[cc lang='bash']
\$ iotop --only --accumulated
Total DISK READ: 0.00 B/s | Total DISK WRITE: 0.00 B/s
TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND
2264 be/4 root 0.00 B 0.00 B 0.00 % 0.34 % [flush-254:0]
162 be/3 root 0.00 B 352.00 K 0.00 % 0.04 % [jbd2/vda-8]
2202 be/4 bind 0.00 B 4.00 K 0.00 % 0.00 % named -u bind
2333 be/4 root 0.00 B 5.72 M 0.00 % 0.00 % collectd -C /etc/collectd/collectd.conf -f
2007 be/4 root 0.00 B 32.00 K 0.00 % 0.00 % rsyslogd -c5
17938 be/4 postfix 0.00 B 0.00 B 0.00 % 0.00 % smtp -t unix -u -c
[/cc]

The information is gathered from "/proc/\$pid/io" file:
[cc lang='bash']
\$ cat /proc/2333/io
rchar: 1485857154
wchar: 20371441
syscr: 10544889
syscw: 44078
read_bytes: 55783424
write_bytes: 88860282880
cancelled_write_bytes: 0
[/cc]

block_dump — Configures block I/O debugging when enabled. All read/write and block dirtying operations done to files are logged accordingly. All output when block_dump is enabled can be retrieved via dmesg. The default value is 0.
[cc lang='bash']
\$ echo 1 > /proc/sys/vm/block_dump
\$ sleep 20
\$ echo 0 > /proc/sys/vm/block_dump
\$ dmesg
...
[839473.076358] bash(19353): READ block 12865224 on vda (32 sectors)
[839473.077429] bash(19353): dirtied inode 393313 (dmesg) on vda
[839473.077572] dmesg(19353): READ block 12865256 on vda (16 sectors)
[839473.080139] rsyslogd(2010): READ block 17345072 on vda (56 sectors)
[839473.085270] rs:main Q:Reg(2007): dirtied inode 263125 (syslog) on vda
[839473.085279] rs:main Q:Reg(2007): dirtied inode 263125 (syslog) on vda
[839473.085282] rs:main Q:Reg(2007): dirtied inode 263125 (syslog) on vda
[839473.085347] rs:main Q:Reg(2007): dirtied inode 264868 (kern.log) on vda
[839473.085358] rs:main Q:Reg(2007): dirtied inode 264868 (kern.log) on vda
[839473.085361] rs:main Q:Reg(2007): dirtied inode 264868 (kern.log) on vda
[839473.085394] rs:main Q:Reg(2007): dirtied inode 268702 (debug) on vda
[839473.085401] rs:main Q:Reg(2007): dirtied inode 268702 (debug) on vda
[839473.085404] rs:main Q:Reg(2007): dirtied inode 268702 (debug) on vda
[839478.832091] jbd2/vda-8(162): WRITE block 29935184 on vda (8 sectors)
[839478.832153] jbd2/vda-8(162): WRITE block 21340104 on vda (8 sectors)
[839478.832159] jbd2/vda-8(162): WRITE block 21340112 on vda (8 sectors)
[839478.832162] jbd2/vda-8(162): WRITE block 21340120 on vda (8 sectors)
[839478.832164] jbd2/vda-8(162): WRITE block 21340128 on vda (8 sectors)
[839478.832167] jbd2/vda-8(162): WRITE block 21340136 on vda (8 sectors)
[839478.832707] jbd2/vda-8(162): WRITE block 21340144 on vda (8 sectors)
[839483.176069] flush-254:0(2264): WRITE block 8389952 on vda (8 sectors)
[839483.176081] flush-254:0(2264): WRITE block 8389968 on vda (8 sectors)
[839483.176085] flush-254:0(2264): WRITE block 8389976 on vda (8 sectors)
[839483.176101] flush-254:0(2264): WRITE block 8390000 on vda (8 sectors)
[839483.176106] flush-254:0(2264): WRITE block 8390048 on vda (8 sectors)
[839483.176112] flush-254:0(2264): WRITE block 8390088 on vda (8 sectors)
[839483.176116] flush-254:0(2264): WRITE block 8390096 on vda (8 sectors)
[839483.176120] flush-254:0(2264): WRITE block 8390152 on vda (8 sectors)
[839483.176124] flush-254:0(2264): WRITE block 8390168 on vda (8 sectors)
[839483.176128] flush-254:0(2264): WRITE block 8390184 on vda (8 sectors)
[839483.176134] flush-254:0(2264): WRITE block 8390264 on vda (8 sectors)
[839483.176138] flush-254:0(2264): WRITE block 8390272 on vda (8 sectors)
[839483.176141] flush-254:0(2264): WRITE block 8390288 on vda (8 sectors)
[839483.176150] flush-254:0(2264): WRITE block 8390304 on vda (8 sectors)
[839483.176154] flush-254:0(2264): WRITE block 8390312 on vda (8 sectors)
[839483.176157] flush-254:0(2264): WRITE block 8390320 on vda (8 sectors)
[839483.176160] flush-254:0(2264): WRITE block 8390328 on vda (8 sectors)
[839483.176163] flush-254:0(2264): WRITE block 8390336 on vda (8 sectors)
[839483.176166] flush-254:0(2264): WRITE block 8390344 on vda (8 sectors)
[839483.176169] flush-254:0(2264): WRITE block 8390352 on vda (8 sectors)
[839483.176172] flush-254:0(2264): WRITE block 8390360 on vda (8 sectors)
[839483.176175] flush-254:0(2264): WRITE block 8390368 on vda (8 sectors)
[839483.176177] flush-254:0(2264): WRITE block 8390376 on vda (8 sectors)
[839483.176181] flush-254:0(2264): WRITE block 8390384 on vda (8 sectors)
[839483.176183] flush-254:0(2264): WRITE block 8390392 on vda (8 sectors)
[839483.176187] flush-254:0(2264): WRITE block 8390400 on vda (8 sectors)
[839483.176190] flush-254:0(2264): WRITE block 8390536 on vda (8 sectors)
[839483.176196] flush-254:0(2264): WRITE block 8390544 on vda (8 sectors)
[839483.176199] flush-254:0(2264): WRITE block 8390552 on vda (8 sectors)
[839483.176202] flush-254:0(2264): WRITE block 8392032 on vda (8 sectors)
[839483.176206] flush-254:0(2264): WRITE block 8392040 on vda (8 sectors)
[839483.176209] flush-254:0(2264): WRITE block 8392056 on vda (8 sectors)
[839483.176213] flush-254:0(2264): WRITE block 8392064 on vda (8 sectors)
[839483.176216] flush-254:0(2264): WRITE block 8392072 on vda (8 sectors)
[839483.176220] flush-254:0(2264): WRITE block 8392080 on vda (8 sectors)
[839483.176222] flush-254:0(2264): WRITE block 8392088 on vda (8 sectors)
[839483.176225] flush-254:0(2264): WRITE block 8392104 on vda (8 sectors)
[839483.176229] flush-254:0(2264): WRITE block 8392120 on vda (8 sectors)
[839483.176234] flush-254:0(2264): WRITE block 8392184 on vda (8 sectors)
[839483.176274] flush-254:0(2264): WRITE block 8392200 on vda (8 sectors)
[839483.176291] flush-254:0(2264): WRITE block 8392216 on vda (8 sectors)
[839483.176295] flush-254:0(2264): WRITE block 8392224 on vda (8 sectors)
[839483.176298] flush-254:0(2264): WRITE block 8392232 on vda (8 sectors)
[839483.176301] flush-254:0(2264): WRITE block 8392240 on vda (8 sectors)
[839483.176305] flush-254:0(2264): WRITE block 8456000 on vda (8 sectors)
[839483.176309] flush-254:0(2264): WRITE block 8456008 on vda (8 sectors)
[839483.176312] flush-254:0(2264): WRITE block 8652400 on vda (8 sectors)
[839483.176316] flush-254:0(2264): WRITE block 8676304 on vda (8 sectors)
[839483.176321] flush-254:0(2264): WRITE block 12583216 on vda (8 sectors)
[839483.176325] flush-254:0(2264): WRITE block 25165952 on vda (8 sectors)
[839483.176329] flush-254:0(2264): WRITE block 25166080 on vda (8 sectors)
[839483.176333] flush-254:0(2264): WRITE block 25167112 on vda (8 sectors)
[839483.176337] flush-254:0(2264): WRITE block 25231664 on vda (8 sectors)
[839483.176375] flush-254:0(2264): WRITE block 25233760 on vda (8 sectors)
[839483.176382] flush-254:0(2264): WRITE block 29360144 on vda (8 sectors)
[839483.176387] flush-254:0(2264): WRITE block 29360160 on vda (8 sectors)
[839483.176391] flush-254:0(2264): WRITE block 29361032 on vda (8 sectors)
[839483.176400] flush-254:0(2264): WRITE block 0 on vda (8 sectors)
[839483.176404] flush-254:0(2264): WRITE block 8 on vda (8 sectors)
[839483.176407] flush-254:0(2264): WRITE block 8388672 on vda (8 sectors)
[839483.176435] flush-254:0(2264): WRITE block 8388736 on vda (8 sectors)
[839483.176439] flush-254:0(2264): WRITE block 8388872 on vda (8 sectors)
[839483.176443] flush-254:0(2264): WRITE block 8389224 on vda (8 sectors)
[839483.176447] flush-254:0(2264): WRITE block 8389304 on vda (8 sectors)
[839483.176450] flush-254:0(2264): WRITE block 8389320 on vda (8 sectors)
[839483.176456] flush-254:0(2264): WRITE block 8389376 on vda (8 sectors)
[839483.176460] flush-254:0(2264): WRITE block 8389408 on vda (8 sectors)
[839483.176464] flush-254:0(2264): WRITE block 8389424 on vda (8 sectors)
[839483.176467] flush-254:0(2264): WRITE block 8389536 on vda (8 sectors)
[839483.176471] flush-254:0(2264): WRITE block 8389600 on vda (8 sectors)
[839483.176478] flush-254:0(2264): WRITE block 8389696 on vda (8 sectors)
[839483.176482] flush-254:0(2264): WRITE block 8389720 on vda (8 sectors)
[839483.176485] flush-254:0(2264): WRITE block 8389784 on vda (8 sectors)
[839483.176489] flush-254:0(2264): WRITE block 8389792 on vda (8 sectors)
[839483.176493] flush-254:0(2264): WRITE block 8389800 on vda (8 sectors)
[839483.176496] flush-254:0(2264): WRITE block 8389824 on vda (8 sectors)
[839483.176500] flush-254:0(2264): WRITE block 8389840 on vda (8 sectors)
[839483.176504] flush-254:0(2264): WRITE block 8389848 on vda (8 sectors)
[839483.176507] flush-254:0(2264): WRITE block 8389856 on vda (8 sectors)
[839483.176510] flush-254:0(2264): WRITE block 8389864 on vda (8 sectors)
[839483.176513] flush-254:0(2264): WRITE block 8389880 on vda (8 sectors)
[839483.176539] flush-254:0(2264): WRITE block 8389912 on vda (8 sectors)
[839483.733003] master(3149): dirtied inode 264613 (pickup) on vda
[839484.832218] jbd2/vda-8(162): WRITE block 21340152 on vda (8 sectors)
[839484.832235] jbd2/vda-8(162): WRITE block 21340160 on vda (8 sectors)
[839484.832240] jbd2/vda-8(162): WRITE block 21340168 on vda (8 sectors)
[839484.832243] jbd2/vda-8(162): WRITE block 21340176 on vda (8 sectors)
[839484.832245] jbd2/vda-8(162): WRITE block 21340184 on vda (8 sectors)
[839484.832773] jbd2/vda-8(162): WRITE block 21340192 on vda (8 sectors)
[839490.832197] jbd2/vda-8(162): WRITE block 21340200 on vda (8 sectors)
[839490.832220] jbd2/vda-8(162): WRITE block 21340208 on vda (8 sectors)
[839490.832228] jbd2/vda-8(162): WRITE block 21340216 on vda (8 sectors)
[839490.832233] jbd2/vda-8(162): WRITE block 21340224 on vda (8 sectors)
[839490.832869] jbd2/vda-8(162): WRITE block 21340232 on vda (8 sectors)
[/cc]