jffs2: Too few erase blocks (1)

jffs2: Too few erase blocks (1)

[Dzuy Nguyen]

Hello,

I've allocated a small (64K) "user_config" partition in my flash for
persistence storage:

mtd0: 00020000 00010000 "u-boot"
mtd1: 00010000 00010000 "Config"
mtd2: 00100000 00010000 "vmlinux"
mtd3: 002a0000 00010000 "rootfs"
mtd4: 00010000 00010000 "user_config"
mtd5: 00020000 00010000 "ART"

When I tried to mount -t jffs2 /dev/mtdblock4, I get

jffs2: Too few erase blocks (1)

I understand that my erasesize is 64K, which gives me only 1 block,
and jffs2 needs more than 1 block, but the kernel defaults the erasesize
to 64K.

If I made a jffs2 file with eraseblock=8, would this work or would I have
to set it at the kernel?

Dzuy

Re: jffs2: Too few erase blocks (1)

[Ricard Wanderlof]

On Mon, 9 Feb 2009, Dzuy Nguyen wrote:

> I've allocated a small (64K) "user_config" partition in my flash for
> persistence storage:
>
> mtd0: 00020000 00010000 "u-boot"
> mtd1: 00010000 00010000 "Config"
> mtd2: 00100000 00010000 "vmlinux"
> mtd3: 002a0000 00010000 "rootfs"
> mtd4: 00010000 00010000 "user_config"
> mtd5: 00020000 00010000 "ART"
>
> When I tried to mount -t jffs2 /dev/mtdblock4, I get
>
> jffs2: Too few erase blocks (1)
>
> I understand that my erasesize is 64K, which gives me only 1 block,
> and jffs2 needs more than 1 block, but the kernel defaults the erasesize
> to 64K.

The kernel does that probably because that is the size of the blocks on 
your flash chip. It is not so much a default as detection of the 
properties of the chip.

> If I made a jffs2 file with eraseblock=8, would this work or would I have
> to set it at the kernel?

You need to allocate more space if you want to use jffs2 quite simply. The 
exact number is not exact; 8 should be ok, meaning you need to partition 
your flash so you have 64K * 8 = 512K in your user_config partition.

If you can't afford that much space, you could consider writing your user 
configurations to a file and just dumping the file with dd into your flash 
partition. Not at all as flexible, but doable in a pinch.

/Ricard
--
Ricard Wolf Wanderlöf                           ricardw(at)axis.com
Axis Communications AB, Lund, Sweden            www.axis.com
Phone +46 46 272 2016                           Fax +46 46 13 61 30

Re: jffs2: Too few erase blocks (1)

[Dzuy Nguyen]

Thanks, Ricard.  I didn't realize that jffs2 is not suitable for a small
partition.  Yes,
64K is all I can afford.  I suppose I can dd the file, but doesn't that
provide no wear
leveling feature that jffs2 does?

Ricard Wanderlof wrote:
> On Mon, 9 Feb 2009, Dzuy Nguyen wrote:
>
>   
>> I've allocated a small (64K) "user_config" partition in my flash for
>> persistence storage:
>>
>> mtd0: 00020000 00010000 "u-boot"
>> mtd1: 00010000 00010000 "Config"
>> mtd2: 00100000 00010000 "vmlinux"
>> mtd3: 002a0000 00010000 "rootfs"
>> mtd4: 00010000 00010000 "user_config"
>> mtd5: 00020000 00010000 "ART"
>>
>> When I tried to mount -t jffs2 /dev/mtdblock4, I get
>>
>> jffs2: Too few erase blocks (1)
>>
>> I understand that my erasesize is 64K, which gives me only 1 block,
>> and jffs2 needs more than 1 block, but the kernel defaults the erasesize
>> to 64K.
>>     
>
> The kernel does that probably because that is the size of the blocks on 
> your flash chip. It is not so much a default as detection of the 
> properties of the chip.
>
>   
>> If I made a jffs2 file with eraseblock=8, would this work or would I have
>> to set it at the kernel?
>>     
>
> You need to allocate more space if you want to use jffs2 quite simply. The 
> exact number is not exact; 8 should be ok, meaning you need to partition 
> your flash so you have 64K * 8 = 512K in your user_config partition.
>
> If you can't afford that much space, you could consider writing your user 
> configurations to a file and just dumping the file with dd into your flash 
> partition. Not at all as flexible, but doable in a pinch.
>
> /Ricard
> --
> Ricard Wolf Wanderlöf                           ricardw(at)axis.com
> Axis Communications AB, Lund, Sweden            www.axis.com
> Phone +46 46 272 2016                           Fax +46 46 13 61 30
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
>   

Re: jffs2: Too few erase blocks (1)

[Ricard Wanderlof]

On Mon, 9 Feb 2009, Dzuy Nguyen wrote:

> Thanks, Ricard.  I didn't realize that jffs2 is not suitable for a small
> partition.  Yes,
> 64K is all I can afford.  I suppose I can dd the file, but doesn't that
> provide no wear
> leveling feature that jffs2 does?

No. But with one eraseblock you can't get much wear levelling anyway.

It might not be too difficult to write an application that appends 
new data to existing data to the partition, erasing the whole block when 
it fills up and write the latest. Then you need something that will search 
for the latest version of the file. Something that jffs2 does, but on a 
smaller scale, acceptable for your application.

/Ricard
--
Ricard Wolf Wanderlöf                           ricardw(at)axis.com
Axis Communications AB, Lund, Sweden            www.axis.com
Phone +46 46 272 2016                           Fax +46 46 13 61 30

Re: jffs2: Too few erase blocks (1)

[Dzuy Nguyen]

I think I'll just use ext2.  ext2 doesn't mind small partition.  Writing
to it
should work the same as dd.

Ricard Wanderlof wrote:
> On Mon, 9 Feb 2009, Dzuy Nguyen wrote:
>
>   
>> Thanks, Ricard.  I didn't realize that jffs2 is not suitable for a small
>> partition.  Yes,
>> 64K is all I can afford.  I suppose I can dd the file, but doesn't that
>> provide no wear
>> leveling feature that jffs2 does?
>>     
>
> No. But with one eraseblock you can't get much wear levelling anyway.
>
> It might not be too difficult to write an application that appends 
> new data to existing data to the partition, erasing the whole block when 
> it fills up and write the latest. Then you need something that will search 
> for the latest version of the file. Something that jffs2 does, but on a 
> smaller scale, acceptable for your application.
>
> /Ricard
> --
> Ricard Wolf Wanderlöf                           ricardw(at)axis.com
> Axis Communications AB, Lund, Sweden            www.axis.com
> Phone +46 46 272 2016                           Fax +46 46 13 61 30
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
>   

Re: jffs2: Too few erase blocks (1)

[Jamie Lokier]

Dzuy Nguyen wrote:
> I think I'll just use ext2.  ext2 doesn't mind small partition.
> Writing to it should work the same as dd.

Be careful.  Writing to ext2 over mtdblock may wear out the flash
faster than dd over mtd.

-- Jamie