unable to modify jffs2

[Xavier DEBREUIL]

I have managed to mount the jffs2 ;
however, it seems that I cannot erase anything or write anything on it

/mnt/jffs2/jffs2_1/bin # df
Filesystem           1k-blocks      Used Available Use% Mounted on
/dev/ram0                 3963      2997       966  76% /
/dev/ram1                 2011        13      1998   1% /mnt/ramdisk/rd1
/dev/mtdblock1            2048      2048         0 100%
/mnt/jffs2/jffs2_1

/mnt/jffs2/jffs2_1/bin # mount 
/dev/ram0 on / type ext2 (rw)
none on /proc type proc (rw)
none on /dev/pts type devpts (rw)
/dev/ram1 on /mnt/ramdisk/rd1 type ext2 (rw)
/dev/mtdblock1 on /mnt/jffs2/jffs2_1 type jffs2 (rw)

I can list, chroot and execute things on the filesystem but no
erasure...
Is there an option I've missed ?

Xavier