RE: Weird status information on JFFS2 File System

RE: Weird status information on JFFS2 File System

[Ashok M Padmanaban]

Hi Navin

Your Jffs2   file system size is 1MB

Jffs2 reserves around 5 sectors( erase sectors) for garbage collection.
So even when ur FS is empty , command df will show that 5 erase sectors
have been already occupied

Regards
ashok


Navin Boppuri wrote:

> Well, I guess I think I know what the problem is. I should not use
/dev/zero to create files to test the file system size. I decided to use
/dev/core instead and that actually creates the correct sized file.
>
> But I still dont understand why the status of my file system is so
screwed up. Even with an empty file sytem, it shows 64% used. And I am
only able to write around 375K of data into this partition, which is
actually 1MB.
>
> Navin.
>
> -----Original Message-----
> From: Navin Boppuri
> Sent: Thursday, February 14, 2002 1:29 PM
> To: linux-mtd@lists.infradead.org
> Subject: Weird status information on JFFS2 File System
>
> Hello all,
>
> I have a JFFS2 file system successfully installed on my flash device.
Here is the output of the drivers during the Linux kernel boot. I have
1MB of flash partition installed as my flash device( I have two 16bit
AMD flash devices connected on a 32 bit bus as one device).
>
>         sp flash device: 1000000 at 40000000
>         Amd/Fujitsu Extended Query Table v1.1 at 0x0040
>         number of CFI chips: 1
>         Creating 1 MTD partitions on "Service Processor flash device":

>         0x00f00000-0x01000000 : "Flash file system"
>         mtd: Giving out device 0 to Flash file system
>
> After I mount my file system using the following command,
>         mount -t jffs2 /dev/mtdblock0 /mnt/jffs2
>
> I confirm that the file system is mounted by looking at /proc/mounts.
>
>         root@sp_06:/mnt/jffs2# cat /proc/mounts
>         /dev/root / nfs
rw,v2,rsize=4096,wsize=4096,hard,udp,nolock,addr=10.10.30.39 0 0
>         proc /proc proc rw 0 0
>         devpts /dev/pts devpts rw 0 0
>         /dev/mtdblock0 /mnt/jffs2 jffs2 rw 0 0
>
> I now look at the disk usage using the df command
>
>         root@sp_06:/mnt/jffs2# df
>         Filesystem           1k-blocks      Used Available Use%
Mounted on
>         /dev/root             30237928  12751536  15950380  45% /
>         /dev/mtdblock0            1024       644       380  63%
/mnt/jffs2
>
>         root@sp_06:/mnt/jffs2# ls -al
>         total 4
>         drwxr-xr-x    1 root     root            0 Jan  1 00:00 .
>         drwxr-xr-x    3 1342     root         4096 Jan 25  2002 ..
>
> I am surprised to see 63% usage without anything in the file system.
>
> I now create the following three files doing this:
>
>                 dd if=/dev/zero of=tmp.out bs=1M count=4 conv=sync
>                 dd if=/dev/zero of=tmp2.out bs=1M count=4 conv=sync
>                 dd if=/dev/zero of=tmp3.out bs=1M count=4 conv=sync
>
> I run out of space while trying to create the tmp3.out command. But I
am able to create almost 10MB of data in my 1MB file system.
>
>         root@sp_06:~# ls -al /mnt/jffs2
>         total 10152
>         drwxr-xr-x    1 root     root            0 Jan  1 00:00 .
>         drwxr-xr-x    3 1342     root         4096 Jan 25  2002 ..
>         -rw-r--r--    1 root     root      4194304 Jan  1 03:01
tmp.out
>         -rw-r--r--    1 root     root      4194304 Jan  1 03:01
tmp2.out
>         -rw-r--r--    1 root     root      2002944 Jan  1 03:01
tmp3.out
>
>         root@sp_06:~# df
>         Filesystem           1k-blocks      Used Available Use%
Mounted on
>         /dev/root             30237928  12751536  15950380  45% /
>         /dev/mtdblock0            1024       932        92  92%
/mnt/jffs2
>
> I doing something really wrong here. What's going on? The kernel
messages are all correct. Then how am I able to access 10MB of flash in
this file system? I am only mapping the last 1MB of flash which is 16MB
in size. And I am confused about the status of my file system each time
I create files.
>
> Can someone give me some pointers on this? Thank you.
>
> Navin.
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/

RE: Weird status information on JFFS2 File System

[Navin Boppuri]

I have two uniform sector (64K each 16 bit) Flash devices connected to a 32 bit bus. So, my sector size is actually 128K. For a 1MB file system, what should be the optimal size of the reserved space for garbage collection? I only have 8 sectors for 1MB out of which 5 sectors are already being taken up by GC. Do I really need 5*128K GC area for 3*128K available space left on the flash? 

Thanks a lot.

Navin.

-----Original Message-----
From: David Woodhouse [mailto:dwmw2@infradead.org]
Sent: Friday, February 15, 2002 10:10 AM
To: Navin Boppuri
Cc: Chris Vagnini; linux-mtd@lists.infradead.org
Subject: Re: Weird status information on JFFS2 File System 



navin.boppuri@newisys.com said:
>  Is there some way I can change the 5 erase blocks default to a
> smaller size? What are the implications of doing that?

grep RESERVED fs/jffs2/nodelist.h

The danger in reducing it too far is that you'll run out of free space 
entirely, so that garbage collection cannot continue and your file system 
gets entirely stuck. We ought to be able to reduce it to only a block or 
two, but the code wants auditing for safety first - we have to ensure that 
we never expand while garbage-collecting.

--
dwmw2

RE: Weird status information on JFFS2 File System

[Navin Boppuri]

Well, I should have read more about the JFFS2 file system. But your answers explain everything.

Is there some way I can change the 5 erase blocks default to a smaller size? What are the implications of doing that?

Navin.



-----Original Message-----
From: Chris Vagnini [mailto:cvagnini@bigfoot.com]
Sent: Thursday, February 14, 2002 11:21 PM
To: Navin Boppuri
Cc: linux-mtd@lists.infradead.org
Subject: Re: Weird status information on JFFS2 File System


Hi Navin,

You're running into two documented behaviors of jffs2

1. jffs2 needs to keep 5 erase blocks of the flash free at all times.  This 
is so that there's always room for garbage collection.  There have been 
discussions of why this is necessary and how it might be reduced in the 
past; search the email archive for details.  These five blocks appear as 
used space in the df command.  Since you're showing 640K used, your flash 
must use sectors of 64K each (x 2 chips).

2. jffs2 compresses the data to be stored the flash.  Extremely 
compressible data (like the contents of /dev/zero) occupy almost no space 
when compressed, so you can fit a *lot* of it.  Most data averages 
compression more like 2:1, unlike the 30-1 or so you were seeing with 
/dev/zero, so you can expect to store about 700KB in your flash which 
starts out with 380K free.  Of course this compression costs you processing 
time, so you might want to turn it off while building jffs2 if speed is 
more important than capacity.

--chris vagnini

At 02:29 PM 2/14/2002, Navin Boppuri wrote:

>Hello all,
>
>I have a JFFS2 file system successfully installed on my flash device. Here 
>is the output of the drivers during the Linux kernel boot. I have 1MB of 
>flash partition installed as my flash device( I have two 16bit AMD flash 
>devices connected on a 32 bit bus as one device).
>
>
>         sp flash device: 1000000 at 40000000
>         Amd/Fujitsu Extended Query Table v1.1 at 0x0040
>         number of CFI chips: 1
>         Creating 1 MTD partitions on "Service Processor flash device":
>         0x00f00000-0x01000000 : "Flash file system"
>         mtd: Giving out device 0 to Flash file system
>
>After I mount my file system using the following command,
>         mount -t jffs2 /dev/mtdblock0 /mnt/jffs2
>
>I confirm that the file system is mounted by looking at /proc/mounts.
>
>         root@sp_06:/mnt/jffs2# cat /proc/mounts
>         /dev/root / nfs 
> rw,v2,rsize=4096,wsize=4096,hard,udp,nolock,addr=10.10.30.39 0 0
>         proc /proc proc rw 0 0
>         devpts /dev/pts devpts rw 0 0
>         /dev/mtdblock0 /mnt/jffs2 jffs2 rw 0 0
>
>I now look at the disk usage using the df command
>
>         root@sp_06:/mnt/jffs2# df
>         Filesystem           1k-blocks      Used Available Use% Mounted on
>         /dev/root             30237928  12751536  15950380  45% /
>         /dev/mtdblock0            1024       644       380  63% /mnt/jffs2
>
>         root@sp_06:/mnt/jffs2# ls -al
>         total 4
>         drwxr-xr-x    1 root     root            0 Jan  1 00:00 .
>         drwxr-xr-x    3 1342     root         4096 Jan 25  2002 ..
>
>I am surprised to see 63% usage without anything in the file system.
>
>I now create the following three files doing this:
>
>                 dd if=/dev/zero of=tmp.out bs=1M count=4 conv=sync
>                 dd if=/dev/zero of=tmp2.out bs=1M count=4 conv=sync
>                 dd if=/dev/zero of=tmp3.out bs=1M count=4 conv=sync
>
>I run out of space while trying to create the tmp3.out command. But I am 
>able to create almost 10MB of data in my 1MB file system.
>
>         root@sp_06:~# ls -al /mnt/jffs2
>         total 10152
>         drwxr-xr-x    1 root     root            0 Jan  1 00:00 .
>         drwxr-xr-x    3 1342     root         4096 Jan 25  2002 ..
>         -rw-r--r--    1 root     root      4194304 Jan  1 03:01 tmp.out
>         -rw-r--r--    1 root     root      4194304 Jan  1 03:01 tmp2.out
>         -rw-r--r--    1 root     root      2002944 Jan  1 03:01 tmp3.out
>
>         root@sp_06:~# df
>         Filesystem           1k-blocks      Used Available Use% Mounted on
>         /dev/root             30237928  12751536  15950380  45% /
>         /dev/mtdblock0            1024       932        92  92% /mnt/jffs2
>
>I doing something really wrong here. What's going on? The kernel messages 
>are all correct. Then how am I able to access 10MB of flash in this file 
>system? I am only mapping the last 1MB of flash which is 16MB in size. And 
>I am confused about the status of my file system each time I create files.
>
>Can someone give me some pointers on this? Thank you.
>
>Navin.
>
>
>______________________________________________________
>Linux MTD discussion mailing list
>http://lists.infradead.org/mailman/listinfo/linux-mtd/

Re: Weird status information on JFFS2 File System

[David Woodhouse]

navin.boppuri@newisys.com said:
>  Is there some way I can change the 5 erase blocks default to a
> smaller size? What are the implications of doing that?

grep RESERVED fs/jffs2/nodelist.h

The danger in reducing it too far is that you'll run out of free space 
entirely, so that garbage collection cannot continue and your file system 
gets entirely stuck. We ought to be able to reduce it to only a block or 
two, but the code wants auditing for safety first - we have to ensure that 
we never expand while garbage-collecting.

--
dwmw2

Re: Weird status information on JFFS2 File System

[Chris Vagnini]

Hi Navin,

You're running into two documented behaviors of jffs2

1. jffs2 needs to keep 5 erase blocks of the flash free at all times.  This 
is so that there's always room for garbage collection.  There have been 
discussions of why this is necessary and how it might be reduced in the 
past; search the email archive for details.  These five blocks appear as 
used space in the df command.  Since you're showing 640K used, your flash 
must use sectors of 64K each (x 2 chips).

2. jffs2 compresses the data to be stored the flash.  Extremely 
compressible data (like the contents of /dev/zero) occupy almost no space 
when compressed, so you can fit a *lot* of it.  Most data averages 
compression more like 2:1, unlike the 30-1 or so you were seeing with 
/dev/zero, so you can expect to store about 700KB in your flash which 
starts out with 380K free.  Of course this compression costs you processing 
time, so you might want to turn it off while building jffs2 if speed is 
more important than capacity.

--chris vagnini

At 02:29 PM 2/14/2002, Navin Boppuri wrote:

>Hello all,
>
>I have a JFFS2 file system successfully installed on my flash device. Here 
>is the output of the drivers during the Linux kernel boot. I have 1MB of 
>flash partition installed as my flash device( I have two 16bit AMD flash 
>devices connected on a 32 bit bus as one device).
>
>
>         sp flash device: 1000000 at 40000000
>         Amd/Fujitsu Extended Query Table v1.1 at 0x0040
>         number of CFI chips: 1
>         Creating 1 MTD partitions on "Service Processor flash device":
>         0x00f00000-0x01000000 : "Flash file system"
>         mtd: Giving out device 0 to Flash file system
>
>After I mount my file system using the following command,
>         mount -t jffs2 /dev/mtdblock0 /mnt/jffs2
>
>I confirm that the file system is mounted by looking at /proc/mounts.
>
>         root@sp_06:/mnt/jffs2# cat /proc/mounts
>         /dev/root / nfs 
> rw,v2,rsize=4096,wsize=4096,hard,udp,nolock,addr=10.10.30.39 0 0
>         proc /proc proc rw 0 0
>         devpts /dev/pts devpts rw 0 0
>         /dev/mtdblock0 /mnt/jffs2 jffs2 rw 0 0
>
>I now look at the disk usage using the df command
>
>         root@sp_06:/mnt/jffs2# df
>         Filesystem           1k-blocks      Used Available Use% Mounted on
>         /dev/root             30237928  12751536  15950380  45% /
>         /dev/mtdblock0            1024       644       380  63% /mnt/jffs2
>
>         root@sp_06:/mnt/jffs2# ls -al
>         total 4
>         drwxr-xr-x    1 root     root            0 Jan  1 00:00 .
>         drwxr-xr-x    3 1342     root         4096 Jan 25  2002 ..
>
>I am surprised to see 63% usage without anything in the file system.
>
>I now create the following three files doing this:
>
>                 dd if=/dev/zero of=tmp.out bs=1M count=4 conv=sync
>                 dd if=/dev/zero of=tmp2.out bs=1M count=4 conv=sync
>                 dd if=/dev/zero of=tmp3.out bs=1M count=4 conv=sync
>
>I run out of space while trying to create the tmp3.out command. But I am 
>able to create almost 10MB of data in my 1MB file system.
>
>         root@sp_06:~# ls -al /mnt/jffs2
>         total 10152
>         drwxr-xr-x    1 root     root            0 Jan  1 00:00 .
>         drwxr-xr-x    3 1342     root         4096 Jan 25  2002 ..
>         -rw-r--r--    1 root     root      4194304 Jan  1 03:01 tmp.out
>         -rw-r--r--    1 root     root      4194304 Jan  1 03:01 tmp2.out
>         -rw-r--r--    1 root     root      2002944 Jan  1 03:01 tmp3.out
>
>         root@sp_06:~# df
>         Filesystem           1k-blocks      Used Available Use% Mounted on
>         /dev/root             30237928  12751536  15950380  45% /
>         /dev/mtdblock0            1024       932        92  92% /mnt/jffs2
>
>I doing something really wrong here. What's going on? The kernel messages 
>are all correct. Then how am I able to access 10MB of flash in this file 
>system? I am only mapping the last 1MB of flash which is 16MB in size. And 
>I am confused about the status of my file system each time I create files.
>
>Can someone give me some pointers on this? Thank you.
>
>Navin.
>
>
>______________________________________________________
>Linux MTD discussion mailing list
>http://lists.infradead.org/mailman/listinfo/linux-mtd/

RE: Weird status information on JFFS2 File System

[Navin Boppuri]

I tried using the JFFS file system instead of JFFS2. Now I see that my file system size is 512Kb instead of 1MB. Also, I am only able to write to around 75% of the file sytem. 

What's going on here? Can somone please give me some inputs on this. I am really new to JFFS and this stuff is driving me crazy.

Navin.

-----Original Message-----
From: Navin Boppuri 
Sent: Thursday, February 14, 2002 2:57 PM
To: linux-mtd@lists.infradead.org
Subject: RE: Weird status information on JFFS2 File System



Well, I guess I think I know what the problem is. I should not use /dev/zero to create files to test the file system size. I decided to use /dev/core instead and that actually creates the correct sized file.

But I still dont understand why the status of my file system is so screwed up. Even with an empty file sytem, it shows 64% used. And I am only able to write around 375K of data into this partition, which is actually 1MB. 

Navin.

-----Original Message-----
From: Navin Boppuri 
Sent: Thursday, February 14, 2002 1:29 PM
To: linux-mtd@lists.infradead.org
Subject: Weird status information on JFFS2 File System


Hello all,

I have a JFFS2 file system successfully installed on my flash device. Here is the output of the drivers during the Linux kernel boot. I have 1MB of flash partition installed as my flash device( I have two 16bit AMD flash devices connected on a 32 bit bus as one device).


	sp flash device: 1000000 at 40000000
	Amd/Fujitsu Extended Query Table v1.1 at 0x0040
	number of CFI chips: 1
	Creating 1 MTD partitions on "Service Processor flash device":
	0x00f00000-0x01000000 : "Flash file system"	
	mtd: Giving out device 0 to Flash file system

After I mount my file system using the following command,
	mount -t jffs2 /dev/mtdblock0 /mnt/jffs2

I confirm that the file system is mounted by looking at /proc/mounts.

	root@sp_06:/mnt/jffs2# cat /proc/mounts
	/dev/root / nfs rw,v2,rsize=4096,wsize=4096,hard,udp,nolock,addr=10.10.30.39 0 0	
	proc /proc proc rw 0 0
	devpts /dev/pts devpts rw 0 0
	/dev/mtdblock0 /mnt/jffs2 jffs2 rw 0 0

I now look at the disk usage using the df command

	root@sp_06:/mnt/jffs2# df
	Filesystem           1k-blocks      Used Available Use% Mounted on
	/dev/root             30237928  12751536  15950380  45% /
	/dev/mtdblock0            1024       644       380  63% /mnt/jffs2

	root@sp_06:/mnt/jffs2# ls -al
	total 4
	drwxr-xr-x    1 root     root            0 Jan  1 00:00 .
	drwxr-xr-x    3 1342     root         4096 Jan 25  2002 ..

I am surprised to see 63% usage without anything in the file system.

I now create the following three files doing this:

		dd if=/dev/zero of=tmp.out bs=1M count=4 conv=sync
		dd if=/dev/zero of=tmp2.out bs=1M count=4 conv=sync
		dd if=/dev/zero of=tmp3.out bs=1M count=4 conv=sync

I run out of space while trying to create the tmp3.out command. But I am able to create almost 10MB of data in my 1MB file system.

	root@sp_06:~# ls -al /mnt/jffs2
	total 10152
	drwxr-xr-x    1 root     root            0 Jan  1 00:00 .
	drwxr-xr-x    3 1342     root         4096 Jan 25  2002 ..
	-rw-r--r--    1 root     root      4194304 Jan  1 03:01 tmp.out
	-rw-r--r--    1 root     root      4194304 Jan  1 03:01 tmp2.out
	-rw-r--r--    1 root     root      2002944 Jan  1 03:01 tmp3.out

	root@sp_06:~# df
	Filesystem           1k-blocks      Used Available Use% Mounted on
	/dev/root             30237928  12751536  15950380  45% /
	/dev/mtdblock0            1024       932        92  92% /mnt/jffs2

I doing something really wrong here. What's going on? The kernel messages are all correct. Then how am I able to access 10MB of flash in this file system? I am only mapping the last 1MB of flash which is 16MB in size. And I am confused about the status of my file system each time I create files.

Can someone give me some pointers on this? Thank you.

Navin.


______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

RE: Weird status information on JFFS2 File System

[Navin Boppuri]

Well, I guess I think I know what the problem is. I should not use /dev/zero to create files to test the file system size. I decided to use /dev/core instead and that actually creates the correct sized file.

But I still dont understand why the status of my file system is so screwed up. Even with an empty file sytem, it shows 64% used. And I am only able to write around 375K of data into this partition, which is actually 1MB. 

Navin.

-----Original Message-----
From: Navin Boppuri 
Sent: Thursday, February 14, 2002 1:29 PM
To: linux-mtd@lists.infradead.org
Subject: Weird status information on JFFS2 File System


Hello all,

I have a JFFS2 file system successfully installed on my flash device. Here is the output of the drivers during the Linux kernel boot. I have 1MB of flash partition installed as my flash device( I have two 16bit AMD flash devices connected on a 32 bit bus as one device).


	sp flash device: 1000000 at 40000000
	Amd/Fujitsu Extended Query Table v1.1 at 0x0040
	number of CFI chips: 1
	Creating 1 MTD partitions on "Service Processor flash device":
	0x00f00000-0x01000000 : "Flash file system"	
	mtd: Giving out device 0 to Flash file system

After I mount my file system using the following command,
	mount -t jffs2 /dev/mtdblock0 /mnt/jffs2

I confirm that the file system is mounted by looking at /proc/mounts.

	root@sp_06:/mnt/jffs2# cat /proc/mounts
	/dev/root / nfs rw,v2,rsize=4096,wsize=4096,hard,udp,nolock,addr=10.10.30.39 0 0	
	proc /proc proc rw 0 0
	devpts /dev/pts devpts rw 0 0
	/dev/mtdblock0 /mnt/jffs2 jffs2 rw 0 0

I now look at the disk usage using the df command

	root@sp_06:/mnt/jffs2# df
	Filesystem           1k-blocks      Used Available Use% Mounted on
	/dev/root             30237928  12751536  15950380  45% /
	/dev/mtdblock0            1024       644       380  63% /mnt/jffs2

	root@sp_06:/mnt/jffs2# ls -al
	total 4
	drwxr-xr-x    1 root     root            0 Jan  1 00:00 .
	drwxr-xr-x    3 1342     root         4096 Jan 25  2002 ..

I am surprised to see 63% usage without anything in the file system.

I now create the following three files doing this:

		dd if=/dev/zero of=tmp.out bs=1M count=4 conv=sync
		dd if=/dev/zero of=tmp2.out bs=1M count=4 conv=sync
		dd if=/dev/zero of=tmp3.out bs=1M count=4 conv=sync

I run out of space while trying to create the tmp3.out command. But I am able to create almost 10MB of data in my 1MB file system.

	root@sp_06:~# ls -al /mnt/jffs2
	total 10152
	drwxr-xr-x    1 root     root            0 Jan  1 00:00 .
	drwxr-xr-x    3 1342     root         4096 Jan 25  2002 ..
	-rw-r--r--    1 root     root      4194304 Jan  1 03:01 tmp.out
	-rw-r--r--    1 root     root      4194304 Jan  1 03:01 tmp2.out
	-rw-r--r--    1 root     root      2002944 Jan  1 03:01 tmp3.out

	root@sp_06:~# df
	Filesystem           1k-blocks      Used Available Use% Mounted on
	/dev/root             30237928  12751536  15950380  45% /
	/dev/mtdblock0            1024       932        92  92% /mnt/jffs2

I doing something really wrong here. What's going on? The kernel messages are all correct. Then how am I able to access 10MB of flash in this file system? I am only mapping the last 1MB of flash which is 16MB in size. And I am confused about the status of my file system each time I create files.

Can someone give me some pointers on this? Thank you.

Navin.


______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

Weird status information on JFFS2 File System

[Navin Boppuri]

Hello all,

I have a JFFS2 file system successfully installed on my flash device. Here is the output of the drivers during the Linux kernel boot. I have 1MB of flash partition installed as my flash device( I have two 16bit AMD flash devices connected on a 32 bit bus as one device).


	sp flash device: 1000000 at 40000000
	Amd/Fujitsu Extended Query Table v1.1 at 0x0040
	number of CFI chips: 1
	Creating 1 MTD partitions on "Service Processor flash device":
	0x00f00000-0x01000000 : "Flash file system"	
	mtd: Giving out device 0 to Flash file system

After I mount my file system using the following command,
	mount -t jffs2 /dev/mtdblock0 /mnt/jffs2

I confirm that the file system is mounted by looking at /proc/mounts.

	root@sp_06:/mnt/jffs2# cat /proc/mounts
	/dev/root / nfs rw,v2,rsize=4096,wsize=4096,hard,udp,nolock,addr=10.10.30.39 0 0	
	proc /proc proc rw 0 0
	devpts /dev/pts devpts rw 0 0
	/dev/mtdblock0 /mnt/jffs2 jffs2 rw 0 0

I now look at the disk usage using the df command

	root@sp_06:/mnt/jffs2# df
	Filesystem           1k-blocks      Used Available Use% Mounted on
	/dev/root             30237928  12751536  15950380  45% /
	/dev/mtdblock0            1024       644       380  63% /mnt/jffs2

	root@sp_06:/mnt/jffs2# ls -al
	total 4
	drwxr-xr-x    1 root     root            0 Jan  1 00:00 .
	drwxr-xr-x    3 1342     root         4096 Jan 25  2002 ..

I am surprised to see 63% usage without anything in the file system.

I now create the following three files doing this:

		dd if=/dev/zero of=tmp.out bs=1M count=4 conv=sync
		dd if=/dev/zero of=tmp2.out bs=1M count=4 conv=sync
		dd if=/dev/zero of=tmp3.out bs=1M count=4 conv=sync

I run out of space while trying to create the tmp3.out command. But I am able to create almost 10MB of data in my 1MB file system.

	root@sp_06:~# ls -al /mnt/jffs2
	total 10152
	drwxr-xr-x    1 root     root            0 Jan  1 00:00 .
	drwxr-xr-x    3 1342     root         4096 Jan 25  2002 ..
	-rw-r--r--    1 root     root      4194304 Jan  1 03:01 tmp.out
	-rw-r--r--    1 root     root      4194304 Jan  1 03:01 tmp2.out
	-rw-r--r--    1 root     root      2002944 Jan  1 03:01 tmp3.out

	root@sp_06:~# df
	Filesystem           1k-blocks      Used Available Use% Mounted on
	/dev/root             30237928  12751536  15950380  45% /
	/dev/mtdblock0            1024       932        92  92% /mnt/jffs2

I doing something really wrong here. What's going on? The kernel messages are all correct. Then how am I able to access 10MB of flash in this file system? I am only mapping the last 1MB of flash which is 16MB in size. And I am confused about the status of my file system each time I create files.

Can someone give me some pointers on this? Thank you.

Navin.