CLEANMARKER!!

CLEANMARKER!!

[Nikhil]

hi all,

I am a bit confused regarding the cleanmarker stuff in JFFS2. I understand
that cleanmarker is written to the eraseblock immediately after a
successfull erase, which indicates that the block is empty and can be used
for writes.

Is there any other situation when the cleanmarker has to be added at the
beginning of the eraseblock?

jffs2dump of an image shows the presence of cleanmarker at the beginning
of all the eraseblocks (even if the block contains some valid data). why
is there a need to write cleanmarker in each erase block while creating
image using mkfs.jffs2?
  
-- 
Thanks & Regards

Nikhil
Project Engineer
NISG, CDAC

Re: CLEANMARKER!!

[Artem B. Bityutskiy]

Nikhil wrote:
> hi all,
> 
> I am a bit confused regarding the cleanmarker stuff in JFFS2. I understand
> that cleanmarker is written to the eraseblock immediately after a
> successfull erase, which indicates that the block is empty and can be used
> for writes.
Right.

> Is there any other situation when the cleanmarker has to be added at the
> beginning of the eraseblock?
No, only after erase.

> jffs2dump of an image shows the presence of cleanmarker at the beginning
> of all the eraseblocks (even if the block contains some valid data). why
> is there a need to write cleanmarker in each erase block while creating
> image using mkfs.jffs2?
There is no real need. mkfs.jffs2 just implemented that way. It just 
tries to be the same as if the same image would be created by means of 
copying files t oa mounted JFFS2, then dumping /dev/mtdX...

-- 
Best Regards,
Artem B. Bityutskiy,
St.-Petersburg, Russia.

Re: CLEANMARKER!!

[Josh Boyer]

On 12/22/05, Artem B. Bityutskiy <dedekind@yandex.ru> wrote:
> Nikhil wrote:
>
> > jffs2dump of an image shows the presence of cleanmarker at the beginning
> > of all the eraseblocks (even if the block contains some valid data). why
> > is there a need to write cleanmarker in each erase block while creating
> > image using mkfs.jffs2?
> There is no real need. mkfs.jffs2 just implemented that way. It just
> tries to be the same as if the same image would be created by means of
> copying files t oa mounted JFFS2, then dumping /dev/mtdX...

It's an optimization of mkfs.jffs2.  If it didn't write those
cleanmarkers in the image, JFFS2 would scan flash, find free
eraseblocks, and go erase them again since the cleanmarker is missing.
 With the cleanmarkers there, the erase of already erased blocks is
omitted.

josh

Re: CLEANMARKER!!

[Artem B. Bityutskiy]

Josh Boyer wrote:
> It's an optimization of mkfs.jffs2.  If it didn't write those
> cleanmarkers in the image, JFFS2 would scan flash, find free
> eraseblocks, and go erase them again since the cleanmarker is missing.
>  With the cleanmarkers there, the erase of already erased blocks is
> omitted.
Well, this is for empty eraseblocks. Those with data could be devoid of 
cleanmarkers.

-- 
Best Regards,
Artem B. Bityutskiy,
St.-Petersburg, Russia.