3 files changed, 149 insertions, 2 deletions
diff --git a/Documentation/block/00-INDEX b/Documentation/block/00-INDEX
index d111e3b23db0..d18ecd827c40 100644
--- a/Documentation/block/00-INDEX
+++ b/Documentation/block/00-INDEX
@@ -3,15 +3,21 @@
 biodoc.txt
 	- Notes on the Generic Block Layer Rewrite in Linux 2.5
 capability.txt
-	- Generic Block Device Capability (/sys/block/<disk>/capability)
+	- Generic Block Device Capability (/sys/block/<device>/capability)
+cfq-iosched.txt
+	- CFQ IO scheduler tunables
+data-integrity.txt
+	- Block data integrity
 deadline-iosched.txt
 	- Deadline IO scheduler tunables
 ioprio.txt
 	- Block io priorities (in CFQ scheduler)
+queue-sysfs.txt
+	- Queue's sysfs entries
 request.txt
 	- The members of struct request (in include/linux/blkdev.h)
 stat.txt
-	- Block layer statistics in /sys/block/<dev>/stat
+	- Block layer statistics in /sys/block/<device>/stat
 switching-sched.txt
 	- Switching I/O schedulers at runtime
 writeback_cache_control.txt
diff --git a/Documentation/block/cfq-iosched.txt b/Documentation/block/cfq-iosched.txt
index 6d670f570451..d89b4fe724d7 100644
--- a/Documentation/block/cfq-iosched.txt
+++ b/Documentation/block/cfq-iosched.txt
@@ -1,3 +1,14 @@
+CFQ (Complete Fairness Queueing)
+===============================
+
+The main aim of CFQ scheduler is to provide a fair allocation of the disk
+I/O bandwidth for all the processes which requests an I/O operation.
+
+CFQ maintains the per process queue for the processes which request I/O
+operation(syncronous requests). In case of asynchronous requests, all the
+requests from all the processes are batched together according to their
+process's I/O priority.
+
 CFQ ioscheduler tunables
 ========================
 
@@ -25,6 +36,72 @@ there are multiple spindles behind single LUN (Host based hardware RAID
 controller or for storage arrays), setting slice_idle=0 might end up in better
 throughput and acceptable latencies.
 
+back_seek_max
+-------------
+This specifies, given in Kbytes, the maximum "distance" for backward seeking.
+The distance is the amount of space from the current head location to the
+sectors that are backward in terms of distance.
+
+This parameter allows the scheduler to anticipate requests in the "backward"
+direction and consider them as being the "next" if they are within this
+distance from the current head location.
+
+back_seek_penalty
+-----------------
+This parameter is used to compute the cost of backward seeking. If the
+backward distance of request is just 1/back_seek_penalty from a "front"
+request, then the seeking cost of two requests is considered equivalent.
+
+So scheduler will not bias toward one or the other request (otherwise scheduler
+will bias toward front request). Default value of back_seek_penalty is 2.
+
+fifo_expire_async
+-----------------
+This parameter is used to set the timeout of asynchronous requests. Default
+value of this is 248ms.
+
+fifo_expire_sync
+----------------
+This parameter is used to set the timeout of synchronous requests. Default
+value of this is 124ms. In case to favor synchronous requests over asynchronous
+one, this value should be decreased relative to fifo_expire_async.
+
+slice_async
+-----------
+This parameter is same as of slice_sync but for asynchronous queue. The
+default value is 40ms.
+
+slice_async_rq
+--------------
+This parameter is used to limit the dispatching of asynchronous request to
+device request queue in queue's slice time. The maximum number of request that
+are allowed to be dispatched also depends upon the io priority. Default value
+for this is 2.
+
+slice_sync
+----------
+When a queue is selected for execution, the queues IO requests are only
+executed for a certain amount of time(time_slice) before switching to another
+queue. This parameter is used to calculate the time slice of synchronous
+queue.
+
+time_slice is computed using the below equation:-
+time_slice = slice_sync + (slice_sync/5 * (4 - prio)). To increase the
+time_slice of synchronous queue, increase the value of slice_sync. Default
+value is 100ms.
+
+quantum
+-------
+This specifies the number of request dispatched to the device queue. In a
+queue's time slice, a request will not be dispatched if the number of request
+in the device exceeds this parameter. This parameter is used for synchronous
+request.
+
+In case of storage with several disk, this setting can limit the parallel
+processing of request. Therefore, increasing the value can imporve the
+performace although this can cause the latency of some I/O to increase due
+to more number of requests.
+
 CFQ IOPS Mode for group scheduling
 ===================================
 Basic CFQ design is to provide priority based time slices. Higher priority
diff --git a/Documentation/block/queue-sysfs.txt b/Documentation/block/queue-sysfs.txt
index 6518a55273e7..e54ac1d53403 100644
--- a/Documentation/block/queue-sysfs.txt
+++ b/Documentation/block/queue-sysfs.txt
@@ -9,20 +9,71 @@ These files are the ones found in the /sys/block/xxx/queue/ directory.
 Files denoted with a RO postfix are readonly and the RW postfix means
 read-write.
 
+add_random (RW)
+----------------
+This file allows to trun off the disk entropy contribution. Default
+value of this file is '1'(on).
+
+discard_granularity (RO)
+-----------------------
+This shows the size of internal allocation of the device in bytes, if
+reported by the device. A value of '0' means device does not support
+the discard functionality.
+
+discard_max_bytes (RO)
+----------------------
+Devices that support discard functionality may have internal limits on
+the number of bytes that can be trimmed or unmapped in a single operation.
+The discard_max_bytes parameter is set by the device driver to the maximum
+number of bytes that can be discarded in a single operation. Discard
+requests issued to the device must not exceed this limit. A discard_max_bytes
+value of 0 means that the device does not support discard functionality.
+
+discard_zeroes_data (RO)
+------------------------
+When read, this file will show if the discarded block are zeroed by the
+device or not. If its value is '1' the blocks are zeroed otherwise not.
+
 hw_sector_size (RO)
 -------------------
 This is the hardware sector size of the device, in bytes.
 
+iostats (RW)
+-------------
+This file is used to control (on/off) the iostats accounting of the
+disk.
+
+logical_block_size (RO)
+-----------------------
+This is the logcal block size of the device, in bytes.
+
 max_hw_sectors_kb (RO)
 ----------------------
 This is the maximum number of kilobytes supported in a single data transfer.
 
+max_integrity_segments (RO)
+---------------------------
+When read, this file shows the max limit of integrity segments as
+set by block layer which a hardware controller can handle.
+
 max_sectors_kb (RW)
 -------------------
 This is the maximum number of kilobytes that the block layer will allow
 for a filesystem request. Must be smaller than or equal to the maximum
 size allowed by the hardware.
 
+max_segments (RO)
+-----------------
+Maximum number of segments of the device.
+
+max_segment_size (RO)
+---------------------
+Maximum segment size of the device.
+
+minimum_io_size (RO)
+--------------------
+This is the smallest preferred io size reported by the device.
+
 nomerges (RW)
 -------------
 This enables the user to disable the lookup logic involved with IO
@@ -45,11 +96,24 @@ per-block-cgroup request pool.  IOW, if there are N block cgroups,
 each request queue may have upto N request pools, each independently
 regulated by nr_requests.
 
+optimal_io_size (RO)
+--------------------
+This is the optimal io size reported by the device.
+
+physical_block_size (RO)
+------------------------
+This is the physical block size of device, in bytes.
+
 read_ahead_kb (RW)
 ------------------
 Maximum number of kilobytes to read-ahead for filesystems on this block
 device.
 
+rotational (RW)
+---------------
+This file is used to stat if the device is of rotational type or
+non-rotational type.
+
 rq_affinity (RW)
 ----------------
 If this option is '1', the block layer will migrate request completions to the