[ECOS] jffs2 questions

[ECOS] jffs2 questions

[Stanislav Meduna]

Hi,

I am trying to use a JFFS2 filesystem in a serial dataflash
device. I encountered the jffs2_open hanging mysteriously,
so I started to investigate.

1) Reinitializing the filesystem resolved the hang.
   Is it possible that a corrupted filesystem (never
   unmounted in these tests, just powered down)
   causes the jffs to mount, but not open a file? From
   what I have read the unclean unmount should not cause
   this.

2) What is the stack usage of jffs2? Is it upper-bounded,
   or could it depend on the filesystem data? Is there
   an upper limit?

3) If I understand this correctly, jffs2 does not like
   small writes. I need to write a logfile into a flash -
   not too often (life of the flash is not an issue),
   but in small chunks. I thought I should use
   CONFIG_JFFS2_FS_WRITEBUFFER defined by CYGOPT_FS_JFFS2_NAND;
   however, the CDL states
     requires        0
   and I can not enable this. Huh?

4) CDL for CYGOPT_FS_JFFS2_GSTHREAD states
     Leave this off till it's been implemented. And don't
     implement it till icache locking has been made thread-safe.

   http://www.ecoscentric.com/ecospro/doc.cgi/html/ecospro-ref/fs-jffs2-usage.html
   just explains what it is and how it can be used. Does this
   mean that the eCosCentric version has other code than
   is in the CVS, or is just the CDL documentation obsolete?

Thanks
-- 
                                    Stano

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Re: [ECOS] jffs2 questions

[Daniel Morris]

On Wed, Jul 15, 2009 at 10:37:15AM +0200, Stanislav Meduna wrote:
> Hi,
> 
> I am trying to use a JFFS2 filesystem in a serial dataflash
> device. I encountered the jffs2_open hanging mysteriously,
> so I started to investigate.
> 
> 1) Reinitializing the filesystem resolved the hang.
>    Is it possible that a corrupted filesystem (never
>    unmounted in these tests, just powered down)
>    causes the jffs to mount, but not open a file? From
>    what I have read the unclean unmount should not cause
>    this.
> 
> 2) What is the stack usage of jffs2? Is it upper-bounded,
>    or could it depend on the filesystem data? Is there
>    an upper limit?
> 
> 3) If I understand this correctly, jffs2 does not like
>    small writes. I need to write a logfile into a flash -
>    not too often (life of the flash is not an issue),
>    but in small chunks. I thought I should use
>    CONFIG_JFFS2_FS_WRITEBUFFER defined by CYGOPT_FS_JFFS2_NAND;
>    however, the CDL states
>      requires        0
>    and I can not enable this. Huh?
> 
> 4) CDL for CYGOPT_FS_JFFS2_GSTHREAD states
>      Leave this off till it's been implemented. And don't
>      implement it till icache locking has been made thread-safe.
> 
>    http://www.ecoscentric.com/ecospro/doc.cgi/html/ecospro-ref/fs-jffs2-usage.html
>    just explains what it is and how it can be used. Does this
>    mean that the eCosCentric version has other code than
>    is in the CVS, or is just the CDL documentation obsolete?
> 

Yes, jffs2 in eCosPro has a number of enhancements, including additions
to satisfy US/DoD Homeland Security mandated requirements.

 Daniel


%<----------------------------------------------------------------------
  Daniel Morris - Sales & Marketing Director
  eCosCentric - The eCos and RedBoot experts
  Tel: +44 1223 245 571 - info@eCosCentric.com
  DDI: +44 1269 591 171 - danielm@eCosCentric.com


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Re: [ECOS] jffs2 questions

[Sergei Gavrikov]

On Wed, Jul 15, 2009 at 10:37:15AM +0200, Stanislav Meduna wrote:
> 2) What is the stack usage of jffs2? Is it upper-bounded,
>    or could it depend on the filesystem data? Is there
>    an upper limit?

AFAIK, JFFS2 uses 40 bytes per inode.
The best what I read about JFFS2 was this resource
http://blog.datalight.com/jffs2-linux-flash-file-system

Sergei

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[ECOS] Re: jffs2 questions

[John Dallaway]

Hi Stano

Stanislav Meduna wrote:

> I am trying to use a JFFS2 filesystem in a serial dataflash
> device. I encountered the jffs2_open hanging mysteriously,
> so I started to investigate.

Are you aware that the version of JFFS2 ported to eCos has issues with
DataFlash? Ref:

  http://sourceware.org/ml/ecos-discuss/2005-01/msg00100.html

Patches are welcome. A complete re-import of JFFS2 for eCos would be
even more welcome.

> 4) CDL for CYGOPT_FS_JFFS2_GSTHREAD states
>      Leave this off till it's been implemented. And don't
>      implement it till icache locking has been made thread-safe.

It looks like the CDL description string is obsolete. According to the
ChangeLog, garbage collection thread support was added 2004-11-14.

John Dallaway

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Re: [ECOS] Re: jffs2 questions

[Stanislav Meduna]

John Dallaway wrote:

>> I am trying to use a JFFS2 filesystem in a serial dataflash
>> device. I encountered the jffs2_open hanging mysteriously,
>> so I started to investigate.
> 
> Are you aware that the version of JFFS2 ported to eCos has issues with
> DataFlash? Ref:
> 
>   http://sourceware.org/ml/ecos-discuss/2005-01/msg00100.html

Oh. The post is more than 4 years old, did not think this it
still an issue :/ Indeed, the ... & ~(c->sector_size-1) is still
there.

Many thanks for the information - I'll see what can be done about it.

Regards
-- 
                                     Stano

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Re: [ECOS] JFFS2 questions

[Jonathan Larmour]

Jani Monoses wrote:
> Hi
> is the readme in jffs2/doc up to date?
> It says JFFS2 has only been tested on the iPAQ and that
> 
> <QUOTE>
> Minor modifications are necessary to the the eCos flash drivers
> 
> io/flash/current/src/flash.c
> 
> devs/flash/intel/strata/current/src/flash_program_buf.c
> 
> to allow byte aligned rather than word aligned writes, and to ensure overwriting an existing
> word is successful (these are supplied in jffs2/current/src).
> </QUOTE>

Nope, the eCos jffs2 port takes care of the alignment itself. Or should do 
anyway.

The readme isn't up to date unfortunately. It's been used on other 
systems, at the very least the synthetic target!

Jifl
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[ECOS] JFFS2 questions

[Jani Monoses]

Hi
is the readme in jffs2/doc up to date?
It says JFFS2 has only been tested on the iPAQ and that

<QUOTE>
Minor modifications are necessary to the the eCos flash drivers

io/flash/current/src/flash.c

devs/flash/intel/strata/current/src/flash_program_buf.c

to allow byte aligned rather than word aligned writes, and to ensure overwriting an existing
word is successful (these are supplied in jffs2/current/src).
</QUOTE>

thanks
Jani.


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