Thanks all for the answers. Sorry, but I've not done full check of a 
problem and my previous description was wrong. Let me describe it again.

The problem is that I have only something like 256 Kb on mtd partition 
after mounting procedure. So I can only copy file (or files) which total 
size less then 256Kb. In a case if the size will be more then 256Kb it 
write only the first part of the file and say "Operation not permitted". 
If I try to copy any more file it says "Couldn't allocate the memory".

I've 128 MB devise, and mtd when it starts booting says something like: 

0x00000000-0x00200000 : "MSP boot partition"
0x00200000-0x00400000 : "Linux boot partition"
0x00400000-0x03600000 : "Comcerto Filesystem partition"
0x03600000-0x06800000 : "Comcerto Filesystem partition2"

As I see from this table I should have something like 52Mb for mtd3 and 
mtd2.

Here is my partition structure which was ok for first version of yaffs.

static struct mtd_partition partition_info128M[] = {
        { name: "MSP boot partition",
          offset: 0,
          size: 2*SZ_1M,
          mask_flags: 0},
        { name: "Linux boot partition",
          offset: MTDPART_OFS_APPEND,
          size: 2*SZ_1M ,
          mask_flags: 0},
        { name: "Comcerto Filesystem partition",
          offset: MTDPART_OFS_APPEND,
          size: 50*SZ_1M ,
          mask_flags: 0},
          { name: "Comcerto Filesystem partition2",
          offset: MTDPART_OFS_APPEND,
          size: 50*SZ_1M ,
          mask_flags: 0}
};

Thank you,
        Yuri Golovach