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 at 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 at 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 at 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 at 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 at 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.