JFFS 2 Question

JFFS 2 Question

[Patrick Hilt]

Hi list!
Is there a way to make sure data is being written to physical flash when using 
JFFS2? In other words, After writing a file on a JFFS2 partition, is there 
anything that can be done to make sure that the data is getting written to 
the flash right away? Would "sync" or "fsync" have that effect?

Thanks a lot in advance for any input!!!

Happy weekend,

Patrick

Re: JFFS 2 Question

[Mike Wellington]

Guess I'm the first one to wake up and see this.

Sync "should" work.  Try it and check by doing
 
>  od -x /jffs2 

and then see if your new data is in the dump.

A foolproof way that is overkill - unmout the 
/jffs2 file system and then remount it.  Put 
that pair of commands in a script so you don't 
get tired of typing it.

-mike@bithead.com




-- Patrick Hilt <philt@pioneer-pdt.com> wrote:
> Hi list!
> Is there a way to make sure data is being written to physical flash
> when using 
> JFFS2? In other words, After writing a file on a JFFS2 partition, is
> there 
> anything that can be done to make sure that the data is getting
> written to 
> the flash right away? Would "sync" or "fsync" have that effect?
> 
> Thanks a lot in advance for any input!!!
> 
> Happy weekend,
> 
> Patrick
> 
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
> 

Re: JFFS 2 Question

[Brad Campbell]

Patrick Hilt wrote:
> Hi list!
> Is there a way to make sure data is being written to physical flash when using 
> JFFS2? In other words, After writing a file on a JFFS2 partition, is there 
> anything that can be done to make sure that the data is getting written to 
> the flash right away? Would "sync" or "fsync" have that effect?

I believe that jffs2 is a synchronous filesystem in any case. By the time your application has 
returned from the write() call, the data is on flash.

It certainly worked that way while I was debugging some software that did stupid things like write 
800kb files 1 byte at a time.

Regards,
Brad

Re: JFFS 2 Question

[Thomas Gleixner]

On Sat, 2004-07-10 at 11:38, Brad Campbell wrote:
> Patrick Hilt wrote:
> > Hi list!
> > Is there a way to make sure data is being written to physical flash when using 
> > JFFS2? In other words, After writing a file on a JFFS2 partition, is there 
> > anything that can be done to make sure that the data is getting written to 
> > the flash right away? Would "sync" or "fsync" have that effect?
> 
> I believe that jffs2 is a synchronous filesystem in any case. By the time your application has 
> returned from the write() call, the data is on flash.

You're right and wrong. :)

On standard NOR FLASH it is synchronous. On NAND/AND FLASH and some
strange NOR FLASH types we must write page aligned and therefor were use
a write buffer of page size, which is either flushed timed by kupdated
or by sync/fsync/ummount.

tglx

Re: JFFS 2 Question

[Wolfgang Denk]

In message <40EFB906.7060701@wasp.net.au> you wrote:
> 
> I believe that jffs2 is a synchronous filesystem in any case. By the time your application has 
> returned from the write() call, the data is on flash.

At least on NAND flash it might just be in the write buffer, though.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
COBOL is for morons.                                 -- E.W. Dijkstra

Re: JFFS 2 Question

[Patrick Hilt]

Hi guys!
Thanks a lot or your input. Definitely appreciate it!!
In the project I am working on, we have been seeing an occasional corruption 
of our JFFS2 partition upon sudden loss of power and we get that even after 
writing to the parition and sync'ing. Could that be caused by the power loss 
happening during a block rotation / garbage collection?

Thanks again,

Patrick


On Friday 09 July 2004 04:08 pm, Patrick Hilt wrote:
> Hi list!
> Is there a way to make sure data is being written to physical flash when
> using JFFS2? In other words, After writing a file on a JFFS2 partition, is
> there anything that can be done to make sure that the data is getting
> written to the flash right away? Would "sync" or "fsync" have that effect?
>
> Thanks a lot in advance for any input!!!
>
> Happy weekend,
>
> Patrick
>
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/