block: ROW: Fix forced dispatch

This patch fixes forced dispatch in the ROW scheduling algorithm.
When the dispatch function is called with the forced flag on, we
can't delay the dispatch of the requests that are in scheduler queues.
Thus, when dispatch is called with forced turned on, we need to cancel
idling, or not to idle at all.

Change-Id: I3aa0da33ad7b59c0731c696f1392b48525b52ddc
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: Add support for reinsert a dispatched req

Add support for reinserting a dispatched request back to the
scheduler's internal data structures.
This capability is used by the device driver when it chooses to
interrupt the current request transmission and execute another (more
urgent) pending request. For example: interrupting long write in order
to handle pending read. The device driver re-inserts the
remaining write request back to the scheduler, to be rescheduled
for transmission later on.

Add API for verifying whether the current scheduler
supports reinserting requests mechanism. If reinsert mechanism isn't
supported by the scheduler, this code path will never be activated.

Change-Id: I5c982a66b651ebf544aae60063ac8a340d79e67f
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: Add API for urgent request handling

This patch add support in block & elevator layers for handling
urgent requests. The decision if a request is urgent or not is taken
by the scheduler. Urgent request notification is passed to the underlying
block device driver (eMMC for example). Block device driver may decide to
interrupt the currently running low priority request to serve the new
urgent request. By doing so READ latency is greatly reduced in read&write
collision scenarios.

Note that if the current scheduler doesn't implement the urgent request
mechanism, this code path is never activated.

Change-Id: I8aa74b9b45c0d3a2221bd4e82ea76eb4103e7cfa
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
row: Adding support for reinsert already dispatched req

Add support for reinserting already dispatched request back to the
schedulers internal data structures.
The request will be reinserted back to the queue (head) it was
dispatched from as if it was never dispatched.

Change-Id: I70954df300774409c25b5821465fb3aa33d8feb5
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block:row: fix idling mechanism in ROW

This patch addresses the following issues found in the ROW idling
mechanism:
1. Fix the delay passed to queue_delayed_work (pass actual delay
   and not the time when to start the work)
2. Change the idle time and the idling-trigger frequency to be
   HZ dependent (instead of using msec_to_jiffies())
3. Destroy idle_workqueue() in queue_exit

Change-Id: If86513ad6b4be44fb7a860f29bd2127197d8d5bf
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
cfq-iosched: Fix null pointer dereference

NULL pointer dereference can happen in cfq_choose_cfqg()
when there are no cfq groups to select other than the
current serving group. Prevent this by adding a NULL
check before dereferencing.

Unable to handle kernel NULL pointer dereference at virtual address
[<c02502cc>] (cfq_dispatch_requests+0x368/0x8c0) from
[<c0243f30>] (blk_peek_request+0x220/0x25c)
[<c0243f30>] (blk_peek_request+0x220/0x25c) from
[<c0243f74>] (blk_fetch_request+0x8/0x1c)
[<c0243f74>] (blk_fetch_request+0x8/0x1c) from
[<c041cedc>] (mmc_queue_thread+0x58/0x120)
[<c041cedc>] (mmc_queue_thread+0x58/0x120) from
[<c00ad310>] (kthread+0x84/0x90)
[<c00ad310>] (kthread+0x84/0x90) from
[<c000eeac>] (kernel_thread_exit+0x0/0x8)

CRs-Fixed: 416466
Change-Id: I1fab93a4334b53e1d7c5dcc8f93cff174bae0d5e
Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>
block: test-iosched infrastructure enhancement

Add functionality to test-iosched so that it could simulate the
ROW scheduler behaviour. The main additions are:
- 3 distinct requests queue with counters
- support for urgent request pending
- reinsert request implementation (callback + dispatch behavior)

Change-Id: I83b5d9e3d2b8cd9a2353afa6a3e6a4cbc83b0cd4
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>
Signed-off-by: Lee Susman <lsusman@codeaurora.org>
row: Add support for urgent request handling

This patch adds support for handling urgent requests.
ROW queue can be marked as "urgent" so if it was un-served in last
dispatch cycle and a request was added to it - it will trigger
issuing an urgent-request-notification to the block device driver.
The block device driver may choose at stop the transmission of current
ongoing request to handle the urgent one. Foe example: long WRITE may
be stopped to handle an urgent READ. This decreases READ latency.

Change-Id: I84954c13f5e3b1b5caeadc9fe1f9aa21208cb35e
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: test-iosched:  Add support for setting rq_disk

Some block devices requires the rq_disk field to be assigned.
This patch exposes a new API to the block device test utility for
getting the rq_disk assigned, in the created request.

Change-Id: I61dc4dad50eb7600728156a6cd08bb1ee134df0d
Signed-off-by: Dolev Raviv <draviv@codeaurora.org>
block: row: Add some debug information on ROW queues

1. Add a counter for number of requests on queue.
2. Add function to print queues status (number requests
   currently on queue and number of already dispatched requests
   in current dispatch cycle).

Change-Id: I1e98b9ca33853e6e6a8ddc53240f6cd6981e6024
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: row: Insert dispatch_quantum into struct row_queue

There is really no point in keeping the dispatch quantum
of a queue outside of it. By inserting it to the row_queue
structure we spare extra level in accessing it.

Change-Id: Ic77571818b643e71f9aafbb2ca93d0a92158b199
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: row: fix sysfs functions - idle_time conversion

idle_time was updated to be stored in msec instead of jiffies.
So there is no need to convert the value when reading from user or
displaying the value to him.

Change-Id: I58e074b204e90a90536d32199ac668112966e9cf
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: row: Aggregate row_queue parameters to one structure

Each ROW queues has several parameters which default values are defined
in separate arrays. This patch aggregates all default values into one
array.
The values in question are:
 - is idling enabled for the queue
 - queue quantum
 - can the queue notify on urgent request

Change-Id: I3821b0a042542295069b340406a16b1000873ec6
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: row: Dispatch requests according to their io-priority

This patch implements "application-hints" which is a way the issuing
application can notify the scheduler on the priority of its request.
This is done by setting the io-priority of the request.
This patch reuses an already existing mechanism of io-priorities developed
for CFQ. Please refer to kernel/Documentation/block/ioprio.txt for
usage example and explanations.

Change-Id: I228ec8e52161b424242bb7bb133418dc8b73925a
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: row: Idling mechanism re-factoring

At the moment idling in ROW is implemented by delayed work that uses
jiffies granularity which is not very accurate. This patch replaces
current idling mechanism implementation with hrtime API, which gives
nanosecond resolution (instead of jiffies).

Change-Id: I86c7b1776d035e1d81571894b300228c8b8f2d92
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: row: Don't notify URGENT if there are un-completed urgent req

When ROW scheduler reports to the block layer that there is an urgent
request pending, the device driver may decide to stop the transmission
of the current request in order to handle the urgent one. If the current
transmitted request is an urgent request - we don't want it to be
stopped.
Due to the above ROW scheduler won't notify of an urgent request if
there are urgent requests in flight.

Change-Id: I2fa186d911b908ec7611682b378b9cdc48637ac7
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: row: Update initial values of ROW data structures

This patch sets the initial values of internal ROW
parameters.

Change-Id: I38132062a7fcbe2e58b9cc757e55caac64d013dc
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
[smuckle@codeaurora.org: ported from msm-3.7]
Signed-off-by: Steve Muckle <smuckle@codeaurora.org>
block: fix test crashing due to synchronization issue

The __blk_run_queue function is called from several contexts. The fix is
replacing it with blk_run_queue function, this function is guarded with
a lock, thus making it thread safe and prevents the crashing.

Change-Id: I3e12fa9c8b9e161375fffa3570abfa46b223a60b
Signed-off-by: Dolev Raviv <draviv@codeaurora.org>
block: row: Re-design urgent request notification mechanism

This patch updates the ROW URGENT notification policy to apply with the
bellow:
- Don't notify URGENT if there is an un-completed URGENT request in driver
- After notifying that URGENT request is present, the next request
  dispatched is the URGENT one.
- At every given moment only 1 request can be marked as URGENT.
  Independent of it's location (driver or scheduler)

Other changes to URGENT policy:
- Only queues that are allowed to notify of an URGENT request pending
are READ queues

Change-Id: I17ff73125bc7a760cea1116b466115a2df635a14
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
block: test-iosched: Sleep before each test

In order to be sure that the packing statistics collected after the test
reflect *only* requests issued by the test (and not real request from
FS) - sleep before each test in order to give an already dispatched
requests time to complete.

Change-Id: If2f40efad1d79084a8ea85afe93cce58e49ff698
CRs-Fixed: 453712
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>