On Wed, Nov 07, 2012 at 10:39:46PM +0100, Andi Kleen wrote: > > Why would that be necessary? We never include the checksum field in > > the calculation when setting it or verifiying it, and the > > verification uses exactly the same method as the original > > calculation to check the CRC, so it doesn't matter if the CRC value > > is zero or not - if it matches (zero or otherwise), the validation > > passes.... > > I thought zero meant the checksum is not there? You stated that > somewhere else. That's only to avoid spurious warnings when moving from an existing kernel to a new kernel that issues advisory warnings on mismatches. For enforcement, though, when the on-disk format changes so that all metadata is CRC protected, determination of whether zero is a valid CRC value is determined by a superblock feature bit, not a magic CRC mapping value... Hence mapping the zero value just for advisory warnings really doesn't buy us that much other than complexity for this single case. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
