where is disk block access in kernel ?

where is disk block access in kernel ?

[Ran Shalit]

Hello,

I would like to monitor the write access to disk blocks (so that I can
monitor the block index in some bitmap)
I think this must be done in kernel (userspace have no such information)
I have tried to search in kernel but did not found where is the API to
access disk blocks.
There is libata-core.c , but I can't find such routines there, and
neither any documentation.

Is there any idea ?

Regards,
Ran

where is disk block access in kernel ?

[Mulyadi Santosa]

On Wed, Mar 2, 2016 at 4:57 PM, Ran Shalit <ranshalit@gmail.com> wrote:

> Hello,
>
> I would like to monitor the write access to disk blocks (so that I can
> monitor the block index in some bitmap)
> I think this must be done in kernel (userspace have no such information)
> I have tried to search in kernel but did not found where is the API to
> access disk blocks.
> There is libata-core.c , but I can't find such routines there, and
> neither any documentation.
>
> Is there any idea ?
>
> Regards,
> Ran
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>


Hi

Sounds like something doable via ftrace.

try to check if it is feasible to be done using ftrace


-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com

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where is disk block access in kernel ?

[Valdis.Kletnieks at vt.edu]

On Wed, 02 Mar 2016 11:57:41 +0200, Ran Shalit said:

> I would like to monitor the write access to disk blocks (so that I can
> monitor the block index in some bitmap)

What exactly are you trying to do with that information? (Hint - figure out
how big a bitmap you need for the blocks on a 2T or 4T drive - or for the
600T to petabyte filesystems I deal with for a living).

Do you need just write access, or read as well?
Do you need the info before or after the disk cache is involved?
Do you need to deal with corner cases like a program writing to a file, and
then unlinking the file before the blocks are written to disk?

As is common for kernel issues, the answer depends a lot on exactly what
the *real* question is....

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