Flash File system is about 256kB approx.
try this code:
unsigned int total_blocks, free_blocks, block_size, total_inodes, free_inodes;
NAFSvolume_stats("FLASH0", &total_blocks, &free_blocks, &block_size, &total_inodes, &free_inodes);
printf("tot=%d Free=%d size=%d\n",total_blocks, free_blocks, block_size);
Julius