#define is_group_blocked(gp)		((gp)->c_flags & IOG_BIO_BLOCKED)
> +
> +#define set_group_down(gp)		((gp)->c_flags |= IOG_GOING_DOWN)
> +#define clear_group_down(gp)		((gp)->c_flags &= ~IOG_GOING_DOWN)
> +#define is_group_down(gp)		((gp)->c_flags & IOG_GOING_DOWN)
> +
> +#define set_group_suspended(gp)		((gp)->c_flags |= IOG_SUSPENDED)
> +#define clear_group_suspended(gp)	((gp)->c_flags &= ~IOG_SUSPENDED)
> +#define is_group_suspended(gp)		((gp)->c_flags & IOG_SUSPENDED)
> +
> +#define set_group_need_up(gp)		((gp)->c_flags |= IOG_NEED_UP)
> +#define clear_group_need_up(gp)		((gp)->c_flags &= ~IOG_NEED_UP)
> +#define group_need_up(gp)		((gp)->c_flags & IOG_NEED_UP)
> +
> +#define set_prio_read(gp)		((gp)->c_flags |= IOG_PRIO_QUEUE)
> +#define clear_prio_read(gp)		((gp)->c_flags &= ~IOG_PRIO_QUEUE)
> +#define is_prio_read(gp) \
> +	((gp)->c_flags & (IOG_PRIO_QUEUE|IOG_PRIO_BIO_WRITE) == IOG_PRIO_QUEUE)
> +
> +#define set_prio_write(gp) \
> +	((gp)->c_flags |= (IOG_PRIO_QUEUE|IOG_PRIO_BIO_WRITE))
> +#define clear_prio_write(gp) \
> +	((gp)->c_flags &= ~(IOG_PRIO_QUEUE|IOG_PRIO_BIO_WRITE))
> +#define is_prio_write(gp) \
> +	((gp)->c_flags & (IOG_PRIO_QUEUE|IOG_PRIO_BIO_WRITE) == \
> +		(IOG_PRIO_QUEUE|IOG_PRIO_BIO_WRITE))
> +
> +#define set_prio_queue(gp, direct) \
> +	((gp)->c_flags |= (IOG_PRIO_QUEUE|direct))
> +#define clear_prio_queue(gp)		clear_prio_write(gp)
> +#define is_prio_queue(gp)		((gp)->c_flags & IOG_PRIO_QUEUE)
> +#define prio_queue_direct(gp)		((gp)->c_flags & IOG_PRIO_BIO_WRITE)
> +
> +struct policy_type {
> +	const char *p_name;
> +	int (*p_policy_init) (struct ioband_device *, int, char **);
> +};
> +
> +extern struct policy_type dm_ioband_policy_type[];
> +
> +struct group_type {
> +	const char *t_name;
> +	int (*t_getid) (struct bio *);
> +};
> +
> +extern struct group_type dm_ioband_group_type[];
> 
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