Merge tag 'for-5.4/block-2019-09-16' of git://git.kernel.dk/linux-block

Pull block updates from Jens Axboe:

 - Two NVMe pull requests:
     - ana log parse fix from Anton
     - nvme quirks support for Apple devices from Ben
     - fix missing bio completion tracing for multipath stack devices
       from Hannes and Mikhail
     - IP TOS settings for nvme rdma and tcp transports from Israel
     - rq_dma_dir cleanups from Israel
     - tracing for Get LBA Status command from Minwoo
     - Some nvme-tcp cleanups from Minwoo, Potnuri and Myself
     - Some consolidation between the fabrics transports for handling
       the CAP register
     - reset race with ns scanning fix for fabrics (move fabrics
       commands to a dedicated request queue with a different lifetime
       from the admin request queue)."
     - controller reset and namespace scan races fixes
     - nvme discovery log change uevent support
     - naming improvements from Keith
     - multiple discovery controllers reject fix from James
     - some regular cleanups from various people

 - Series fixing (and re-fixing) null_blk debug printing and nr_devices
   checks (André)

 - A few pull requests from Song, with fixes from Andy, Guoqing,
   Guilherme, Neil, Nigel, and Yufen.

 - REQ_OP_ZONE_RESET_ALL support (Chaitanya)

 - Bio merge handling unification (Christoph)

 - Pick default elevator correctly for devices with special needs
   (Damien)

 - Block stats fixes (Hou)

 - Timeout and support devices nbd fixes (Mike)

 - Series fixing races around elevator switching and device add/remove
   (Ming)

 - sed-opal cleanups (Revanth)

 - Per device weight support for BFQ (Fam)

 - Support for blk-iocost, a new model that can properly account cost of
   IO workloads. (Tejun)

 - blk-cgroup writeback fixes (Tejun)

 - paride queue init fixes (zhengbin)

 - blk_set_runtime_active() cleanup (Stanley)

 - Block segment mapping optimizations (Bart)

 - lightnvm fixes (Hans/Minwoo/YueHaibing)

 - Various little fixes and cleanups

* tag 'for-5.4/block-2019-09-16' of git://git.kernel.dk/linux-block: (186 commits)
  null_blk: format pr_* logs with pr_fmt
  null_blk: match the type of parameter nr_devices
  null_blk: do not fail the module load with zero devices
  block: also check RQF_STATS in blk_mq_need_time_stamp()
  block: make rq sector size accessible for block stats
  bfq: Fix bfq linkage error
  raid5: use bio_end_sector in r5_next_bio
  raid5: remove STRIPE_OPS_REQ_PENDING
  md: add feature flag MD_FEATURE_RAID0_LAYOUT
  md/raid0: avoid RAID0 data corruption due to layout confusion.
  raid5: don't set STRIPE_HANDLE to stripe which is in batch list
  raid5: don't increment read_errors on EILSEQ return
  nvmet: fix a wrong error status returned in error log page
  nvme: send discovery log page change events to userspace
  nvme: add uevent variables for controller devices
  nvme: enable aen regardless of the presence of I/O queues
  nvme-fabrics: allow discovery subsystems accept a kato
  nvmet: Use PTR_ERR_OR_ZERO() in nvmet_init_discovery()
  nvme: Remove redundant assignment of cq vector
  nvme: Assign subsys instance from first ctrl
  ...

Documentation/admin-guide/cgroup-v2.rst

@@ -1469,6 +1469,103 @@ IO Interface Files
 	  8:16 rbytes=1459200 wbytes=314773504 rios=192 wios=353 dbytes=0 dios=0
 	  8:0 rbytes=90430464 wbytes=299008000 rios=8950 wios=1252 dbytes=50331648 dios=3021
 
+  io.cost.qos
+	A read-write nested-keyed file with exists only on the root
+	cgroup.
+
+	This file configures the Quality of Service of the IO cost
+	model based controller (CONFIG_BLK_CGROUP_IOCOST) which
+	currently implements "io.weight" proportional control.  Lines
+	are keyed by $MAJ:$MIN device numbers and not ordered.  The
+	line for a given device is populated on the first write for
+	the device on "io.cost.qos" or "io.cost.model".  The following
+	nested keys are defined.
+
+	  ======	=====================================
+	  enable	Weight-based control enable
+	  ctrl		"auto" or "user"
+	  rpct		Read latency percentile    [0, 100]
+	  rlat		Read latency threshold
+	  wpct		Write latency percentile   [0, 100]
+	  wlat		Write latency threshold
+	  min		Minimum scaling percentage [1, 10000]
+	  max		Maximum scaling percentage [1, 10000]
+	  ======	=====================================
+
+	The controller is disabled by default and can be enabled by
+	setting "enable" to 1.  "rpct" and "wpct" parameters default
+	to zero and the controller uses internal device saturation
+	state to adjust the overall IO rate between "min" and "max".
+
+	When a better control quality is needed, latency QoS
+	parameters can be configured.  For example::
+
+	  8:16 enable=1 ctrl=auto rpct=95.00 rlat=75000 wpct=95.00 wlat=150000 min=50.00 max=150.0
+
+	shows that on sdb, the controller is enabled, will consider
+	the device saturated if the 95th percentile of read completion
+	latencies is above 75ms or write 150ms, and adjust the overall
+	IO issue rate between 50% and 150% accordingly.
+
+	The lower the saturation point, the better the latency QoS at
+	the cost of aggregate bandwidth.  The narrower the allowed
+	adjustment range between "min" and "max", the more conformant
+	to the cost model the IO behavior.  Note that the IO issue
+	base rate may be far off from 100% and setting "min" and "max"
+	blindly can lead to a significant loss of device capacity or
+	control quality.  "min" and "max" are useful for regulating
+	devices which show wide temporary behavior changes - e.g. a
+	ssd which accepts writes at the line speed for a while and
+	then completely stalls for multiple seconds.
+
+	When "ctrl" is "auto", the parameters are controlled by the
+	kernel and may change automatically.  Setting "ctrl" to "user"
+	or setting any of the percentile and latency parameters puts
+	it into "user" mode and disables the automatic changes.  The
+	automatic mode can be restored by setting "ctrl" to "auto".
+
+  io.cost.model
+	A read-write nested-keyed file with exists only on the root
+	cgroup.
+
+	This file configures the cost model of the IO cost model based
+	controller (CONFIG_BLK_CGROUP_IOCOST) which currently
+	implements "io.weight" proportional control.  Lines are keyed
+	by $MAJ:$MIN device numbers and not ordered.  The line for a
+	given device is populated on the first write for the device on
+	"io.cost.qos" or "io.cost.model".  The following nested keys
+	are defined.
+
+	  =====		================================
+	  ctrl		"auto" or "user"
+	  model		The cost model in use - "linear"
+	  =====		================================
+
+	When "ctrl" is "auto", the kernel may change all parameters
+	dynamically.  When "ctrl" is set to "user" or any other
+	parameters are written to, "ctrl" become "user" and the
+	automatic changes are disabled.
+
+	When "model" is "linear", the following model parameters are
+	defined.
+
+	  =============	========================================
+	  [r|w]bps	The maximum sequential IO throughput
+	  [r|w]seqiops	The maximum 4k sequential IOs per second
+	  [r|w]randiops	The maximum 4k random IOs per second
+	  =============	========================================
+
+	From the above, the builtin linear model determines the base
+	costs of a sequential and random IO and the cost coefficient
+	for the IO size.  While simple, this model can cover most
+	common device classes acceptably.
+
+	The IO cost model isn't expected to be accurate in absolute
+	sense and is scaled to the device behavior dynamically.
+
+	If needed, tools/cgroup/iocost_coef_gen.py can be used to
+	generate device-specific coefficients.
+
   io.weight
 	A read-write flat-keyed file which exists on non-root cgroups.
 	The default is "default 100".

Documentation/admin-guide/kernel-parameters.txt

@@ -1201,12 +1201,6 @@
 			See comment before function elanfreq_setup() in
 			arch/x86/kernel/cpu/cpufreq/elanfreq.c.
 
-	elevator=	[IOSCHED]
-			Format: { "mq-deadline" | "kyber" | "bfq" }
-			See Documentation/block/deadline-iosched.rst,
-			Documentation/block/kyber-iosched.rst and
-			Documentation/block/bfq-iosched.rst for details.
-
 	elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
 			Specifies physical address of start of kernel core
 			image elf header and optionally the size. Generally

Documentation/admin-guide/kernel-per-CPU-kthreads.rst

@@ -274,22 +274,20 @@ To reduce its OS jitter, do any of the following:
 		(based on an earlier one from Gilad Ben-Yossef) that
 		reduces or even eliminates vmstat overhead for some
 		workloads at https://lkml.org/lkml/2013/9/4/379.
-	e.	Boot with "elevator=noop" to avoid workqueue use by
-		the block layer.
-	f.	If running on high-end powerpc servers, build with
+	e.	If running on high-end powerpc servers, build with
 		CONFIG_PPC_RTAS_DAEMON=n.  This prevents the RTAS
 		daemon from running on each CPU every second or so.
 		(This will require editing Kconfig files and will defeat
 		this platform's RAS functionality.)  This avoids jitter
 		due to the rtas_event_scan() function.
 		WARNING:  Please check your CPU specifications to
 		make sure that this is safe on your particular system.
-	g.	If running on Cell Processor, build your kernel with
+	f.	If running on Cell Processor, build your kernel with
 		CBE_CPUFREQ_SPU_GOVERNOR=n to avoid OS jitter from
 		spu_gov_work().
 		WARNING:  Please check your CPU specifications to
 		make sure that this is safe on your particular system.
-	h.	If running on PowerMAC, build your kernel with
+	g.	If running on PowerMAC, build your kernel with
 		CONFIG_PMAC_RACKMETER=n to disable the CPU-meter,
 		avoiding OS jitter from rackmeter_do_timer().
 

Documentation/block/null_blk.rst

@@ -1,19 +1,16 @@
+.. SPDX-License-Identifier: GPL-2.0
+
 ========================
 Null block device driver
 ========================
 
-1. Overview
-===========
+Overview
+========
 
-The null block device (/dev/nullb*) is used for benchmarking the various
+The null block device (``/dev/nullb*``) is used for benchmarking the various
 block-layer implementations. It emulates a block device of X gigabytes in size.
-The following instances are possible:
-
-  Single-queue block-layer
-
-    - Request-based.
-    - Single submission queue per device.
-    - Implements IO scheduling algorithms (CFQ, Deadline, noop).
+It does not execute any read/write operation, just mark them as complete in
+the request queue. The following instances are possible:
 
   Multi-queue block-layer
 
@@ -27,15 +24,15 @@ The following instances are possible:
 
 All of them have a completion queue for each core in the system.
 
-2. Module parameters applicable for all instances
-=================================================
+Module parameters
+=================
 
 queue_mode=[0-2]: Default: 2-Multi-queue
   Selects which block-layer the module should instantiate with.
 
   =  ============
   0  Bio-based
-  1  Single-queue
+  1  Single-queue (deprecated)
   2  Multi-queue
   =  ============
 
@@ -67,17 +64,19 @@ irqmode=[0-2]: Default: 1-Soft-irq
 completion_nsec=[ns]: Default: 10,000ns
   Combined with irqmode=2 (timer). The time each completion event must wait.
 
-submit_queues=[1..nr_cpus]:
+submit_queues=[1..nr_cpus]: Default: 1
   The number of submission queues attached to the device driver. If unset, it
   defaults to 1. For multi-queue, it is ignored when use_per_node_hctx module
   parameter is 1.
 
 hw_queue_depth=[0..qdepth]: Default: 64
   The hardware queue depth of the device.
 
-III: Multi-queue specific parameters
+Multi-queue specific parameters
+-------------------------------
 
 use_per_node_hctx=[0/1]: Default: 0
+  Number of hardware context queues.
 
   =  =====================================================================
   0  The number of submit queues are set to the value of the submit_queues
@@ -87,13 +86,15 @@ use_per_node_hctx=[0/1]: Default: 0
   =  =====================================================================
 
 no_sched=[0/1]: Default: 0
+  Enable/disable the io scheduler.
 
   =  ======================================
   0  nullb* use default blk-mq io scheduler
   1  nullb* doesn't use io scheduler
   =  ======================================
 
 blocking=[0/1]: Default: 0
+  Blocking behavior of the request queue.
 
   =  ===============================================================
   0  Register as a non-blocking blk-mq driver device.
@@ -103,6 +104,7 @@ blocking=[0/1]: Default: 0
   =  ===============================================================
 
 shared_tags=[0/1]: Default: 0
+  Sharing tags between devices.
 
   =  ================================================================
   0  Tag set is not shared.
@@ -111,6 +113,7 @@ shared_tags=[0/1]: Default: 0
   =  ================================================================
 
 zoned=[0/1]: Default: 0
+  Device is a random-access or a zoned block device.
 
   =  ======================================================================
   0  Block device is exposed as a random-access block device.

Documentation/block/switching-sched.rst

@@ -2,10 +2,6 @@
 Switching Scheduler
 ===================
 
-To choose IO schedulers at boot time, use the argument 'elevator=deadline'.
-'noop' and 'cfq' (the default) are also available. IO schedulers are assigned
-globally at boot time only presently.
-
 Each io queue has a set of io scheduler tunables associated with it. These
 tunables control how the io scheduler works. You can find these entries
 in::

block/Kconfig

@@ -26,6 +26,9 @@ menuconfig BLOCK
 
 if BLOCK
 
+config BLK_RQ_ALLOC_TIME
+	bool
+
 config BLK_SCSI_REQUEST
 	bool
 
@@ -132,6 +135,16 @@ config BLK_CGROUP_IOLATENCY
 
 	Note, this is an experimental interface and could be changed someday.
 
+config BLK_CGROUP_IOCOST
+	bool "Enable support for cost model based cgroup IO controller"
+	depends on BLK_CGROUP=y
+	select BLK_RQ_ALLOC_TIME
+	---help---
+	Enabling this option enables the .weight interface for cost
+	model based proportional IO control.  The IO controller
+	distributes IO capacity between different groups based on
+	their share of the overall weight distribution.
+
 config BLK_WBT_MQ
 	bool "Multiqueue writeback throttling"
 	default y

block/Makefile

@@ -18,6 +18,7 @@ obj-$(CONFIG_BLK_DEV_BSGLIB)	+= bsg-lib.o
 obj-$(CONFIG_BLK_CGROUP)	+= blk-cgroup.o
 obj-$(CONFIG_BLK_DEV_THROTTLING)	+= blk-throttle.o
 obj-$(CONFIG_BLK_CGROUP_IOLATENCY)	+= blk-iolatency.o
+obj-$(CONFIG_BLK_CGROUP_IOCOST)	+= blk-iocost.o
 obj-$(CONFIG_MQ_IOSCHED_DEADLINE)	+= mq-deadline.o
 obj-$(CONFIG_MQ_IOSCHED_KYBER)	+= kyber-iosched.o
 bfq-y				:= bfq-iosched.o bfq-wf2q.o bfq-cgroup.o