[SOLVED] Meaning of "READ block xxx on sdXX" from kernel message

mhtrinh · 2012-08-10 16:06:37

Hi,

I activate kernel debug with :
echo 1 > /proc/sys/vm/block_dump

Now, dmesg I got a lot of "READ block xxx on sdXX" :
[12501.346573] ls(4079): READ block 43098492 on sda2 (1 sectors)
[12501.346619] ls(4079): READ block 43098493 on sda2 (1 sectors)
[12501.346667] ls(4079): READ block 43098494 on sda2 (1 sectors)
[12501.346714] ls(4079): READ block 43098495 on sda2 (1 sectors)
[12501.346774] ls(4079): READ block 43098496 on sda2 (1 sectors)
[12501.346824] ls(4079): READ block 43098497 on sda2 (1 sectors)
[12501.346871] ls(4079): READ block 43098498 on sda2 (1 sectors)
[12501.346918] ls(4079): READ block 43098499 on sda2 (1 sectors)

I would like to understand what are those block number. They seems to not correspond to block in debugfs's icheck command. How can I dump the content of those block or which file are they from ?

Last edited by mhtrinh (2012-08-14 18:54:47)

Ljie1991 · 2012-08-12 14:47:38

I think it's a device file,the command "echo" will use syscall open and read,and it will call the functions which registered in the file_ops struct in kernel ,so the syscall read do you function read in file_ops,transmit the message to user space,also the return value of the "read() of echo".
I am so sorry i can not explain it clearly,maybe i was wrong,and my english is bad,a chinese.
I study ARM+Linux as a novice..

mhtrinh · 2012-08-12 23:59:13

Hello,

I'm back with the solution : at least for my system, debugfs_block_id = kernel_block_id / 8

For example with :

<7>[12091.038936] firefox(4491): READ block 4037656 on sda6 (384 sectors)

To get what is read, with 4037656 / 8= 504707

[root@hpmini ~]# debugfs /dev/sda6
debugfs 1.41.14 (22-Dec-2010)
debugfs:  icheck 504707
Block	Inode number
504707	45727
debugfs:  quit
[root@hpmini ~]# find / -xdev -inum 45727
/usr/share/fonts/misc/cu12.pcf.gz

Ljie1991 · 2012-08-13 03:36:51

:cool

Arch Linux

#1 2012-08-10 16:06:37

[SOLVED] Meaning of "READ block xxx on sdXX" from kernel message

#2 2012-08-12 14:47:38

Re: [SOLVED] Meaning of "READ block xxx on sdXX" from kernel message

#3 2012-08-12 23:59:13

Re: [SOLVED] Meaning of "READ block xxx on sdXX" from kernel message

#4 2012-08-13 03:36:51

Re: [SOLVED] Meaning of "READ block xxx on sdXX" from kernel message

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