two questions about jffs2

two questions about jffs2

[Vahid Fereydunkolahi]

Hi,
 How does jffs2 handle the bad blocks on the NAND
flash? ( I noticed that at initialization jffs2 scans
the devivce and creates a bad block list, but it never
uses the bad block list. It seems that if the block is
bad it is not put into the block list).

Does current jffs2 and mtd support the NAND devices
with Page size more than 528 bytes?


Regards,
--vahid



		
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Re: two questions about jffs2

[Artem B. Bityuckiy]

On Tue, 2005-05-03 at 17:15 -0700, Vahid Fereydunkolahi wrote:
> Hi,
>  How does jffs2 handle the bad blocks on the NAND
> flash? ( I noticed that at initialization jffs2 scans
> the devivce and creates a bad block list, but it never
> uses the bad block list. It seems that if the block is
> bad it is not put into the block list).
JFFS2 handles bad blocks just fine. Some info may be found at the MTD
web site. Visit it please.

> Does current jffs2 and mtd support the NAND devices
> with Page size more than 528 bytes?
Yes, it does.

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

Re: two questions about jffs2

[Vahid Fereydunkolahi]

The comment "JFFS2 handles bad blocks just fine." is
an strange comment. As far as I know the handling of
the bad blocks must be managed by the file system and
mtd device will only check for bad blocks for erase operation.


		
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Re: two questions about jffs2

[Michael]

--- Vahid Fereydunkolahi <fereydunk@yahoo.com> wrote:
> The comment "JFFS2 handles bad blocks just fine." is
> an strange comment. As far as I know the handling of
> the bad blocks must be managed by the file system and
> mtd device will only check for bad blocks for erase operation.
> 

I think you just embarrased yourself.  JFFS2 is Journalling Flash
File System 2, which works overtop of MTD, the Memory Technology
Devices [driver layer].

And I think it handles them just fine, too.  Did you look at
linux-mtd.infradead.org?  There's lots of good info there, and it's
a lot easier than searching the mailing list. (which is useful as
well)

Mike

Re: two questions about jffs2

[Vahid Fereydunkolahi]

I am not sure if you even understand the question, so
please behave.

The question is: if the file system supposed to
address the issue of the bad blocks then JFFS2, which
is the file system must handle the bad blocks, This
includes all the read and write operations. The only
thing MTD checks is the erase operation on the blocks.

--vahid
--- Michael <xemc@yahoo.com> wrote:
> 
> --- Vahid Fereydunkolahi <fereydunk@yahoo.com>
> wrote:
> > The comment "JFFS2 handles bad blocks just fine."
> is
> > an strange comment. As far as I know the handling
> of
> > the bad blocks must be managed by the file system
> and
> > mtd device will only check for bad blocks for
> erase operation.
> > 
> 
> I think you just embarrased yourself.  JFFS2 is
> Journalling Flash
> File System 2, which works overtop of MTD, the
> Memory Technology
> Devices [driver layer].
> 
> And I think it handles them just fine, too.  Did you
> look at
> linux-mtd.infradead.org?  There's lots of good info
> there, and it's
> a lot easier than searching the mailing list. (which
> is useful as
> well)
> 
> Mike
> 


		
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Re: two questions about jffs2

[Josh Boyer]

On Wed, 2005-05-04 at 13:18 -0700, Vahid Fereydunkolahi wrote:
> I am not sure if you even understand the question, so
> please behave.

Speaking of behaving, please don't top post on this list.

> 
> The question is: if the file system supposed to
> address the issue of the bad blocks then JFFS2, which
> is the file system must handle the bad blocks, This
> includes all the read and write operations. The only
> thing MTD checks is the erase operation on the blocks.

Perhaps if you restate the question someone may be able to help you.
The above isn't very clear.

JFFS2 handles bad blocks.  It does this by detecting a block is bad, and
then never doing anything with said block.  The definition of a bad
block is that it is marked as such in the spare area at manufacturing
time. Any write/erase operation to such a block would cause this
information to be lost.  Therefore, JFFS2 does not touch these blocks
during runtime.

josh

Re: two questions about jffs2

[Thomas Gleixner]

On Wed, 2005-05-04 at 15:43 -0500, Josh Boyer wrote:

> JFFS2 handles bad blocks.  It does this by detecting a block is bad, and
> then never doing anything with said block.  The definition of a bad
> block is that it is marked as such in the spare area at manufacturing
> time. Any write/erase operation to such a block would cause this
> information to be lost.  Therefore, JFFS2 does not touch these blocks
> during runtime.

Even if the filesystem misbehaves the nand driver in the mtd layer
refuses to write/erase bad blocks. 

tglx