Date:   Sun, 29 Mar 2020 10:47:10 -0700
From:   Chaitanya Kulkarni <chaitanya.kulkarni@....com>
To:     hch@....de, martin.petersen@...cle.com
Cc:     darrick.wong@...cle.com, axboe@...nel.dk, tytso@....edu,
        adilger.kernel@...ger.ca, ming.lei@...hat.com, jthumshirn@...e.de,
        minwoo.im.dev@...il.com, chaitanya.kulkarni@....com,
        damien.lemoal@....com, andrea.parri@...rulasolutions.com,
        hare@...e.com, tj@...nel.org, hannes@...xchg.org,
        khlebnikov@...dex-team.ru, ajay.joshi@....com, bvanassche@....org,
        arnd@...db.de, houtao1@...wei.com, asml.silence@...il.com,
        linux-block@...r.kernel.org, linux-ext4@...r.kernel.org
Subject: [PATCH 0/4] block: Add support for REQ_OP_ASSIGN_RANGE

Hi,

This patch-series is based on the original RFC patch series:-
https://www.spinics.net/lists/linux-block/msg47933.html.

I've designed a rough testcase based on the information present
in the mailing list archive for original RFC, it may need
some corrections from the author.

If anyone is interested, test results are at the end of this patch.

Following is the original cover-letter :-

Information about continuous extent placement may be useful
for some block devices. Say, distributed network filesystems,
which provide block device interface, may use this information
for better blocks placement over the nodes in their cluster,
and for better performance. Block devices, which map a file
on another filesystem (loop), may request the same length extent
on underlining filesystem for less fragmentation and for batching
allocation requests. Also, hypervisors like QEMU may use this
information for optimization of cluster allocations.

This patchset introduces REQ_OP_ASSIGN_RANGE, which is going
to be used for forwarding user's fallocate(0) requests into
block device internals. It rather similar to existing
REQ_OP_DISCARD, REQ_OP_WRITE_ZEROES, etc. The corresponding
exported primitive is called blkdev_issue_assign_range().
See [1/3] for the details.

Patch [2/3] teaches loop driver to handle REQ_OP_ASSIGN_RANGE
requests by calling fallocate(0).

Patch [3/3] makes ext4 to notify a block device about fallocate(0).

Here is a simple test I did:
https://gist.github.com/tkhai/5b788651cdb74c1dbff3500745878856

I attached a file on ext4 to loop. Then, created ext4 partition
on loop device and started the test in the partition. Direct-io
is enabled on loop.

The test fallocates 4G file and writes from some offset with
given step, then it chooses another offset and repeats. After
the test all the blocks in the file become written.

The results shows that batching extents-assigning requests improves
the performance:

Before patchset: real ~ 1min 27sec
After patchset:  real ~ 1min 16sec (18% better)

Ordinary fallocate() before writes improves the performance
by batching the requests. These results just show, the same
is in case of forwarding extents information to underlining
filesystem.

Regards,
Chaitanya

Changes from RFC:-

1. Add missing plumbing for REQ_OP_ASSIGN_RANGE similar to write-zeores.
2. Add a prep patch to create a helper to submit payloadless bios.
3. Design a testcases around the description present in the
   cover-letter.

Chaitanya Kulkarni (1):
  block: create payloadless issue bio helper

Kirill Tkhai (3):
  block: Add support for REQ_OP_ASSIGN_RANGE
  loop: Forward REQ_OP_ASSIGN_RANGE into fallocate(0)
  ext4: Notify block device about alloc-assigned blk

 block/blk-core.c          |   5 ++
 block/blk-lib.c           | 115 +++++++++++++++++++++++++++++++-------
 block/blk-merge.c         |  21 +++++++
 block/blk-settings.c      |  19 +++++++
 block/blk-zoned.c         |   1 +
 block/bounce.c            |   1 +
 drivers/block/loop.c      |   5 ++
 fs/ext4/ext4.h            |   2 +
 fs/ext4/extents.c         |  12 +++-
 include/linux/bio.h       |   9 ++-
 include/linux/blk_types.h |   2 +
 include/linux/blkdev.h    |  34 +++++++++++
 12 files changed, 201 insertions(+), 25 deletions(-)

1. Setup :-
-----------
# git log --oneline -5 
c64a4c781915 (HEAD -> req-op-assign-range) ext4: Notify block device about alloc-assigned blk
000cbc6720a4 loop: Forward REQ_OP_ASSIGN_RANGE into fallocate(0)
89ceed8cac80 block: Add support for REQ_OP_ASSIGN_RANGE
a798743e87e7 block: create payloadless issue bio helper
b53df2e7442c (tag: block-5.6-2020-03-13) block: Fix partition support for host aware zoned block devices

# cat /proc/kallsyms | grep -i blkdev_issue_assign_range
ffffffffa3264a80 T blkdev_issue_assign_range
ffffffffa4027184 r __ksymtab_blkdev_issue_assign_range
ffffffffa40524be r __kstrtabns_blkdev_issue_assign_range
ffffffffa405a8eb r __kstrtab_blkdev_issue_assign_range

2. Test program, will be moved to blktest once code is upstream :-
-----------------
#define _GNU_SOURCE
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>

#define BLOCK_SIZE 4096
#define STEP (BLOCK_SIZE * 16)
#define SIZE (1024 * 1024 * 1024ULL)

int main(int argc, char *argv[])
{
	int fd, step, ret = 0;
	unsigned long i;
	void *buf;

	if (posix_memalign(&buf, BLOCK_SIZE, SIZE)) {
		perror("alloc");
		exit(1);
	}

	fd = open("/mnt/loop0/file.img", O_RDWR | O_CREAT | O_DIRECT);
	if (fd < 0) {
		perror("open");
		exit(1);
	}

	if (ftruncate(fd, SIZE)) {
		perror("ftruncate");
		exit(1);
	}

	ret = fallocate(fd, 0, 0, SIZE);
	if (ret) {
		perror("fallocate");
		exit(1);
	}
	
	for (step = STEP - BLOCK_SIZE; step >= 0; step -= BLOCK_SIZE) {
		printf("step=%u\n", step);
		for (i = step; i < SIZE; i += STEP) {
			errno = 0;
			if (pwrite(fd, buf, BLOCK_SIZE, i) != BLOCK_SIZE) {
				perror("pwrite");
				exit(1);
			}
		}

		if (fsync(fd)) {
			perror("fsync");
			exit(1);
		}
	}
	return 0;
}

3. Test script, will be moved to blktests once code is upstream :-
------------------------------------------------------------------
# cat req_op_assign_test.sh 
#!/bin/bash -x

NULLB_FILE="/mnt/backend/data"
NULLB_MNT="/mnt/backend"
LOOP_MNT="/mnt/loop0"

delete_loop()
{
	umount ${LOOP_MNT}
	losetup -D
	sleep 3
}

delete_nullb()
{
	umount ${NULLB_MNT}
	echo 1 > config/nullb/nullb0/power
	rmdir config/nullb/nullb0
	sleep 3
}

unload_modules()
{
	rmmod drivers/block/loop.ko
	rmmod fs/ext4/ext4.ko
	rmmod drivers/block/null_blk.ko
	lsmod | grep -e ext4 -e loop -e null_blk
}

unload()
{
	delete_loop
	delete_nullb
	unload_modules
}

load_ext4()
{
	make -j $(nproc) M=fs/ext4 modules
	local src=fs/ext4/
	local dest=/lib/modules/`uname -r`/kernel/fs/ext4
	\cp ${src}/ext4.ko ${dest}/

	modprobe mbcache
	modprobe jbd2
	sleep 1
	insmod fs/ext4/ext4.ko
	sleep 1
}

load_nullb()
{
	local src=drivers/block/
	local dest=/lib/modules/`uname -r`/kernel/drivers/block
	\cp ${src}/null_blk.ko ${dest}/

	modprobe null_blk nr_devices=0
	sleep 1

	mkdir config/nullb/nullb0
	tree config/nullb/nullb0

	echo 1 > config/nullb/nullb0/memory_backed
	echo 512 > config/nullb/nullb0/blocksize 

	# 20 GB
	echo 20480 > config/nullb/nullb0/size 
	echo 1 > config/nullb/nullb0/power
	sleep 2
	IDX=`cat config/nullb/nullb0/index`
	lsblk | grep null${IDX}
	sleep 1

	mkfs.ext4 /dev/nullb0 
	mount /dev/nullb0 ${NULLB_MNT}
	sleep 1
	mount | grep nullb

	# 10 GB
	dd if=/dev/zero of=${NULLB_FILE} count=2621440 bs=4096
}

load_loop()
{
	local src=drivers/block/
	local dest=/lib/modules/`uname -r`/kernel/drivers/block
	\cp ${src}/loop.ko ${dest}/

	insmod drivers/block/loop.ko max_loop=1
	sleep 3
	/root/util-linux/losetup --direct-io=off /dev/loop0 ${NULLB_FILE}
	sleep 3
	/root/util-linux/losetup
	ls -l /dev/loop*
	dmesg -c 
	mkfs.ext4 /dev/loop0
	mount /dev/loop0 ${LOOP_MNT}
	mount | grep loop0
}

load()
{
	make -j $(nproc) M=drivers/block modules

	load_ext4
	load_nullb
	load_loop
	sleep 1
	sync
	sync
	sync
}

unload
load
time ./test

4. Test Results :-
------------------

# ./req_op_assign_test.sh 
+ NULLB_FILE=/mnt/backend/data
+ NULLB_MNT=/mnt/backend
+ LOOP_MNT=/mnt/loop0
+ unload
+ delete_loop
+ umount /mnt/loop0
+ losetup -D
+ sleep 3
+ delete_nullb
+ umount /mnt/backend
+ echo 1
+ rmdir config/nullb/nullb0
+ sleep 3
+ unload_modules
+ rmmod drivers/block/loop.ko
+ rmmod fs/ext4/ext4.ko
+ rmmod drivers/block/null_blk.ko
+ lsmod
+ grep -e ext4 -e loop -e null_blk
+ load
++ nproc
+ make -j 32 M=drivers/block modules
  CC [M]  drivers/block/loop.o
  MODPOST 11 modules
  CC [M]  drivers/block/loop.mod.o
  LD [M]  drivers/block/loop.ko
+ load_ext4
++ nproc
+ make -j 32 M=fs/ext4 modules
  CC [M]  fs/ext4/balloc.o
  CC [M]  fs/ext4/bitmap.o
  CC [M]  fs/ext4/block_validity.o
  CC [M]  fs/ext4/dir.o
  CC [M]  fs/ext4/ext4_jbd2.o
  CC [M]  fs/ext4/extents.o
  CC [M]  fs/ext4/extents_status.o
  CC [M]  fs/ext4/file.o
  CC [M]  fs/ext4/fsmap.o
  CC [M]  fs/ext4/fsync.o
  CC [M]  fs/ext4/hash.o
  CC [M]  fs/ext4/ialloc.o
  CC [M]  fs/ext4/indirect.o
  CC [M]  fs/ext4/inline.o
  CC [M]  fs/ext4/inode.o
  CC [M]  fs/ext4/ioctl.o
  CC [M]  fs/ext4/mballoc.o
  CC [M]  fs/ext4/migrate.o
  CC [M]  fs/ext4/mmp.o
  CC [M]  fs/ext4/move_extent.o
  CC [M]  fs/ext4/namei.o
  CC [M]  fs/ext4/page-io.o
  CC [M]  fs/ext4/readpage.o
  CC [M]  fs/ext4/resize.o
  CC [M]  fs/ext4/super.o
  CC [M]  fs/ext4/symlink.o
  CC [M]  fs/ext4/sysfs.o
  CC [M]  fs/ext4/xattr.o
  CC [M]  fs/ext4/xattr_trusted.o
  CC [M]  fs/ext4/xattr_user.o
  CC [M]  fs/ext4/acl.o
  CC [M]  fs/ext4/xattr_security.o
  LD [M]  fs/ext4/ext4.o
  MODPOST 1 modules
  LD [M]  fs/ext4/ext4.ko
+ local src=fs/ext4/
++ uname -r
+ local dest=/lib/modules/5.6.0-rc3lbk+/kernel/fs/ext4
+ cp fs/ext4//ext4.ko /lib/modules/5.6.0-rc3lbk+/kernel/fs/ext4/
+ modprobe mbcache
+ modprobe jbd2
+ sleep 1
+ insmod fs/ext4/ext4.ko
+ sleep 1
+ load_nullb
+ local src=drivers/block/
++ uname -r
+ local dest=/lib/modules/5.6.0-rc3lbk+/kernel/drivers/block
+ cp drivers/block//null_blk.ko /lib/modules/5.6.0-rc3lbk+/kernel/drivers/block/
+ modprobe null_blk nr_devices=0
+ sleep 1
+ mkdir config/nullb/nullb0
+ tree config/nullb/nullb0
config/nullb/nullb0
├── badblocks
├── blocking
├── blocksize
├── cache_size
├── completion_nsec
├── discard
├── home_node
├── hw_queue_depth
├── index
├── irqmode
├── mbps
├── memory_backed
├── power
├── queue_mode
├── size
├── submit_queues
├── use_per_node_hctx
├── zoned
├── zone_nr_conv
└── zone_size

0 directories, 20 files
+ echo 1
+ echo 512
+ echo 20480
+ echo 1
+ sleep 2
++ cat config/nullb/nullb0/index
+ IDX=0
+ lsblk
+ grep null0
+ sleep 1
+ mkfs.ext4 /dev/nullb0
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
1310720 inodes, 5242880 blocks
262144 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2153775104
160 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks: 
	32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
	4096000

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done   

+ mount /dev/nullb0 /mnt/backend
+ sleep 1
+ mount
+ grep nullb
/dev/nullb0 on /mnt/backend type ext4 (rw,relatime,seclabel)
+ dd if=/dev/zero of=/mnt/backend/data count=2621440 bs=4096
2621440+0 records in
2621440+0 records out
10737418240 bytes (11 GB) copied, 27.4579 s, 391 MB/s
+ load_loop
+ local src=drivers/block/
++ uname -r
+ local dest=/lib/modules/5.6.0-rc3lbk+/kernel/drivers/block
+ cp drivers/block//loop.ko /lib/modules/5.6.0-rc3lbk+/kernel/drivers/block/
+ insmod drivers/block/loop.ko max_loop=1
+ sleep 3
+ /root/util-linux/losetup --direct-io=off /dev/loop0 /mnt/backend/data
+ sleep 3
+ /root/util-linux/losetup
NAME       SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE         DIO LOG-SEC
/dev/loop0         0      0         0  0 /mnt/backend/data   0     512
+ ls -l /dev/loop0 /dev/loop-control
brw-rw----. 1 root disk  7,   0 Mar 29 10:28 /dev/loop0
crw-rw----. 1 root disk 10, 237 Mar 29 10:28 /dev/loop-control
+ dmesg -c
[42963.967060] null_blk: module loaded
[42968.419481] EXT4-fs (nullb0): mounted filesystem with ordered data mode. Opts: (null)
[42996.928141] loop: module loaded
+ mkfs.ext4 /dev/loop0
mke2fs 1.42.9 (28-Dec-2013)
Discarding device blocks: done                            
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
655360 inodes, 2621440 blocks
131072 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2151677952
80 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks: 
	32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done 

+ mount /dev/loop0 /mnt/loop0
+ mount
+ grep loop0
/dev/loop0 on /mnt/loop0 type ext4 (rw,relatime,seclabel)
+ sleep 1
+ sync
+ sync
+ sync
+ ./test
step=61440
step=57344
step=53248
step=49152
step=45056
step=40960
step=36864
step=32768
step=28672
step=24576
step=20480
step=16384
step=12288
step=8192
step=4096
step=0

real	9m34.472s
user	0m0.062s
sys	0m5.783s

-- 
2.22.0

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