On 10/10/11 10:50 AM, Eric Sandeen wrote: > When looking at the maximal filesystem size issue, I found myself > wondering what the "- 8" is in here, it's not commented > or documented anywhere: > > #define EXT2_MAX_BLOCKS_PER_GROUP(s) (((1 << 16) - 8) * \ > (EXT2_CLUSTER_SIZE(s) / \ > EXT2_BLOCK_SIZE(s))) > > > (pre-bigalloc, it was just ((1 << 16) - 8) ) > > Anyone know? Ah, Darrick pointed out http://osdir.com/ml/file-systems.ext2.devel/2006-03/msg00032.html So it would have been - 1, to not overflow __u16, but since we have multiples of 8, we get - 8. But now we have bg_free_blocks_count_hi, giving us 32 bits of counter. With EXT4_FEATURE_INCOMPAT_64BIT, MAX_BLOCKS_PER_GROUP should grow, no? -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
