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Commit 36869cb9 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'for-4.10/block' of git://git.kernel.dk/linux-block 

Pull block layer updates from Jens Axboe:
 "This is the main block pull request this series. Contrary to previous
  release, I've kept the core and driver changes in the same branch. We
  always ended up having dependencies between the two for obvious
  reasons, so makes more sense to keep them together. That said, I'll
  probably try and keep more topical branches going forward, especially
  for cycles that end up being as busy as this one.

  The major parts of this pull request is:

   - Improved support for O_DIRECT on block devices, with a small
     private implementation instead of using the pig that is
     fs/direct-io.c. From Christoph.

   - Request completion tracking in a scalable fashion. This is utilized
     by two components in this pull, the new hybrid polling and the
     writeback queue throttling code.

   - Improved support for polling with O_DIRECT, adding a hybrid mode
     that combines pure polling with an initial sleep. From me.

   - Support for automatic throttling of writeback queues on the block
     side. This uses feedback from the device completion latencies to
     scale the queue on the block side up or down. From me.

   - Support from SMR drives in the block layer and for SD. From Hannes
     and Shaun.

   - Multi-connection support for nbd. From Josef.

   - Cleanup of request and bio flags, so we have a clear split between
     which are bio (or rq) private, and which ones are shared. From
     Christoph.

   - A set of patches from Bart, that improve how we handle queue
     stopping and starting in blk-mq.

   - Support for WRITE_ZEROES from Chaitanya.

   - Lightnvm updates from Javier/Matias.

   - Supoort for FC for the nvme-over-fabrics code. From James Smart.

   - A bunch of fixes from a whole slew of people, too many to name
     here"

* 'for-4.10/block' of git://git.kernel.dk/linux-block: (182 commits)
  blk-stat: fix a few cases of missing batch flushing
  blk-flush: run the queue when inserting blk-mq flush
  elevator: make the rqhash helpers exported
  blk-mq: abstract out blk_mq_dispatch_rq_list() helper
  blk-mq: add blk_mq_start_stopped_hw_queue()
  block: improve handling of the magic discard payload
  blk-wbt: don't throttle discard or write zeroes
  nbd: use dev_err_ratelimited in io path
  nbd: reset the setup task for NBD_CLEAR_SOCK
  nvme-fabrics: Add FC LLDD loopback driver to test FC-NVME
  nvme-fabrics: Add target support for FC transport
  nvme-fabrics: Add host support for FC transport
  nvme-fabrics: Add FC transport LLDD api definitions
  nvme-fabrics: Add FC transport FC-NVME definitions
  nvme-fabrics: Add FC transport error codes to nvme.h
  Add type 0x28 NVME type code to scsi fc headers
  nvme-fabrics: patch target code in prep for FC transport support
  nvme-fabrics: set sqe.command_id in core not transports
  parser: add u64 number parser
  nvme-rdma: align to generic ib_event logging helper
  ...
parents 9439b371 7cd54aa8

Documentation/ABI/testing/sysfs-block

+42 −0
Original line number Diff line number Diff line
@@ -235,3 +235,45 @@ Description: 
		write_same_max_bytes is 0, write same is not supported

		by the device.



What:		/sys/block/<disk>/queue/write_zeroes_max_bytes

Date:		November 2016

Contact:	Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>

Description:

		Devices that support write zeroes operation in which a

		single request can be issued to zero out the range of

		contiguous blocks on storage without having any payload

		in the request. This can be used to optimize writing zeroes

		to the devices. write_zeroes_max_bytes indicates how many

		bytes can be written in a single write zeroes command. If

		write_zeroes_max_bytes is 0, write zeroes is not supported

		by the device.



What:		/sys/block/<disk>/queue/zoned

Date:		September 2016

Contact:	Damien Le Moal <damien.lemoal@hgst.com>

Description:

		zoned indicates if the device is a zoned block device

		and the zone model of the device if it is indeed zoned.

		The possible values indicated by zoned are "none" for

		regular block devices and "host-aware" or "host-managed"

		for zoned block devices. The characteristics of

		host-aware and host-managed zoned block devices are

		described in the ZBC (Zoned Block Commands) and ZAC

		(Zoned Device ATA Command Set) standards. These standards

		also define the "drive-managed" zone model. However,

		since drive-managed zoned block devices do not support

		zone commands, they will be treated as regular block

		devices and zoned will report "none".



What:		/sys/block/<disk>/queue/chunk_sectors

Date:		September 2016

Contact:	Hannes Reinecke <hare@suse.com>

Description:

		chunk_sectors has different meaning depending on the type

		of the disk. For a RAID device (dm-raid), chunk_sectors

		indicates the size in 512B sectors of the RAID volume

		stripe segment. For a zoned block device, either

		host-aware or host-managed, chunk_sectors indicates the

		size of 512B sectors of the zones of the device, with

		the eventual exception of the last zone of the device

		which may be smaller.

Documentation/block/biodoc.txt

+3 −3
Original line number Diff line number Diff line
@@ -348,7 +348,7 @@ Drivers can now specify a request prepare function (q->prep_rq_fn) that the 
block layer would invoke to pre-build device commands for a given request,

or perform other preparatory processing for the request. This is routine is

called by elv_next_request(), i.e. typically just before servicing a request.

(The prepare function would not be called for requests that have REQ_DONTPREP

(The prepare function would not be called for requests that have RQF_DONTPREP

enabled)



Aside:
@@ -553,8 +553,8 @@ struct request { 
	struct request_list *rl;

}

	

See the rq_flag_bits definitions for an explanation of the various flags

available. Some bits are used by the block layer or i/o scheduler.

See the req_ops and req_flag_bits definitions for an explanation of the various

flags available. Some bits are used by the block layer or i/o scheduler.

	

The behaviour of the various sector counts are almost the same as before,

except that since we have multi-segment bios, current_nr_sectors refers

Documentation/block/cfq-iosched.txt

+16 −16
Original line number Diff line number Diff line
@@ -240,11 +240,11 @@ All cfq queues doing synchronous sequential IO go on to sync-idle tree. 
On this tree we idle on each queue individually.



All synchronous non-sequential queues go on sync-noidle tree. Also any

request which are marked with REQ_NOIDLE go on this service tree. On this

tree we do not idle on individual queues instead idle on the whole group

of queues or the tree. So if there are 4 queues waiting for IO to dispatch

we will idle only once last queue has dispatched the IO and there is

no more IO on this service tree.

synchronous write request which is not marked with REQ_IDLE goes on this

service tree. On this tree we do not idle on individual queues instead idle

on the whole group of queues or the tree. So if there are 4 queues waiting

for IO to dispatch we will idle only once last queue has dispatched the IO

and there is no more IO on this service tree.



All async writes go on async service tree. There is no idling on async

queues.
@@ -257,17 +257,17 @@ tree idling provides isolation with buffered write queues on async tree. 


FAQ

===

Q1. Why to idle at all on queues marked with REQ_NOIDLE.

Q1. Why to idle at all on queues not marked with REQ_IDLE.



A1. We only do tree idle (all queues on sync-noidle tree) on queues marked

    with REQ_NOIDLE. This helps in providing isolation with all the sync-idle

A1. We only do tree idle (all queues on sync-noidle tree) on queues not marked

    with REQ_IDLE. This helps in providing isolation with all the sync-idle

    queues. Otherwise in presence of many sequential readers, other

    synchronous IO might not get fair share of disk.



    For example, if there are 10 sequential readers doing IO and they get

    100ms each. If a REQ_NOIDLE request comes in, it will be scheduled

    roughly after 1 second. If after completion of REQ_NOIDLE request we

    do not idle, and after a couple of milli seconds a another REQ_NOIDLE

    100ms each. If a !REQ_IDLE request comes in, it will be scheduled

    roughly after 1 second. If after completion of !REQ_IDLE request we

    do not idle, and after a couple of milli seconds a another !REQ_IDLE

    request comes in, again it will be scheduled after 1second. Repeat it

    and notice how a workload can lose its disk share and suffer due to

    multiple sequential readers.
@@ -276,16 +276,16 @@ A1. We only do tree idle (all queues on sync-noidle tree) on queues marked 
    context of fsync, and later some journaling data is written. Journaling

    data comes in only after fsync has finished its IO (atleast for ext4

    that seemed to be the case). Now if one decides not to idle on fsync

    thread due to REQ_NOIDLE, then next journaling write will not get

    thread due to !REQ_IDLE, then next journaling write will not get

    scheduled for another second. A process doing small fsync, will suffer

    badly in presence of multiple sequential readers.



    Hence doing tree idling on threads using REQ_NOIDLE flag on requests

    Hence doing tree idling on threads using !REQ_IDLE flag on requests

    provides isolation from multiple sequential readers and at the same

    time we do not idle on individual threads.



Q2. When to specify REQ_NOIDLE

A2. I would think whenever one is doing synchronous write and not expecting

Q2. When to specify REQ_IDLE

A2. I would think whenever one is doing synchronous write and expecting

    more writes to be dispatched from same context soon, should be able

    to specify REQ_NOIDLE on writes and that probably should work well for

    to specify REQ_IDLE on writes and that probably should work well for

    most of the cases.

Documentation/block/null_blk.txt

+1 −1
Original line number Diff line number Diff line
@@ -72,4 +72,4 @@ use_per_node_hctx=[0/1]: Default: 0 
     queue for each CPU node in the system.



use_lightnvm=[0/1]: Default: 0

  Register device with LightNVM. Requires blk-mq to be used.
 
  Register device with LightNVM. Requires blk-mq and CONFIG_NVM to be enabled.

Documentation/block/queue-sysfs.txt

+23 −0
Original line number Diff line number Diff line
@@ -58,6 +58,20 @@ When read, this file shows the total number of block IO polls and how 
many returned success.  Writing '0' to this file will disable polling

for this device.  Writing any non-zero value will enable this feature.



io_poll_delay (RW)

------------------

If polling is enabled, this controls what kind of polling will be

performed. It defaults to -1, which is classic polling. In this mode,

the CPU will repeatedly ask for completions without giving up any time.

If set to 0, a hybrid polling mode is used, where the kernel will attempt

to make an educated guess at when the IO will complete. Based on this

guess, the kernel will put the process issuing IO to sleep for an amount

of time, before entering a classic poll loop. This mode might be a

little slower than pure classic polling, but it will be more efficient.

If set to a value larger than 0, the kernel will put the process issuing

IO to sleep for this amont of microseconds before entering classic

polling.



iostats (RW)

-------------

This file is used to control (on/off) the iostats accounting of the
@@ -169,5 +183,14 @@ This is the number of bytes the device can write in a single write-same 
command.  A value of '0' means write-same is not supported by this

device.



wb_lat_usec (RW)

----------------

If the device is registered for writeback throttling, then this file shows

the target minimum read latency. If this latency is exceeded in a given

window of time (see wb_window_usec), then the writeback throttling will start

scaling back writes. Writing a value of '0' to this file disables the

feature. Writing a value of '-1' to this file resets the value to the

default setting.





Jens Axboe <jens.axboe@oracle.com>, February 2009