On Mar 29, 2006 17:38 -0800, Mingming Cao wrote: > There are places in ext3 code to use "int" to represent block numbers in > kernel(not on-disk). This seems the "only" reason that why we can only > have 8TB ext3 rather than 16TB. Most times it just a bug with no > particular reason why not use unsigned 32 bit value, so the fix is easy. > > However, it is not so straightforward fix for the ext3 block allocation > code, as ext3_new_block() returns a block number, and "-1" to indicating > block allocation failure. Ext3 block reservation code, called by > ext3_new_block(), thus also use "int" for block numbers in some places. What might make the code a lot clearer, easier to audit, and easier to fix in the future is to declare new types for fs block offsets and group block offsets. Something like "ext3_fsblk" and "ext3_grblk". That way, we can declare ext3_fsblk as "unsigned long" and "ext3_grblk" as "unsigned int", and we could optionally change ext3_fsblk to be "unsigned long long" later to support 64-bit filesystems without having to re-patch all of the code. It would be more clear what type of block offset a function is handling (fs-wide or group-relative). If we wanted to be able to overload the block number with an error code we could use ERR_PTR and PTR_ERR like macros, and just restrict the filesystem to 2^32 - 1024 blocks until we extend it to 64 bits. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc. - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
